diversity Review Approaches and Advantages of Increased Crop Genetic Diversity in the Fields Bal Krishna Joshi 1,*, Krishna Hari Ghimire 1, Shree Prasad Neupane 2 , Devendra Gauchan 3 and Dejene K. Mengistu 4 1 Nepal Agricultural Research Council, Kathmandu P.O. Box 3055, Nepal; krishnahar.ghimire@narc.gov.np 2 Local Initiatives for Biodiversity, Research and Development, Pokhara P.O. Box 324, Nepal; shree.neupane@libird.org 3 Bioversity International, Kathmandu P.O. Box 3055, Nepal; d.gauchan@cgiar.org 4 Bioversity International, Addis Ababa P.O. Box 5689, Ethiopia; d.mengistu@cgiar.org * Correspondence: bk.joshi@narc.gov.np Abstract: Crop genetic diversity is the most important factor for a long-term sustainable production system. Breeding and production strategies for developing and growing uniform and homogenous varieties have created many problems. Such populations are static and very sensitive to unpredictable stresses. In Nepal, more than 80% of the seed system is informal, which has contributed greatly to creating and maintaining genetic diversity within the field. This paper aims to assess and present the approaches and advantages of increased crop genetic diversity in the fields, based on the experiences of implementing on-farm conservation activities carried out in Nepal for last two decades. Some of the evidence has been derived from an ongoing evolutionary plant breeding (EPB) project being implemented in Nepal. The information is supplemented with field assessments, focus group discussion, and a literature review. The major approaches to increase crop genetic diversity are evolutionary plant breeding, cultivar mixture, landrace enhancement, informal seed systems, the bulk method, diversifying the seed sources, participatory plant breeding, open pollination, etc. EPB and cultivar mixture are very simple and effective approaches to increase crop genetic diversity at field level. The involvement of farmers in these approaches helps to accelerate the population improvement, maintaining the higher degree of genetic diversity. The major advantages of increased Citation: Joshi, B.K.; Ghimire, K.H.; crop genetic diversity are seed maintenance by farmers themselves, minimal risk of crop failure, Neupane, S.P.; Gauchan, D.; resilience to unpredictable stresses, increased amount of diversified nutrition, production increment, Mengistu, D.K. Approaches and ease of producing organically, etc. However, there are some issues and problems associated with Advantages of Increased Crop mixtures and intra-varietal diversity; for example, not being able to harvest by machine, maturing at Genetic Diversity in the Fields. a different date, difficulty in maintaining seeds and registration, etc. Crop genetic diversity should be Diversity 2023, 15, 603. https:// considered as a sustainable approach for a climate-resilient and self-dependent production system. doi.org/10.3390/d15050603 The higher the genetic diversity in farming land, the more chance of receiving multiple benefits in the Academic Editor: Samir C. Debnath agriculture system. Received: 4 April 2023 Keywords: evolutionary population; informal seed system; landrace; resilience; varietal mixture Revised: 19 April 2023 Accepted: 26 April 2023 Published: 28 April 2023 1. Introduction Crop genetic diversity has been created by nature, and managed, utilized and main- Copyright: © 2023 by the authors. tained by farmers across the world. Farmers always transfer their crop diversity to the Licensee MDPI, Basel, Switzerland. next generations and other farming communities [1,2]. Before the green revolution, ge- This article is an open access article netic diversity was very high in the fields. Even in Nepal, where the modern varieties distributed under the terms and have not reached, there is higher genetic diversity being maintained by farmers compared conditions of the Creative Commons to farming areas of modern varieties. It is commonly said by agriculturists that native Attribution (CC BY) license (https:// landraces perform poorly and cannot meet the demands of the human population in the creativecommons.org/licenses/by/ world. As advances have been made in agriculture, the grain yields of a few crops have 4.0/). Diversity 2023, 15, 603. https://doi.org/10.3390/d15050603 https://www.mdpi.com/journal/diversity Diversity 2023, 15, 603 2 of 11 increased significantly; however, crop genetic diversity in the fields is decreasing [3] and some farmers’ rights are being transferred partly to other institutes. Genetic diversity has now been confined in buildings with static conditions and is being exploited by agricultural researchers, especially by plant breeders for their business. For example, the Consultative Group for International Agricultural Research (CGIAR) has more than 700,000 crop acces- sions collected from different parts of countries. CGIAR uses this diversity for developing better genotypes and then transfers them to farming areas. There are many other private and public organizations that are doing similar