FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm.No. 18 Allium spp. edited by M. Diekmann in collaboration with the Research Institute of Crop Production, Prague – Ruzyne 2 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Previously published Technical Guidelines for the Safe Movement of Germplasm These guidelines describe technical procedures that minimize the risk of pest intro- ductions with movement of germplasm for research, crop improvement, plant breeding, exploration or conservation. The recommendations in these guidelines are intended for germplasm for research, conservation and basic plant breeding programmes. Recommendations for commercial consignments are not the objective of these guidelines. Cocoa 1989 Edible Aroids Musa (1 st edition) Sweet Potato Yam Legumes Cassava Citrus Grapevine Vanilla 1989 1989 1989 1989 1990 1991 1991 1991 1991 Coconut 1993 Sugarcane 1993 Small fruits (Fragaria, Ribes, Rubus, Vaccinium) 1994 Small Grain Temperate Cereals 1995 Musa spp. (2nd edition) 1996 Stone Fruits 1996 Eucalyptus spp. 1996 No. 18. Allium spp. 3 CONTENTS Introduction......................................................4 Participant s in th e Meetin g . . . . . . . . . . . . . . . . . . . . . . . . 8 Acknowledgemen t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Genera l Recommendation s . . . . . . . . . . . . . . . . . . . . . . . . 11 Acronyms and Definitions of Terms as Used in this Publication . . . . . . . . . . . . . . . . . . . . 15 Sources of Antisera an d Monoclona l Antibodie s . . . . . . .. . . . . . . . . . . . . . . 17 Description s of Pests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Viruses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Garlic common latent carlavirus (GCLV) . . . . . .. . . . . . . . . . . . . . . . . 19 Garlic dwarf reovirus . . . . . . . . . . . . . . . . . .21 Leek yellow stripe potyvirus (LYSV) . . . . . . . . . . . . . . . . .23 Mite-borne filamentous viruses (MbFV) . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Onion yellow dwarf potyvirus (OYDV) . . . . . . . . . . . . . . . . . . . .28 Shallot latent carlaviru s (SLV) ................30 Shallot yellow stripe potyvirus (SYSV)..... 32 Otherviruses . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 Fungi . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Alternaria porri(purple blotch) . . . . . . . . . . . 35 Botyofinia squamosa (Botrytis leaf blight) ................................37 Botrytis allii (neck rot) . . . . . . . . . . . . . . . . . . . 39 Cladosporium allii-cepae (Cladosporium leaf blotch) . . . . . . . . . . . . .41 Fusarium spp. (Fusarium basal rot ) . . . . . . 42 Peronospora destructor (onio n down y mildew) . . . . . . . . . . . . . . . . . . . . .. ..43 Sclerotium cepivorum (onion white rot) .........44 Stemphylium vesicarium (Stemphyliu m leaf blight ) . . . . . . . . . . . . . . . . . 45 Minor fungal and bacterial pathogens . . . . . . . 46 Nematodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Ditylenchus dipsaci (stem an d bul b nematode ) . . . . . . . . . . . . . . . .. . . . . 47 Arthropods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 Aceria tulipae (garlic mite) . . . . . . . . . . . . . . . . .49 Rhizoglyphus robini, Rhizoglyphus callae (bul b mites ) .. . . . . . . . . . . . . . . . . . . . . . . .. 50 Bibliography.............................................................51 Sample Germplasm Health Statement . . . . . . . . . 59 4 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm INTRODUCTION Collecting, conservation and utilization of plant genetic resources and their global distri- bution are essential components of international crop improvement programmes. Inevitably, the movement of germplasm involves a risk of accidentally introducing plant pests1 along with the host plant. In particular, pathogens that are often symptomless, such as viruses, pose a special risk. In order to manage this risk, effective testing (indexing) procedures are required to ensure that distributed material is free of pests that are of concern. The ever-increasing volume of germplasm exchanged internationally, coupled with recent advances in biotechnology, has created a pressing need for crop-specific over- views of the existing knowledge in all disciplines relating to the phytosanitary safety of germplasm transfer. This has prompted FAO and IPGRI to launch a collaborative pro- gramme for the safe and expeditious movement of germplasm, reflecting the comple- mentarity of their mandates with regard to the safe movement of germplasm. FAO, as the depository of the International Plant Protection Convention of 1951, has a long-stan- ding mandate to assist its member governments to strengthen their plant quarantine services, while IPGRI’s mandate -inter alia -is to further the collecting, conservation and use of the genetic diversity of useful plants for the benefit of people throughout the world. The purpose of the joint FAO/IPGRI programme is to generate a series of crop-speci- fic technical guidelines that provide relevant information on disease indexing and other procedures that will help to ensure phytosanitary safety when germplasm is moved internationally. The recommendations in these guidelines are intended for small, spe- cialized consignments, e.g. for research, conservation and basic plant breeding pro- grammes. Recommendations for commercial consignments are not the objective of these guidelines. These technical guidelines are produced by meetings of panels of experts on the crop concerned, who have been selected in consultation with the relevant specialized insti- tutions and research centres. The experts contribute to the elaboration of the guidelines in their private capacities and do not represent the organizations for whom they work. 1 The word ‘pest’ is used in this document as it is defined in the International Plant Protection Convention. It encompasses all harmful biotic agents ranging from viroids to weeds. No. 18. Allium spp. 5 The guidelines are intended to be the best possible advice for institutions involved in germplasm exchange for research, conservation and basic plant breeding. FAO, IPGRI and the contributing experts cannot be held responsible for any failures resulting from the application of the present guidelines. They reflect the consensus of the crop specia- lists who attended the meeting, based on the best scientific knowledge available at the time of the meeting. The experts who have contributed to this document are listed after this introduction. The guidelines are written in a short, concise style, in order to keep the volume of the document to a minimum and to facilitate updating. Suggestions for further reading are given at the end, along with the references cited in the text (mostly for geographical distribution, media and other specific information). The guidelines are divided into two parts. The first part makes general recommendations on how best to move Allium germ- plasm. The second part covers the important pests. The information given on a parti- cular pest is not exhaustive but concentrates on aspects that are most relevant to the safe movement of germplasm. Only pests which may be transmitted when germplasm is moved in the recommended form (in vitro for garlic and shallot, seeds for onion) are described in these guidelines. Urocystis, Puccinia and other pathogens transmitted by vegetative material are not covered. The scientific and common names of Allium spe- cies are given in Tables 1 and 2 on the next pages. The present guidelines were developed at an FAO-sponsored meeting held in Prague, Czech Republic from 17 to 19 July, 1995. The meeting was hosted by the Research Institute of Crop Production in Prague-Ruzyne. Guideline update To be useful, the guidelines need to be updated when necessary. We ask our readers to kindly bring to our attention any developments that possibly require a review of the guidelines, such as new records, new detection methods or new control methods. For your convenience, a form is provided on the last page of this publication. Series editors: Dr M. Diekmann, IPGRI, Rome, Italy Dr T. Putter, FAO, Rome, Italy 6 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Table 1. Cultivated species of Allium (Hanelt 1990) Botanical names of the designation of taxa A. ampeloprasum L. Leek group Kurrat group Great-headed-garlic group Synonyms A. porrum L. A. ampeloprasum L. var. porrum (L.) Gay A. kurrat Schweinf. ex Krause A. porrum L. var. aegyptiacum Schweinf. A. ampeloprasum L. var. holmense (Mill.), Aschers. et Graebn. English names Leek Kurrat A. ampeloprasum L. var. ampeloprasum auct. A. ampeloprasum var. pater-familias (Boiss.) Rgl. A. ampeloprasum var. bulbilliferum Lloyd Great-headed garlic Pearl onion group A. ampeloprasum var. sectivum Lued. A. cepa L. Common onion group A. cepa var. cepa L. A. cepa var. typicum Rgl. Aggregatum group A. chinense G. Don A. ascalonicum auct. non Strand A. cepa var. ascalonicum Backer A. cepa var. aggregatum G. Don A. cepa var. solanina Alef. A. cepa var. perutile Stearn A. bakeri Rgl. A. exsertum (Lindl.) Baker non G. Don A. fistulosum L. A. bouddhae Deb. A. x proliferum (Moench) Schrad. A. cepa var. viviparum (Metzg.) Alef. A. cepa var. bulbiferum Rgl. A. cepa var. prolifera (Moench) Alef. A. canadense auct. non L. Onion Shallot Potato onion Ever-ready onion Rakkyo; Ch’iao T’ou Japanese bunching onion; Welsh onion Top onion Tree onion Egyptian onion Catawissa onion No. 18. Allium spp. 7 Botanical names of the designation of taxa Synonyms English names A. cepa Proliferum group A. wakegi Araki A. aobanum Araki A. fistulosum var. caespitosum A. sativum L. Wakegi onion Common garlic group A. sativum L. var. sativum A. sativum L. var. typicum Rgl. A. pekinense Prokh. Garlic Ophioscorodon group A. sativum L. var. ophioscorodon (Link) Doell A. opkioscorodon Link A. sativum L. var. controversum (Schrad.) Moore jr. A. schoenoprasum L. A. sibiricum L. A. alpinum (DC.) Hegetschw. A. riparium Opiz A. montanum Schrank non Schmidt Chives A. tuberosum Rottl. ex Spr. A. uliginosum G. Don A. chinense Maxim. et auct. non G. Don A. odorum auct. non L. Chinese chives; Nira Table 2. Wild and ornamental species of Allium (after Hyam and Pankhurst 1995) Botanical name English name A. bourgeani Rech: Fil. A. commutatum Guss. A. moly L. A. oleraceum L. A. scorodoprasum L. A. ursinum L. A. vineale L. Wild leek Wild leek Moly, lily onion, yellow onion Field garlic Sand leek Bear’s garlic, ramsons Crow garlic 8 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm PARTICIPANTS IN THE MEETING Dr Marlene Diekmann IPGRI Via delle Sette Chiese 142 00145 Rome ITALY Fax: 0039-6-5750309 e-mail: m.diekmann@cgnet.com Dr Sylvia K. Green AVRDC PO Box 42 Shanhua - Tainan 74199 TAIWAN Fax: 00886-6-5830009 Tel.: 00886-6-5837801 e-mail: s.k.green@cgnet.com Dr Pavel Havranek Genová Banka VURV Praha, pracoviste Olomouc Slechtitelu 11 783 71 Olomouc CZECH REPUBLIC Fax and Tel.: 0042-68-5228355 e-mail: havranp@risc.upol.cz Dr Martin Hommes Inst. für Pflanzenschutz im Gartenbau BBA Messeweg 11/12 38104 Braunschweig GERMANY Fax: 0049-531-2993009 Tel. 0049-531-2994404 e-mail: m.hommes@bba.de Dr Dietrich E. Lesemann Inst. für Pflanzenvirologie, Mikrobiologie und biologische Sicherheit BBA Messeweg 11/12 38104 Braunschweig GERMANY Fax: 0049-531-2993006 Tel.: 0049-531-2993730 e-mail: d.e.lesemann@bba.de Dr James W. Lorbeer Cornell University Plant Pathology