Epicuticular Wax: Its Deposition During the Reproductive Stages of Wheat in Response to Heat Stress.

Cuticular wax protects the shoot from pathogen attack as well as water loss through transpiration. Intracuticular waxes determine epidermal conductance and epicuticular wax is associated with water transpiration and spectral reflectance. Recent studies in our lab identified natural variation in leaf wax thickness among wheat varieties. Some of these varieties have shown increased wax deposition prior to stress, while others increased their deposition when exposed to heat stress at 10 DAP (days after pollination). This study is based on the measure of epicuticular wax during the developmental stages of spring and winter wheat. Leaf punches for wax extraction were collected at full emergence of the spike, 3 DAFE, 6 DAFE, 9 DAFE, 10 DAP, 13 DAP and 15 DAP. Kauz, Tam401, Tam 112 and Halberd have shown high levels of glaucousness on the flag leaves. Cutter and Australith showed little glaucousness during the developmental period. Twelve heat tolerant and heat susceptible lines were selected for this study to determine the amount of epicuticular wax present during heat stress conditions compared to ideal conditions. Leaf samples were also collected for RNA extraction and used for expression studies to determine which genes associated with wax deposition if any are favorably expressed during heat stress. The results from this study will provide important information on the role of wax as one part of the complex system that provides heat tolerance and help plant breeders develop new heat tolerant wheat cultivars.