Abstract
Understanding the level of drought tolerance of the varieties available in each country is of paramount importance for breeding common bean for drought adaptation. The goal of this study was to evaluate 25 common bean genotypes of which 24 were released/recommended varieties for production by farmers and one was a drought tolerant check. The genotypes were planted at two sites in Ethiopia, Hawasssa and Amaro, using variable sowing dates, one that was early to avoid drought and one that was late to expose the crop to drought. The experiments were repeated over two years in Hawassa and one year in Amaro. This resulted in treatments with high and low total seasonal rainfall and six environments for analysis. The impact of drought stress on the trait expression of the varieties was not uniform across traits assessed and varieties tested. The effect of drought on photosynthate translocation and partitioning traits was much greater than on yield component traits in the varieties studied. This indicating less breeding efforts has been made in improving the varieties ability to mobilize photosynthate to the developing grain as compared to the yield component traits. Drought tolerant varieties like Hawassa Dume maintained better photosynthate translocation and partitioning than the drought sensitive varieties like Brown Speckled bean. Hawassa Dume also showed better yield stability and performed well under both drought stress and nonstress conditions. Our results indicate the relevance of high levels of photosynthate translocation and partitioning as an effective selection objective for improving drought tolerance in common bean. The information generated on the drought tolerance of the available varieties should help in the design of a breeding strategy that incorporates adaptation traits with commercial characteristics preferred by common bean farmers for varieties to be grown in diverse environments.
Highlights
Common bean (Phaseolus vulgaris L.) is the most important food legume in Ethiopia
Common bean provides vital nutrients such as proteins, vitamins and minerals to the diets of the resource poor [2] but in Ethiopia is important in providing fodder for feeding livestock and contributes to soil fertility improvement through atmospheric nitrogen fixation during the cropping season [3]
Common bean production in Ethiopia mainly occurs on smallholder farms prone to either intermittent or ter
Summary
Common bean (Phaseolus vulgaris L.) is the most important food legume in Ethiopia. While traditionally a food security crop throughout the country, its importance as a cash crop is gaining momentum in recent years through the sale of small white beans. These exportoriented beans have evolved into an important source of foreign currency for the country and income for smallholder farmers [1]. Common beans add diversity to production systems on resource poor farmers’ fields and contributes to the stability of farming systems in Ethiopia. Common bean production in Ethiopia mainly occurs on smallholder farms prone to either intermittent or ter-
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