business. Crop genetic diversity in the fields is the most important factor for sustainable and secured agriculture. Farmers have realized the demerits of cultivating uniform and mono- genotyped varieties in a large area. There are many cases of failures of modern crop varieties. Farmers have many traditional practices that help to maintain and increase the crop genetic diversity in the fields. However, these practices are not now in practice in many areas after modern varieties have been adopted. Only a few varieties dominate the farming areas, e.g., the Srijana tomato variety, the Mansuli rice variety, etc., in Nepal. This system also replaced many native and localized crop landraces. Realizing the genetic erosion from the fields, some organizations started working on increasing the genetic diversity in the fields and have developed different approaches that also help to conserve genetic diversity in a dynamic state [4–7]). These approaches are also good for strengthening agroecological services [8,9] as well as for diversifying the produce in households and markets. This paper, therefore, documents the existing approaches and practices used to in- crease genetic diversity in the fields, so that this information can contribute to maintaining, increasing, and utilizing diversity across the farming areas. An increased understanding of the importance of genetic diversity will further guide policy and strategy formulation and development [10,11]. The information in this paper is based on the past and current experiences of implementing on-farm conservation and evolutionary plant breeding projects which have been implemented in Nepal in the last two decades and it is supplemented with field assessments along with traditional knowledge and practices, focus group discussion, and literature review. Knowledge gained from the field experiments and interaction with breeders has also been documented. Information was also generated from farmers’ field days, national and regional workshops, participatory varietal selection experiments and participatory preferential ranking works carried out over the multilocation and multicrops. 2. Crop Genetic Diversity Crop genetic diversity includes diversity from domesticated species to alleles. Farmers mostly diversify production domains by using different species, crops, varieties, landraces and trait-specific genotypes. Crop genetic diversity is defined as any variation within and between crop cultivars, including their genotypic and phenotypic characters. Crops are domesticated plants used extensively for human benefit and managed by humans in their agricultural systems, e.g., rice, bean, apple, potato, forage species, etc. Cultivars are crop genotypes that are subject to cultivation practices, and this includes both varieties and landraces. Varieties are crop genotypes developed by breeders and cultivated in farming areas. Landraces are traditional genotypes, locally adapted, genetically altered by nature and maintained by farmers over a long period, and also called farmer’s variety. Diversity can be of different types, e.g., intra and inter crop diversity, intra and inter cultivar diversity, intra and inter varietal diversity, intra and inter landrace diversity, etc. Within cultivars, there are two types based on genetic diversity. One is called a monomorphic cultivar, and is uniform, homozygous and morphologically and genetically the same. The other is polymorphic, which is heterozygous with more than one type or different types of forms at both phenotypic and genotypic levels. The variability in these genetic resources (which is governed by many drivers) can be measured using different approaches at different levels [12]. Major drivers of crop genetic diversity are land type, season, market demand, family demand, technology availability, and incentives, etc. Crop genetic diversity has been considered very important for food, nutrition, business, health and environmental security. Diversity 2023, 15, 603 3 of 11 3. Diversity in Research and Production Systems Agricultural researchers collect germplasm (basket of genetic diversity), both native and exotic, including wild relatives from fields and institutes. They also create and maintain diversity through hybridization, mutation, genetic engineering, etc. Much of the diversity has been mostly confined in the buildings, e.g., gene banks or other reservoirs, and only a few selective lines have been used for cultivation purposes due to their high production performance, which has resulted in the narrowing down of crop genetic diversity in the field [2,13]. More-importantly, genotypes in research fields have much less interaction with environmental factors in conventional breeding systems, as most of the research activities are carried out within the research stations. Conversely, participatory plant breeding allows a high level of acclimatization of variety with the target environment as most of the research activities are conducted in the farmers’ field. In formal cases, the