Abstract
BackgroundCommon bean is the most important staple grain legume for direct human consumption and nutrition. It complements major sources of carbohydrates, including cereals, root crop, or plantain, as a source of dietary proteins. It is also a significant source of vitamins and minerals like iron and zinc. To fully play its nutritional role, however, its robustness against stresses needs to be strengthened. Foremost among these is drought, which commonly affects its productivity and seed quality. Previous studies have shown that photosynthate remobilization and partitioning is one of the main mechanisms of drought tolerance and overall productivity in common bean.ResultsIn this study, we sought to determine the inheritance of pod harvest index (PHI), a measure of the partitioning of pod biomass to seed biomass, relative to that of grain yield. We evaluated a recombinant inbred population of the cross of ICA Bunsi and SXB405, both from the Mesoamerican gene pool, to determine the effects of intermittent and terminal drought stresses on the genetic architecture of photosynthate allocation and remobilization in pods of common bean. The population was grown for two seasons, under well-watered conditions and terminal and intermittent drought stress in one year, and well-watered conditions and terminal drought stress in the second year. There was a significant effect of the water regime and year on all the traits, at both the phenotypic and QTL levels. We found nine QTLs for pod harvest index, including a major (17% of variation explained), stable QTL on linkage group Pv07. We also found eight QTLs for yield, three of which clustered with PHI QTLs, underscoring the importance of photosynthate remobilization in productivity. We also found evidence for substantial epistasis, explaining a considerable part of the variation for yield and PHI.ConclusionOur results highlight the genetic relationship between PHI and yield and confirm the role of PHI in selection of both additive and epistatic effects controlling drought tolerance. These results are a key component to strengthen the robustness of common bean against drought stresses.
Highlights
Common bean is the most important staple grain legume for direct human consumption and nutrition
Through the detailed phenotypic and genetic evaluations under different irrigation regimes, we have identified a substantial number of genomic regions associated with photosynthate allocation and remobilization under drought stress in common bean
We found a significant effect of the water regime on all the traits, at both the phenotypic and Quantitative trait locus (QTL) levels
Summary
Common bean is the most important staple grain legume for direct human consumption and nutrition It complements major sources of carbohydrates, including cereals, root crop, or plantain, as a source of dietary proteins. To fully play its nutritional role, its robustness against stresses needs to be strengthened Foremost among these is drought, which commonly affects its productivity and seed quality. Photosynthate partitioning and remobilization are important mechanisms of drought tolerance in common bean [5, 6]. Stress during flowering can induce flower drop and, in turn, cause more vigorous, compensatory vegetative growth, while drought stress during pod filling would cause more biomass production and decreased sink strength, resulting in a low harvest index [5]. Pod walls serve as a temporary storage of carbohydrates before rapid seed growth and efficient translocation of carbohydrates during grain filling. Carbohydrate storage in pod walls and their translocation to seeds is of great importance for productivity [14]
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