Genomic Evolution of Drought Adaptive Stomata of Wild Cereals

Drought is a major environmental stress threatening biodiversity and human civilization. Grasses cover more than 40% of the world land area and provide habitats for many animal species and represent the main source of grain and forage. Securing staple food for humans and animal feed (e.g. Wheat and barley) by future crop improvement depends on wild progenitors of cereal crops. However, the ecological and evolutionary significance of their wild relatives was not comprehensively studied in an integrated physiological, transcriptomic and genomic framework. Here, we assessed the genetic basis of adaptation and quantified the selection pressures that act on natural variation in wild barley (Hordeum spontaneum), wild emmer wheat (Triticum dicoccoides), and Brachypodium collected from contrasting African Slope and European Slope of the Evolution Canyon I, Israel. We report that hot-dry savannoid tropical African Slope contrasting with the abutting cool humid temperate European slope, has shaped the distinct stomatal and photosynthetic traits of H. spontaneum, T. dicoccoides and Brachypodium, which have strong genomic and transcriptomic basis for stomatal regulation, photosynthesis, and drought tolerance. Moreover, polyploidy may provide drought adaptive advantages to tetraploid B. hybridum at African Slope. We highlight the value of evaluating wild relatives in search of novel alleles and provides clues to resilience mechanisms underlying crop adaptations to abiotic stress. This study will provide useful information for the breeding of resilient wheat and barley in a changing global warming climate with higher temperature and more frequent drought events.