Field production of quality sweetpotato planting material Guidelines for using rapid multiplication technology to produce quality sweetpotato planting material in an open field 1. INTRODUCTION B. SITE SELECTION These guidelines outline the basic steps in Select a site that is: production of sweetpotato vine cuttings (seed) i. Near a reliable water source with year-round availability of in open nurseries using rapid multiplication water for irrigation. Check local bye laws for any restrictions technology (RMT). It covers the standard bed on use of swampy areas, riverbanks etc. size, spacing and other agronomic practices. It is meant for use by any seed producer seeking to ii. Not steep and has level terrain to avoid water loss from run- produce planting material in open fields. off when irrigating. iii. Secure with low risk of theft, vandalism, or damage by 2. PROCEDURE livestock, (as close to one’s home as possible). iv. Easily accessible for regular management and monitoring A. SOURCING STARTER MATERIAL activities, seed inspection by regulators, and purchase by i. Obtain clean, virus-tested starter material from customers. a known source, e.g., a National Agricultural v. Free of shade to allow maximum penetration of sunlight Research Institute (NARI) or a private sector and rainwater, but avoid windy areas which may facilitate seed enterprise. Pre-basic seed (vine cuttings) mite infestations. are produced from virus tested tissue culture plantlets and multiplied under screen house vi. Not heavily infested with weeds, especially perennial weeds. conditions (protected from virus-vector pests). vii. Compliant with the national sweetpotato seed standards for rotation practice, and isolation distance. C. LAND PREPARATION which leaves you with one meter width on which i. Clear bushes or other foliage and till the soil at least to prepare your rows. Therefore, you will have 5 one day before bed preparation. rows spaced at 20 cm. Each row will accommodate 30 plants spaced at 10 cm, giving you a plant ii. Soil tillage is best done when the soil is moist. Apply population of 300 per bed. water if this is done during the dry period. D. BED PREPARATION i. Rapid multiplication technology allows production of large quantities of planting material within a short time. Plants are planted using close spacing (20 cm x 10 cm) which favours production of vines but compromises production of storage roots. Recommended spacing is 20 cm between rows and 10 cm between plants. However, this can be adapted (e.g., 20 cm x 20 cm) to local conditions. ii. A standard rapid multiplication bed is 6 m long by 1.2 m wide. Long, narrow beds allow easy management. The size of beds may be adapted to v. Only one variety should be planted on each bed. local conditions and needs. vi. A mulch of rice husks or any other available organic iii. Leave a space of 0.5 m between beds to allow easy material may be spread over the soil after planting to access. suppress weeds. vii. Label each bed clearly indicating date of planting, name of the variety, source of planting material and generation. Labels should be waterproof. iv. Prepare sunken beds if in an area that requires frequent irrigation and raised beds if in a marshy area. v. Beds should be at a right angle to any field slope so viii. After two weeks, check the establishment rate, and as to reduce water run-off and soil erosion. fill any gaps with new cuttings to maintain optimum plant population density. vi. Mix well-decomposed organic manure into the soil of the beds at a ratio of four 20-litre (by volume) ix. Check that the cuttings are well covered with soil buckets per bed shortly before planting time. and cover any that have become exposed during watering. E. PLANTING F. WEED MANAGEMENT i. Plan well so that the vines produced will be ready for harvesting during the peak period of demand i. Do regular monitoring and remove any weeds by for planting material from farmers. The number of hand. rapid multiplication beds planted should depend on ii. Remove any weeds emerging around the planted the quantities of planting material required by local area. farmers. ii. Water the seed beds lightly prior to planting. G. PEST AND DISEASE MANAGEMENT iii. As the plants grow, cut the vines into cuttings of 3-4 i. Do regular scouting of the multiplication plots nodes (~10-20cm) in length. removing (roguing) plants that are not true-to-type and those showing virus symptoms (i.e. stunting, leaf iv. Plant the 3-4 node cuttings upright at a spacing of discoloration or deformation), leaving only healthy, 20 cm x 10 cm with two nodes buried under the soil. vigorous plants. Leave 10 cm from plants to the edges of the bed, ii. Regular watering and hilling up to cover cracks on the soil minimizes weevil risk. a iii. In cases of serious pest infestation, apply a pesticide such as those containing Cypermethrin. Any pesticide should be applied as per the manufacturer’s recommended rates and following guidelines for safe use and disposal. Consult your local extension officer and agrovet before using b pesticides. Always follow safe use instructions (including avoiding contamination of water sources), personal protection and safe disposal of containers. a) Inspecting the crop for visual symptoms. b) Roguing out infected plants. iv. Depending on soil fertility, nitrogenous fertilizers such as NPK and urea may be applied at a rate of H. IRRIGATION 200 g/bed after harvesting to boost vine growth. Consult the local extension officer