Dept. Ithaca, NY 14853 USA Fax: 001-607-2554471 Tel.: 001-607-2553245 e-mail: jwl5@cornell.edu Dr Hervé Lot INRA Station de Pathologie Vegetale BP 94 84143 Montfavet Cedex FRANCE Fax: 0033-49031-6335 Tel.: 0033-49031-6370 No. 18. Allium spp. 9 Dr Satoshi T. Ohki College of Agriculture Osaka Prefecture University Gakuen-cho Sakai, Osaka 593 JAPAN Fax: 0081-722-520341 Tel.: 0081-722-521161 e-mail: ohki@plant.osakafu-u.ac.jp Dr Tonie Putter FAO-AGPP Via delle Terme di Caracalla 00100 Rome ITALY Fax: 0039-6-52256347 Tel.: 0039-6-52254022 e-mail: tony.putter@fao.org Dr René A.A. van der Vlugt IPO-DLO PO Box 9060 6700 GW Wageningen THE NETHERLANDS Fax: 0031-317-410113 Tel.: 0031-317-476000 e-mail: r.a.a.vandervlugt@ipo.dlo.nl Dr Heinrich J. Vetten Inst. für Pflanzenvirologie, Mikrobiologie und biologische Sicherheit BBA Messeweg 11/12 38104 Braunschweig GERMANY Fax: 0049-531-2993006 Tel: 0049-531-2993720 e-mail: h.j.vetten@bba.de 10 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm ACKNOWLEDGEMENT Dr C.M. Messiaen, Ancien Moulinage - Melas, 07400 Le Teil, France kindly provided first drafts on many of the fungal pathogens described in these guidelines, as well as comments on the manuscript. No. 18. Allium spp. GENERAL RECOMMENDATIONS 11 Germplasm should be obtained from the safest source possible. There is, for example, a pathogen-tested Allium collection accessible at the Asian Vegetable Research and Development Center (AVRDC), PO Box 42, Shanhua - Tainan 74199, Taiwan. If available, true seed of germplasm should be preferred for the movement of Allium germplasm since seed poses a minimal risk of moving and introducing pests. Germplasm for which true seed is not available should be moved as pathogen-tested in vitro cultures. If this is not possible, full quarantine measures must be taken until the vegetative material or seed is cultured in vitro. In vitro material should be tested for viruses known to affect Allium in the country of origin of the germplasm. Electron microscopy will allow the detection of all virus particles, including those not yet described. Indexing procedures and results should be documented, e.g. in a germplasm health statement. A sample copy is included at the end of this publication. The transfer of germplasm should be carefully planned in consultation with quarantine authorities and the relevant indexing laboratory. Technical recommendations The following ‘decision tree’ should help those who intend to move Allium germplasm to use the safest mode of movement possible. Can the germplasm be moved as seed? la If ‘yes’ follow the recommendations under A (Movement of seeds) as this is the safest method of moving Allium germplasm. To date, only the pests listed in Table 3 are reported to be transmitted on Allium seed. No virus has been reported to be seedborne in Allium spp. lb If the germplasm can definitely not be moved as seed, your next decision is to determine if it can be shipped as in vitro material. If ‘yes’ go to 2 and follow the recommendations under B (Movement of in vitro germplasm); if ‘no’ go to 3 2 The germplasm should be sent to an appropriate tissue culture laboratory in the country of origin. In vitro plantlets may be infected with any or all of the following viruses, which are described in these guidelines. 12 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Garlic common latent carlavirus (GCLV) Garlic dwarf reovirus Leek yellow stripe potyvirus (LYSV) Mite-borne filamentous viruses (MbFV) Onion yellow dwarf potyvirus (OYDV) Shallot latent carlavirus (SLV) and serologically related carlaviruses Shallot yellow stripe potyvirus (SYSV) Other viruses that have not been characterized yet may also be present. 3 You are at this point in the decision hierarchy because the germplasm you want to ship cannot be sent as seed or shipped in vitro. If vegetative material is shipped, it should be submitted to quarantine. A 24-h incubation in a moist chamber and examination, e.g. for sclerotia of Botrytis squamosa, is recommended. Infected germplasm should be autoclaved. Pests that may be moved with bulbs and cloves include in addition to the viruses listed above: Fungi Alternaria porri Botryotinia squamosa anamorph: Botrytis squamosa Botrytis allii Cladosporium allii-cepae Fusarium spp. Peronospora destructor Sclerotium cepivorum Stemphylium vesicarium Nematode Ditylenchus dipsaci Mites Aceria tulipae Rhizoglyphus robini, Rhizoglyphus setosus and Caloglypus spp. No. 18. Allium spp. Table 3. Seedborne pests in Allium spp. 13 Pest Internally seedborne Externally seedborne Concomitant contamination Fungi Alternaria porri X Botrytis allii X X Fusarium spp. Possibly Possibly X Sclerotium cepivorum X Stemphylium vesicarium X X Nematode Ditylenchus dipsaci X Note: no virus has been reported to be seedborne in Allium spp. A. Movement of seeds Seeds should preferably be collected from healthy looking plants that have been tested for seed-transmitted pests. Donor plants should be carefully inspected to confirm the absence of insects, mites and nematodes. Seeds should be cleaned and surface-disinfected with 0.5% sodium hypochlorite for 10 minutes at room temperature to eliminate externally seedborne pathogens. Seeds should be treated with an appropriate pesticide. B. Movement of in vitro germplasm 1. Sterile cultures should be obtained from meristems of pregerminated cloves according to the following procedure: if required, break dormancy by subjecting bulbs/cloves to a 4°C cold treatment (shallot approx. 3 weeks, garlic 2 months) remove the scales surface-sterilize the cloves with 70% ethanol for 1 min, followed by three rinses with sterile distilled water, then with 1% sodium hypochlorite for 15 min, followed by three rinses with sterile distilled water remove meristem (0.3-0.6 mm) and give each meristem a code for future reference 14 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm place one meristem per tube on MS medium for 14 days, then transfer to MS medium with 50 mg/L virazole after 6 weeks on MS + virazole medium, excise a 0.5-cm shoot tip and transfer to MS medium with 0.5 mg/L NAA until four leaves have developed move test tubes to a 22°C insect-proof greenhouse for acclimatization for 1 week prior to transferring the plantlets to small plastic pots with autoclaved soil transfer to 15-cm clay pots when plants have reached maturity, withhold water for l-2 weeks and dry the first growth-cycle bulbs after breaking dormancy, plant the cloves for a second growth cycle perform virus-indexing by serological or other recently developed appropriate methods - on in vitro plantlets just before transferring them to soil - on mature plants at the end of the first and second growth cycles - several times during the two growth cycles. 2. When indexing procedures reveal that the plants are free of viruses of concern, their bulbs/cloves can be planted in the field or shipped either directly or after in vitro mass propagation. 3. For the movement of in vitro germplasm, charcoal, fungicides or antibiotics should not be added to the medium. In vitro cultures should be shipped in transparent tubes and visually inspected for bacteria, fungi and arthropods. Contaminated germplasm should be destroyed. No. 18. Allium spp. 15 ACRONYMS AND DEFINlTlONS OF TERMS AS USED IN THlS PUBLICATION Cosmopolitan This expression is used to describe the distribution of pathogens which are reported to occur in all continents and in many countries of these continents FAO Food and Agriculture Organization of the United Nations Germplasm A set of different genotypes conserved or used in breeding programmes Incidence Frequency of occurrence of a disease; usually the percentage of affected plants in an area IPGRI International Plant Genetic Resources Institute MAB Monoclonal antibodies Scape Leafless flower stalk Seedborne Carried in, on or with seeds; may be applied to pathogens and non-pathogenic microorganisms Seed-transmitted Refers to a pathogen’s passage from seeds to seedlings or plants Set Small bulb for planting Severity Amount or intensity of disease in an individual plant Significance Under this heading information on the economic significance of a pest is summarized. Where relevant, information pertinent to germplasm collecting is included. 16 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Treatment In this publication only treatments that may be applied to germplasm are mentioned. It should be noted that treatments (e.g. fungicide for fungal pathogens, heat treatment for viruses) are rarely eradicative and that any treatment needs to be followed by extensive testing to establish the success rate. No. 18. Allium spp. 17 SOURCES OF ANTISERA AND MONOCLONAL ANTIBODIES (MAB) Recent studies provided strong evidence that the majority of vegetatively propagated Allium spp. are commonly infected by several distinct viruses. Former attempts to cha- racterize viruses infecting garlic and other Allium spp. often led to confusing results and to an inappropriate naming of viruses, e.g. garlic yellow stripe virus, garlic yellow streak virus and garlic mosaic virus. Later studies showed that researchers coining these names had actually worked on mixtures of some of the now formally described viruses. This was also the reason that many antisera produced in the former studies against virus preparations from naturally infected Allium spp. contained antibodies to a range of dif- ferent viruses, rendering them unsuitable for the identification of Allium viruses. However, provided that these antisera do not react with host components (and cryptic viruses) and, most importantly, have been examined for their suitability to sensitively detect some of the major viruses in vegetatively propagated Allium spp., they can be used for virusindexing in a virus elimination programme, in combination with antise- ra and MAB to Allium viruses not detected by the oligospecific antisera. High-titered antisera and MAB which are specific to clearly defined Allium viruses are commercial- ly available from the sources listed in Table 4. The list is not exhaustive and listed com- panies are not recommended over others not listed. Table 4. Commercially available sources of high-titered antisera and MAB that are specific to clearly defined Allium viruses Company Antisera and MAB to: BIOREBA AG Chr. Merian-Ring 7 CH-4153 Reinach BL Switzerland GCLV, Garlic MbFV, LYSV, OYDV, SLV (MAB), SYSV (MAB) DSM - Arbeitsgruppe Pflanzenviren Messeweg 11-12 D-38104 Braunschweig Germany see BIOREBA AG 18 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm IPO-DLO Dr. J. Vink PO Box 9060 NL-6700 Wageningen The Netherlands OYDV SANOFI DIAGNOSTICS PASTEUR 3 Bd. Raymond Poincaré - BP 3 92430 Marnes-La-Coquette France LYSV, OYDV No. 18. Allium spp. 19 DESCRIPTION OF PESTS Viruses Garlic common latent carlavirus (GCLV) The filamentous particles are approximately 650 nm long and slightly flexuous. Garlic latent carlavirus sensu Delecolle and Lot (1981) is included in this description. Significance On its own it is of minor importance but in combination with other viruses it may cause serious crop losses. High incidence in garlic cultivars in Europe and many other areas of the world (South America, Central America, India, China). Symptoms Very weak or no symptoms in singly infected garlic and leek. Symptoms caused by potyviruses may be aggravated by the presence of GCLV (e.g. in leek) (Graichen 1991). Hosts Natural: GCLV has a wide host range within the Alliaceae family. It predominantly occurs in garlic (van Dijk 1993), but has been found in more than 50 Allium spp. in a germplasm collection (Graichen, pers. comm.). Experimental: apart from the local lesion hosts Celosia argentea, Chenopodium quinoa, C. amaranticolor, some other Chenopodium spp., Nicotiana occidentalis and several species of the Alliaceae are systemically infected by GCLV (van Dijk 1993). Geographical distribution Cosmopolitan. GCLV has been detected in most garlic-growing countries but not in traditional garlic varieties of Japan, Taiwan and Thailand (Barg et al. 1994). In these countries, however, GCLV can be found in local markets and in garlic varieties imported for consumption or for germplasm evaluation trials (Barg et al. 1997). Transmission It is transmitted (with difficulties) by mechanical inoculation; aphid transmission is suspected (van Dijk 1993; Barg et al. 1994, 1997). True seed transmission has not been reported. The main mode of virus transmission in Allium is by vegetative propagation, particularly of garlic cultivars. 