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1.
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
2.
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
3.
Maize is a staple food crop in many developing countries. However, if seven major maize producing countries are excluded from
this group, data indicate that only 34% of the maize area is planted with improved seed despite considerable effort invested
in maize breeding. This has led researchers to investigate other options, such as farmer-participatory plant breeding, for
delivering the benefits of plant breeding knowledge and technology to farmers in developing countries. This paper describes
short-term results from participatory maize breeding studies in Mexico and Honduras. Results from three selection cycles in
Mexico suggest that stratified mass selection without pollination control, with selections carried out by researchers in farmers'
fields, may be effective at improving yield in farmers' local varieties. In Honduras, mass selection with pollination control,
where selections were done by collaborating farmers in their own fields on their own varieties, showed trends (non-significant)
towards yield improvement. Farmer selection seemed to offer the greatest yield benefit over experiment station selection on
the farm with the lowest yield potential, suggesting that farmer-participatory approaches may be most advantageous in marginal
environments where experiment station conditions differ most dramatically from farmers' conditions. These studies highlighted
the importance of seed systems knowledge in designing participatory plant breeding programs. For cross-pollinated crops, they
also highlighted the need to balance progress from selection and demands on farmers' time and labor in choosing breeding methods.
Further work is needed to investigate farmer-participatory breeding approaches that can address post-harvest traits.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
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
5.
Summary Changes in the weed flora of agro-ecosystems can occur as long-term changes or temporary fluctuations in species composition.
The rate at which weed population shifts occur depends on the selection pressure imposed, genetic variability among weed populations,
plant characteristics and environmental factors. Agronomic practices associated with cropping systems including crop rotation,
tillage, herbicide use, soil amendments, and mechanization of harvesting that impart a range of selection pressures on weed
populations are discussed in this review. Widespread use of herbicides has had the greatest impact on weed selection in recent
years. Evolution of herbicide resistant weeds presents an enormous challenge to farmers. Development of herbicide tolerant
crops has provided another tool for farmers however the selection pressure on weeds and potential impact on weed population
shifts will require judicious use of this technology. Simulation models provide an excellent opportunity to predict future
weed population shifts in response to management practices. Further insight into future management changes on weed selection
must proceed towards an investigation of the processes rather than the outcomes. In particular, this must involve an understanding
of the ecological factors and processes that are likely to determine the weed responses to particular management regimes. 相似文献
6.
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
7.
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
8.
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
9.
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
10.
Summary Individual plant selection for yield in lentil is problematic at a commercial crop density primarily because of inter-plant entanglement by tendrils. Visual plant selection for yield was compared with random selection in the F 5 at three plant densities (66, 133 and 200 seeds/m 2) by an evaluation of F 7 progeny yields over two seasons in two populations of lentil. Random plant sampling was as effective as visual plant selection in isolating high-yielding F 7 lines. The plant density of the selection environment did not affect the response to selection. The correlations between the seed number of selected F 5 plants and the mean yield of their F 7 progenies were r=+–0.26 and –0.06 in two populations, indicating the lack of positive response to plant selection for seed number. The results show that 1) random sampling is the most economic of the methods tested of plant selection for yield and 2) the plant density of the environment for plant selection can be low enough to avoid inter-plant entanglement by tendrils, allowing a focus in plant selection on characters, other than yield, of importance to the breeding program and with a higher heritability than yield. 相似文献
11.
Summary The effects of bulk breeding on yield and its components in two high-yeilding and two low-yielding bean populations when grown at crop densities are interpreted in terms of gene action and selection. There was considerable additive variation in the crosses, dominance effects were variable but tended to be negative. The results were compared with results obtained at low density by another worker with the same populations, and this showed that interpretations of gene action in hybrid vigour depend on the test environment used. The interpretations were also compared with plant breeding interpretations made on the same material ( Hamblin, 1977), and it was found that a single pattern of response to natural selection, in plant breeding terms, may be explained by more than one genetic interpretation and, conversely, a single genetic interpretation may result in different patterns of response in plant breeding terms. The value of composite crosses in plant breeding are discussed and it is concluded that there is a greater chance of producing improved lines from a large number of simple crosses than from a smaller number of composite crosses. 相似文献
12.
