Drought plasticity QTLs specifically contribute to the genotype x water availability interaction in maize
Résumé
Concerns regarding high maize yield losses due to increasing occurrences of drought events are growing, and breeders are still looking for molecular markers for drought tolerance. However, the genetic determinism of traits in response to drought is highly complex and identification of causal regions is a tremendous task. Here, we exploit the phenotypic data obtained from four experiments carried out on a phenotyping platform, where a diversity panel of 254 maize hybrids was grown under well-watered and water deficit conditions. To dissociate drought effect from other environmental factors, we performed multi-environment genome-wide association study on steady-state means or drought plasticity indices computed for six ecophysiological traits. We identify 102 steady-state QTLs and 40 plasticity QTLs. Most of them were new compared to those obtained from a previous study on the same dataset. Our results show that plasticity QTLs cover genetic regions not identified by steady-state QTLs. Furthermore, for all traits, except one, plasticity QTLs are specifically involved in the genotype by water availability interaction, for which they explain between 60\% and 100\% of the variance. Altogether, steady-state and plasticity QTLs captured more than 75\% of the genotype by water availability interaction variance, and allowed to find new genetic regions. Overall, our results demonstrate the importance of considering plasticity indices in multiple environments to decipher the genetic architecture of trait response to stress.
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