Search

Early maturity is an important target of cotton (Gossypium hirsutum L.) breeding programs. The selection and popularization of early-maturing cotton cultivars have significantly alleviated the problem of optimizing farmland cropping systems when planting cotton and cereals. However, breeding early-maturity cotton with high yields and high-quality crops is sharply constrained by the genetic complexity of the early-maturity trait. Despite the use of modern biotechnological tools, the exact genetic mechanisms underlying early maturity are still not fully understood. Here, we systematically summarize the progress made in understanding the genetic mechanisms responsible for early maturity using the classical quantitative inheritance model, the major gene–polygene mixed inheritance model, quantitative trait locus (QTL) mapping, gene cloning and functional analyses. We also discuss the phenotypic selection strategy in breeding early-maturing cotton cultivars, the application of related QTLs and functional genomic research. We suggest selecting for early-maturity indicators, especially flower and boll period, in early generations but selecting yield percentage before frost continuously among generations. The stable QTLs and related markers involved in early maturity can be used efficiently in breeding programs, and QTL fine-mapping, interaction and omics studies should be performed, along with the mining and in-depth functional analyses of novel genes. Such research will offer new perspectives on the practical breeding and functional genomics of early-maturity cotton.

Breeding methods applied to faba bean are either based on self pollination by developing lines under insect proof cages or based on open pollination by developing lines under natural pollination conditions. The purpose of this research is to compare the performance of pedigree selection method (PSM) as a self pollinated breeding method and recurrent selection methods (RSM) and synthetics as an open pollinated method. Eleven diverse accessions were used to develop in F6 generation 24 lines using PSM, 35 lines using RSM and nine synthetics from 2012 to 2016. The different developed lines were evaluated in two winter cropping seasons (2014/2015) and (2016/2017) in an alpha design with two replications. Significant differences among lines and among breeding methods were obtained for biological and grain yield, days to flowering, days to maturity, branches per plant, pods per plant, hundred seed weight. Synthetic populations had higher yield than RSM lines; whereas RSM lines revealed higher yield performance than PSM lines. Multivariate analysis indicates that most of the variation among different lines developed by different methods is due to variation in number of branches, days to flowering, biological and grain yield. Open pollinated cultivars were found to be more appropriate to increase the yield in farmers’ fields and may play a critical role in conserving wild pollinators, but ensuring optimal yields might require capacity building for farmers concerning wild pollinators.

In Brazil there is a limitation in the choice of commercial papaya hybrids for cropping. This factor is responsible for the crop vulnerability to the pests and diseases attack, being of great importance the investigations that aim at the availability of new genotypes. In papaya breeding programs to developed new hybrids, the lines should be evaluated by their combining ability. This step is important to select the superior parents for superior hybrid production. The objective of this research was to evaluate the combining ability of recombinant inbred lines by using elite testers in order to select papaya hybrid combinations with productive capacity and fruit quality, to supply the new cultivars demand, mainly from the Solo group. 34 genotypes were evaluated in a randomized complete block design with six replicates and three plants per plot. The specific combining ability (SCA) was estimated based on 12 traits related to fruit quality and yield. The hybrid combinations SS-72/12 × UCLCF01-01, SS-72/12 × UCLCF01-02, SS-72/12 × UCLCF01-09, Sekati × UCLCF01-04, Sekati × UCLCF01-10 and JS-12 × UCLCF01-17 were superior for presenting positive estimates of the SCA effects for the number of commercial fruits, fruit weight, pulp and fruit firmness and soluble solids that are the most important traits for the crop. These Solo and Formosa hybrid combinations have great potential to supply the consumer market demand, especially the small fruit hybrids, constituting national and international novelty as the first Solo hybrids.

