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1.
Farmer participation is increasingly seen as a key to develop technologies which are more relevant to farmers' communities. In plant breeding, farmer participation is seen as key to increase the probability of adoption of new varieties. This paper addresses the issue of selection efficiency in participatory plant breeding by testing the effect of selection environment and of who did the selection in one cropping season (1997) on the performance of the selected lines in the following cropping season (1998). Selection environment had a larger effect on response to selection than who did the selection, confirming the importance of decentralized selection. Selections made by the breeder and the farmers in 1997, differed in 1998 for a number of traits, but seldom for grain yield. When the difference for grain yield was significant, breeder's selection was more effective on station, while farmers' selection was more effective in farmers' fields. The results of this study indicate that it is possible to organize a plant breeding program with the objective of adapting crops to a multitude of both physical and socio-economic environments: such a breeding program will, at the same time, increase productivity and stability, enhance biodiversity and produce environmentally friendly cultivars. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
This paper describes how plant breeders and farmers worked together to produce improved varieties of maize for the low-resource farmers of the Panchmahals district of Gujarat, India. Initially, farmers tested a range of maize varieties in a participatory varietal selection (PVS) programme. However, none of these proved to be very popular with farmers, although farmers who had more fertile fields adopted the variety Shweta from Uttar Pradesh. Hence, in 1994 a participatory plant breeding (PPB)programme was begun to generate new, more appropriate varieties. Yellow- and white-endospermed maize varieties were crossed that had been either adopted to some extent following PVS or had attributes, such as very early maturity,that farmers had said were desirable. In subsequent generations, the population was improved by mass selection for traits identified by farmers. In some generations,farmers did this in populations which were grown by breeders on land rented from a farmer. Soil fertility management was lower than that normally used on the research-station. The breeding programme produced several varieties that have performed well in research-station and on-farm trials. One of them, GDRM-187, has been officially released as GM-6 for cultivation in hill areas of Gujarat state,India. It yielded 18% more than the local control in research-station trials, while being seven days earlier to silk. In farmers' fields, where average yields were lower, the yield advantage was 28% and farmers perceived GDRM-187 to have better grain quality than local landraces. PPB produced a variety that was earlier to mature than any of those produced by conventional maize breeding, and took fewer years to do so. The returns from PPB,compared to conventional breeding, are higher because it is cheaper and benefits to farmers are realised earlier. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

3.
The paper describes experiments on farmer participation in plant breeding conducted in three countries (Morocco, Syria and Tunisia) on barley, which is the predominant annual rainfed crop in the most marginal areas of these countries. Trials with different types and number of breeding material were planted both on research stations and in farmers' fields. Selection was done by professional breeders and farmers and data were gathered on breeders' and farmers' selection criteria and selection efficiency. The trials reflected the situation of the crop in the three countries, with high yields on station, low yields in some of the most marginal farmers' fields, and poor correlations between research stations and farmers' fields, as well as between farmers' fields. Grain yield was by far the most commonly used selection criterion by the farmers. However, farmers also made a widespread use of selection criteria not normally used by breeders such as grain filling and straw yield, as well as other characteristics of the straw (color) and of the leaves because of the importance of the crop as source of animal feed. A major difference between the selection criteria used by breeders and farmers was disease resistance, almost entirely neglected by the latter. Farmer selection was effective in identifying some of the highest yielding lines in the farmers' own fields and also in those cases where they performed selection on station. The coincidence between entries selected by the breeder and the farmers was high in Morocco but very low in Syria and Tunisia. There were substantial differences between the lines selected by the breeders on station and those selected by farmers in their fields. In Syria, decentralized-participatory selection was significantly more efficient in identifying the highest yielding entries in farmers' fields than any other selection strategy. This work demonstrates that it is possible to organize a plant breeding program so that farmers become major actors in the selection of new cultivars. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

4.
Formal plant breeders could contribute much to collaboration with farmers for improving crop varieties for local use. To do so outside researchers must have some understanding of local selection practices and their impact on crop populations in terms of the genetic theory underlying plant breeding. In this research we integrated methods from social and biological sciences to better understand selection and its consequences from farmers' perspectives but based on the concepts used by plant breeders. Among the households we worked with, farmers' selection practices were not always effective yet they understood the reasons for this and had no expectations for response to selection in some traits given the methods available to them. Farmers' statements, practices and genetic perceptions regarding selection and the genetic response of their maize populations to their selection indicate selection objectives different than may be typically assumed, suggesting a role for plant breeder collaboration with farmers. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