genotypes are mostly handled and exposed to the chemical pro- duction system, i.e., chemical fertilizers and pesticides. The advancement of genotypes is based on a single trait and targeted to make them homozygous and uniform. The various diverse genotypes are discarded, and only a few selected genotypes are used in the research fields. This has resulted in the loss of allelic diversity from the gene pool shared by landraces and other crop cultivars. Thousands of diverse genotypes are discarded each year in the research stations, and therefore a very narrow genetic base population and genotypes are then tested in farmers’ fields. In contrast to the research station, diversity is very high in the farmer-managed production system. Any genotypes have to interact with many different environmental factors for their adoption, as the cultivars ultimately have to be grown in open field conditions. Due to diverse factors in the production fields and households, farmers consider multiple traits. Farmers generally allow nature to select the genotypes for next season’s planting. The diversity found, therefore, is higher in crops managed by farmers from seeding to storing seeds by themselves in comparison to crops that are taken from a formal seed system. Phenotypic variability, including off-types (of the same crop), is continuously retained in informal seed systems, which helps to create and maintain genetic diversity. Additionally, in the production system managed through the formal seed system, some farmers’ rights have been knowingly or unknowingly transferred to other seed companies, e.g., the production and marketing rights of seeds of different classes. In this system, seeds are produced in different locations, other than grain production sites, (which may be far from the grain production domain). This may sometimes cause an environmental shock to varieties in the production system. 4. Approaches for Increasing Diversity During the field visit, focus group discussions, and interaction with farmers, several different approaches and methods (Table 1) were found in farming and research areas to increase genetic diversity in many different crops. Some approaches are traditional, and some have been developed by researchers and transferred to farmers. These approaches are practiced by farmers mainly on rice, wheat, maize, bean, oilseed crops, vegetables, finger millet, foxtail millet, barely, proso millet, amaranths, soybean and other grain legumes. Some approaches look very simple but help significantly to maintain and increase the diversity in the fields. Farmers, growers and researchers who love genetic diversity are following these approaches and producing benefits. These approaches look highly practicable for the on-farm conservation and restoration of crop biodiversity. Germplasm exchange and repatriation based on climate analog tools are also very effective to obtain higher production and conservation of diversity in the fields. Multiple approaches might be good to use even in a single landrace for producing higher benefits as well as to accelerate their conservation on-farm [14,15]. Diversity 2023, 15, 603 4 of 11 Table 1. Approaches for increasing crop diversity in the fields. Scheme Approach Explanation and Applied Crop Groups Remarks 1. Bulk method Bulking of seeds from different plants, and/or from different Some farmers have more than one separate field fields, blocks, plots and plants. In cereals and grain legumes to grow crops which helps to bulk the seeds from different fields p harvesting together for both seeds and grains from all 2. Bulk seed Cro processing fields and threshing, cleaning, drying and storing together. In No selection and separation of seeds for next cereals and grain legumes season’s planting Classes- Making different classes of crops in the field, selecting within Classes can be made based on the farmer’s 3. bulking classes, and mixing selected seeds from all classes. In rice preferred traits and other important selection and bean morphological traits, seed color, size, etc. Many different landraces are made available to the local It also includes a community seed bank and 4. Community community. They also conserved the same landraces from facilitates the exchange of seeds, and adds new genebank different farmers and sites. In cereals, grain legumes, collections. Mixed seed collection from different and vegetables farmers helps to increase diversity 5. Crossing Hybridization of two or more different genotypes to obtain Segregating lines provide diversity segregating lines. In rice and maize selection options 6. Cultivar Growing more than one landrace/variety together in the same Continuous mixing can help generate mixture fields. In cereals and grain legumes new genotypes Multiple Different seed suppliers can provide many different genotypes ply broad genetic base 7. sources for of the same crops. Seed sources from the local shop, relatives, Informal seed sources sup seeds neighbors, community seed bank, market, etc., help to increase