Phenotypic plasticity and its genetic regulation for yield, nitrogen fixation and δ13C in chickpea crops under varying water regimes

Combining a plasticity approach and F-ST genome scan method we determined positions in the chickpea genome associated with the responses of seed yield, nitrogen fixation and delta C-13 to water supply.We measured yield components, nitrogen fixation, soil nitrogen uptake and carbon isotope composition (delta C-13) in a collection of chickpea genotypes grown in environments where water availability was the main source of yield variation. We aimed to quantify the phenotypic plasticity of these traits using variance ratios, and to explore their genetic basis using F-ST genome scan. Fifty-five genes in three genomic regions were found to be under selection for plasticity of yield; 54 genes in four genomic regions for the plasticity of seeds per m(2); 48 genes in four genomic regions for the plasticity of delta C-13; 54 genes in two genomic regions for plasticity of flowering time; 48 genes in five genomic regions for plasticity of nitrogen fixation and 49 genes in three genomic regions for plasticity of nitrogen uptake from soil. Plasticity of yield was related to plasticity of nitrogen uptake from soil, and unrelated to plasticity of nitrogen fixation, highlighting the need for closer attention to nitrogen uptake in legumes. Whereas the theoretical link between delta C-13 and transpiration efficiency is strong, the actual link with yield is erratic due to trade-offs and scaling issues. Genes associated with plasticity of delta C-13 were identified that may help to untangle the delta C-13-yield relationship. Combining a plasticity perspective to deal with complex GxE interactions with F-ST genome scan may help understand and improve both crop adaptation to stress and yield potential.