Aspects of durable resistance in wheat to yellow rust

In Kenya, the number of virulence factors of the yellow rust populations showed a considerable increase and a wide variability. Selecting for complete to near complete resistance to yellow rust and other cereal rust diseases, was followed by a rapid erosion of resistance.Partial resistance in wheat to yellow rust appeared to be difficult to select for. However, quantitatively resistant (QR) genotypes with a reduced disease severity (DS) and intermediate infection types (IT) were frequently observed. In addition, a fair number of wheat cultivars seemed to be durably resistant (DR) as their resistance was effective even after more than 25 years.DS and area under disease progress curve proved to be suitable parameters to measure QR while IT was too unstable a trait to rely on. QR can assessed reliably in small plots since there was no interplot interference observed. During screening and selection for QR, the level of nitrogen (N), heading date, observation date and leaf position are factors that should be considered by the breeder. DS and IT increased moderately with increased Nitrogen level. The magnitude of such increase was not the same for all genotypes.Selection for QR can be best carried out by discarding the most susceptible and most resistant plants or lines. In the field QR genotypes different significantly in DS and IT while race specificity to some yellow rust races and ineffective seedling resistance genes to race 134E150 were observed. By assessing the stability over environment's of a range of genotypes, genotype x location interaction occurred fairly often for QR while the durably resistant cultivars showed by far the least interactions with location indicating high environmental stability for DR.The resistance in five genotypes with different levels of QR seems to be based on rather few factors, one for Pr-2 to some three for Pr-7. The five genotypes seem to have factors in common or different factors that are strongly linked. The resistance in five durably resistant cultivars seemed to be based predominantly on a complex of strongly linked factors that inherited almost as a single factor in crosses with the highly susceptible Morocco

Can Cultivars from participatory plant breeding improve seed provision to small-scale farmers?

Seed provision for small-scale farmers deals with multiple constraints. These include, on the supply side, high seed production costs and poor adaptedness of the cultivars, and on the demand side, anticyclical demand and low and variable sales. Approaches to improve seed provision to this sector of farmers have so far not been very successful. This paper discusses how well-adapted cultivars developed through participatory plant breeding (PPB) initiatives create new opportunities for production and distribution of quality seed. It reviews supply and demand-side issues, based on research and experiences with seed production. Given better adaptation of PPB-cultivars, the diffusion of seed of PPB initiatives should not be a major bottleneck. But constraints in the provision of quality seed from cultivars that are commonly used remain and need to be addressed. Major points of attention are cost-effective seed production and distribution, high information linked transaction costs, and appropriate seed production technology. Research on these issues is needed to understand farmers¿ seed demand. At the same time, these issues need to be taken into account in new seed production initiatives that apply integrated approaches. Long term commitment by farmers to produce, distribute and use seeds is a condition. Even if seed production is not economically sustainable at household or organization level, farmer-based seed systems generate benefits to society as a whole that justify long term public investment to maintain the

Aspects of participatory plant breeding for quinoa in marginal areas of Ecuador

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 the