Generation of a Mutant Population for TILLING Common Bean Genotype BAT 93

Common bean (Phaseolus vulgaris) is the major food legume worldwide, making it an important target for novel approaches of genetic analysis. This study evaluated the use of ethyl methane sulfonate (EMS) for the generation of a mutant population for targeted induced local lesions in genomes (TILLING) in common bean. TILLING is a powerful reverse genetics approach that uses a large mutant population for identification of mutants in loci of interest. Based on overall survival, development, and yield of treated seed, 40 mm EMS was found to be an appropriate concentration for the generation of a mutant population in common bean genotype BAT 93. Higher concentrations of EMS resulted in survival rates of less than 10% and lower concentrations resulted in the generation of fewer mutants. Based on TILLING results from other species, a population of 5000 lines is estimated to be sufficient for saturation of the common bean genome. Phenotypic mutation frequencies and the isolation of targeted mutations in the BAT 93 mutant population indicate that mutagenesis was effective.

Asymmetrical leaves induced by water deficit show asymmetric photosynthesis in common bean

In this study we tested the hypothesis that leaf asymmetric growth induced by water deficit in common bean (Phaseolus vulgaris L.) might be correlated with different net photosynthesis rates between the two opposed leaflets (right and left) considering a bilateral symmetric plane. In order to induce developmental instability, the drought-sensitive common bean genotype "Jalo Precoce" was subjected to periods of suspended irrigation during its vegetative growth. Developmental instability was evaluated by measurements of leaflets asymmetry, and the effects of drought on gas exchanges were taken in both symmetrical leaflets (right and left) in relation to the central leaflet. Water deficit induced an increase of 80 % in leaf asymmetry. Net photosynthesis of P. vulgaris was affected by water deficit in two ways, reducing its physiological yield and increasing its variability between leaflets. Thus, as we hypothesized, the increase in developmental instability, measured by leaf symmetry deviations, was supported by a variable net photosynthesis distribution in the leaves induced by drought.

FARMER PARTICIPATION IN COMMON BEAN GENOTYPE EVALUATION: THE CASE OF EASTERN ETHIOPIA

Advanced genotypes of common bean (Phaseolus vulgaris L.) were tested on-station and on-farm to evaluate their performance and acceptability under farmers' circumstances. Farmers were given seed of the genotypes to plant a minimum area of 100 m2 to be grown as a sole crop or intercropped with sorghum according to their preference. Yield, seed colour, taste, maturity time, disease reaction, growth habit and many other bean characteristics were assessed by farmers. The promising genotypes were higher yielding than the farmers' genotypes in most testing sites. Pairwise ranking of the genotypes showed that in export-oriented western Hararghe, white pea bean (navy bean) type Awash-1 and food bean G-2816 were preferred. In eastern Hararghe GLP ×92 and G-2816 were highly preferred but white pea beans were not preferred. Genotypes in advanced observation nurseries were also evaluated by the farmers and some of the genotypes have been promoted for further testing in yield trials. Selection criteria have been proposed by the farmers in each region. Future breeding and selection of genotypes will incorporate the proposed selection criteria and priorities of the two regions.