Insect pests pose major challenges to optimum productivity of amaranth in Africa and Asia. The use of insecticides is the main control strategy, but is expensive and may pose health and environmental concerns, especially if proper care is not taken. Host plant resistance offers a cheap and sustainable pest management alternative. Open field experiments were conducted during two cropping seasons in 2016 and 2017 to screen 35 amaranth accessions and lines for resistance to leaf-webbers and stem weevils. The diversity (H) of lepidopteran defoliators and their parasitoids on each accession ranged from 0.00 to 1.57 and 0.00 to 1.65, respectively during the long rainy season and from 0.00 to 1.58 and 0.00 to 1.01 in the short rainy season. Accessions VI036227, RVI00027, VI054569, VI033487, VI044432, VI048076, VI049639, VI049530 and VI049698 had high levels of pest resistance with significantly lower infestations (≤ 11.11 ± 2.14%) and damage (≤ 68.06 ± 3.90%) by leaf-webbers and leaf-worms. Stem weevil infestations ranged from 68.70 ± 2.0% to 90.42 ± 1.0% during the long and short rainy seasons, respectively. Accessions VI047517-B, VI036227 and VI056563 had the least stem weevil infestations (

Genotype by environment interaction remains a substantial issue in all breeding programs. Crop genotypes are generally developed in a central breeding location, but always require the evaluation of breeding products in different environments. This is particularly relevant in countries that have a wide range of climates. Eighteen cassava genotypes were evaluated in Cameroon in eight environments—varying in seasonal rainfall and temperature patterns and soil characteristics—over two cropping seasons. Soil nutrient content was analyzed and trials were established in a randomized complete block design in three replications. Response of genotypes to major cassava pests and diseases, yield and carotenoids content was evaluated. It was observed that four genotypes did not show cassava mosaic disease (CMD) symptoms irrespective of the environments. The local check had highest CMD incidence and severity across all environments. Average number of whitefly per plant across all environments was highest on TMS 96/0023. Average cassava green mite (CGM) infestation was low on all the genotypes. Fresh root yield of five genotypes ranged between 25 and 30 tons per ha for both years. Significant and positive correlation was found across locations between fresh root yield and soil K, P and Mg. AMMI analysis revealed highly significant differences among genotypes and environments and significant genotype × environment interaction for most of the estimated traits, indicating variability in genotypes performance with environment.

The benefits of improving nitrogen use efficiency (NUE) in crops are typically studied through the performance of the individual crop. However, in order to increase yields in a sustainable way, improving NUE of the cropping systems must be the aim. We did a model simulation study to investigate how improvement of NUE traits of individual crops affects the succeeding crops and the NUE of the crop rotation. Based on experimental results parameterization was altered for different types of improved NUE in the EU-Rotate_N model, e.g. through higher N harvest index, reduced litter loss or improved root depth penetration rate. The different ways of improving NUE have different effects on the cropping system, affecting either N uptake, the ability of the crop to hold on to N already taken up, or the fraction of crop N being harvested. Due to the different modes of action, the model simulations show that these changes in NUE traits will also have different effects on N leaching loss and on N availability and N loss in the following years. Simulations also show that the effect of genotypes with improved NUE depend on environment and crop management. This is true for the improved crop itself and when its effect is analyzed for the whole cropping system. The environmental conditions, crop choices and management will all affect the fate of the N left in the soil, and whether this will contribute mainly to leaching loss or be used for production in later crops. As an example, increasing pre-crop fertilization was shown to affect the leaching after the following oilseed rape crop with up to 50 kg N ha−1 taken up before it was lost to the environment when pre-crop fertilization as well as root depth penetration rate was high. All in all, the simulations illustrate the concept of NUE as the result of interactions between genotype, environment and crop management (G×E×M). The benefits of improving nitrogen use efficiency (NUE) in crops are typically studied through the performance of the individual crop. However, in order to increase yields in a sustainable way, improving NUE of the cropping systems must be the aim. We did a model simulation study to investigate how improvement of NUE traits of individual crops affects the succeeding crops and the NUE of the crop rotation. Based on experimental results parameterization was altered for different types of improved NUE in the EU-Rotate_N model, e.g. through higher N harvest index, reduced litter loss or improved root depth penetration rate. The different ways of improving NUE have different effects on the cropping system, affecting either N uptake, the ability of the crop to hold on to N already taken up, or the fraction of crop N being harvested. Due to the different modes of action, the model simulations show that these changes in NUE traits will also have different effects on N leaching loss and on N availability and N loss in the following years. Simulations also show that the effect of genotypes with improved NUE depend on environment and crop management. This is true for the improved crop itself and when its effect is analyzed for the whole cropping system. The environmental conditions, crop choices and management will all affect the fate of the N left in the soil, and whether this will contribute mainly to leaching loss or be used for production in later crops. As an example, increasing pre-crop fertilization was shown to affect the leaching after the following oilseed rape crop with up to 50 kg N ha-1 taken up before it was lost to the environment when pre-crop fertilization as well as root depth penetration rate was high. All in all, the simulations illustrate the concept of NUE as the result of interactions between genotype, environment and crop management (G×E×M).