5.
Despite the presence of large numbers of improved maize cultivars, farmers in the Hararghe highlands of eastern Ethiopia persistently grow local cultivars and are not benefiting from the varietal improvement program. By growing local cultivars farmers obtain an average yield of 1.2 t -1 whereas research has released cultivars yielding 5–11 t -1under on-station conditions. Recognizing this and the important role maize is playing in the livelihood system of farmers in eastern Ethiopia; Participatory Varietal Selection (PVS) was conducted for three consecutive seasons (1996–1998) in three locations. The objectives of the study were to identify farmers' cultivar selection criteria for future breeding, to enable farmers to assess the performance of improved cultivars under their management, to increase farmers' access to the cultivars of their preference by injecting source seed into the local seed system, and to investigate whether breeding for wide adaptation like for the Hararghe highlands has any drawbacks or not. The study indicated farmers' maize varietal selection criteria together with the differences in selection criteria across locations classified under the same adaptation zone. Though farmers selected some of the many improved cultivars tested, no improved cultivar had all the characteristics, which farmers want in a single cultivar. To be able to combine cultivar selection traits farmers considered cultivar combinations in all locations, but not the single `best' cultivar. Despite the yield advantage of hybrids, farmers selected Open Pollinated Varieties (OPVs) because they had more preferred traits. Farmers also preferred to retain their local cultivars despite their lower yield compared to most of the improved cultivars. Both situations confirmed how resource poor farmers' cultivar requirements are much more diverse than yield per se. Gender and social group-driven difference in cultivar preference was also observed. The study revealed the need for proper zoning of the Hararghe highlands as a prerequisite to developing better adapted maize cultivars to the varied agro ecological and socioeconomic niches. As shown in this study, proper zoning, due consideration to farmers' relevant selection traits and wider use of participatory approaches should be adapted to develop cultivars which can gain farmers acceptance. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

6.
We describe a participatory plant breeding (PPB) programme in rice for the rainfed uplands of eastern India. Collaborative participation (farmers grew and selected in segregating materials in their fields) and consultative participation (farmers selected among progenies in researchers' plots) were used. The PPB was started with only two crosses and, of these, Kalinga III/IR64 was the most successful and produced two released varieties: Ashoka 200F from collaborative breeding and Ashoka 228 from consultative breeding. Both yielded significantly more than control varieties, including Kalinga III, in research trials and in participatory trials in farmers' fields. Qualitative data from participatory trials was highly informative, statistically analysable, and cheaper to obtain than quantitative data. In low-yielding research-station and on-farm trials the two new upland varieties showed no significant genotype × environment interaction with the check varieties. However, in higher-yielding All India Coordinated Rice Improvement Project trials, both varieties were more adapted to low yielding environments than the national check variety. Farmers liked the varieties for their early maturity, improved lodging resistance, higher fodder and grain yield, long-slender grains and excellent cooking quality. Before certified seed production, farmer groups have produced large quantities of seed that have spread widely through informal channels. The returns from PPB, compared to conventional breeding, were higher because it cost less, the genetic gains per year were higher, and the benefits to farmers were realised earlier. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

7.
D. Louette  M. Smale 《Euphytica》2000,113(1):25-41
Experimental results and farmer surveys from a Mexican community located in the buffer zone of a biosphere reserve indicate that farmers' seed selection practices protect the phenological integrity of their traditional maize varieties as they define them, despite numerous factors contributing to genetic instability. Analysis of morphological and genetic data suggests that when subjected to significant gene flow through cross-pollination, ear characteristics are maintained through farmers' selection even though other characteristics may continue to evolve. Because the effects of farmers' selection practices are confined largely to ear characteristics, their practices appear to offer only limited scope for variety improvement. Farmers' expectations of what they can achieve through seed selection are similarly limited. These findings suggest complementary roles for professional breeders and Mexican farmers in enhancing mass selection methods to improve maize landraces on farms – if farmers themselves perceive benefits from the collaboration. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