materials, whereas formal seed sources generally the diversity. In cereals and vegetables supply uniform varieties ersity to farmers for selection and 8. Diversity block Many blocks or plots of different cultivars within a field. It provides div In cereals helps maintain the diversity within a targeted locality Display of all crops and their seeds/germplasm by many 9. Diversity fair farmers in one place at a certain time. In cereals, grain legumes All available crop diversity can be seen, and vegetables exchanged and traded 10. Diversity field Farmers and experts discuss and observe crops diversity in the Similar to farmer’s field school, but focuses on school field. In cereals genetic diversity 11. Diversity kit Planting pack with a mini pack of many different crops’ seeds. It includes the elite line, released variety and In cereals, grain legumes and vegetables native landraces of many suitable crops Mixing and growing many more (>10) landraces and varieties 12. Evolutionary together, focusing on developing dynamic mixture population Very easy way to conserve crop biodiversity plant breeding or by using many segregating or recombinant inbred lines. In through uses rice and bean change or marketing of seeds among farmers without any 13. Informal seed Ex d system exists in many communities system formal regulations. In cereals, grain legumes, vegetables The very ol and fruits for multiple crop species sect-friendly Ecological agriculture favors insects which help to pollinate 14. In farming system and maintain genetic diversity. In maize, oil seed crops and Insect field genebank accelerates pollination in vegetables many crops 15. Landrace Participatory selection of landraces for their genetic Farmers prefer to grow landraces if their genetic enhancement improvement. In cereals and grain legumes performance enhanced 16. Mass selection Selection of particular seeds from different plants and mixing Simple and common practices, but effective in them. In cereals and grain legumes large population size 17. Mix cropping Growing more than one crop in the same field. In maize, finger millet, pumpkin and cowpea Increased diversity at species levels 18. National Collection of all types of crop diversity from around the atriate the landraces as well as to Genebank country and distribution to farming communities. In cereals, Useful to rep grain legumes, vegetables and oil seed crops establish diversity blocks in the target location 19. Negative Removing seeds or plants that are not suitable or cannot selection produce seeds very well. In vegetables Selection pressure is very low 20. Open Pollination and fertilization go naturally. In cereals, grain Pollinators help to accelerate the creation of pollination legumes, vegetables and oil seed crops genetic diversity Involvement of farmers and breeders in selection and 21. Participatory plant breeding evaluation, including hybridization and handling of Segregating lines are generally handled in a segregating lines. In rice, wheat and buckwheat target environment Diversity 2023, 15, 603 5 of 11 Table 1. Cont. Scheme Approach Explanation and Applied Crop Groups Remarks Event for farmers in a certain place to exchange seeds of mainly 22. Participatory e seed exchange rare, endangered landraces. In cereals, grain legumes Organize during seed scarcity, i.e., after th and vegetables earthquake, flooding, etc. Participatory Growing of a few fixed genotypes (generally 5-10) in farmers’ 23. varietal fields along with local in farmers’ management system. In rice, Farmers can select more than one variety. selection wheat, maize and grain legumes Different farmers can select a different variety Growing of landraces that were available in the past but not n be collected from the 24. Repatriation now. Additionally, a climate analog tool can be used to identify Such materials ca the suitable germplasm to repatriate the climatically smart National and Global Genebank. Landraces can germplasm. In rice, bean, proso millet and foxtail millet be collected from climatically analog sites 25. Multiline variety Growing more than one different line. In rice and bean Usually, these are breeding lines and differ from each other for certain traits 26. Near isogenic Lines that are genetically identical except for the allele at one lines locus. In rice Applicable to mostly for monogenic traits 27. Site-specific Development and maintenance of a variety for a particular site. A large number of different varieties are needed variety In cereals and grain legumes for a diverse agroecosystem Growing the Growing the same variety over a period in the same field for 28. same variety different generations. In cereals, grain legumes and oil Selection choices and mutation along with over a time seed crops natural crossing create and maintain diversity Cultivated varieties may cross with wild relatives available It is common in rice that crosses with wild rice 29. Hybrid swarm near to the field and grow their progeny in the field. In rice and available near the