International audience; The move toward resilient and productive agriculture requires, among other innovations, the design of new sustainable farming systems in which the variety plays a main role. Plant breeding strategies adapted to organic farming conditions have to deal with limiting factors. Whereas in north-west France, it is known that trials carried out under high-input management do not give a good prediction of genotype performance in organic conditions, less is known about the relative stability of wheat genotypes between low-input (LI) and organic cropping systems. A retrospective analysis of 34 winter wheat trials conducted from 2004 to 2011 was performed to determine whether data obtained on genotypes grown under LI conditions can be used to predict genotype performance in organic (ORG) target conditions. Every year, ORG and LI (no fungicide or growth regulators, N balance sheet-60 kgN/ha, weed control with herbicides) trials including 25-30 genotypes describing a large range of genetic diversity were sown in three different agro-climatic regions across north-west France. Genotype performance in ORG management system was reduced from 25 to 40 % for yield and from 10 to 22 % for grain protein content. Estimates of genotypic values appeared to be more precise under LI than ORG conditions. Because of high genetic correlations between LI and ORG conditions, the relative efficiency of indirect selection from LI to ORG conditions was approximately 1. Spearman's rank correlations were high (Rs = 0.54-0.92) and genotype rank inversions generally had a minor extent. However, in 2005 and 2010, almost 50 % of the lines had to be retained in LI to keep 80 % of the top 20 % of genotypes in organic conditions. Compared with previous results from high-input conditions, LI management provided a better prediction of genotype performance under ORG conditions but crossover genotype x management interactions could be observed between both systems. Overall, combining information provided from both LI and ORG crop management systems appears to be a good process for building efficient and adapted breeding schemes for ORG farming conditions.

Genetic progress has brought about a dramatic increase in yield potential per se for almost all production areas around the world. The present study examines the relationship of wheat yield with year of release, yield components, harvest index (HI), biomass production, and plant height. We used aggregative data from 1945 to 2010 to calculate genetic gain in wheat yield across different zones in China. A deeper understanding of these issues facilitates the identification of specific yield-limiting factors that can be used for future breeding strategies. Absolute yield gain for the different zones was found to range from 20 to 103 kg ha−1 year−1, whereas relative yield gain ranged from 0.33 to 1.42 % per year. When data from all the Chinese wheat production zones was pooled, yield gain at the national level had an absolute value of 66 kg ha−1 year−1 and a relative value of 1 % per year. Grain weight and spike weight, rather than the other yield components, are significantly correlated with year of release for most zones, suggesting that these two were the most promising traits for breeders in the past. These two traits are also responsible for the significant genetic progress in wheat yield in China since 1949. HI and biomass production also showed strong correlation with year of release and grain yield. In China, HI and grain weight have experienced such a substantial increase that both have almost reached their theoretical maxima in the period 1945–2010. Further improvement in the yield potential of wheat will have to involve increase in biomass production and grain number. This paper also reviews cropping systems and technologies as well as improvement in physiological trait from 1945 onwards during the period of genetic gain.

Malnutrition or ‘hidden hunger’ severely stunts human potential due to imbalanced diets and a lack of vital vitamins and minerals. Hunger and obesity are its extremes. Hardy, multipurpose legumes that can be used as vegetables or grains by smallholders or large enterprises and with multiple manufacturing uses have a vital role to play in overcoming growing malnutrition in South Asia, Africa, and the Pacific. Population growth over the next 40 years will require a doubling of food production in developing countries and climate change will make achieving this goal more uncertain. Mungbean (Vigna radiata (L.) Wilzcek) and vegetable soybean (Glycine max (L.) Merrill) can be consumed as highly nutritious vegetables or grains and are well suited to smallholder production under adverse climatic conditions. Both are well established in intensive cropping systems in Asia, but are little known elsewhere. Recent collaborative plant breeding efforts in Asia produced high yielding, disease-resistant mungbean varieties that mature synchronously in 60–65 days. This revolutionized the industry, allowing the crop to be added to smallholder rice/wheat rotations and leading to a major increase in global production Vegetable soybeans are larger and more nutritious than grain soybeans, but constitute less than 2% of global soybean production. Well known as fresh vegetables in East Asia, they are highly suited to smallholder agriculture or home gardens, producing among the highest yields of crop protein per unit area. More promotion and minor adaptive research can make these regional successes more widely available to help overcome malnutrition.