8.
Summary As organic farming refrains from high and chemical inputs it needs varieties better adapted to organic conditions to improve the yield stability and quality of crops. In order to make genebank accessions more accessible for the utilisation in organic breeding programmes, a participatory research project with farmers was carried out in 2002 and 2003. From the Dutch genebank collection 37 onion accessions, divided into five different groups (according to their market use), were selected and planted at a commercial organic farm. Farmer participation in characterisation and evaluation of the material resulted in including additional plant traits for genebank characterisation as well as new selection criteria for breeding. It also provided researchers insight into how organic farmers evaluate and value certain plant traits. Variation for important properties was found within and between the five groups. To establish base populations, the farmers, in collaboration with the researchers, selected the best genotypes within the five groups of onion accessions. The new base populations may be exploited in order to achieve better-adapted material for organic farming systems.  相似文献   

9.
The cost of participatory barley breeding   总被引:2,自引:0,他引:2  
Farmer participation in agricultural research is increasingly seen as a powerful methodology to increase the relevance of technologies developed to benefit farmers' communities. In plant breeding, farmer participation is considered as a way to increase the probability of adoption of new varieties. However, the higher expected cost of participatory plant breeding (PPB) is seen as one of the main obstacles to its wider adoption.This paper addresses the issue of the different costs to an Institution of running a PPB program or a non-participatory program and uses the barley-breeding program at the International Center for Agricultural Research in the Dry Areas (ICARDA) as a case study.Observations and data collection were carried out during one full cropping season on the cost of the three main components of the breeding program, i.e. the management of the field trials (land and seedbed preparation, planting, fertilizer application, weed control, harvesting, and seed threshing, cleaning, treating and packaging), the travel to farmers' fields or to the research sites, and the human resources (scientists, technical staff, local workers and farmers) involved in breeding activities.We compared two options for the centralized–non-participatory breeding program, differing in the number of sites (8 and 16) used for the on-farm trials, with 160 options for the decentralized-participatory breeding program, differing in the combination of number of sites (from 4 to 16) and number of trials per site (from 1 to 10).The results show that in both decentralized-participatory and centralized–non-participatory plant breeding the cost of managing the field trials is the highest followed by the cost of human resources and that of travel: the contribution of each component to the total cost varies with the various options and the various combinations of the number of sites and of farmers.The comparison of the aggregated costs indicates that in the case of the ICARDA' barley-breeding program there are no relevant differences between the participatory and the non-participatory plant breeding programs. This is largely associated with the fact that the decentralized-participatory breeding program reaches the same level of development of the breeding material 3 years earlier than the centralized–non-participatory breeding program. Depending on the type of centralized-breeding program and on the combination of number of sites and number of farmers per site in the participatory program, the aggregated costs of the participatory program are lower than those of the centralized-breeding program by between 5 and 28%. At the same level of cost of the centralized program, the model of participatory program used in this study generates more information due to the use of more trials at each site. This improves selection efficiency and provides an analytical tool to optimize the number of sites and of farmers per site.  相似文献   

10.
It is widely recognized that conventional plant breeding has been more beneficial to farmers in high-potential environments or those who can profitably modify their environment to suit new cultivars, than to the poorest farmers who cannot afford to modify their environment through the application of additional inputs and cannot risk the replacement of their traditional, well known and reliable varieties. As a consequence, low yields, crop failures, malnutrition, famine, and eventually poverty still affect a large proportion of humanity. Participatory plant breeding (PPB) is seen by several scientists as a way to overcome the limitations of conventional breeding by offering farmers the possibility to choose, in their own environment, which varieties suit better their needs and conditions. PPB exploits the potential gains of breeding for specific adaptation through decentralized selection, defined as selection in the target environment, and is the ultimate conceptual consequence of a positive interpretation of genotype × environment interactions. The paper describes a model of PPB developed by The International Center for Agricultural Research in the Dry Areas and used successfully in several countries in West Asia and North Africa. Genetic variability is generated by breeders, selection is conducted jointly by breeders, farmers, and extension specialists in a number of target environments, and the best selections are used in further cycles of recombination and selection. Technically, the process is similar to conventional breeding, with three main differences. Testing and selection take place on-farm rather than on-station, key decisions are taken jointly by farmers and the breeder, and the process can be independently implemented at a large number of locations. The model also incorporates seed production. Farmers handle the initial phases, multiplying promising breeding material in village-based seed production systems. The PPB model is flexible; it can generate populations, pure lines, and eventually mixtures of pure lines in self-pollinated crops; as well as hybrids, populations, and synthetics in cross-pollinated crops. PPB has several advantages. New varieties reach the release phase much faster than in conventional breeding, and are better suited to farmers’ needs and willingness to invest in inputs and management. Release and seed multiplication activities concentrate on varieties known to be farmer-acceptable. These advantages are particularly relevant to developing countries where large investments in plant breeding have not yielded returns, and many “improved” varieties developed through conventional breeding are not adopted by farmers. PPB also ensures that biodiversity is maintained or increased because different varieties are selected at different locations. In addition to the economical benefits, participatory research has a number of psychological, moral, and ethical benefits, which are the consequence of a progressive empowerment of the farmers’ communities; these benefits affect sectors of their life beyond the agricultural aspects. In conclusion, PPB, as a case of demand driven research, gives voice to farmers, including those who have been traditionally the most marginalized such as the women, and elevates local knowledge to the role of science.  相似文献   