20 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Detection Serological methods allow easy and specific detection of GCLV by immunoelectron microscopy and ELISA. Owing to a close serological relationship between GCLV and carnation latent virus (CLV) (Barg et al. 1997), most antisera to CLV also permit serolo- gical detection of GCLV by either method (Conci et al. 1992). For further reading, see p. 51. No. 18. Allium spp. 21 Garlic dwarf reovirus Garlic dwarf disease is associated with the presence of a reovirus named garlic dwarf virus (GDV). Particles appear icosahedral, double-shelled and 65-70 nm in diameter in pH 7.0 phosphate buffer when stained with uranyl acetate or ammonium molybdate. Several properties suggest it is a member of the Fijivirus genus. However, preliminary results show differences from the type members of the three Fijivirus groups. As the virus is not mechanically transmissible and there is no vector known, Koch’s postulates are not yet fulfilled. Significance So far, limited distribution and low incidence in garlic crops for consumption. High potential for crop destruction. Symptoms Initial symptoms are red tips of the basal leaves. The majority of the affected plants do not develop normally, showing a ‘tulip’ or a ‘fan’ appearance, with all leaves originating from the same point (Fig. 1). Occasionally, the pseudostems develop normally initially, but later they develop no or very short internodes (Fig. 2). In some cases, plants are dwar- fed but seem to recover, since new leaves emerge with regular internodes. The leaves of the most severely dwarfed plants assume a darker green colour. Vein swelling and, rarely, small enations may be present. The bulbs from diseased plants often appear pear-sha- ped, spongy and wrinkled (Fig. 3). Most cloves are small but some may be normal size. Hosts Garlic. Fig. 1. Garlic cv. Thermidrome infected with garlic dwarf virus (GDV). showing. shortened internodes (right), healthy plant on the left. (Dr H. Lot, INRA, Montfavet) 22 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Geographical distribution Reported only in a restricted area of southern France (eastern Rhône valley). Transmission No vectors are known. The incidence and distribution pattern of the disease do not sug- gest a very effective vector (probably a planthopper). Preliminary results suggest that the different types of symptoms described may occur from infected planting material (Lot, unpublished results). Detection Virus particles may be observed by e l ec t ron microscope in leaf dips and more easily by ISEM. The virus is also detected efficiently in leaf extracts by standard DAS-ELISA. For further reading, see p. 51. Fig. 2. (above) Dwarfing of garlic cv. Thermidrome grown from GDV-infected cloves; Dl and D3 showed symptoms at an early stage, while D4 initially developed normally. (Dr H. Lot, INRA, Montfavet) Fig. 3. (right) Cross-section through bulbs of garlic cv. Thermidrome infected with garlic dwarf virus (GDV), healthy bulb on the left. (Dr H. Lot, INRA, Montfavet) No. 18. Allium spp. 23 Leek yellow stripe potyvirus (LYSV) The flexuous and filamentous particles are approximately 820 nm long. Significance In western Europe, autumn and winter crops of leek are severely affected. Major out- breaks occur in all year-round cultivation areas of commercial crops. LYSV may cause yield reduction up to 50%. Quality losses by yellow striping are also reported. Recent data proved that the virus may cause a 15-50% reduction in garlic bulb yield, depending on isolates and cultivars (Lot and Delecolle, unpublished results). Symptoms On leek a more or less clear yellow striping on the leaf blade from its base upward is common. Rarely plants may become entirely chlorotic and slightly flaccid. Infected plants suffer from early frosts and may be killed. Symptoms are highly variable depending on susceptibility of cultivars. Aggravation of the symptoms was reported when plants were co-infected with shal- lot la tent virus and garlic common latent carlavirus (Paludan 1980; Graichen 1991). Fig. 4. (above) Leaf of garlic cv. Messidrome with early symptoms of leek yellow stripe potyvirus (LYSV). (Dr H. Lot, INRA, Montfavet) Fig. 5. (right) Basal leaf and young leaf of garlic cv. Messidrome infected with leek yellow stripe potyvirus (LYSV). (Dr H. Lot, INRA, Montfavet) 24 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm On garlic, symptoms include irregular light and dark green striping on the young lea- ves (Fig. 4), turning to yellow on the basal and intermediate leaves (Fig. 5), especially in the distant part of the blade. The virus does not affect significantly the height of plants but reduces the diameter of the pseudostem and of the bulbs. Co-infection with OYDV accentuates the symptoms (Fig. 6), making them indistinguishable from those due to OYDV (Fig. 7), especially on very susceptible cultivars. Hosts Natural: LYSV is restricted to Allium spp.: leek, garlic, great-headed garlic and pearl onion are affected as well as many wild species and ornamental Allium. A. cepa (onion and shallot) is rarely infected. Experimental: Chenopodium amaranticolor, C. quinoa, C. murale and C. album react with local lesions. Geographical distribution On leek, the virus was reported from several countries in Europe and South America, as well as from Australia and New Zealand. LYSV infecting garlic was first reported by Walkey et al. in 1987, but the virus has now been identified in most countries where gar- lic is grown. Fig. 6. Garlic plot cv. Messidrome showing from left to right: healthy plants, plants infected with leek yellow stripe potyvirus (LYSV), plants infected with onion yellow dwarf potyvirus (OYD) and a mixed infection with both viruses. (Dr H. Lot, INRA, Montfavet) No. 18. Allium spp. 25 Transmission The virus is transmitted by aphids in a non-persistent manner and by mechanical ino- culation (Bos et al. 1978). True seed transmission in leek does not occur. Overwintering plants are the only source of infection. The rate of infected garlic cloves depends on the time of infection. Host specialization of isolates is reported. For instance, natural transmission from LYSV- infected garlic to leek seems quite rare. This host specificity of isolates was also demon- strated by mechanical inoculation: LYSV isolates from leek hardly infect garlic and vice versa. Detection ISEM decoration tests are particularly useful to detect LYSV and the possible contaminant virus(es) in plants co-infected with other viruses. ELISA is currently used for routine tests of lea- ves or cloves, but the antiserum used must be carefully chosen since antibodies with narrow or wide specificity exist (Barg 1995). An indirect dot-immunobinding assay is also effective in detecting the virus in Al l ium extracts. The virus is serologically distantly related to onion yellow dwarf virus (OYDV). Its relationship with two other potyviruses infecting Allium, Welsh onion yellow stripe virus and shallot yellow stripe virus depends on the strain (van Dijk 1993; Barg 1995). For further reading, see p. 52. Fig. 7. Severe streaks on garlic resulting from a mixed infection with leek yellow stripe potyvirus (LYSV) and onion yellow dwarf potyvirus (OYD). (Dr D.E. Lesemann, BBA, Braunschweig) 26 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Mite-borne filamentous viruses (MbFV) MbFV form a new, as yet unclassified plant virus group with unusually flexuous cross- banded particles of 700-800 nm in length. Phylogenetically they are between poty- and carlaviruses. Included in this group are onion mite-borne latent and shallot mite-borne latent viruses (van Dijk et al. 1991), shallot virus X (Kanyuka et al. 1992; Vishnichenko et al. 1993), garlic viruses A, B, C and D (Sumi et al. 1993) and garlic mite-borne mosaic virus (Yamashita et al. 1996). It is currently unclear to what extent some of these names repre- sent synonyms. Significance Economic significance not yet determined Symptoms Generally MbFV induce no or only very mild symptoms (e.g. faint short stripes) in Allium spp., hence the name mite-borne latent viruses. Hosts Natural: The viruses have been reported from garlic, onion, shallot, sand leek, rakkyo and several wild leek species (A. ampeloprasum complex). Isolates seem restricted to particular Allium spp. Experimental: Host range seems to be restricted to Allium spp. Crow garlic appears to be a good experimental, although symptomless host for all MbFV isolates repor- ted so far. Local lesions are produced only on Chenopodium murale, C. amaranticolor, C. quinoa or Atriplex hortensis, with not all viruses being able to infect all these test plants (van Dijk et al. 1991; van Dijk and van der Vlugt 1994). Geographical distribution Cosmopolitan. Transmission The eriophyid wheat curl mite Aceria tulipae is a very efficient vector on crops in the field as well as on stored bulbs (van Dijk et al. 1991). Also through mechanical inoculation. No data are available on seed transmission. The high incidence in many vegetatively pro- pagated Allium spp. in Europe and Asia, especially garlic, onion and shallot, is because the viruses spread easily with infected planting material and viruliferous mites on har- vested bulbs and cloves. No. 18. Allium spp. 27 Detection Owing to high coat-protein variability, MbFV are difficult to detect by serological methods. Typical highly flexuous morphology and cross-banding of particles distingui- shes MbFV from poty- and carlaviruses in the electron microscope. For further reading, see p. 52. 