Arguably the most important adaptive criterion in annual crops is appropriate phenology that minimizes exposure to climatic stresses and maximizes productivity in target environments. To date this has been achieved empirically by selecting among diverse genotypes in target locations. This approach is likely to become inadequate with pending climate change because selection is imposed on the outcome (flowering time) rather than the underlying mechanism (i.e. responses to daylength, ambient or vernalizing temperatures). In contrast to the cereals, in legumes the interaction between phenological mechanisms and environmental selection pressure is largely unknown. This paper addresses this shortcoming through photothermal modelling of chickpea germplasm from the world’s key production areas using a meta-analysis of multi-environment trials located from 49° N to 35° S. Germplasm origin had significant effects on temperature and daylength responsiveness, the former strongly correlated to vegetative phase temperatures at the collection or development site (r = 0.8). Accordingly, temperature responses increase from winter- to spring-sown Mediterranean and Australian material, and then to north, central & southern India. Germplasm origin also affects the relationship between photoperiod and temperature response. In Eastern Mediterranean material a strong negative relationship (r = −0.77) enables temperature insensitive genotypes to compensate through a strong photoperiod response. Clearly, chickpea evolution has selected for different phenological mechanisms across the habitat range. Given that under the anticipated global warming temperature sensitive cultivars will flower relatively earlier than those responding largely to photoperiod, it is important to exploit this diversity in developing better-adapted genotypes for future cropping environments.

Major changes have occurred in the global wheat-rust disease landscape over the last century. At the turn of the twentieth century pioneering rust research was driven by the need to combat devastating stem rust epidemics. A fundamental understanding of rust genetics and dispersal pathways emerged from this early work. Stem rust epidemics were also the driver behind the breeding programs that resulted in the green revolution of the 1960/70s. Successful incorporation of durable stem rust resistance into high yielding semi-dwarf wheat cultivars would change the wheat-rust disease situation beyond recognition. Associated intensification of the wheat cropping systems would also produce dramatic changes. Despite localized outbreaks, by the early 1990s stem rust was a disease under control. During this period of low stem rust incidence, yellow rust began to emerge as a substantial threat. Breakdown of Yr9 resistance resulted in damaging epidemics in Asia; an exotic incursion introduced yellow rust into Australia with highly significant subsequent impacts. The Australian incursion was almost certainly transmitted via an air traveller and the exponential growth in international air travel has increased the probability of other cross-continental movements. By the start of the twenty-first century, new rust threats had emerged. Durable stem rust resistance was broken down by the Ug99 race lineage identified in East Africa; new aggressive strains of yellow rust adapted to warmer temperatures were identified and spread across continents at a rapid rate. As in the past, major rust developments are one driver of global initiatives to mitigate the threat. Climate change and the response of pathogens to changing conditions are possible emerging issues, although other changes may prove to be more significant. Throughout this century of change a consistent theme is the adaptability of wheat-rust pathogens to cause recurring damage. Maintaining the gains of the previous decades will require sustained, collaborative, multi-disciplinary efforts. To keep pace with the evolving threats posed by wheat rusts there is a clear need for continuous vigilance and surveillance of both pathogen and host. Current international monitoring and surveillance efforts are described along with associated challenges.

An important step towards reducing the vulnerability of wheat in Africa and Asia to the Ug99 race of the stem rust pathogen is the substitution of current susceptible varieties with superior resistant varieties. In the 2008–2009 cropping season both seed multiplication and dissemination of Ug99 resistant varieties were initiated in Afghanistan, Bangladesh, Egypt, Ethiopia, Iran, India, Nepal and Pakistan. Ug99 resistant varieties must occupy about 5% of the area sown to wheat in each country to ensure sufficient seed to displace current popular varieties. Because of the underdeveloped seed industry and small farm sizes in most of these countries, various strategies are being applied for rapid multiplication and dissemination of resistant varieties. Approaches being used include pre-release seed multiplication while candidate resistant lines are being tested in national evaluation trials and farmer participatory selection. Resistant varieties are already released in Afghanistan, Bangladesh, Egypt and Pakistan and more varieties are expected to be released in 2010 in these and other countries. Our results show that some new Ug99 resistant lines have yield superiority over dominant local varieties. Activities and progress in seed multiplication using existing and new Ug99 resistant varieties are discussed.