11.
A number of breeding institutions developed a project to assess importance of participatory plant breeding approaches for rainfed rice improvement in eastern India. The results of the first two years of participatory varietal selection are reported here. The objective was to evaluate the respective effects of participation of farmers in varietal evaluation and decentralization of varietal testing from breeding stations to farmers' fields on varietal ranking. Fields representing various hydrological situations were chosen in two to three villages at four rainfed lowland sites and one upland site. Sets of 15 to 25 varieties were tested both in farmers' fields and on-station in 1997 and 1998 and ranked by both farmers and breeders. The effect of participation was judged by comparing the rankings attributed by farmers and breeders to a given set of material in a given trial. The effect of decentralization was determined through comparisons between individual breeders' rankings across trials. Farmers' rankings were not randomly allocated, but agreement within the farmers' group was not always very strong. Except at one site, concordance among breeders' ranking was high, but, because of the limited number of breeders involved, it was seldom significant. In about two-thirds of the trials, there was a good agreement between farmers' and breeders' mean rankings. The consensus was particularly strong when severe constraints induced contrasting behavior in the genotypes. The decentralization effect appeared to be moderate, but variations due to a breeder effect were recorded. The part of genotype by environment interactions for grain yield due to location within one site and year was evaluated through various methods, showing more effect of G × E interactions at some sites than at others. Crossover interactions inducing changes in ranks represented a limited part of the yearly G × E interactions at all sites. Both farmer participation and decentralization of varietal testing in farmers' field would help in best matching the varieties to the needs, although their combined contribution would be more useful in some sites than in others. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

12.
Linking participatory plant breeding to the seed supply system   总被引:1,自引:0,他引:1  
There is a strong link between formal plant breeding and seed supply. In developed countries, it was the emergence of systematic plant breeding that generated new named varieties and stimulated organized seed multiplication and marketing by commercial companies. In developing countries likewise, the experience of the ‘Green Revolution’ in the 1960’s led to the establishment in the following decade of national seed projects which could deliver the products of plant breeding more effectively from breeder to farmer. The provision of a secure conduit leading from research to agriculture remains a major justification for formal seed systems. The limitations of formal breeding approaches have been recognized in recent years, especially for crops grown in marginal and diverse environments, where farmers’ requirements are more complex. This has prompted interest in alternative participatory plant breeding strategies in which farmers can play an active role in the selection process. There has been a parallel recognition of the role of the informal seed sector, as the major seed supplier in many crops and areas where the regular sale of seed by formal organizations is difficult. The question which arise therefore is—“How do participatory breeding approaches relate to both formal and informal seed systems?” The purpose of this paper is to examine the technical, regulatory and policy aspects of this question, with emphasis on the following issues:
  • The nature and definition of participatory plant breeding (PPB) outputs,
  • Maintaining the identity and integrity of PPB outputs
  • The relevance of official variety evaluation and registration procedures
  • Maximizing the diffusion and impact of PPB outputs
  • Innovative seed supply systems linked to PPB activities
  • The role of policy in facilitating alternative seed delivery systems
The synthesis of this discussion is that PPB initiatives must be linked to a secure diffusion strategy within and beyond the participating communities if the technical and social benefits of this approach are to be fully realized. National policies relating to seeds and regulatory frameworks must also take account of this approach to avoid downstream constraints.  相似文献   