28 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Onion yellow dwarf potyvirus (OYDV) The flexuous filamentous particles are approximately 775 nm long. Significance Yellow dwarf can be very damaging to susceptible crops of onion and shallot, especial- ly where sanitation procedures are not followed. Incidence up to 50% is reported for onion in many countries. It is also commonly found on garlic. Symptoms Stunting is the main symptom in onion and shallot. Leaves show irregular yel- low striping to almost complete yel- lowing and also downward curling, flattening and crinkling (Fig. 8). Also deterioration during storage and pre- mature sprouting of bulbs may occur. In garlic, varied symptoms of very mild chlorotic stripes to bright yellow stripes depending on virus isolate and culti- vars appear. Also reduction in growth and bulb size occur. In combination with other viruses, symptoms may be aggravated. Fig. 8. Stunting and yellow stripes on onion caused by onion yellow dwarf potyvirus (OYD). (Dr D.E. Lesemann, BBA, Braunschweig) No. 18. Allium spp. 29 Hosts Natural: restricted to Allium spp.; leek does not appear to be affected. Experimental: An isolate of OYDV that is particularly aggressive on shallot also local- ly infects Chenopodium murale. Geographical distribution Cosmopolitan. Transmission OYDV is transmitted by over 50 aphid species in a non-persistent manner and by mecha- nical inoculation (Bos 1976). Seed transmission is not reported in onion (Louie and Lorbeer 1966). The main route of natural spread is by vector transmission and through vegetati- ve propagation of infected hosts. Detection ELISA and decoration tests are useful to identify the virus (van Dijk 1993). For further reading, see p. 53. 30 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Shallot latent carlavirus (SLV) The slightly flexuous, filamentous particles are approximately 650 nm long. Included in this description are Sint-Jan’s onion latent, garlic latent (sensu Japanese authors) and other serologically related carlaviruses. Significance On its own it is of minor importance but in combination with other viruses it may cause serious crop losses. Symptoms Basically symptomless in singly infected garlic, shallot, onion and leek. Symptoms cau- sed by potyviruses may be aggravated by the presence of SLV (e.g. in leek) (Paludan 1980; Graichen 1991). Hosts Natural: SLV has a wide host range within the Alliaceae family. It predominantly occurs in shallot and garlic but was found in more than 80 Allium spp. in a germpla- sm collection (Graichen, pers. comm.). Experimental: apart from some local lesion hosts, e.g. Chenopodium spp., Celosia argen- tea and Vicia faba (van Dijk 1993), SLV systemically infects Nicotiana occidentalis and N. hesperis and a wide range of members of the Alliaceae. Geographical distribution Widely distributed in many countries of Asia and Europe (Bos 1982; van Dijk 1993; Barg et al. 1997). There is also a confirmed report for Mexico (Barg et al. 1997). Transmission Mechanical transmission and transmission by aphids in a non-persistent manner are pos- sible means of natural spread. However, aphid transmission of SLV is less efficient than that of potyviruses (Bos 1982; van Dijk 1993). Under natural conditions, SLV is mainly disseminated and maintained by vegetative propagation which is particularly signifi- cant for garlic and shallot. True seed transmission of SLV has not been reported. Detection Serological methods allow detection of SLV by immunoelectron microscopy and to some extent by ELISA. Because of serological diversity among SLV strains, antisera to SLV do not generally permit highly sensitive and specific detection of all SLV strains. Monoclonal antibodies reveal at least six different reaction types (Barg et al. 1994, 1997). These inclu- No. 18. Allium spp. 31 de SLV isolates from garlic in Japan and Sint-Jan’s onion latent virus (van Dijk 1993). The latter reacts with several SLV antisera but not with any of the MABs to SLV (Barg et al. 1997). Additional strains of SLV-related carlaviruses may exist in traditional garlic and shallot varieties of Thailand (and other east Asian countries) which may be difficult to detect by ELISA when antisera to the more widespread strains of SLV are used. For further reading, see p. 53. 32 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Shallot yellow stripe potyvirus (SYSV) The flexuous particles are approximately 700-800 nm long. Included in this description is Welsh onion yellow stripe virus sensu van Dijk (1993), which can be considered an iso- late of SYSV (van der Vlugt, pers. comm.). Significance Economic significance not yet established but only mild plant symptoms occur. Symptoms Mild striping in young leaves of shallot plants and distinct mosaic-like yellow striping in onion. Hosts Natural: shallot, multiplier onion, Chinese chive, garlic, onion and rakkyo. Experimental: a virulent isolate of SYSV causes severe malformation, stunting, necro- sis and sometimes plant death on onion ‘Stuttgarter Riesen’ and yellow striping and etching on garlic and Formosan lily (Lilium formosanum). Welsh onion yellow stripe virus causes local lesions on Chenopodium quinoa and C. amaranticolor. Geographical distribution Widespread in Asia. Transmission Transmitted by mechanical inoculation and aphids (van Dijk 1993). Natural spread through infected planting material. No data on seed transmission. Detection SYSV can be detected by immunoelectron microscopy with antisera against SYSV, which are, however, unsuitable for ELISA. When these antisera are used in combination with monoclonal antibodies to SYSV in TAS-ELISA, specific detection of SYSV is possible by (Barg et al. 1997). For further reading, see p. 54. No. 18. Allium spp. 33 Other viruses reported to occur in Allium spp. There are several other viruses which predominantly occur in other crops but which have sporadically been isolated from vegetatively propagated Allium spp. They appear to be of minor importance because of their restricted distribution. However, they warrant attention in areas from which they have not been reported. Some of them, such as nepo- viruses, are likely to be transmitted by true seed. Isometric seed-transmitted cryptic viruses (tentative members of the Partitiviridae) Isometric particles with a diameter of about 34 nm have been detected in onion, Welsh onion and leek by electron microscopy and immunoelectron microscopy with antisera to onion yellow dwarf and leek yellow stripe potyviruses. Such particles were also found to be co-purified with potyviruses from Allium spp. They were seed-transmitted in nume- rous onion and Welsh onion varieties at levels of almost 100%, but were not sap trans- missible. They are tentatively classified as members of the family Partitiviridae (cryptic viruses). In spite of their high seed transmission rate and their worldwide distribution, they may have no economic importance as they do not cause symptoms or yield loss. However, antisera containing antibodies to them can give false positive reactions in virus- indexing work (Barg et al. 1994). Leek yellows virus This putative luteovirus with isometric particles approximately 30 nm in diameter was detected in leek and rakkyo (Allium chinense) showing symptoms of yellowing in Japan (Araki et al. 1981). Virus particles were observed in phloem cells, and phloem necrosis is often observed in infected hosts. The virus is not transmissible by sap and, being a luteo- virus, is expected to be not seed-transmissible. For further reading, see p. 54. 34 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Other viruses of minor or regional importance Virus Reported from Host Arabis mosaic nepovirus shallot and tree onion cucumber mosaic cucumovirus garlic leek white stripe virus leek lettuce necrotic yellows rhabdovirus garlic tobacco mosaic tobamovirus garlic and onion tobacco necrosis necrovirus tobacco rattle tobravirus shallot garlic, onion, A. moly, A. ursinum and A. vineale tomato black ring nepovirus shallot and other Allium spp. turnip mosaic potyvirus garlic ornamental A. ampeloprasum Country Germany, The Netherlands former Yugoslavia France Australia Russia The Netherlands van Dijk (1993) The Netherlands, Denmark and Germany Kristensen & Engsbro (1966) Graichen (1975) van Dijk (1993) van Slogteren (1958) Northern Ireland, Germany, The Netherlands Slovenia Israel Reference Graichen (1975) van Dijk (1993) Stefanac (1980) Lot et al. (1996) Sward (1990) Vasiljeva & Mozhaeva (1978) Calvert & Harrison (1963) Graichen (1975) van Dijk (1993) Ravnika, pers. comm. Gera et al. 1997 No. 18. Allium spp. 35 Fungi Alternaria porri (pu ple blotch) Alternaria porri (Ellis) Cif. is a dematiaceous fungus producing very large conidia of 50- 100 x 15-25 µm, with a filiform apical appendage 30-150 µm (absent in some isolates, which can be mistaken for Stemphylium). Most isolates of this fungus produce a purple pigment in the leaf spots as well as in culture media. Several other Alternaria species cause leaf spots, but not purple blotch. Significance A major leaf-spot agent on A1lium spp. under warm weather conditions. Symptoms Purple blotch lesions are oval, with a well-delimited margin between dry infected tissue and the healthy part of the leaf or scape. With pigment-producing isolates, the central part of the spot is purple. The fungus sporulates there, appearing as a tenuous black mould. Since conidia are very large, they can be seen with a strong magnifying glass. When several spots appear on a leaf, its apical part becomes yellow and withers. Hollow scapes can be broken at the level of a large lesion. Hosts Onion, shallot, leek and garlic. Geographical distribution Cosmopolitan. Biology and transmission The cardinal temperatures of 15°C -26°C -34°C are much higher than for downy mildew or Botrytis leaf blight. The conidia are very robust; they can persist more than one year on plant debris. Chlamydospores are reported to occur in the soil and only one may indu- ce a leaf spot. Sporulation of A. porri is sparse (no more than one to several hundred coni- dia per leaf spot). Alternaria porri is particularly prevalent in the humid tropics where rain showers (removing sporulation inhibitors) are followed by sunshine (inducing spo- rulation) and dry weather (favouring conidial dissemination). Onion and leek seeds produced under these conditions can carry mycelia and spores of A. porri. The necks of shallot or garlic bulbs originating from diseased plants may also be contaminated. 36 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Detection Microscopic examination of seeds and bulbs and isolation from seeds on culture media. Colonies of A. porri are dark grey and often produce the purple pigment. For further reading, see p. 55. No. 18. Allium spp. 37 Botryotinia squamosa (Botrytis leaf blight) Teleomorph: Botryotinia squamosa Vien.