Mapping the genetic loci regulating drought adaptive traits; leaf epicuticular wax, canopy temperature, and drought susceptibility index in Triticum aestivum L.

Authors: MOHAMMED, S - Texas A&M University; Huggins, Trevis; BEECHER, F - Monsanto Company; CHICK, C - Texas A&M University; MASON, R - University Of Arkansas; SENGODON, P - Monsanto Company; PAUDEL, A - Texas A&M University; IBRAHIM, A.M - Texas A&M University; Tilley, Michael - Mike; HAYS, D - Texas A&M University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2021
Publication Date: 1/12/2021
Citation: Mohammed, S., Huggins, T.D., Beecher, F., Chick, C., Mason, R.E., Sengodon, P., Paudel, A., Ibrahim, A.H., Tilley, M., Hays, D.B. 2021. Mapping the genetic loci regulating drought adaptive traits; leaf epicuticular wax, canopy temperature, and drought susceptibility index in Triticum aestivum L.. Theoretical and Applied Genetics. https://doi.org/10.1002/csc2.20458.
DOI: https://doi.org/10.1002/csc2.20458

Interpretive Summary: Water stress during wheat (Triticum aestivum L.) reproductive stages is a primary constraint that limits grain yield in developed and developing countries. Soil water deficit conditions combined with high temperatures (dry air and soil) during vegetative and reproductive stages, also increases seed abortion and limit overall grain yield. Without adequate irrigation, dryland wheat production in the U.S. High Plains is severely limited due to poor soil moisture, irregular and inadequate precipitation. As such, new wheat cultivars that possess improved drought adaptive (water deficit tolerance) traits such as transpiration efficiency, water use efficiency, and cooler canopies are urgently needed. Enhanced exploitation of the wheat genome and interdisciplinary activities, may offer the potential to dissect factors limiting grain yield under water deficit conditions. Leaf epicuticular wax (EW) or glaucousness is expressed as gray-white blanket like structure on the surface of leaves and has been shown to be associated with various physiological traits such as increased residual water content, reduced transpiration rate, increased water use efficiency, increased light reflectance and reduced heat susceptibility index (HSI) and yield potential. The objective of the present study was to identify quantitative trait loci (QTL) regulating increased leaf EW content and determine their interaction with cooler canopies, drought susceptibility index (DSI) and grain yield components such as mean single head weight (MSHW), thousand kernel weight (TKW), and kernel number per spike. Results of this study demonstrated the linkage of loci associated with leaf epicuticular wax, canopy temperatures and drought susceptibility index have a significant impact on yield attributes.

Technical Abstract: Recombinant inbred lines (RILs) derived from US North Dakota variety and Australian elite variety with constricted range of plant height, flowering time and significant segregation of physiological traits of interest, such as leaf epicuticular wax (EW), canopy temperatures (CT) and drought susceptibility index (DSI) were selected. Earlier studies have shown the significant impact of leaf glaucousness and cooler canopies on wheat yield. However, phenotypic and genetic studies on these physiological traits as responses to heat/water deficit and grain yield improvements were poor. The RIL population of over 180 individuals and their parents were phenotype for physiological and phenological traits across five environments. Two distinct drip irrigated moisture regimes were maintained consistently across all environments. A 90K infinium SNPs library was run across parents and RILs to develop genetic linkage groups of polymorphic SNPs and map QTL for traits of interest. Leaf EW was shown to be genetic variable although significantly increase wax production under heat/moisture deficit stress. Co-localized QTL for the leaf EW, cooler canopies, DSI and grain attributes were detected on chromosomes 1A, 2B, 3B, 6B, 7A, and 7B loci. 2B, 7A and 7B. The waxy SNP QTL in 2B and 3B displayed sequence similarity to an ABC transporter gene in Arabidopsis and the 7B QTL had sequence similarity to the Sorghum ethylene insensitive gene. Halberd parent played role in donating more alleles for moisture stress tolerance and Len donates higher yield allelic variants. Numerous significant QTL were identified in this study, to dissect the wheat performance under moisture stress. The identified genetic loci were important potential tools in breeding to improve moisture stress tolerant germplasm.