and agrovet for i. Irrigate immediately after planting and give light appropriate type and proper use of fertilizer. irrigation daily for 15 days until establishment. The frequency of irrigation thereafter should depend on K. PACKING prevailing weather conditions. Do not irrigate during the rainy season if rains are consistent as this might i. Cut each vine into 5- to 7-node (25-30 cm) cuttings lead to waterlogging. and arrange them into bundles of desirable quantities e.g., 200-300 cuttings per bundle. ii. Use a watering can if the area under production is small. Use motorized (petrol/solar-powered pump) when the area under production is large. iii. It is best to water in the early morning and/or late afternoon. I. INSPECTION i. The national seed regulatory body should inspect the vine multiplication plot to assess whether the planting material being produced meets the standards in the country’s seed regulations. ii. The seed producer should register with the seed regulatory body. A minimum of two inspections ii. The bundles can be packed into jute or are typically done, the first about 4-6 weeks after polypropylene grain sacks. Jute sacks are better planting when disease symptoms would first start than the grain sacks because they allow more to show up, and at which point the seed producer air movement. If using grain (polypropylene) will be advised to rogue out diseased plants. The sacks, pierce them to increase air flow. In case of second inspection should be done about 2 weeks transportation of large quantities, the vines can just before harvest. If the pest/disease level is above the be arranged into bundles of desirable quantities and tolerance level, the plot will be rejected. During the packed directly on a vehicle without packing in sacks. second inspection, an estimate of the quantity of planting material which can be harvested from the iii. Do not overfill the sacks to avoid damaging the vines. plot is done. iv. The distance which the planting material will travel, or the estimated time before the material will be planted, J. HARVESTING AND POST-HARVEST MANAGEMENT can influence the type of packing materials used. i. After 6 to 8 weeks the vines are ready for the first v. Clearly label each variety whether distributed in harvest. This should be done early in the morning sacks or bundles. The label should contain the or late afternoon to avoid excessive evaporation, variety name, name and contact details of the wilting and transplanting shock. multiplier and date of harvest. ii. Cut apical portions of vines at 10 – 15 cm above the soil level, leaving the stump with some nodes to support secondary vine growth and to ensure harvested cuttings are free from weevils. iii. First ratoon or second vine harvesting can be done after 40 to 60 days depending on weather conditions and management. Two to three ratoons can be produced but the number is guided by each country’s regulations on seed production. vi. If possible, include details of the characteristics are used, the vines are more likely to get squashed of the variety on the back of the label. A separate and overheated during transport. information leaflet on the varietal characteristics iii. Transport the vines during the cool part of the and good agronomic practices for root production day to minimize rotting or drying out of the vines. can be distributed with the planting material, if Tarpaulins should be used to cover the vines when resources allow. it rains during transportation, otherwise they will L. TRANSPORTATION deteriorate and become unusable. i. Take care when loading sacks or bundles onto trucks iv. Make sure you transport the vines as soon to avoid squashing and damaging the vines. after harvesting as possible, as there can often be unexpected delays during transport and ii. Use open medium-sized (6 - 8 tons) trucks for distribution. transporting vines to reduce damage. If large trucks FURTHER REFERENCE RESOURCES 1. Stathers, T.; McEwan, M.; Gibson, R.; Mwanga, R.O.M.; Carey, E.E.; Namanda, S.; Low, J.W.; Ogero, K.; Rajendran, S.; Abidin, P.E.; Malinga, J.; Agili, S.; Andrade, M.I.; Mkumbira; J. 2018. Everything you ever wanted to know about sweetpotato. Topic 5: Sweetpotato seed systems. Reaching agents of change ToT manual. International Potato Center, Lima, Perú. 118 p. https://hdl.handle.net/10568/98337. ACKNOWLEDGEMENTS These guidelines were developed as part of the seed systems research conducted by Work Package 4 of the Genetic Advances and Innovative Seed Systems for Sweetpotato (SweetGAINS) project funded by Bill and Melinda Gates Foundation (BMGF). Design and layout were supported by the Sweetpotato Component of the Program for Seed System Innovations for Vegetatively-propagated crops in Africa (PROSSIVA). It was a collaborative effort between the International Potato Center (CIP), the National Crops Resources Research Institute (NaCRRI) of Uganda and the Tanzania Agricultural Research Institute (TARI). CITATION Ogero K.O, McEwan M.A., and Namanda S. 2023. Guidelines for use of rapid multiplication technology in open field production of quality planting material for sweetpotato. International Potato Center. Lima, Peru. CIP thanks all donors and organizations that globally support its work through their contributions to the CGIAR Trust Fund. https://www.cgiar.org/funders/ © 2023. This publication is copyrighted by the International Potato Center (CIP). It is licensed for use under the Creative Commons Attribution 4.0 International License