-Bourg., syn. Sclerotinia squamosa; anamorph: Botrytis squamosa J. C. Walker (Maude 1990; Lorbeer 1992). The fungus is characterized by hyaline conidia 14-23 x 11-16 µm in size and the production of masses of small scle- rotia when the fungus is grown in pure culture. Significance Botrytis leaf blight is an important foliar disease of onion, particularly in North America, Europe and Asia. The disease can cause significant reduction in bulb size and hence yield. Symptoms Initial symptoms of the disease are small elliptical white to straw-coloured lesions of l-5 mm diameter, which mostly occur on the side of the leaf exposed to sunlight. Each lesion usually is surrounded by a greenish-white halo that appears water-soaked. A lengthways sunken slit often occurs in the centre of the lesion. The older leaves are the most susceptible and they typically wilt and blight within 5-7 days of infection and lesion formation. The pathogen in some instances can infect the outer tissues of the bulb, cau- sing a disease known as small sclerotial neck rot (Walker 1952). Hosts The pathogen is reported to cause disease only in the genus Allium (Farr et al. 1989). It is most important on onion (A. cepa). Geographical distribution Cosmopolitan in temperate regions (Lorbeer 1992; Brewster 1994). Biology and transmission Botrytis squamosa survives as sclerotia on onion bulbs, sets and transplants as well as in the soil. Conidia are produced on conidiophores either emerging from the mycelium infecting the host tissue or from sclerotia on the host tissue or in the soil. Airborne coni- dia are the primary form of inoculum in epidemics. Infected bulbs can transport the pathogen from one region to another. The fungus is not seed-transmitted. The apothe- cial stage (perfect state) of the fungus is not important in transmission of the pathogen, but serves an important role in the production of genetic diversity of the pathogen (Maude 1990; Lorbeer 1992). FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm38 Detection Culture suspected conidia or sclerotia on media. The fungus is easily differentiated from other Botrytis species on the basis of conidial size and the abundant production of small sclerotia. For further reading, see p. 55. No. 18. Allium spp. 39 Botrytis allii (neck rot) Teleomorph: Botryotinia aclada author ???, anamorph: Botrytis allii Munn. The conidial layer is shorter and more compact than that of B. cinerea, with a conidia size of 10-15 x 8- 11 µm. Sclerotia are flat and 2-4 mm. Significance Prior to the widespread use of seed treatment, Botrytis allii was the principal cause of decay in storage of onion and shallot bulbs. Grey shallot is particularly susceptible to rot in storage. Symptoms Onion seedling blight can be caused by B. allii. Frequently the fungus remains epiphytic on the leaves of the growing plants and invades senescent tissues at the beginning of maturity. This infection induces apical bulb rot in storage, appearing successively as a grey mould, then as black sclerotia. On plants grown for seeds, B. allii can invade the decaying leaves at the base of the scape and then girdle the floral stem with a whitish lesion. Shallot may be invaded in the same way as onion. Hosts Onion and shallot. Geographical distribution Cosmopolitan in temperate regions. Biology and transmission One of the major factors that induce latent infection of growing plants and subsequent bulb rot is seed contamination: there is a strong correlation between the contamination of the seeds by B. allii and the amount of neck-rot decay in bulbs (Maude 1983a). Sclerotia of the fungus can survive in soil for about 2 years and longer in dry conditions, e.g. in soil mixed with stored bulbs. At harvest, infections of the section where the necks are cut are possible, thus increasing the percentage of the bulbs which will rot in storage. Botrytis allii is highly sensitive to temperature and is usually destroyed by temperatures over 30°C. It cannot invade dry senescent tissues. Detection Direct plating on agar. 40 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Treatment Since B. allii does not survive temperatures higher than 30°C, drying bulbs after harvest with hot air circulation (35°C) will eliminate the pathogen from already contaminated necks and prevent the contamination of freshly cut healthy ones. Onion seeds are coated with a fungicide (benomyl, benomyl + thiram or iprodione at l-2 g/kg of seeds). Shallot mother bulbs from lots having shown a proportion of neck rot can be either treated with hot water (see Ditylenchus dipsaci), with addition of the same fungicides at l-2 g/L (for cepa shallots), or coated with benomyl or a dicarboximide fun- gicide (for grey shallots). For further reading, see p. 55. No. 18. Allium spp. 41 Cladosporium allii-cepae (Cladosporium leaf blotch) Teleomorph: Mycosphaerella allii-cepae Jordan, Maude and Burchill (Jordan et al. 1986); anamorph: Cladosporium allii-cepae (Ranoj.) M.B. Ellis (syn. Heterosporium allii cepae Ranoj.). Considered as Cladosporium allii (Ellis and G. Martin) P. M. Kirk and J. G. Crompton by Farr et al. (1989). Conidiophores of the pathogen are solitary or in groups, brown in colour and generally 80-160 µm long. The conidia are mostly borne singularly and are pale brown and 1-septate (Maude 1990). Significance The disease has occurred only infrequently and mainly in temperate growing areas in the past. Severe outbreaks were reported only from Ireland and the UK (Maude 1990). Symptoms The fungus produces elliptical yellow to greyish lesions which run parallel to leaf veins. After the fruiting structures and conidia are produced, the lesions become brown to dark brown. The disease can occur at any time in the growth of the plant, but mostly occurs after bulbing and particularly when the leaves commence senescing. Lesions on onion leaves are 0.5 x 1.5 cm and are smaller than on other Allium species (Hill 1995). Hosts Allium spp. (including onion, shallot, Welsh onion and a number of wild species), Sisyrinchium spp., Triteleia spp. (Farr et al. 1989; Maude 1990). Geographical distribution Ireland and UK (Maude 1990); Canada and USA (Hill 1995). Biology and transmission The fungus can persist for 3 months on onion debris. The fungus is not seedborne (Maude 1990). Detection The pathogen can be detected by direct examination of potentially infected plant parts and plant debris on the soil surface after incubation in a moist chamber for l-3 days. For further reading, see p. 56. 42 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Fusarium spp. (Fusarium basal rot) Fusarium oxysporum Schltdl. emend. Snyder and H.N. Hansen f. sp. cepae (Hanzawa). A num- ber of synonyms are known (Entwistle 1990). The fungus produces microconidia (usually unicellular and spheroid), macroconidia (fusiform or ellipsoid and mostly 3-4 septate) and chlamydospores (7.5 to 10 µm in diameter) which form in roots and soil (Entwistle 1990). Significance Infected plants will have a reduced seed yield. Economic losses were reported from Italy, South Africa, Japan and the United States (Farr et al. 1989; Havey 1995). Symptoms Delayed seedling emergence, seedling damping off, stunted growth of infected plants, decay of the basal plate area in growing plants and basal rot of bulbs in storage. Infection of seedlings and enlarging plants is accompanied by leaf chlorosis and dieback resulting in the desiccation of leaves which usually remain upright. Roots of infected plants are brown to dark brown in colour (Havey 1995). Hosts Onion, chive, garlic and shallot. Geographical distribution Cosmopolitan. Biology and transmission Mainly transmitted by infected transplants, sets, bulbs and possibly garlic cloves. Vegetative planting material may be infected by the fungus but remain symptomless. Seed transmission has not been observed, although some reports of isolation from seed have been made (Entwistle 1990). Soil infested with chlamydospores adhering to the plant parts may also serve as a source of inoculum (Entwistle 1990; Havey 1995). These spores when close to roots germinate and penetrate healthy root cells or invade through wounds in the roots. The fungus then invades the vascular system of the plant. In mature plants the infection remains in the basal plate area for some time before spreading to the fleshy bulb scales and causing decay of the bulb. Detection The pathogen can be isolated from diseased roots, stem plate tissues and onion bulb scales. It can be detected in soil by the use of selective media (Abawi and Lorbeer 1972). For further reading, see p. 56. No. 18. Allium spp. 43 Peronospora destructor (onion downy mildew) Peronospora destructor (Berk.) Casp. has pyriform to fusiform sporangia, 18-29 µm long and borne terminally on sterigmata of nonseptate sporangiophores. Significance The disease can be serious on onion and other Allium species grown for bulbs or seed, especially when relatively cool, moist weather prevails. Symptoms The disease is characterized by pale-green, yellowish to brownish, oval to cylindrical shaped areas on leaves and seed stalks. The fungus produces masses of sporangiopho- res and sporangia. The sporangia are transparent to grey in colour at first and then turn violet. The leaves become girdled in the region where the sporangia are formed, then collapse and wilt. The dead tissue typically is rapidly colonized by Stemphylium botryo- sum which forms masses of black spores on the necrotic leaf tissue. Bulb growth is redu- ced by the disease and the bulb tissue (especially the neck area) becomes spongy which causes the bulb to lack storage quality (Walker 1952; Maude 1990). Hosts Onion, shallot, leek and chive. Geographical distribution Cosmopolitan in temperate climates. Biology and transmission The pathogen overwinters primarily as mycelia in infected onion bulbs that remain in onion fields or in nearby cull piles. The pathogen can also overwinter in perennial varie- ties of onion in home gardens (Walker 1952). Local dissemination is primarily by air- borne sporangia, which do not form zoospores but germinate directly by forming one or two germ tubes and infect onion leaves by penetrating the stoma. Long-range dissemi- nation is primarily by systemically infected propagative material (bulbs, sets, trans- plants). The fungus is not seedborne (Maude 1990; Brewster 1994). Detection The fungus is an obligate parasite. Propagative material should be put in a moist cham- ber and checked for sporangia. For further reading, see p. 56. 44 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Sclerotium cepivorum (onion white rot) Sclerotium cepivorum Berk. produces spherical black sclerotia 0.3-0.5 mm in diameter and aerial white mycelium. Some isolates produce larger sclerotia (up to 1 mm) and fewer mycelia. Significance S. cepivorum induces one of the most important Allium diseases, killing onion and leek plantlets in the seedbeds or in the seed furrow. At a later stage severe losses are caused by basal rot on onion, leek, garlic and shallot. Symptoms For plantlets as well as for maturing bulbs, the disease starts with a translucent rot of roots. On maturing bulbs of onion, shallot and garlic the symptom is a basal rot with white mycelia on which sclerotia appear later. A 'black rot' of garlic may appear in plots previously invaded by wild AIlium spp. Hosts Allium spp. Geographical distribution Cosmopolitan, except tropical lowlands. Biology and transmission Cardinal temperatures for mycelial growth are 10°C -18°C -24°C. The sclerotia can remain dormant in the soil for some years. Late infections can remain almost symptomless and are the main source of infection in garlic and shallot seed cloves or mother bulbs. Detection Inspection for the presence of sclerotia and white mycelium. Treatment No eradicative treatment available. For further reading, see p. 56. No. 18. Allium spp. 45 Stemphylium vesicarium (Stemphylium leaf blight) Teleomorph: Pleospora allii (Rabenh.) Ces. & De Not., anamorph: Stemphylium vesicarium (Wallr.) E. Simmons. Conidia are oblong to oval, 25-42 µm, dark in colour with l-5 tran- sverse septa and often constricted at the middle one or three most central of the septa. The conidia can be distinguished by microscopic examination from those of S. botryosum. Significance During the past 20 years this disease has become increasingly important in temperate and tropical regions throughout the world. It is a major disease of onion in Southeast Asia and India (Gupta et al. 1994) and epidemics have caused significant losses in Texas and New York in North America (Miller et al. 1978; Lorbeer 1993). It frequently occurs at the same time and on the same plants as Alternaria porri, the cause of purple blotch, as a disease complex. Symptoms The disease is characterized at first by small yellow to brown lesions which rapidly enlarge to elongated spindle-shaped to ovate-elongate lesions which, if numerous, coalesce followed by blighting of the leaves. Hosts The fungus occurs on a wide variety of herbaceous plants including Allium, Asparagus, Eichhornia, Juncus and Triticum. Geographical distribution Cosmopolitan. Biology and transmission The fungus is seedborne and airborne. It can be transmitted as conidia and mycelia on other hosts as well as Allium. Detection Standard agar-plating procedures. For further reading, see p. 57. 