Top ranking varieties are tested in multiple environments before and after registration in order to assess their value for cultivation and use (VCU testing). Recently, interest has increased in obtaining varieties specifically adapted to organic farming conditions. This raised the question if an independent system of trials may be required for this purpose. To help answering this question, through the exchange network of European cereal researchers SUSVAR (www.cost860.dk), a number of data sets of agronomic traits from barley, wheat and winter triticale, from trials performed in Denmark, Sweden, The Netherlands, France, Switzerland, UK and Germany, were made available and analysed using an approach based on mixed models involving parameters describing genetic correlation between the two types of experiments, i.e., organic and non-organic (high or low input). Estimated variance components and correlations were used to evaluate response to selection and index selection. The response to index selection was analysed as a function of the fraction of available trials assigned to the organic system. The genetic correlations were interpreted in terms of ranking agreement. We found high genetic correlations between both systems for most traits in all countries. Despite high genetic correlations, the chances of very good agreement in observed rankings were moderate. Combining information from both organic and non-organic systems is shown to be beneficial. Further, ignoring information from non-organic trials when making decisions regarding performance under organic conditions is a sub-optimal strategy.

The International Maize and Wheat Improvement Center (CIMMYT) aims to genetically enhance both crops and generate public sector-provided products for the resource poor, e.g., drought tolerant wheat and insect resistant maize, and through international-national partnerships facilitate the acquisition of improved germplasm for non-mandate crops in the cropping systems where maize and wheat thrives; e.g., GM-papaya through a national food security undertaking in Bangladesh. The Center also engages in public awareness campaigns in projects such as Insect Resistance Maize for Africa (IRMA), which includes food, feed and environmental safety, monitoring of resistance and establishment of refugia, non-target effects and gene flow. Monitoring of genetic resources is a wide concern among the centers of the Consultative Group on International Agricultural Research (CGIAR), with an emphasis on the quality of gene banks. Decisions, policies and procedures about monitoring should be science-based, and this requires education, an area where CIMMYT and other CGIAR centers can play an important role. There will be a need to continue to evaluate the need for, and type of monitoring, as new (and unique) products are developed and released in the emergent economies of the world.

Twenty-four cowpea genotypes were evaluated under sole cropping or additive series intercropping with sorghum from 2004 to 2005 at four sites representative of the Guinea and Sudan savannah ecologies in Ghana. The aim was to determine whether cowpea breeding programs that emphasize selection under sole-crop conditions have the potential to produce cultivars that are effective under additive series intercropping. Genotype × cropping systems interaction was significant for days to 50% flowering but not for grain yield, biomass and other studied traits. Genotypic yield reaction to cropping systems indicated that bridging the yield gap between sole cropping and intercropping systems is best addressed by agronomic interventions that reduce stress on intercrop cowpea rather than by selecting for specifically adapted genotypes for intercropping. Significant genotype × environment interactions were observed for all traits when data was pooled over cropping systems. Partitioning of the genotype × environment interaction variance indicated that days to 50% flowering was dominated by heterogeneity of genotypic variance, whereas genotype × environment interactions for grain yield and biomass was mainly due to imperfect correlations. Large differences in genotypic yield stability were observed as estimated by the among-environment variance, regression of yield on the environmental index, Kataoka’s index, and by partitioning of genotype × environment interaction sum of squares into components attributable to each genotype. The results suggest that in regions where genotype × environment interaction for yield frequently causes re-ranking across environments, genotypes with the least contribution to the interaction sum of squares are likely to be most productive. On the whole, the results support the contention that breeding under sole-crop conditions has the potential to produce cultivars effective under intercropping conditions.