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
13.
Changes in allele type, allele frequency and genetic diversity because of selection by individual farmers and breeders were assessed using simple sequence repeats (SSRs) during one cycle of selection in a decentralized participatory barley breeding programme. Selection by both breeders and farmers resulted in the loss of a number of alleles in the majority of the locations, with more alleles lost in the heterogeneous breeding materials than in the fixed genotypes, indicating selection against undesirable traits uncovered in the heterogeneous breeding materials that are presumably linked to SSR alleles. After selection, significant allelic frequency changes were observed at several loci in both the germplasm groups. As the selection was conducted independently in each location, an allele had a chance of being selected in more than one location, and therefore considering the whole study area the allelic composition and diversity of the original genetic materials was maintained after the selection. The study showed the importance of decentralized participatory plant breeding in maintaining genetic diversity that helps stabilize and sustain production in unpredictable production conditions. 相似文献
14.
In the Andean region, the Preduza project and its partners combined breeding for durable disease resistance using locally
adapted cultivars and farmer participatory methods. The approach taken resembles participatory variety selection (PVS). Farmers
participated in the selection of advanced materials, rather than finished cultivars. This paper describes this approach and
reports experiences with farmers–breeders collaboration.
As breeders involved farmers as participants, they learned more about the most important criteria of male and female farmers
for preferred cultivars in the marginal environments of Andean cropping systems. This approach encouraged the use of locally
adapted cultivars (often landraces), made the breeders less dependent on foreign materials, and has resulted in selection
and development of new wheat, barley, common bean, quinoa, potato and maize cultivars.
Breeding programmes based on crossing locally adapted cultivars followed by selection by the breeders in the early phases
of the breeding programmes and by participatory selection with the farmers in the more advanced stages of the breeding programmes
appeared successful. It became clear that breeders must be well acquainted with the farmer preferences such as the requirements
for specific agronomic, storage, processing and marketing traits.
Over a period of five years the centralized formal breeding approach predominantly based on material produced by the international
institutes was replaced by decentralized breeding approaches based largely on local germplasm with extensive farmer participation. 相似文献
15.
Although the effect of local adaptation is well documented in evolutionary biology, few studies have quantified the impact of local adaptation in plant breeding. Decentralized plant breeding programs have the potential to harness local adaptation for crop improvement, but the effectiveness of such models is understudied. We quantified the ability of a decentralized participatory plant breeding program to improve Weed-competitive ability (WCA) in organic spring wheat. After four farmers in the northeast United States selected wheat populations for WCA and its correlated trait of early vigor, we tracked gains in selection and local adaptation. On average, farmers enhanced competitive ability of selected genotypes by 11.46%. Measured gains from selection for early vigor and early canopy cover, however, varied among testing environments. Gains in selection were highly related to the genetic correlation coefficient between selection and testing environment (r?=?0.77 and r?=?0.80 for early vigor and canopy cover, respectively). To accurately measure gains from selection for decentralized breeding programs, testing environments should be chosen that are similar to where selection took place. Inconsistent weed competition among site-years limited conclusions from the analysis of local adaptation for weed competitive ability. Detecting local adaptation in plant breeding, which typically uses a small number of selection cycles compared to evolutionary biology, likely requires many genotypes, environments, and years for adequate statistical power. The ecological complexity of weed competitive ability further complicates experimental design and challenges the ability to measure local adaption. 相似文献
16.
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
17.
The Generation Challenge Programme is a research and capacity building network that uses plant genetic diversity, advanced genomic science, and comparative biology to develop tools and technologies that enable plant breeders in the developing world to produce better crop varieties for resource-poor farmers. 相似文献
18.