field. Many different wild rice genotypes can be observed in the next generation Shattered seeds and off-types During harvest in some crops, seeds fall in the field and grow 30. in the next together the next season with a seeded plant population. Off This favors growing both in situ and on-farm season’s plant types are also included in the farming system. In rice, wheat materials together population and finger millet Manual weeding Manual weeding during flowering helps to pollinate the 31. during flowers by shaking plants. Similarly, when picking fruits, seeds Weeding and traveling during flowering flowering and in indeterminant plants may shake plants to pollinate. In maize accelerates the cross-pollination multiple and oil seed crops harvests 32. Natural Growing landraces with minimum human interferences and selection survival of the fittest applied. In cereals and grain legumes No selection during harvest and seed cleaning Parent– 33. offspring mix Growing parental lines and their offspring together in the same Farmers sometimes mix newly harvested seeds plantation field. In finger millet, sponge gourd and cucumber with the previous year’s seeds need different crops and landraces for their 34. Ethnicity Ethnic groups Diverse ethnic groups live together and may specific variety cultural and religious purposes. Based on their requirements, variety is developed and grown. In cereals have different genotypes Natural agents for Sometimes, natural factors/agents, e.g., birds, insects, wind 35. translocating and flood, transfer seeds and other planting materials from one New genotypes can be observed in the fields and planting location to another. In wild rice, amaranth and proso millet harvested together with normal plants materials Note: This table is based on the experiences of farmers, authors, and a brief interview with agrobiodiversity-rich farmers and researchers. For increasing diversity, farmers’ practices are, relatively, better than modern agri- cultural practices. When creating diversity in the fields, different multiple traits should be considered for the selection of genotypes. Trait-based selection for mixing landraces and varieties depends on the biotic and abiotic stresses (Table 2). For example, different root-length cultivars are suitable for cultivation in drought areas. However, maturity and cooking methods should be the same for all mixed landraces and varieties. In the case of the in-determinant type, maturity is not applicable for consideration. Diversity 2023, 15, x FOR PEER REVIEW 7 of 12 Diversity 2023, 15, 603 6 of 11 Table 2. Important traits for mixing cultivars (landraces and varieties) against different conditions. For Space Use (All Dimen- Table 2. Important traFitosrf oDr imseixaisneg acnudlti vInarsse(clta nPdersatsce s and vaFroiert iDesr)oauggahints t different conSditmioinlas.rity in Traits sions) For Space Use (All• DimDeinffseiroennst) root lFeonrgDthisse ase an•d InsDeicftfePreesntst reactionF coarpDarcoituiegsh t • Deep roSoitm ilarity in Traits • Different root lengatnhds textures • Different reactwionithca ipnasceictite ps ests and diseases • Erect plant/leaf and textures • Different plant heigwhitt h insec•t pesDtsifafnedrednits eleaasef sand• stemD teeexp- root • Different plant • Maturity • Different plan•t • Cooking method heDigihftferent plant• struDctiuffreeres nt leaf atnud • Maturity res • Erect plant/leafheights •and Ccaono-king method • Different plant structures stem textures • Different plant and shape • Different colors and sizes opy and time and shape • Different colors and sizes and time heights and canopy • • Milling • Milling • Different sizes and can- • A different scent, and second- • Large but few Different sizes and canopy • A different scent, and • Large but few leaves opy secondary metaarbyo lmiteestabolites leaves 5. Advantages o5f. IAndcrveaansteadgeCsr ofp IDncirveearseitdy Crop Diversity Increased diversInitcyreiansethde dfiiveeldrseitnys uinr etsheth feiehlda revnessutraens dthme ihnairmveizset santhde mriisnkimofizcerso pthe risk of crop failure due to bofathilubrieo tdicuea ntod baobtiho tbicioftaic taonrsd [a1b6i,1o7ti]c. fCarcotoprsd [iv16e,r1s7it]y. Ccroonptr dibivuetersityo cyoienltdributes to yield stability and insetacbt ialintyd apneds tinrseescits taanndc ep/estot lrersaisntcaencdeu/teolteoraancber odaude tgoe an ebtriocabda gsendeetirci vbeadse derived from from diverse gedrmivperlsaes mgesrmouprlcaessm[ 1s8o,u1r9c]e. sA [1f8e,1w9]a. dAv faenwta agdevsaanstsaogceisa taesdsowciiatthedh iwghithin htrigah- intra-varietal varietal diversitydiavrergsiitvye anrein gFivigeunr ien1 F. iJguumrel i1M. Jaurmshli M(Faigrushrei (1Filgefutr)ei s1h liegfth)l yis phoiglyhmlyo prpolhyimc orphic and as and as a result wa erehsauvlte woeb shearvvee doblseesrsvdedis eleasse dpirsesasue rperaesswureel laass waelol was vau lolnwe rvaublinlietryatboility to climate- climate-related arbeiloattiecds tarbeisosteisc. sDtruesesteos.c Dlimuea tioc cvlaimriatioc nvsaarinadtiothnes raenqdu tihreem reqnutsiroefmdeifnftesr