Knowing pests and diseases that may cause injuries and are likely to affect plant health and quality is critical to minimizing the gap between attainable yield and actual yield. In this paper, we highlight concepts and strategies aimed at controlling major biotic constraints affecting wheat in intensive production systems and present emerging challenges, with a special attention to the developing world. Disease epidemics result from the combination of inoculum, favorable environment, and host susceptibility. Changes in cropping systems as a result of adoption of conservation agriculture may have serious implications. Necrotrophic pathogens such as those responsible for tan spot or septorias are likely to emerge, and Fusarium head blight may increase. However, resistance breeding combined with rotations, timely sowing, and irrigation or even fungicide utilization, if affordable, are part of integrated crop management practices that can minimize losses. In South Asia, the effect of spot blotch, a devastating foliar disease caused by Cochliobolus sativus, can be minimized by reducing physiological stress through timely sowing and adequate use of fertilizers, which demonstrates the complex relationships among crop physiology, disease resistance, and yield. Although some root rots that induce premature death of tillers in cooler high-yielding humid environments can be important, the dryland crown rot (Fusarium spp.), common root rot (C. sativus), and the cereal nematode (Heterodera spp. and Pratylenchus spp.) should not be ignored. These are all known to be much more damaging under suboptimal moisture (rainfed or supplementary irrigation), particularly where plant growth is stressed. Climate change is likely to modify the wheat disease spectrum in some regions, and pathogens or pests considered unimportant today may turn out to be potential new threats in future.

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.

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.

Approaches are needed to broaden the genetic base and improve earliness and yield potential of large-seeded beans under sustainable cropping systems. The objective of this research was to develop adapted dwarf bean populations having a commercial seed quality and yield suitable for the production in the South of Europe. The original base populations were produced from crosses between genotypes within each Mesoamerica, Nueva Granada and Peru races, and between Peru and Nueva Granada, and Mesoamerica and Nueva Granada races. Visual mass selection for plant performance was practised in the F2 and F3 generations. In the F4 and F5, single plants were harvested under two cropping systems (sole cropping and intercropping with maize). From F4, selection was based on precocity, combined with seed yield and seed commercial type. The F4:7 selected lines from each original population were compared with their parents and five checks at four environments and two cropping systems. Differences among environments, populations, parents and checks were observed for all traits. Under intercropping with maize, there was a 50% reduction in seed yield. Yield of parents and checks belonging to Andean South American races, intraracial (Nueva Granada × Nueva Granada) and interracial (Nueva Granada × Peru) populations, was higher than that of those of Middle American origin. Intraracial crosses within large-seeded Andean South American (Peru race) and Middle American gene pools (Mesoamerica race) did not produce lines yielding more than the highest yielding parent. Only two large-seeded lines selected from crosses between small- and large-seeded gene pools out-yielded the best parent and check cultivar., Research was supported by a Plan Nacional I+D+I (AGF93-0756-C02) and Xunta de Galicia (INFRA91-015) projects from the Spanish Government. The authors are grateful to the Diputación de Pontevedra and A.P. Rodiño for farm facilities and Lidia Otones for technical assistance. A.B. Monteagudo, A.M González, A.P. Rodiño and M. Lema acknowledge fellowships from the Xunta de Galicia, CSIC and Diputación de Pontevedra, that allowed them to carry out this study. Special thanks to J.D. Kelly for anthracnose, S.P. Singh for BCMV and BCMNV, M.A. Pastor-Corrales for rust and C. Asensio for bacterial inocula., MCYT, Xunta de Galicia, Diputación Provincial de Pontevedra, CSIC

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.

On-farm varietal biodiversity was studied through household surveys in two high potential production systems in Chitwan and Nawalparasi districts of the Nepal Terai and in Lunawada sub-district, Gujarat, India. Diversity was extremely low in Chaite rice in the Nepal study area (weighted diversity 0.04) and low in main season rice in the India study area (weighted diversity 0.34). In both areas, one cultivar dominated, CH 45 in Nepal and GR11 in India. In the India study area, biodiversity varied with the socio-economic group and better-off farmers had a greater varietal diversity. Participatory varietal selection (PVS) identified new varieties that farmers preferred. Their adoption by farmers increased on-farm varietal biodiversity within the three cropping seasons studied. Despite the commonly assumed uniformity of high potential production systems, the new varieties occupied specific niches in the farming system. Farmers' preferences for different varieties – there were large differences in quality traits and maturity period among the new varieties – should help to maintain biodiversity. Overall production is expected to increase as each niche becomes occupied increasingly by the best-adapted variety. PVS is a simple and powerful method of increasing food production in the high potential production systems that produce most of the developing world's grain.

