The role of leaf epicuticular wax in the adaptation of wheat (Triticum aestivum L.) to high temperatures and moisture deficit conditions

Authors: MOHAMMED, S - University Of Virginia; HUGGINS, T - Texas A&M University; BEECHER, F - Monsanto Corporation; CHICK, C - Texas A&M University; SENGODON, P - Texas A&M University; MONDAL, S - International Maize & Wheat Improvement Center (CIMMYT); PAUDEL, A - Texas A&M University; IBRAHIM, A - Texas A&M University; Tilley, Michael - Mike; HAYS, DIRK - Texas A&M University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2017
Publication Date: 3/7/2018
Citation: Mohammed, S., Huggins, T., Beecher, F., Chick, C., Sengodon, P., Mondal, S., Paudel, A., Ibrahim, A., Tilley, M., Hays, D.B. 2018. The role of leaf epicuticular wax in the adaptation of wheat (Triticum aestivum L.) to high temperatures and moisture deficit conditions. Crop Science. 58:679-689.

Interpretive Summary: Wheat is globally the most important crop and the second most utilized food crop in the developing world. With increasing population, higher wheat yields will be required in the future during increasing incidences of drought and high temperature stress due to global climate change. Some wheat lines are drought-susceptible and when exposed to water and heat stress exhibit poor growth and poor seed set resulting in decreased yield. Leaf epicuticular wax (EW) is often seen as a bluish-green covering on leaf surfaces and is associated with increased drought tolerance in cereals and many other crops. An inbred population was created from two wheat cultivars that exhibit differential response to drought. A total of 180 lines were grown for two years in five environments under controlled and water deficit conditions to evaluate their heat and drought tolerance. This study showed that EW correlates with higher grain yields, yield stability, and lower canopy temperatures and transpiration in response to drought stress. Results have demonstrated that both wax content and composition are important for ideal adaptation to drought and heat stress. These may provide marker-assisted selection tools and aid in the rapid advancement of water-deficit and heat-tolerant wheat cultivars.

Technical Abstract: Water deficit is one of the primary causes of decreasing wheat (Triticum aestivum L.) yields globally, resulting in 50–90% yield reduction for at least 60 Mha of cropland in developing countries (Reynolds et al. 2000). Previous studies have identified associations in genomic regions with cooler canopies, a heat susceptible index, and grain yield components in winter wheat. The aim of this project was to define the role of leaf epicuticular wax (EW) as a drought-adaptive trait for yield stability. To test this hypothesis, a recombinant inbred line (RIL) population, created from two spring wheat cultivars (Halberd and Len), was used. The parent lines of this population were selected owing to their differential response to drought with Halberd exhibiting better tolerance to water-deficit conditions. The RILs exhibited significant segregation for leaf EW, canopy temperature (CT), and drought susceptibility index (DSI). Over two years in five environments, an alpha lattice design was used with 180 recombinants, two replicates, and two distinct treatments (water-deficit and control). The inheritance of leaf EW was low (15%) due to significant interactions with environments. The RILs grown under water-deficit conditions produced significantly higher EW content (19% to 30%) compared to those grown under the control conditions. Leaf EW significantly correlated with plot yield (r = 32%), DSI (r = -40%), and leaf CT (r = -32%) under water-deficit conditions. In addition, EW and CT correlated with higher yield stability, as measured by DSI and Eberhart stability across environments under water-deficit conditions. This study explains the interrelationship between leaf EW and CT in improving moisture stress adaptability in wheat.