The Role of Leaf Epicuticular Wax in the Adaptation of Wheat ( Triticum aestivum L.) to High Temperatures and Moisture Deficit Conditions

Water deficit is one of the primary causes of decreasing wheat (Triticum aestivum L.) yields. Previous studies have identified associations in genomic regions with cooler canopies, the heat-susceptible index, and grain yield in spring wheat. This project aimed to define the role of leaf epicuticular wax (EW) as a drought-adaptive trait for improving the production and stability of yield attributes. A recombinant inbred line (RIL) population created from two spring wheat cultivars ('Halberd' and 'Len') was used. The parent lines were selected because of their different responses to drought, with Halberd exhibiting better water deficit tolerance. In five environments, an a lattice design with two replications and two distinct moisture treatments (water deficit and irrigated) were implemented. The RILs exhibited significant segregation for leaf EW, canopy temperature (CT) and drought susceptibility index (DSI). The inheritance of leaf EW was low (0.15) because of significant environment interactions. The RILs grown under water deficit produced significantly higher EW content (19-30%) compared with those under irrigation. The leaf EW significantly correlated with plot yield (r = 0.32) and leaf CT (r = -0.32) and the DSI for mean single head weight (r = -0.23) at Uvalde 2012 under water deficit. In addition, EW and CT correlated with stability parameters (DSI, regression of coefficient, and regression mean square) of different yield components within and across water deficit environments. This study explains the inter-relationship between leaf EW and CT in improving wheat adaptability to moisture and heat stress.