eonf tdifferent prod- products to meeutctthse top rmefeeerte tnhcee porfefcelirentcse, othf eclmienajtos,r itthye omf afajorrmiteyr osfi nfaNrmeeprasl ignr Nowepaal agrrgoew a large num- number of cropbsepr eocfi ecrsoapn sdpetchieisr avnadr itehteieirs vaasriweteiells as wlaenldl raasc leasn.drGarcoews. iGnrgowvainrige tvieasrieotfies of the same the same crops cisroepass yis aenadsya alsnod parlsoov ipdreosvimdeusl tmipuleltibpelne ebfietnse. fiTtsh.i sThisisv iesr vyeirmy pimorptoarnttanfot rfor sustainable sustainable agricauglrtuicrualltubruasli nbeusssiensemsseasin mtaaininintaginainfugn ac tfiuonactliaognraol eacgorsoyescteomsy.sMteman. yMfarnmy efrasrmers are very are very familiafrawmitlhiart hweitahd vthaen taadgveasnotafgiensc roefa isnecdrecarsoepd dcrivoepr sdiitvyeirnsityh einfi tehlde sf.ieIlndsm. Iann my any areas, we areas, we observobedserthveadt ftahramt fearrsmgerrosw grdoiwff edriefnfetrcernotp crsoppe cspieesciteosg teotghetrhaesr aws ewllealls ams mixeixded populations populations of voafr vieatriieestiaens danladn ldanradcreasce(sF i(gFuigruer2e) 2. )S. oSmome ep prarcatcitciecesso offf afarrmmeerrssa arree giiven in Table 3, along Table 3, along wiwthitthh tehireiard avdavnatnagtaegse. sF. aFramrmeresrks ekeepepse seedesdfsr formomsu scuhchm mixiexdedp oppouplualtaiotinosnsfo fror the next sea- the next season, swohni,c whhfaicvho rfasvnoartsu nraltuserlaelc steiolenc.tiAolno.n Aglsoidngestihdies ,tthhies,y thareey raerseil riensitliteonctl itmo caltiemate and other and other enviroennmviernotnaml feancttaolr sfa[c2t0o]r,si n[c2l0u]d, iingclwudeiendgs [w21ee],dasn [d21p]e, rafonrdm p, reerlfaotrimve, lyr,elbaettitveerly, better than than other newlyotdhevr enleowpelyd dneavrerolowpegde neatrircobwa sgeevnaetrice tbieas.e varieties. Figure 1. AdvantaFgigeus raen 1d. dAidsavdavnatangteasg easndof dpiosalydmvaonrtpahgiecs aonf dpuolnyimfoorrmphciucl tainvdar us.nAiforromw csuilntidviacrast.e Arrows indicate either an increase e(uitphearr aronw in)correadseec (rueaps aer(rdooww) nora drreocwre)aisne t(hdeowtrnai tarinrocwlu)d iend thine thraeita irnroclwudbeodx .in the arrow box. DivDerisvietrys i2t0y2230,2 135, ,1 x5 ,F6O03R PEER REVIEW 7 o8f 1o1f 12 FiFgiugruer e2.2 G. Geneneetitcic ddiviveerrssiittyy iinn tthhee ffiieelldd:: ((AA)) CCrrooppm mixixtuturere(r (irciece+ +fo fxotxatial iml milleiltle+t b+r binrjianljaanl danodth oetrhs)erins) in HHumumlala ddisisttrriicctt,, ((BB)) tthhrreeees sisistetrerc rcorposp(sm (amizaei,zpeu, pmupmkipnkainnd abneda nb)eiannE)a isnt NEaespta Nl, (eCp)atlw, (oCb)e tawnola bnedarnac leasnd- raicneJsu imn lJauamndlaR aunkdu Rmudkiustmric dtsi,s(tDri)ctesv, o(lDut)i oenvaorlyutriiocenparoyp urilcaeti opnopinuJluamtioland iins tJruicmt (l5a0 driicsetrliacnt d(5ra0c reisc)e. land- races). Table 3. Farmers’ practices of mixing landraces and varieties of bean, finger millet and rice in Nepal. Table 3. Farmers’ practices of mixing landraces and varieties of bean, finger millet and rice in Ne- Crop Mixpianlg. Components Site Advantages Crop Mixing Components Site Less damageAfrdovmadnitsaegaseess ( anthracnose, Bean >20 landraces Jumla rust, leaf spot, blight, etc.), 2–3 months Less damacgoen tfirnoumou ds ihsaeravseests, (taasntythracnose, Bean >20 landraces Jumla rust, leaf spot, blight, etc.), 2–3 months con- Finger millet Dalle Kodo + Bhotyangre Kodo + Chyalthe Kodo Jugu, Dolakha High yield, good forage, fewer diseases tinu(bolausst ,hsmaruvte, sbtli,g thats)ty Finger mil- Dalle Kodo + Bhotyangre Kodo + Chyal- Jugu, High yield, good forage, fewer diseases let Rice Kali Marshi + Chandanath-1 + Chtahned Kanoadtho- 2 DJuomllaa Less damage by blast, taste remains as kha (blaslto,c saml launtd, rbalcieght) Kali Marshi + Chandanath-1 + Chan- Less damage by blast, taste remains as lo- Rice R ice Gurdi + Mansara Pame, Kaski Better even in drought condition, less danath-2 Jumla damage bycainls leacnt pdersatcsea nd diseases Rice Kalo Patle + Machhapuchhre-3 + Lekali Dhikur PoPkahmarei,, KaskiBetterN eovednam ina gderboyuagmhto ncokenyd, ihtiigohne,r lgersasi ndam- Rice Gurdi + Mansara Kaski yiaeglde, bleyss idnasmecatg pe ebsytsd iasenadse d, nisoelaosdegsi n g 1. Mana Muri + Sano Gurdhi, Dhikur 2. Kathe Dhan + Panhele, Rice R ice Kalo Patle + Machhapuchhre-3 + Lekali Pokhari, No 3. Thimaha + Anga + Mansara, Kaski L doadmginaggeto bleyra an tm, leosnskdeaym, ahgiegbhyeirn gsercatin Kaski yiel 4. Kalo Patle + Chommrong + pde, sltessasn ddadmiseaagsee sb, yta sdtyis, ehaigshe,g nraoin loydieglding 1. Mana MuMria c+h Shapnuoch Ghrue-r3dhi, 2. Kathe Dhan + PanheSloeu, r3ce. :T[1h7i].maha + Anga + Lodging tolerant, less damage by insect Rice Mansara,4. Kalo Patle + Chommrong + Kaski pests and diseases, tasty, high grain yield MachhpTuhcehhFrige-u3r e 2 depicts traditional farmers practices of growing mixtures of crops on the same piece of land (Figure 2A), such as rice, foxtail millet and brinjal (eggplant or Soauurbceer: g[1in7]e. ); the mixed cropping of maize, pumpkin, and beans in East Nepal (Figure 2B); seeds harvested from diverse beans in the Jumla and Rukum districts of Nepal (Figure 2C); andTahme fixigtuurree o2f driecpeicctosm trpaodsietdioonfaol vfaerrm50erlsa npdraracctiecsegs roofw gnroownitnhge msaimxteuprelost o(fF cigroupres 2oDn) t.he same piece of land (Figure 2A), such as rice, foxtail millet and brinjal (eggplant or auber- gine); the mixed cropping of maize, pumpkin, and beans in East Nepal (Figure 2B); seeds harvested from diverse beans in the Jumla and Rukum districts of Nepal (Figure 2C); and Diversity 2023, 15, 603 8 of 11 Mixtures are planted deliberately to avoid the complete failure of farms in case of the occurrence of biotic and abiotic stresses (Figure 1; Table 3). 