This study compares genebank-conserved and farmer managed populations of the same farmers' varieties of rice. Seven varieties
that had been collected twice, in the early 1980s and in 1991, were recollected in 1997 after having been grown continuously
in farmers' fields. Since the first genebank collection, rice cultivation in the Meking delta has been intensified with a
rather abrupt switch from single to double cropping, more use of chemical fertilisers, improved water management, and more
market oriented production. Many farmers' varieties have been maintained as a second crop but with a considerably delayed
planting time compared to previous practice. In this experiment, the ex situ materials represent adaptation to pre-intensification conditions while the in situ populations have been exposed to the intensive production system for a number of years. The materials were tested in the
wet season of 1997 under current farmers' management practices in an on-farm field experiment within the area where the varieties
originated. Agronomic, stress resistance and morphological traits and variation at 7 isozyme loci were observed in the field
or laboratory. Analysis of variance (ANOVA) and Principal Component Analyses (PCA) were used to study differences in agronomic
and morphological traits between ex and in situ populations. Isozyme variation was analyzed by Nei's diversity indices and Wright's F-statistics. Farmer-managed populations
showed a general trend of later flowering and maturity time, more uniformity of grain quality, lower frequency of undesired
off-types, and reduced drought stress tolerance compared with corresponding ex situ populations. There were no significant differences in grain yield or tolerance to biotic stresses. Allelic frequencies of
isozymes showed no consistent differences that could be related to changes of the farming system. These results are interpreted
as an adaptation to the changed farming system and include natural and farmers' selection for maturity time (all varieties
are photoperiodic)and market standards. The poorer drought tolerance may reflect the fact that such stress was common before
intensification but is not normally a factor under the current water management regime. For in situconservation strategies this case sheds some light on the survival of allelic diversity vs. adaptedness. Isozyme data indicate
maintenance of allelic diversity. Adaptedness, however, is at risk under on-farm conservation. Natural and intentional selection
will normally not remain constant over time. Consequent genetic changes include loss of adaptation to past conditions and
building up of adaptation to new. In this case such changes have happened surprisingly fast. However, changes are limited
to adaptation to factors of the environment and to market-relevant quality traits. Yield seems to be unaffected. Considering
needs for crop improvement this case has kept the materials `updated' with respect to adaptation and unchanged with respect
to yield potential.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
Plant breeders can help farmers increase food production by breeding new cultivars better adapted to their chosen farming systems, but these must be capable of providing the necessary plant inputs for the required levels of crop production in 2050. Until 200 years ago the farmers themselves were the plant selectors. Plant domestications, extensive crop dispersions and farmers’ selections produced thousands of locally adapted landraces of cultivated plants. During the twentieth century these were largely replaced by relatively few high yielding cultivars and the natural habitats of many of their wild relatives became endangered. Hence in situ and ex situ conservation, and evaluation and use of plant genetic resources is vital for future plant breeding. The development of scientific breeding from the beginning of the twentieth century was based on understanding the mechanism of inheritance and the mating systems of crop plants. The types of genetically uniform, high yielding cultivars that have been bred from genetically heterogeneous landraces were determined by the mode of reproduction and mating system of the cultivated plant species: inbred line (wheat) and hybrid (rice) cultivars for inbreeding species, hybrid (maize) cultivars for outbreeding species, and clonal (potato) cultivars for vegetatively propagated species. When genetically heterogeneous crops are desired, mixtures of cultivars and synthetic cultivars can be produced. Future progress in crop improvement will come from three complementary approaches: use of hybridization and selection in further conventional breeding, base broadening and introgression; mutation breeding, cisgenesis and gene editing; and genetically modified crops. 相似文献
20.
Pigeonpea is an important food legume crop of semi‐arid tropical regions. Plateauing of pigeonpea yield has been worrying breeders for the past 6–7 decades. Serious breeding efforts made during this period resulted in various high‐yielding and disease resistant cultivars. However, the gains in pigeonpea productivity have been modest. The authors, while reviewing this situation, conclude that long generation turnover, complexity of biological traits, low selection response and overreliance upon pedigree breeding present the key bottlenecks for this situation. In this paper, some alternative breeding approaches and technologies are suggested for the genetic enhancement of yield stability and stress response of pigeonpea. 相似文献
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