46 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Minor fungal and bacterial pathogens Pathogen Aspergillus niger Botryotinia porri, anamorph: Botrytis porri Penicillium corymbiferum and P. cyclopium Phytophthora porri Disease caused Symptoms black mould soft rot followed by black mould grey mould rot of external leaf sheaths along the pseudostem of leek and garlic green rot rot of bulbs resulting in yellowing and tip- burn of the first leaves, occasionally in plant death downy mildew ‘white tip of leek’, lesions also at the border of leaves Pseudomonas fluorescens maladie café au lait’ Pseudomonas viridiflava leaf streak and bulb rot Xanthomonas campestris Xanthomonas blight Hosts onion and shallot leek Belgium, and garlic France garlic, occasionally onion and shallot leek, Countries reported Reference Cosmopolitan Prasad et al. (1986) Presly (1985) Cosmopolitan Bruna (1985) Europe occasionally onion Tichelaar and van Kesteren (1967) slimy, light brown garlic France lesions on the external sheaths of the pseudostem, progressing downwards water-soaked dark onion USA green lesions, developing into streaks white flecks with onion Hawaii, water-soaked margins; Barbados tip dieback Samson (1982) Gitaitis et al. (1991) Alvarez et al. (1978) No. 18. Allium spp. 47 Nematodes Ditylenchus dipsaci (stem and bulb nematode) Ditylenchus dipsaci (Kühn) Filipjev is an endoparasitic nematode whose adults can reach a length of 1 mm and a width of 20-35 µm. They swim actively when emerging from diseased tissues crushed in water. Significance A major pest of Allium spp. in temperate climates and the high-altitude regions of the tropics and subtropics. Symptoms Young infected onion plants are stunted, curved (Figs. 9 and 10), with an inflated basal part (bloat). If they survive, they produce bulbs with spongious rot of the external scales, which is the dominant symptom in shallot. On garlic attacked during bulb enlargement, D. dipsaci induces a reddish rot of the basal part of the bulb. The growing cloves become separated from each other. The leaves of diseased plants show a purplish discolouration and the pseudostem is stunted. Hosts More than 400 host plants have been described for D. dipsaci. The species is subdivided in races. The Allium race also attacks oats, sugar beet, Swiss chard, spinach and legumes (bean, pea, soyabean). Onion, garlic and shallot are affected more than leek. Geographical distribution Cosmopolitan, except tropical lowlands. Fig. 9. Deformation and early senescence of leaves caused by Ditylenchus dipsaci. (Dr R.A. Sikora, Bonn University) 48 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Biology and transmission Cardinal temperatures for nematode activity and infection are 10°C -22°C -30°C. In soil, they survive as fourth stage larvae at temperatures not exceeding 35°C. In onion true seeds or garlic and shallot mother bulbs the nematodes remain in a condition of anhy- drobiosis, under which they can survive a long time and become active again when rehy- drated. The larvae penetrate Allium plants at the point of emergence of roots through the leaf sheath and can invade the short true stem of the plant, causing its disintegration, or between and inside the leaf-sheaths and the scape (Fig. 11) and move into the onion umbels. Detection Bulbs are cut into four pieces and macerated in water for 12 hours: rehydrated larvae move into the water and can be isolated by successive sievings following the standard nematological methods. Treatment Hot wa te r t r ea tmen t fo r e l imina t ion of Ditylenchus from bulbs and onion seeds. Mobile Ditylenchus are killed after 1 hour at 44.5°C or 2 hours at 43°C. Anhydrobiotic larvae are more resistant. The most effective method is therefore to leave the bulbs for 10 hours in cold water (20°C) to rehydrate the nematodes, then to put them in water for 1 hour at 48°C for garlic or 2 hours at 43°C for shallot. For further reading, see p. 58. Fig. 10. (above) Deformed onions with Ditylenchus dipsaci infestation. (Dr R.A. Sikora, Bonn University) Fig. 11. (right) Ditylenchus dipsaci in plant tissue. (Dr R.A. Sikora, Bonn University) No. 18. Allium spp. 49 Arthropods Aceria tulipae (g rlic mite) Aceria tulipae (Keifer) (Synonym: Eriophyes tulipae), a mite between 0.1 and 0.25 mm long, belonging to the family Eriophyidae (gall mites). They are worm-like in shape and have two pairs of legs at the anterior end of the body. Significance This mite is a serious pest of garlic but also occasionally damages onion and shallot. It is a vector of several viruses in the field and in storage. Damage Yellow streaks and twisted growth of the leaves, reduction in plant growth and shrivel- ling of bulbs in storage. In stored bulbs secondary rots may occur. The damage to folia- ge may be confused with virus symptoms. When infected cloves are planted, Aceria infec- tions appear in leaves as localized distortions and mosaics. Leaves are often folded together and difficult to separate. Hosts Allium species, particularly garlic; other monocotyledons. Geographical distribution Cosmopolitan. Biology The females lay round, colourless eggs of 0.06 mm diameter on bulbs. There are two nymphal stages similar in appearance to the adults. Mites can mainly be found along the hollow crease of the leaf mid-vein. At maturity, the mites move down towards the bulb. Unfavourable conditions are survived by entering diapause. Transmission by infested plant material and by wind transportation. Detection Careful inspections of bulbs and other plant material for infestation by mites. Treatment No specific treatment recommended. For further reading, see p. 58. 50 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Rhizoglyphus robini Claparede (Synonym: R. echinopus) Rhizoglyphus callae Oud mans Small yellow white mites with a globular body up to 0.9 mm long belonging to the mite family Acaridae (bulb mites). Adult mites with four pairs of short stout legs. Significance These mites attack bulbs, corms and tubers of different plant species and are occasionally serious pests on stored onion and garlic bulbs. Their virus vector status is unknown. Damage Heavy infestation of bulbs in storage leads to a pulpy, rotting mass. Usually, these mites feed on bulbs which have been damaged by other pests or diseases or mechanically. Hosts Polyphagous on many bulb-, corm- or tuber-forming plants. Geographical distribution Cosmopolitan. Biology The females lay up to 100 eggs of 0.2 mm diameter singly on bulbs, corms or tubers. Under favourable conditions it takes less than 15 days to complete the life cycle. In adver- se conditions a specialized shiny brown immature stage is formed. Transmission is by insects and other animals to which the mites are attached and by infested plant material. Detection Careful inspections of bulbs and other plant parts for infestation by bulb mites. Treatment No specific treatment recommended. No. 18. Allium spp. BIBLIOGRAPHY General references Hanelt, P. 1990. Taxonomy, Evolution and History. Pp. l-26 in Onions and Allied Crops. Volume I. Botany, Physiology and Genetics (H.D. Rabinowitch and J.L. Brewster, eds.). CRC Press, Inc., Boca Raton, FL, USA. Hyam, R. and R. Pankhurst. 1995. Plants and Their Names. A Concise Dictionary. Oxford University Press, Oxford, UK. Messiaen, C.M., D. Blancard, R. Rouxel and R. Lafon. 1991. Les Maladies des Plantes Maraîchères, 3e édition. INRA, Paris, France. Messiaen, C.M., J. Cohat, J.P. Leroux, M. Pichon and A. Beyries. 1993. Les allium alimentaires reproduits par voie végétative. INRA, Paris, France. Rabinowitch, H.D. and J.L. Brewster (eds.). 1990. Onions and Allied Crops. Volume I. Botany, Physiology and Genetics. CRC Press, Inc., Boca Raton, FL, USA. Schwartz, H.F. and S.K. Mohan (eds.). 1995. Compendium of Onion and Garlic Diseases, APS Press, St. Paul, MN, USA. Walker, J.C. 1952. Diseases of Vegetable Crops, McGraw-Hill, New York, USA. Viruses Garlic common latent carlavirus (GCLV) Barg, E., D.E. Lesemann, H.J. Vetten and S.K. Green. 1994. Identification, partial characterization and distribution of viruses infecting Allium crops in 51 South and South-east Asian countries. Acta Hortic. 358:251-258. Barg, E., D.E. Lesemann, H.J. Vetten and S.K. Green. 1997. Viruses of alliums and their distribution in different Allium crops and geographical regions. Acta Hortic. (In press) Bellardi, M.G., F. Marani, L. Betti and A.L. Rabiti. 1995. Detection of garlic common latent virus (GCLV) in Allium sativum L. in Italy. Phytopath. Medit. 34:58-61. Conci, V.C., S.F. Nome and R.G. Milne. 1992. Filamentous viruses of garlic in Argentina. Plant Dis. 76: 594-596. Delecolle, B. and H. Lot. 1981. Viroses de l’ail: I. Mise en évidence et essais de caractérisation par immuno-électromicroscopie d'un complexe de trois virus chez différentes populations d’ail atteintes de mosaïque. Agronomie 1:763-770. Graichen, K. 1991. Gelbstreifigkeit des Porrees verursacht erhebliche Pflanzenausfälle. Gartenbau 38:17-19. van Dijk, P. 1993. Carlavirus isolates from cultivated Allium species represent three viruses. Neth. J. Plant Pathol. 99:233-257. Verbeek, M., P. van Dijk and P.M.A. van Well. 1995. Efficiency of eradication of four viruses from garlic (Allium sativum) by meristem-tip culture. Eur. J. Plant Pathol. 101:231-239. Ga lic dwarf reovirus Lot, H., B. Delecolle, G. Boccardo, C. Marzachi and R.G. Milne. 1994. Partial characterization of reovirus-like particles associated with garlic dwarf disease. Plant Pathol. 43: 537-546. 52 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Barg, E. 1995. Serologische und molekulargenetische Untersuchungen zur Variabilität Allium-Arten infizierender, filamentöser Viren. Ph.D. thesis, University of Göttingen, Germany. Bos, L., N. Huijberts, H. Huttingaand D.Z. Maat. 1978. Leek yellow stripe virus and its relationships to onion yellow dwarf virus: characterization, ecology and possible control. Neth. J. Plant Pathol. 84:185-204. Bos, L. 1981. Leek yellow stripe virus, AAB Descriptions of Plant Viruses, No. 240. Association of Applied Biologists, Wellesbourne, UK. Graichen, K. 1991. Gelbstreifigkeit des Porrees verursacht erhebliche Pflanzenausfälle. Gartenbau 38:17-19. Graichen, K., H. Kegler, H.E. Schmidt, J. Richter, U. Meyer and F. Kampe. 1988. Quantitative resistance of leek to leek yellow stripe virus. Arch. Gartenbau 36:77-81. Marys, E., 0. Carballo and M.L. Izaguirre-Mayoral. 1994. Isolation and characterization of viruses present in four clones of garlic (Allium sativum) in Venezuela. J. Phytopathol. 142:227-234. Noda, C., T. Maea and N. Inouye. 1989. Detection of leek yellow stripe virus by dot immunobinding assay. Nogaku-Kenkyu 61: 269-277. Paludan, N. 1980. Virus attack on leek: survey, diagnosis, tolerance of varieties and winter hardiness. Tidsskrift Planteavl. 84: 371-385. Nagakubo, T., M. Kubo and K. Oeda. 1994. Nucleotide sequences of the 3’ region of two major viruses from mosaic-diseased garlic: molecular evidence of mixed infection by a potyvirus and a carlavirus. Phytopathology 84:640-645. Schönfelder, M., M. Körbler, E. Barg, D.