Breeding programmes in common bean (Phaseolus vulgaris L.) have mainly focused on performance under monoculture conditions. Interactions among cultivars and cropping systems do occur and genotypes bred for pure cropping may not be suitable for intercropping. This study was undertaken to obtain estimates of genetic parameters of quality traits for bush bean landraces grown in two cropping systems, and the interrelationships of these traits between pure cropping and intercropping with maize (Zea mays L.). Field experiments were conducted at two locations for two years. Expression of most traits was not strongly influenced by genotype × environment interactions. Heritability estimates were similar in both cropping systems for most pod and seed quality traits. Positive correlations were observed between pure cropping and intercropping for pod characters (weight, length, width and texture) and seed characters (dry and imbided weight, length, hardness, coat proportion, water absorption and crude protein). Use of a selection index is suggested for breeding for seed size, water absorption,coat proportion and crude protein for both cropping systems. However, larger gains would be expected in pure cropping for most traits. Bean accessions PHA-0267, PHA-0285, PHA-0286 and PHA-0299 should be used for developing acceptable culinary and high protein breeding lines for either cropping system.

Progress from plant breeding has been slow in some marginal environments. Conventional or formal plant breeding (FPB) programs conducted by international agricultural research centres or national programs in developing countries have been criticized for ignoring indigenous germplasm, failing to breed for conditions facing poor farmers, and emphasizing selection for broad versus local adaptation. A suite of techniques, referred to as participatory plant breeding (PPB) and including farmer-participatory or farmer-led selection, on-farm evaluation, and use of local landraces, has been advocated in response to this critique. PPB programs are diverse in scope and approach, but often rely heavily on farmer visual evaluation or phenotypic mass selection to select for simply-inherited traits, with limited replicated yield testing in multiple-environment trials (MET), one of the main tools of FPB. Prediction equations derived from selection theory can be used to examine the conditions under which idealized versions of FPB and PPB may be expected to achieve genetic progress for traits such as yield. The effectiveness of any selection environment is determined by both the genetic correlation between genotype performance in it and the target environment (r G) and the heritability of genotypic differences in the selection environment (H s). r is a measure of the accuracy with which performance of genotypes in the selection environment predicts performance in the target environment; H s is a measure of the precision with which performance differences among genotypes can be measured in the selection environment. We compare FPB and PPB with respect to these determinants of selection response, using examples from self-pollinated species. Particular areas examined include: (i) selection for broad versus specific adaptation; (ii) on-station versus on-farm selection; and (iii) selection under high-yield versus low-yield conditions. In general, PPB systems attempt to maximize gains through the use of on-farm evaluation and the skills of farmer-selectors to maximize r G. FPB exploits METs to maximize H s. PPB is most likely to develop cultivars that out-perform the products of FPB when it is applied in low-yield cropping systems, because it is in such situations that r G between high-yield breeding nurseries and low-yield target environments is likely to be low or negative. To make continued gains, and to compete with internationally-supported FPB programs, PPB systems will need to counter the obscuring effects of uncontrollable within-field, site-to-site, and year-to-year heterogeneity. Simple and robust designs for on-farm METs are needed for this purpose.

