Investigating Drought Stress Responses of Diverse Natural Variants of Brassica

Water availability is one of the greatest challenges to maximizing crop production potential. The water use efficiency of lines chosen from 150 diverse accessions (cultivars) of the plant Brassica napus originating from diverse climatic habitats was determined using stable carbon isotope ratios of leaf material. These Brassica lines include both spring and semi-winter cultivars that show large differences in responses to water availability. Plant physiological responses have been investigated to determine the mechanisms responsible for natural variation in drought tolerance. The physiological responses of lines showing extremes in water use efficiency support the hypothesis that gas exchange regulation contributes to differences of water use efficiency between lines. Abiotic stresses, including drought, trigger production of the plant hormone abscisic acid (ABA), which through a complex signal transduction pathway closes stomatal pores, reducing transpirational water loss. Preliminary experiments suggest there are differences in ABA-mediated stomatal regulation between these lines. In addition to characterizing the phenotypes of these diverse accessions, we have developed a robust technique for testing responsiveness of ABA-mediated stomatal closure.