6. Practices for Narrowing Diversity Farmers’ traditional knowledge and practices favor creating and maintaining both intra and inter-varietal diversity. However, as advances are made in agriculture, many practices are moving towards narrowing genetic diversity. For example, plant breeders test and evaluate only the selective genotypes in many locations and countries. Genotypes that perform well in multiple sites are promoted and integrated into the formal seed system [22]. The promotion of stable genotypes based on genotype by environmental interaction across the world leads to the narrowing of the genetic diversity in the fields. CGIAR-based materials are tested in a similar fashion. This system also includes the collection of as much diversity as possible from the fields and stores in the buildings and then the expansion of a few high-yielding varieties (uniform and monogenotype) in many areas. The recommendation of a single variety in a large area in many countries drastically replaces the many site-specific crop landraces. In many breeding institutes, a single breeder leads the breeding work and a narrow perspective dominates the breeding process. The majority of breeding work focuses on a single trait, i.e., grain yield. Neither single-led breeding work or single-trait-based breeding programs could broaden the genetic base across the locations [10]. Research and development in these institutes also focuses on only a few selected crops. Due to this, the geographical coverage of a few crops is increasing, resulting in the cultivation of narrow diversity at species and varietal levels. The dissemination method of newly developed varieties, along with incentives, also promotes narrow genetic base varieties. Farmer field trials (FFT) and minikit are very common methods adopted by many countries to disseminate varieties. The expansion of growing F1 hybrid and genetically engineered varieties is very high. All of these varieties are practically non-evolutionary and therefore cannot maintain genetic diversity in the field. Other breeding methods, e.g., pure line selection, pedigree methods, backcross, etc., also develop very narrow genetic base varieties. On the other hand, sources of planting materials are dominated by a few companies. Covering large areas with a single source of seed supplier leads to genetic erosion from the fields. In fruit species, the use of the same rootstock for large numbers of varieties, as well as clonal propagation, has also drastically reduced and narrowed down the diversity. Similarly, mechanization is another practice that triggers the growth of uniform varieties. Many breeding works also targeted the development of homogenous varieties so that mechanized farming could be possible. The policy also favors uniform and distinct varieties. The system of the distinctness, uniformity and stability (DUS) test promotes homozygous varieties rather than increasing the diversity in the fields. 7. Impact of Narrow Genetic Diversity Narrow genetic diversity is mainly due to the replacement of landraces by modern va- rieties. Modern varieties have very low intra-varietal diversity compared to landraces [23]. Selection responses in such narrow genetic diversity are almost negligible. Because of the lack of buffering capacity, these varieties are vulnerable to both biotic and abiotic stresses [15,20] and there are many cases of a complete failure of production in many crops. In addition. insect pollinators prefer to visit fields where diversity is high, both at intra- and inter-varietal levels. Ecological services from such a narrow genetic base are very poor. Very specific parts (i.e., above and below ground) are exploited all the time if the same narrow genetic base varieties are grown over time. If farmers keep seeds for the next generation themselves the performance may reduce, and with it the formal system target to increase the seed replacement rate each year. This also indicates the detachment of farmers’ rights from their age-old rights. The environment, growing conditions, and everything in the production system keeps changing. Many different types of living organisms become connected due to which agroe- Diversity 2023, 15, 603 9 of 11 cosystem and soil remain balanced and functional. The narrow genetic varieties are not evolutionary, and natural selection does not work. Nutritionally, the products from such varieties are high in carbohydrates and low in other important nutrients compared to lan- draces [24]. The narrowing of crop genetic diversity also limits plant breeding [25], genetic advancement such as marker assisted selection [26] and disease resistance enhancement in crops [27]. 