Drought sensitivity of leaflet growth, biomass accumulation, and resource partitioning predicts yield in common bean

While drought limits yield largely by its impact on photosynthesis and therefore biomass accumulation, biomass is not the strongest predictor of yield under drought. Instead, resource partitioning efficiency, measured by how much total pod weight is contained in seeds at maturity (Pod Harvest Index), is the stronger correlate in Phaseolus vulgaris. Using 20 field-grown genotypes, we expanded on this finding by pairing yield and resource partitioning data with growth rates of leaflets and pods. We hypothesized that genotypes which decreased partitioning and yield most under drought would also have strongest decreases in growth rates. We found that while neither leaflet nor pod growth rates correlated with seed yield or partitioning, impacts to leaflet growth rates under drought correlate with impacts to yield and partitioning. As expected, biomass production correlated with yield, yet correlations between the decreases to these two traits under drought were even stronger. This suggests that while biomass contributes to yield, biomass sensitivity to drought is a stronger predictor. Lastly, under drought, genotypes may achieve similar canopy biomass yet different yields, which can be explained by higher or lower partitioning efficiencies. Our findings suggest that inherent sensitivity to drought may be used as a predictor of yield.\n\nHIGHLIGHTIn common bean, higher biomass accumulation under drought alone does not guarantee higher yield, as maintenance of higher growth rates and partitioning processes act as an additional requirement.