Shifts in plant architecture drive species-specific responses to drought in a Sorghum recombinant inbred line population

Drought stress severely impedes plant growth, development, and yield. Therefore, it is critical to uncover the genetic mechanisms underlying drought resistance to ensure future food security. To identify the genetic controls of these responses in Sorghum, an agriculturally and economically important grain crop, an interspecific recombinant inbred line (RIL) population was established by crossing a domesticated inbred line of Sorghum bicolor (TX7000) with its wild relative, Sorghum propinquum. This RIL population was evaluated under drought conditions, allowing for the identification of quantitative trait loci (QTL) that contribute to drought resistance. We detected eight QTL in the drought population that explain a significant portion of the observed variation for four traits (height, aboveground biomass, relative water content, and leaf temperature/transpiration). The allelic effects of, and the candidate genes within, these QTL emphasize: (1) the influence of domestication on drought-responsive phenotypes, such as height and aboveground biomass, and (2) how control of water uptake and/or loss can be driven by species-specific plant architecture. Our findings shed light on the interconnected roles of shoot and root responses in drought resistance as it relates to regulation of water uptake and/or loss, while the detected allelic effects demonstrate how maintenance of grain production and yield under drought is a likely result of domestication-derived drought tolerance.