8. Policy Dimension In Nepal, there are three types of seed systems, namely formal, informal and non- formal. The formal system handles released and registered varieties under the National Seed Board. An informal seed system ensures the exchange and transfer of very diverse and heterozygous landraces generation after generation, which means it is a carrier of genetic diversity. However, for the integration of any variety into a formal system, it has to be uniform and homozygous as per the existing seed regulation, which highly discourages cultivar mixture and landrace diversity. A formal seed system is the utmost for the commercial production and marketing of any crop varieties and landraces. Any type of genetic variation at species and varietal levels is not favored by the existing seed policy. Incentives are also not provided for non-registered landraces and cultivar mixtures. In the formal seed system, farmers are mostly excluded to multiply seeds of some seed classes, e.g., breeder seeds and foundation seeds, due to requirements of universities degrees and well-managed seed processing infrastructures. This also discourages farmers from continuously engaging in seed sectors, especially for maintaining on-farm diversity. This is also a situation detaching farmers’ rights from farmers and increasing their dependency on other agencies for seeds and other inputs. There is also a debate on treating landraces either as public or private goods for farmers, but many private companies and institutes handle varieties as private goods. Still, many farmers have very unique landraces with high genetic variation; therefore, policies should favor the promotion and maintenance of genetic variation at field level, and landraces should be private goods. 9. Conclusions Genetic diversity in the fields has been decreasing since the Green Revolution. Crop diversity is stored statically in confined areas called genebanks, whereas uniform and homozygotic varieties are increasingly covering the farming areas. Globalizing the crop genetic resources and then favoring widely adapted varieties across the world has resulted in a very narrow genetic base in formally developed crop varieties. However, genetic diversity is most important for securing crop harvests even under adverse climatic and biotic stresses. Many farmers and agriculturists are now increasingly realizing the necessity of maintaining genetic diversity in the fields. Many different approaches have therefore been developed, restarted and applied in major crop species, e.g., rice, wheat, barley, bean, finger millet, etc. As the diversity increased in the fields, their evolutionary rate also enhanced to where better genotypes could be produced and selected for the next generation. Some approaches are also very effective to help farmers to save seeds from their own fields for next season’s planting. Ecological and evolutionary approaches should be considered worldwide for every crop species to increase the diversity in the fields. Author Contributions: Conceptualization, B.K.J.; methodology, B.K.J., S.P.N. and D.G.; validation, D.K.M., B.K.J. and D.G.; investigation, B.K.J. and S.P.N.; resources, D.K.M. and B.K.J.; writing—original draft preparation, B.K.J.; writing—review and editing, S.P.N., K.H.G., D.G. and D.K.M.; visualization, B.K.J.; project administration, B.K.J., S.P.N. and K.H.G.; funding acquisition, D.K.M. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the International Fund for Agricultural Development (IFAD), grant number 2000001629, through the projet, EPB-IFAD and The APC was funded by EPB-IFAD project. Institutional Review Board Statement: Not applicable. Diversity 2023, 15, 603 10 of 11 Data Availability Statement: Not applicable. Acknowledgments: This is an output of the IFAD project, Use of Genetic Diversity and Evolutionary Plant Breeding for Enhanced Farmer Resilience to Climate Change, Sustainable Crop Productivity and Nutrition under Rainfed Conditions, A1341. We acknowledged Bioversity International and IFAD for financial and technical support. Farmers and breeders from across the country were highly acknowledged for providing information. We thank NARC, LI-BIRD and MoALD for creating a favorable environment and supporting some activities. The contributions of workshop participants are highly appreciated. Conflicts of Interest: The authors declare no conflict of interest. References 1. Fadda, C. The Farmer’s Role in Creating New Genetic Diversity. In Farmers’ Crop Varieties and Farmers’ Rights: Challenges in Taxonomy and Law; Halewood, M., Ed.; Routledge: London, UK, 2016; pp. 43–55. 2. Joshi, B.K. 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