13.
Genetic improvement of soybean varieties released in India from 1969 to 1993   总被引:11,自引:0,他引:11  
Summary Soybean is an important oilseed crop in India and varieties with high yield potential are being developed since 1969. This study was conducted to assess the impact of breeding on yield and plant characteristics during the last 25 years. A 3-year field experiment was conducted to evaluate forty three soybean varieties belonging to two different selection cycles and representing most of the varieties developed in the domestic breeding programme of India from 1969 to 1993. Varieties resulting from selection cycle 1 showed 4 times higher seed yield and harvest index as compared to the farm traditional variety Kalitur. This yield increase was due to an increase in biomass, pods plant–1, mean seed weight and longer seed filling duration, but a reduced plant height and improved lodging tolerance, less seeds pod–1 and early flowering and maturity dates. The varieties of selection cycle 2 showed 19% higher seed yields and 16% increase in harvest index over selection cycle 1 accompanied by longer seed filling duration, more seeds pod–1 and reduced plant height. The annual genetic gain in seed yield of soybean varieties released in India from 1969 to 1993 was approximately 22 kg ha–1.  相似文献   

14.
Two generations of recurrent phenotypic selection for seed yield per plant under controlled pollination were carried out to combine improved seed yield with improved forage grass performance in perennial ryegrass (Lolium perenne L.). Selected and unselected varieties (AberDartand AberElan respectively) and control varieties were grown for seed in pots in a glasshouse experiment and in two field plot experiments over 5 harvest years. Seed yield components and seed yield were measured. Significant improvements in seed yield of the selected AberDart over the unselected AberElan were observed both in individual plants grown in the glasshouse and in field plots. Detailed observations of the individual components of seed yield showed that the increased seed yield of AberDart can be attributed to a higher proportion of ovules forming seeds (% seedset), greater seed number per tiller and more reproductive tillers per plant. This improvement in seed yield of AberDart was also observed when it was grown in field plots with AberElan, experimental selection lines and commercial varieties. AberDart produced more seeds per tiller than the other commercial varieties and selection lines studied. The implication of this approach for the breeding of perennial ryegrass varieties that combine good agronomic performance and acceptable seed yields is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

15.
Rice is an important staple food and cash crop. Although many varieties of rice have been developed to date, few are adopted possibly because researchers did not take into account farmers’ preferences and perceptions on varieties during the development process. Because farmers increasingly rely on low-yielding landraces, production fails to meet demand. To provide an understanding of farmers’ preferences for rice cultivars and perceptions on drought stress and management practices as inputs to rice breeding research, this study was conducted in the Sikasso region of Mali in September 2005 using participatory rural appraisal approach. A total number of 125 farmers were randomly selected from 10 villages in three ecologies and interviewed individually and in groups. Results showed that farmers’ preferences, crop management practices and ranking of production constraints differed significantly across ecologies. Whereas farmers in the irrigated ecologies preferred high-yielding, long duration rice varieties, those in the upland and lowland ecologies preferred tall plants of short duration. While upland and lowland farmers preferred red and white long grains, respectively, irrigated ecologies were indifferent about grain colour. Farmers appeared willing to trade-off yield for grain quality and plant height, inconsistent with traditional breeders’ selection criteria. The high preference for tall varieties among farmers in the upland and lowland ecologies also contrasted sharply with the model of dwarf rice varieties responsible for the green revolution in Asia. The implication of these findings for rice breeders is that different plant idiotypes complemented by effective drought management practices should target different ecologies to increase impact.  相似文献   

16.
The exchange of elite breeding materials across regions is an important way in which multinational maize breeding programmes access new genetic variation, improve efficiency and reduce costs. Our objectives were to examine whether CIMMYT's breeding programmes for tropical and subtropical environments in Mexico and Eastern and Southern Africa (ESA) can effectively share materials. Sets of selected and unselected lines were evaluated for per se and testcross performance in multiple environments in Mexico and ESA for grain yield, days to anthesis and plant height. Genotypic correlations between performance in Mexico and ESA as testcross and line per se were high (≥ 0.72) for all experiments, and indirect selection efficiency ranged from 67 to over 100% for all traits. Lines selected in ESA or Latin America performed equally well in each region, indicating selection was for broad rather than regional adaptation. Thus, breeding programmes of CIMMYT in both Mexico and ESA can benefit tremendously by exchanging breeding materials and test results, and elite selections from each region should be fast‐tracked for evaluation in the other.  相似文献   

