Select Page

Maize (Zea mays L.) is the largest cereal crop cultivated for food, feed and fuel throughout the world. Although yields of maize have increased concomitantly during the past decades, drought sensitivity continues to limit yield, especially in rainfed production systems subject to unpredictable or limited fresh water resources. The cuticle, a hydrophobic layer of cuticular waxes and cutin synthesized by plant shoot epidermal cells, limits excess water loss and protects plants against pathogen attack. While cuticular evaporation (CE) accounts for about 5-10% of water loss in well-watered plants during the day, it is the major source of water loss when stomata are closed, at night and under water-limited conditions. Modifying the rate of CE through selection in maize breeding programs may therefore offer a novel means to improve drought tolerance without compromising stomatal regulation of photosynthesis.

We are conducting an evaluation of ~450 maize inbred lines from the Wisconsin diversity panel for CE rates in two contrasting environments: Maricopa, AZ and San Diego, CA in 2016 and 2017. A genome-wide association study will be implemented to discover candidate genes and favorable alleles that regulate cuticle function as a barrier to water loss. To complement the identification of these candidate genes, a transcriptomic analysis will be performed on developing leaves of 100 selected CE outliers. Comparison of gene expression among those outliers will help elucidate the co-expression network relating cuticle composition to CE rate. In collaboration with Laurie Smith (University of California-San Diego), Michael Scanlon (Cornell University) and Isabel Molina (Algoma University), we will develop a better understanding of the genetic basis of CE rate with parallel studies on leaf development, cuticle biochemical composition, and epidermal gene expression relevant to cuticle formation.

Finally, the 100 CE outliers will be evaluated for yield and yield components under well-watered and water-limited conditions to assess the impact of variation in CE rates on maize drought tolerance in collaboration with Andrew French (USDA-ARS, Maricopa, AZ). Our ultimate goal is to develop a system-level understanding of the genetic basis of CE rate, its relationship to cuticle composition, and the potential impact on maize productivity, and to provide breeding strategies for improved maize drought tolerance through cuticular modification.

Funding: NSF PGRP IOS-1444507.