-E. Lesemann and H.J. Vetten. 1996. Sequence analysis of leek yellow stripe virus isolates differing in biological and serological properties. Xth Internatl. Congress of Virology, Jerusalem, Israel, August 11-16, 1996. Abst. No. PW37-2, p. 209. Tsuneyoshi, T. and S. I. Sumi. 1996. Differentiation among garlic viruses in mixed infections based on RT-PCR procedures and direct tissue blotting immunoassays. Phytopathology 86:253-259. van Dijk, P. 1993. Survey and characterization of potyviruses and their strains of Allium species. Neth. J. Plant Pathol. 99 Suppl. 2:1-48. Walkey, D.G.A., M.J.W. Webb, C.J. Bolland and A. Miller. 1987. Production of virus-free garlic (Allium sativum) and shallot (A. ascalonicum) by meristem tip-culture. J. Hort. Sci. 62:211-220. Walkey, D.G.A. 1990. Virus diseases. Pp. 191-212 in Onions and Allied Crops, Volume II. (H.D. Rabinowitch and J.L. Brewster, eds.). CRC Press, Inc., Boca Raton, EL, USA. Mite-borne filamentous viruses (MbFV) Kanyuka, K.V., V.K. Vishnichenko, K.E. Levay, D.Y. Kondrikov, E.V. Ryabov and S.K. Zavriev. 1992. Nucleotide sequence of shallot virus X RNA reveals a 5’- proximal cistron closely related to those of the potexviruses and a unique arrangement of the 3’-proximal cistrons. J. Gen. Virol. 73:2553-2560. Sumi, S.I., T. Tsuneyoshi and H. Furutani. 1993. Novel rod-shaped viruses isolated from garlic, Allium sativum, possessing a unique genome organization. J. Gen. Virol. 74:1879-1885. No. 18. Allium spp. 53 Tsuneyoshi, T. and S.I. Sumi. 1996. Differentiation among garlic viruses in mixed infections based on RT-PCR procedures and direct tissue blotting immunoassays. Phytopathology 86:253-259. van Dijk, P., M. Verbeek and L. Bos. 1991. Mite-borne virus isolates from cultivated Allium species and their classification into two new rymoviruses in the family Potyviridae. Neth. J. Plant Pathol. 97:381-399. van Dijk, P. and R.A.A. van der Vlugt. 1994. New mite- borne virus isolates from rakkyo, shallot and wild leek species. Eur. J. Plant Pathol. 100:269-277. Vishnichenko, V.K., T.N. Konareva and S.K. Zavriev. 1993. A new filamentous virus in shallot. Plant Pathol. 42:121-126. Yamashita, K., J. Sakai and K. Hanada. 1996. Characterization of a new virus from garlic (Allium sativum L.), garlic mite-borne mosaic virus. Ann. Phytopathol. Soc. Jpn. 62:483-489. Onion yellow dwarf potyvirus (OYDV) Bos, L. 1976. Onion yellow dwarf virus. CMI/AAB Descriptions of Plant Viruses No. 158. Delecolle, B. and H. Lot. 1981. Viroses de l’ail. I. Mise en évidence et essais de caractérisation par immunoelectomicroscopie d'un complexe de trois virus chez différentes populations d’ail atteintes de mosaïque. Agronomie 1:763-769. Kobayashi, K., P. Rabinowicz, F. Bravo-Almonacid, M. Helguera, V. Conci, H. Lot and A. Mentaberry. 1996. Coat protein gene sequences of garlic and onion isolates of the onion yellow dwarf potyvirus (OYDV). Arch. Virol. 141:2277-2287. Louie, R. and J.W. Lorbeer. 1966. Mechanical transmission of onion yellow dwarf virus. Phytopathology 56:1020-1023. Marys, E., O. Carballo and M.L. Izaguirre-Mayoral. 1994. Isolation and characterization of viruses present in four clones of garlic (Allium sativum) in Venezuela. J. Phytopathol. 142:227-234. Melhus, I.E., C.S. Reddy, W.J. Henderson and E. Vestal. 1929. A new virus disease epidemic on onions. Phytopathology 19:73-77. van Dijk, P. 1993. Survey and characterization of potyviruses and their strains of Allium species. Neth. J. Plant Pathol. 99, Suppl. 2:1-48. Walkey, D.G.A. 1990. Virus diseases. Pp. 191-212 in Onions and Allied Crops, Volume II (H.D. Rabinowitch and J.L. Brewster, eds.). CRC Press, Inc., Boca Raton, FL, USA. Shallot latent carlavirus (SLV) and serologically related carlaviruses Barg, E., D.E. Lesemann, H.J. Vetten and S.K. Green. 1994. Identification, partial characterization and distribution of viruses infecting Allium crops in South and South-east Asian countries, Acta Hortic. 358:251-258. Barg, E., D.E. Lesemann, H.J. Vetten and S.K. Green. 1997. Viruses of alliums and their distribution in different Allium crops and geographical regions. Acta Hortic. (In press). Bos, L. 1982. Shallot latent virus. CMI/AAB Descriptions of Plant Viruses. No. 250. Conci, V.C., S.F. Nome and. R.G. Milne. 1992. Filamentous viruses of garlic in Argentine. Plant Dis. 76: 594-596. 54 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Graichen, K. 1991. Gelbstreifigkeit des Porrees verursacht erhebliche Gartenbau 38:17-19. Pflanzenausfälle. Paludan, N. 1980. Virus attack on leek: Survey, diagnosis, tolerance of varieties and winter hardiness. Tidsskr. Planteavl. 84:371-385. van Dijk, P. 1993. Carlavirus isolates from cultivated Allium species represent three viruses. Neth. J. Plant Pathol. 99:233-257. Walkey, D.G.A., M.J.W. Webb, C.J. Bolland and A. Miller. 1987. Production of virus-free garlic (Allium sativum L.) and shallot (A. ascalonicum L.) by meristem-tip culture. J. Hort. Sci. 62:211-220. Shallot yellow stripe potyvirus (SYSV) Barg, E., D.E. Lesemann, H.J. Vetten and S.K. Green. 1997. Viruses of alliums and their distribution in different Allium crops and geographical regions. Acta Hortic. (In press). van Dijk, P. and R. Sutarya. 1992. Virus diseases of shallot, garlic and Welsh onion in Java, Indonesia and prospects for their control. Onion Newsletter for the Tropics 4:57-61. van Dijk, P., 1993. Survey and characterization of potyviruses and their strains of Allium species. Neth. J. Plant Pathol. 99 Suppl. 2: l-48. Delecolle, B. and H. Lot. 1985. Application of detecting onion yellow dwarf virus in garlic and shallot seeds and plants. Phytoparasitica 13: 266-267. Other viruses of minor or regional importance Araki, M., S. Yamashita, Y. Doi and K. Yora. 1981 Leek yellows virus. Ann. Phytopathol. Soc. Japan 47: 138 (Abstr. in Japanese). Barg, E., D.E. Lesemann, H.J. Vetten and S.K. Green. 1994. Identification, partial characterization and distribution of viruses infecting Allium crops in South and South-east Asian countries. Acta Hortic. 358:251-258. Bos, L. 1992. Viruses and virus diseases of Allium species. Acta Hortic. 127:11-29. Calvert, E.L. and B.D. Harrison. 1963. Outbreaks of tomato blackring virus in onion and leek crops in Northern Ireland. Hortic. Res. 2:115-120. Gera, A., D.-E. Lesemann, J. Cohen, A. Franck, S. Levy and R. Salomon. 1997. The natural occurrence of turnip mosaic potyvirus in Allium ampeloprasum. J. Phytopathol. (in press). Graichen, K. 1975. Allium-Arten als natürliche Wirte nematodenübertragbarer Viren. Arch. Phytopath. Pflsch. Berlin 11:399-403. Kristensen, H.R. and B. Engsbro. 1966. Undersoegelser og forsoeg vedroerende jordbårne vira. Tiddskr. Planteavl. 70:353-379. Lot, H., L. Rubino, B. Delecolle, M. Jacquemond, C. Turturo and M. Russo. 1996. Characterization, nucleotide sequence and genome organization of leek white stripe virus, a putative new species of the genus necrovirus. Arch. Virol. 141:2375-2386. Stefanac, Z. 1980. Cucumber mosaic virus in garlic. Acta Bot. Croat. 39:21-26. Sward, R.J. 1990. Lettuce necrotic yellows rhabdovirus and other viruses infecting garlic. Australasian Plant Pathol. 19:46-51. No. 18. Allium spp. 55 van Dijk, P. 1993. Carlavirus isolates from cultivated Allium species represent three viruses. Neth. J. Plant Pathol. 99:233-257. van Slogteren, D.H.M. 1958. Ratelvirus als oorzaak van ziekten in bloembolgewassen en de mogelijkheden de infectie door middel van grondontsmetting te bestrijden. Tijdschr. PlZiekt. 64:452-462. Vasiljeva, T.Y. and K.A. Mozhaeva. 1978. Properties of a TMV strain isolated from plants of the genus Allium. Pp. 75-77 in Plant Virus Strains (V.G. Reifman et al., eds.) Proc. Inst. Biol. Pedol., Vladivostok, Russia. Fungi Alternaria porri Everts, K.L. and M.L. Lacy. 1990. The influence of dew duration, relative humidity and leaf senescence on conidial formation and infection of onion by Alternaria porri. Phytopathology 80:1203-1207. Miller, M.E. and M.L. Lacy. 1995. Purple blotch. Pp. 23-24 in Compendium of Onion and Garlic Diseases (H.F. Schwartz and S.K. Mohan, eds.). APS Press, St. Paul, MN, USA. Botryotinia squamosa Brewster, J.L. 1994. Onions and Other Vegetable Alliums. CAB International, Wallingford, UK. Bergquist, R.R. and J.W. Lorbeer. 1971. Reaction of Allium spp. and Allium cepa to Botryotinia (Botrytis) squamosa. Plant Dis. Reptr. 55:394-398. Farr, D.F., G.F. Bills, G.P. Chamuris and A.Y. Rossman. 1989. Fungi on Plants and Plant Products in the United States. APS Press, St. Paul, MN, USA. Lacy, M.L. and J.W. Lorbeer. 1995. Botrytis leaf blight. Pp. 16-18 in Compendium of Onion and Garlic Diseases (H.F. Schwartz and S.K. Mohan, eds.). AI’S Press, St. Paul, MN, USA. Lorbeer, J.W. 1992. Botrytis leaf blight of onion. Pp. 186-211 in Plant Diseases of International Importance. Volume II. Diseases of vegetables and oil seed crops (H.S. Chaube, J. Kumar, A.N. Mukhopadhyay and U.S. Sing, eds.). Prentice Hall, Englewood Cliffs, NJ, USA. Maude, R.B. 1990. Leaf diseases of onions. Pp. 173-189 in Onions and Allied Crops Vol. II (H.D. Rabinowitch and J.L. Brewster, eds.). CRC Press, Boca Raton, FL, USA. Walker, J.C. 1952. Diseases of Vegetable Crops. McGraw-Hill, New York. Botrytis alli Maude, R.B. 1983a. The correlation between seed- borne infection by Botrytis allii and neck rot development in store. Seed Sci. Technol. 11:829- 834. Maude, R.B. 1983b. Eradicative seed treatments. Seed Sci. Technol. 11:907-920. Maude, R.B. and A.H. Presly. 1977. Neck rot (Botrytis allii) of bulb onions. I. Seed-borne infection and its relationship to the disease in onion crops. Ann. Appl. Biol. 86:163-180. Maude, R.B. and A.H. Presly. 1977. Neck rot (Botrytis allii) of bulb onions. II. Seed borne infection and its relationship to the disease in storage and the effect of seed treatment. Ann. Appl. Biol. 86:181-188. Maude, R.B., M.R. Shipway, A.H. Presly and D. O’Connor. 1984. The effects of direct harvesting 56 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm and drying systems on the incidence and control of neck rot (Botrytis allii) in onions. Plant Pathol. 33:263-268. Cladosporium allii-cepae Brewster, J. L. 1994. Onions and Other Vegetable Alliums. CAB International, Wallingford, UK.. Farr, D.F., G.F. Bills, G.P. Chamuris and A.Y. Rossman. 1989. Fungi on Plants and Plant Products in the United States. APS Press, St. Paul, MN, USA. Hill, J.P. 1995. Cladosporium leaf blotch. Pp. 21-22 in Compendium of Onion and Garlic Diseases (H.F. Schwartz and S.K. Mohan, eds.). APS Press, St. Paul, MN, USA. Jordan, M.M., R.B. Maude and R.T. Burchill. 1986. Development of the teleomorph (Mycosphaerella allii-cepae sp. nov.) of Cladosporium allii-cepae (leaf blotch of onion): Trans. Br. Mycol. Soc. 86:387-392. Jordan, M.M., R.B. Maude and R.T. Burchill. 1990. Sources, survival and transmission of Cladosporium allii and C. allii-cepae leaf blotch pathogens of leek and onion. Plant Pathol. 39:237-241. Maude,R.B. 1990. Leaf diseases of onions. Pp. 173-189 in Onions and Allied Crops. Vol. II (H.D. Rabinowitch and J.L. Brewster, eds.). CRC Press, Boca Raton, FL, USA. Fusarium spp. Abawi, G.S. and J.W. Lorbeer. 1972: Several aspects of the ecology and pathology of Fusarium oxysporum. f. sp. cepae. Phytopathology 62:870-876. Entwistle, A.R. 1990. Root diseases. Pp. 103-154 in Onions and Allied Crops. Volume II (H.D. Rabinowitch and J.L. Brewster, eds.). CRC Press, Boca Raton, FL, USA. Farr, D.F., G.F. Bills, G.P. Chamuris and A.Y. Rossman. 