17.
Summary A participatory breeding programme involving farmers in two Ghanaian communities and scientists from CRI (Ghana) and NRI (UK) to develop superior cassava cultivars is described. Initial situation analyses of the communities indicated that cassava is increasing in importance both as a food and a cash crop. Most farmers utilised landraces of cassava; modern varieties were scarcely mentioned. Seeds of 16 half-sib families obtained from a crossing block in Nigeria at the International Institute of Tropical Agriculture were planted in a field in each community. During seedling and subsequent clonal generations, accessions selected either by farmers or scientists were retained to the next generation. This selection process has identified 29 superior accessions from amongst 1350 original seedlings. Farmers were relatively consistent in their selection from year to year and their selections corresponded with their stated criteria. Official variety release requires additional multilocational and inspection trials and postharvest assays but otherwise seems harmonious with a participatory breeding approach; our early involvement of farmers may facilitate early release, an important factor in cost-effectiveness. A stakeholder workshop confirmed the need for improved markets for cassava; surveys of current and potential markets have led to field trials with cassava processors. Adoption of a participatory approach, with farmers and scientists taking on new roles and decentralisation of activities, implies a concomitant transfer of influence and resources.  相似文献   

18.
Formal public sector soybean breeding in Africa spans over four decades, and it was initiated by the International Institute of Tropical Agricultural (IITA). As the demand of soybean continues to outstrip production, strategic projects such the Tropical Legume (TL) were initiated, in which the main goal was to enhance the productivity of soybean in the farmers’ fields in Sub‐Saharan Africa. One of the strategies to enhance the productivity of soybean in the farmers’ fields is through developing and deploying improved soybean varieties in the target countries. Through the TL I and TL II projects, a number of varieties were released in the target countries, Kenya, Nigeria, Malawi and Mozambique by employing participatory variety selection (PVS). This review provides highlights of the achievements made by IITA breeding programme and insights of what needs to be done to enhance yield improvement for soybean in Africa using demand‐driven breeding approaches.  相似文献   

19.
Summary Field trials were carried out in Ecuador with two indigenous communities, Ninín Cachipata and La Esperanza, to determine farmers’ preferences for quinoa (Chenopodium quinoa Willd.) cultivars and to improve PPB processes. More women than men participated, reflecting that quinoa, a primarily subsistence crop, is mainly managed by women. Farmers’ field selection criteria for quinoa in the field were mostly based on yield, earliness and plant colour; however only breeders’ measurements of yield and panicle height significantly correlated to farmer selection scores. Older women gave higher scores than younger women or men, apparently due to a concept of no cultivar being without value. Working in same gender pairs improved evaluation richness. INIAP technicians were more discriminating in their evaluations than farmers. They also used additional selection criteria of disease resistance and uniformity. At seed selection, farmers from Ninín Cachipata, where food security is not assured, chose lines based on yield, while farmers from La Esperanza, where resources are less limiting, also considered seed size, colour, saponin content and marketability. Field characteristics were not taken into consideration at seed selection, signifying that farmers are less interested in those characteristics, or that it was difficult for them to correlate field data when presented in tabular form with seed characteristics. Future trials with small farmers should have fewer lines or replications to avoid farmer fatigue during evaluation. Farmers who grow primarily for subsistence in semi-arid environments have more interest in growing quinoa, and more to gain from having improved cultivars; therefore future participatory efforts should focus on them.  相似文献   

20.
Heterogeneous environments make it difficult to apply consistent selection pressure because often it is difficult to identify a single or a few superior genotypes across all sets of conditions. However, when the target system is characterized by heterogeneity of environmental stress, varieties developed in high-yielding conditions may fail to satisfy farmers’ needs. Although this type of system is often found in marginal environments of developing countries, heterogeneous environmental conditions are also a feature of organic and low-external-input systems in developed countries. To meet the needs of these systems, breeding programs must decentralize selection, and although decentralized selection can be done in formal breeding programs, it is more efficient to involve farmers in the selection and testing of early generation materials. Breeding within these target systems is challenging, both genetically and logistically, but can identify varieties that are adapted to farming systems in marginal environments or that use very few external inputs. A great deal has been published in recent years on the need for local adaptation and participatory plant breeding; this article reviews and synthesizes that literature.  相似文献   

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