Investigation of Compositional Differences in Epicuticular Wax Between Wheat Lines.

Plant epicuticular leaf wax has been shown to affect the plant's ability to withstand heat and drought stress. In particular, the epicuticular layer is hypothesized to affect agronomic characteristics by altering reflectance, water loss, and canopy temperature. Selection based on variation in wax content and composition therefore has the potential for improving plant performance under abiotic stress. This study aims to investigate variation between lines in terms of wax composition. A wheat association mapping panel containing 294 heat tolerant lines selected by the International Center for Maize and Wheat Improvement (CIMMYT), grown under both drought and irrigated conditions, will be evaluated for total wax as well as wax composition. Plants will be grown in multiple locations, both in Texas and at CIMMYT in Mexico. Wax composition will be measured using direct analysis in real-time mass spectrometry (DART-MS). Individual lines will be compared based on the differences in the DART-MS fingerprint of epicuticular wax. Differences between the treatments will also be assessed. Specific DART-MS signals which display significant variation between lines will be used in the identification of QTLs using a diversity array technology (DArT) map developed by CIMMYT. QTLs associated with variation in the chemical composition of the epicuticular wax layer, and their association with resistance to abiotic stress, will therefore have been characterized.