1989. Fungi on Plants and Plant Products in the United States. APS Press, St. Paul, MN, USA. Havey, M.J. 1995. Fusarium basal plate rot. Pp. 10-11 in Compendium of Onion and Garlic Diseases. (H.F. Schwartz and S.K. Mohan, eds.). APS Press, St. Paul, MN, USA. Peronospora destructor Brewster, J.L. 1994. Onions and Other Vegetable Alliums. CAB International, Wallingford, UK. Farr, D.F., G.F. Bills, G.P. Chamuris and A.Y. Rossman. 1989: Fungi on Plants and Plant Products in the United States. APS Press, St. Paul, MN, USA. Maude, R.B. 1990. Leaf diseases of onion. Pp. 173-189 in Onions and Allied Crops. Vol. II (H.D. Rabinowitch and J.L. Brewster, eds.). CRC Press, Boca Raton, FL, USA. Schwartz, H.F. 1995. Downy mildew. Pp. 20-21 in Compendium of Onion and Garlic Diseases (H.F. Schwartz and S.K. Mohan, eds.). APS Press, St. Paul, MN, USA. Walker, J.C. 1952. Diseases of Vegetable Crops. McGraw-Hill, New York, USA. Sclerotium cepivorum Adams, P.B. 1987. Effects of soil temperature, moisture and depth on survival and activity of Sclerotinia minor, Sclerotium cepivorum and Sporidesmium sclerofivorum. Plant Dis. 71:170-174. Coley-Smith, J.R., R.A. Reese and N.I. Georgy. 1987. Differential stimulation of germination of sclerotia of Sclerotium cepivorum by cultivars of No. 18. Allium spp. 57 onion and its effect on white rot disease. Plant Pathol. 36:246-257. Crowe, F. 1995. White Rot. Pp. 14-16 in Compendium of Onion and Garlic Diseases (H. F. Schwartz and S. K. Mohan, eds.). AI’S Press, St. Paul, MN, USA. Entwistle, A.R. 1988. Opportunities for the microbial control of Allium white rot. EPPO Bulletin 18:19- 28. Entwistle, A.R. 1990. Allium white rot and its control. Soil Use Manage. 4:201-209. Stemphylium vesicarium Aveling, T.A.S., H.G. Snyman and S.P. Naude. 1993. Evaluation of seed treatments for reducing Alternaria porri and Stemphylium vesicarium on onion seed. Plant Dis. 77:1009-1011. Ellis, M.B. 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute; Kew, UK. Farr, D.F., G.F. Bills, G.P. Chamuris and A.Y. Rossman. 1989. Fungi on Plants and Plant Products in the United States. AI’S Press, St. Paul, MN, USA. Gupta, R.P., K.J. Srivastava and U.B. Pandey. 1994. Disease and insect pests of onion in India. Acta Hortic. 358:265-269. Lorbeer, J.W. 1993. A serious outbreak of Stemphylium leaf blight of onion in New York. Pp. 32-37 in Proceedings of the 1993 National Onion Research Conference. Department of Fruit and Vegetable Science, Cornell University, Ithaca, NY, USA. Miller, M.E. 1995. Stemphylium leaf blight and stalk rot. Pp. 25-26 in Compendium of Onion and Garlic Diseases (H.F. Schwartz and S.K. Mohan, eds.). APS Press, St. Paul, MN, USA. Miller, M.E., R.A. Taber and J.M. Amador. 1978. Stemphylium blight of onion in South Texas. Plant Dis. Reptr. 62:851-853. Rao, N.N.R. and M.S. Paugi. 1975. Stemphylium leaf blight of onion. Mycopathologia 56:113-118. Shiskoff, N. and J.W. Lorbeer. 1989. Etiology of Stemphylium leaf blight of onion. Phytopathology 79:301-304. Minor fungal and bacterial pathogens Alvarez, A.M., I.W. Buddenhagen, E.S. Buddenhagen and H.Y. Domen. 1978. Bacterial blight of onion, a new disease caused by Xanthomonus sp. Phytopathology 68:1132-1136. Bruna, V.A. 1985. Identificacion de Penicillium corymbiferum Westling causante de1 moho azul en ajo (Allium sativum L.). Agric. Tec. 45:353-356. Gitaitis, R.D., R.E. Baird, R.W. Beaver, D.R. Sumner, J.D. Gay and D.A. Smittle. 1991. Bacterial blight of sweet onion caused by Pseudomonas viridiflava in Vidalia, Georgia. Plant Dis. 75:1180-1182. Prasad, B.K., T.S.P. Sinha, U. Shanker and S. Kumar. 1986. Decay of garlic bulb in the field: a new disease report. Ind. Phytopathol. 39-622-624. Presly, A.H. 1985. Studies on Botrytis spp. occurring on onions (Allium cepa) and leeks (Allium porrum). Plant Pathol. 34: 422-427. Samson, R. 1982. A biovar of Pseudomonas fluorescens pathogenic to Allium sativum. Pp. 60-64 in Proc. Fifth Int. Conf. Plant Pathogenic Bacteria, CIAT, Cali, Colombia. Tichelaar, C.M. and A.A. van Kesteren. 1967. Attack of onion by Phytophthora porri. Neth. J. Plant Pathol. 73:103-104. 58 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm Nematodes Ditylenchus dipsaci (stem and bulb nematode) Caubel, G. and R. Samson. 1984. Influence du nematode des tiges, Ditylenchus dipsaci (Kühn) Fil. dans le développement de la bacteriose “café au lait” de l’ail (Allium sativum L.) occasionnée par un biovar de Pseudomonas fluorescens Migula. Agronomie 4:311-313. Green, C.D. and S. Sime. 1979. The dispersal of Ditylenchus dipsaci with vegetable seeds. Ann. Appl. Biology 92:263-270. Hooper, D.J. 1972. Ditylenchus dipsaci. C.I.H. Descriptions of Plant Parasitic Nematodes No. 69. Commonwealth Institute of Helminthology, St. Albans, UK. Johnson, A.W. 1995. Stem and bulb nematode (bloat). Pp. 35-37 in Compendium of Onion and Garlic Diseases (H. F. Schwartz and S. K. Mohan, eds.). APS Press, St. Paul, MN, USA. Seinhorst, J.W. and J.L. Koert. 1971. Stem nematodes in onion seed. Gewasbescherming 1:25-31. Arthropods Baker, E.W. and G.W. Wharton. 1952. An Introduction in Acarologie. Macmillan Company, New York, USA. Soni, S.K. and P.R. Ellis. 1990. Insect pests. Pp. 213-271 in Onions and Allied Crops, Vol. 2 (H.D. Rabinowitch and J.A. Brewster, eds.) CRC Press, Boca Raton, FL, USA. No. 18. Allium spp. 59 SAMPLE GERMPLASM HEALTH STATEMENT No. This statement provides additional information on the phytosanitary state of the plant germplasm described herein. It should not be considered as a substitute for the Phytosanitary Certificate. IMPORT PERMIT PHYTOSANITARY CERTIFICATE No. Issued by Date No. Issued by Date ORIGIN OF THE GERMPLASM [ ] The material in this package was obtained from meristems cultured in vitro, which were found free of viral pathogens using recommended virus-detection techniques. [ ] The material in this package was obtained from [plant species] meristems, aseptically grown in vitro from the terminal buds of stakes previously subjected to thermo-therapy for [time] These stakes were originally obtained from [plant species] free from symptoms of [d iseases] . [ ] The germplasm described here has been produced under glasshouse or screenhouse conditions, in sterilized soil and in the absence of any visible pathogen or pest of quarantine significance. [ ] The germplasm described here has been produced under intensive chemical protection in fields and regions isolated from commercial or experimental plantings of this species. These fields are exclusively used for the pest-controlled multiplication of germplasm. [ ] The germplasm described here has been multiplied under field conditions, which do not guarantee the absence of pests or pathogens of quarantine importance. PATHOGEN DETECTlON METHODS [ ] The germplasm described here was produced under periodic field supervision by a pathologist / virologist and it was found to be free from pathogens of quarantine significance. 60 FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm [ ] Representative seed samples of the germplasm described here were assayed in the Seed Health Laboratory at [institute] , following the methods recommended in the FAO/IPGRI Technical Guidelines for the Safe Movement of [crop] Germplasm: [ ] extraction / washing test for [nematodes, fungi] [ ] culture on agar media for [fungi] [ ] serological for [ v i ruses ] No pathogens of quarantine significance were detected. [ ] The plants selected as sources of meristems for in vitro culture were assayed using the following tests for the diagnosis of viral diseases. [ ] electrophoretic [ ] serological [ ] biological (grafting) SEED TREATMENT [ ] Seeds were treated with a solution of sodium hypochlorite. [ ] Seeds were subjected to a dry heat treatment at [temperature] °C for [x] d a y s . [ ] Seeds were scarified with sulphuric acid. [ ] Seeds were treated with [fungicide(s)] at [rate] . [ ] [other] ADDITIONAL INFORMATION FOR FURTHER INFORMATION Please contact: DECLARATION We hereby declare that the information provided in this germplasm health statement was obtained in good faith, according to our technical capabilities at the time of the test. Neither [institute] nor its scientific staff assumes any legal responsibility in relation to the declaration. Date Signature Comments on Technical Guidelines for the Safe Movement of Allium Germplasm Please send to: Germplasm Health Scientist IPGRI Via delle Sette Chiese 142 00145 Rome, Italy Fax: +39-6-5750309 and d Chief, Forestry Resources Development Service FAO Via delle Terme di Caracalla 00100 Rome, Italy Fax: +39-6-5225-5137 I would like to bring the following [ ] inaccuracy (ies) [ ] new development (s) [ ] omission (s) [ ] concerns to the attention of the editors: Disease Comments From: Name Address Date Signature No. 18. Allium spp. FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm are published under the joint auspices of the Plant Production and Protection Division of the Food and Agriculture Organization of the United Nations (FAO) and the International Plant Genetic Resources Institute (IPGRI). The designations employed, and the presentation of material in these Guidelines, do not imply the expression of any opinion whatsoever on the part of FAO, IPGRI or the CGIAR concerning the legal status of any coun- try, territory, city or area or its authorities, or concerning the delimitation of its frontiers or boundaries. Similarly, the views expressed are those of the authors and editors and do not necessarily reflect the views of FAO, IPGRI or the CGIAR. In addition, the mention of specific companies or of their products or brand names does not imply any endorsement or recom- mendation on the part of FAO, IPGRI or the CGIAR. The International Plant Genetic Resources Institute (IPGRI) is an autonomous interna- tional scientific organization operating under the aegis of the Consultative Group on International Agricultural Research (CGIAR). IPGRI’s mandate is to advance the con- servation and use of plant genetic resources for the benefit of present and future gene- rations. IPGRI works in partnership with other organizations, undertaking research, training and the provision of scientific and technical advice and information, and has a particularly strong programme link with the Food and Agriculture Organization of the United Nations. Financial support for the research agenda of IPGRI is provided by the Governments of Australia, Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, India, Italy, Japan, the Republic of Korea, Luxembourg, Mexico, the Netherlands, Norway, the Philippines, Spain, Sweden, Switzerland, the UK and the USA, and by the Asian Development Bank, CTA, European Union, IDRC, IFAD, Interamerican Development Bank, UNDP and the World Bank. Citation: Diekmann, M. 1997. FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm. No. 18. Allium spp. Food and Agriculture Organization of the United Nations, Rome/International Plant Genetic Resources Institute, Rome. ISBN 92-9043-346-9 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photo- copying or otherwise, without the prior permission of the copyright owner. Applications for such permission, with a statement of the purpose and extent of the reproduction, should be addressed to the Publications Office, IPGRI Headquarters, Via delle Sette Chiese 142, 00145 Rome, Italy. © FAO/IPGRI 1997