Drought is a major source of abiotic stress for plants, and poses an increasing threat to conservation, economic activities, and agriculture as climate change increases the stochasticity of precipitation events worldwide. Drought tolerance can vary widely between plant species, across differently adapted populations within species, and across a plant’s life span. Water stress decreases photosynthesis, and can diminish vegetative growth and reproductive allocation, both of which have serious consequences for agricultural and bio-energy crops. This research examines the physiological and transcriptomic responses to water limitation across populations and age in the wild foxtail millet, Setaria viridis, a close relative of the agriculturally important foxtail millet, Setaria italica. We assessed differences in drought tolerance across populations in greenhouse drought stress experiments comparing 9 populations of S. viridis from locations with diverse precipitation regimes. We next compared drought tolerance in plants from 2 populations using plants of 3 different ages from each population. In both experiments, we measured pot weight, fluorescence, and photosynthetic rate to evaluate plant responses to drought stress. We also assessed flowering time and total flower number across population and life stage. Aboveground biomass and root surface area were also compared across populations.
Results/Conclusions
In our first experiment, drought response varied significantly across the 9 populations, though there was no evidence that plants from drier home ranges were more drought tolerant. Flowering time differed significantly across populations. In our second experiment, population and age both significantly affected drought tolerance, though there was no evidence of interaction between these two factors. Aboveground biomass and roots surface area both varied significantly between populations but did not have a significant correlation with drought tolerance. Ongoing experiments on S. viridis will assess the physiological and transcriptomic response of different populations to chilling and salinity stress as well as drought. Ultimately, this area of research will help elucidate effects of population adaptation and life stage on abiotic stress response in a close relative of an important agricultural crop.