Decentralized selection, defined as selection in the target environment, has been used to emphasize favorable interactions when significant genotype by environment interactions exist. However, crop breeding based on decentralized selection can still miss its objectives if it does not utilize the farmers' knowledge of the crops and the environment, and it may fail to fit crops to the specific needs and uses of farmers' communities unless it becomes participatory.One cycle of decentralized participatory selection was conducted in eleven locations in Syria. 208 barley entries (fixed lines and segregating populations) were planted unreplicated in two research stations and in the fields of nine Syrian (host) farmers, where they were managed (except planting) by the farmers themselves. Visual selection was conducted by a breeder at all locations and by the host farmers on their own fields and on both stations. In five farm locations, there was also a one-time group selection by neighboring farmers.Host farmers were able to handle the large number of entries making observations during the cropping season using different scoring methods. They did not use the performance of entries on station for their final selection and used a higher selection pressure than the breeder. In their own fields, they selected about one tenth the number of entries selected by the breeder, while on station the farmers selected, on average, about half the number of lines selected by the breeder. For some broad attributes, such as modern germplasm versus landraces, selection was mostly driven by environmental effects. Selection for other attributes was partly environmentally driven and partly based on individual farmers preferences.Selection preferences were similar for fixed or segregating populations. There was wider diversity among farmers' selections in their own fields than among farmers' selections on research stations and among breeder's selections, irrespective of where the selection was conducted. Larger kernels, higher grain yield and biomass, and taller plants (particularly in environmentally stressed locations) were the characteristics most frequently used as selection criteria by both breeder and farmers.Entries selected by the farmers yielded as much, and in one case significantly more, than those selected by the breeder.Decentralized-participatory selection was significantly more efficient in identifying the highest yielding entries in farmers' fields than any other type of selection. There was also evidence suggesting that the breeder was more efficient in selecting higheryielding entries in the research station in a high rainfall area, while the farmers were more efficient in selecting under stress conditions. The results suggest that farmers can handle selection choices among a large number of lines, and because farmers' selections are at least as high yielding as breeder's selections, it is possible to transfer the responsibility of selection to farmers in their fields.

Common bean, Phaseolus vulgaris L. is intercropped or relay cropped with maize in many Andean highlands of Colombia and Peru. Breeding beans for the target multiple cropping systems is essential for the development of productive and sustainable agriculture for the Andean smallholders. Outline of the breeding programme should follow the farming system approach with the establishment of on-farm trials and early farmers involvement. Bean breeding is oriented to minimize intercrop competition and to stabilize complementarity with maize. Genetic traits needed for improved varieties are divided as follows : traits not interacting with the cropping systems, traits specific to intercrops and traits related with socioeconomic and seed quality aspects. Screening, prebreeding and recombination nursery are better made under sole cropping while varietal improvement and on-farm trials are conducted under the target multiple cropping systems. Breeding schemes may involve recurrent, pedigree and bulk hybrid selection. The given application concerns the genetic improvement of P. coccineus, P. polyanthus and interspecific hybrids of P. vulgaris for both simultaneous and relay intercropping in Colombia and Peru. Earliness, cold tolerance, resistance to fungus diseases (mainly Ascochyta leaf blight and anthracnosis) and seed yield potential were the major objectives of the bean improvement programme. Priority has been given to the exploitation of the large diversity available in the secondary gene pool of common bean.

To improve the quality of buckwheat flour, we investigated the effect of the cropping season on the rutin content in various cultivars of common buckwheat (Fagopyrum esculentum Moench.). Thirty cultivars of buckwheat were grown under both long day conditions (the summer cropping) and short day conditions (the late summer cropping). The inter-varietal variations and the effect of the cropping season on the rutin content were examined. The rutin content was determined by high performance liquid chromatography (HPLC). Results show that the average rutin content in the late summer cropping was about half that of the summer cropping. There were wide inter-varietal variations of rutin content in the summer cropping. The differences in rutin content in the late summer cropping were less pronounced. Rutin content was closely correlated with the flowering period in summer (r=0.735***). The later flowering cultivars produced a higher content of rutin than the earlier flowering cultivars in the summer cropping. The differences in the cumulative solar radiation received in the two seasons seems to be a reasonable explanation for this increase in the rutin content of the buckwheat flour. The rutin content of early flowering cultivars, which are suitable for long day conditions, is positively correlated with yield in the summer cropping. However, the rutin content in the intermediate and late summer ecotype cultivars, which are suitable for short day conditions, shows no correlation with yield in the late-summer cropping. In conclusion, there are wide inter-varietal variations of rutin content in buckwheat flour and the rutin content increases under long day conditions.

This paper proposes experimental designs that may permit two species to be selected simultaneously for yield and ecological combining ability. The interpretation of data based on these designs is considered and the simplest way in which the designs might be used in a breeding programme is discussed.

Very quick-growing spinach material has been raised for winter cropping in glasshouses by crossing some glasshouse varieties with an extremely quick-bolting parent and subsequent selection in winter glasshouse crops. The resulting material gave increased leaf production in winter cropping under glass and did not bolt too rapidly.