Genome-Wide Association Study Reveals Natural Variations Contributing to Drought Resistance in Crops

Abstract

Crops are often cultivated in regions where they will face environmental adversities; resulting in substantial yield loss which can ultimately lead to food and societal problems. Thus, significant efforts have been made to breed stress tolerant cultivars in an attempt to minimize these problems and to produce more stability with respect to crop yields across broad geographies. Since stress tolerance is a complex and multi-genic trait, advancements with classical breeding approaches have been challenging. On the other hand, molecular breeding, which is based on transgenics, marker-assisted selection and genome editing technologies; holds great promise to enable farmers to better cope with these challenges. However, identification of the key genetic components underlying the trait is critical and will serve as the foundation for future crop genetic improvement. Recently, genome-wide association studies have made significant contributions to facilitate the discovery of natural variation contributing to stress tolerance in crops. From these studies, the identified loci can serve as targets for genomic selection or editing to enable the molecular design of new cultivars. Here, we summarize research progress on this issue and focus on the genetic basis of drought tolerance as revealed by genome-wide association studies and quantitative trait loci mapping. Although many favorable loci have been identified, elucidation of their molecular mechanisms contributing to increased stress tolerance still remains a challenge. Thus, continuous efforts are still required to functionally dissect this complex trait through comprehensive approaches, such as system biological studies. It is expected that proper application of the acquired knowledge will enable the development of stress tolerant cultivars; allowing agricultural production to become more sustainable under dynamic environmental conditions.

<strong>When water runs dry and temperature heats up: </strong><strong>Understanding the mechanisms in rice tolerance to drought and </strong><strong>high temperature stress conditions</strong>

“…By utilizing evolutionary and historical recombination events at the population level, GWAS serve as an instrument to define complex trait differences at the sequence level (Lafarge et al, 2017). Likewise, GWAS can construe the evolution trend and/or the manmade selection of an essential trait (Wang and Qin, 2017). Methodologies for more advanced models have evolved from its simplest form called marker-by marker analysis (Lafarge et al, 2017).…”

“…Moreover, a recent review on GWAS and QTL mapping concluded that natural variations responsible for drought resistance occur in crops and comprehensive approaches such as systems biological studies can be utilized to further elucidate the molecular mechanisms of identified loci (Wang and Qin, 2017). Combined analyses of GWAS and high-throughput phenotyping in rice showed meaningful insights into the genetic architecture of 15 essential traits related to morphology, biomass and yield (Yang et al, 2014b).…”

“…Despite of the numerous promising loci identified thus far, elucidation of their molecular mechanisms responsible for improved stress tolerance remains to be explored through systems biological studies and comprehensive approaches (Wang and Qin, 2017).…”

“…Breeding climate-resilient varieties also poses great challenges to scientists owing to the complexities of screening techniques, component traits, developmental stage or age of plants, environmental interactions including a profound understanding of the various morphological, physiological and biochemical mechanisms specific to DS and HTS. Although complex traits such as genetic loci have been discovered, these should be dissected functionally through comprehensive approaches like systems biology (Wang and Qin, 2017).…”

Regulatory changes in TaSNAC8‐6A are associated with drought tolerance in wheat seedlings

“…In this study, we used linkage disequilibrium (LD)-based association mapping, a powerful tool for dissecting complex agronomic traits and identifying alleles that can contribute to crop improvement, in conjunction with candidate gene association analysis for detecting DNA polymorphisms (e.g. SNPs) or genetic markers within, or tightly linked to genes contributing to complex traits (Huang et al, 2011;Liu et al, 2017;Wang and Qin, 2017;Xiao et al, 2017). This approach has previously been successfully applied to detect allelic diversity of genes controlling crop drought tolerance, especially in rice and maize (Liu et al, 2013;Mao et al, 2015;Singh et al, 2015;Songyikhangsuthor et al, 2014;Wang et al, 2016;Xiang et al, 2017;Xiong et al, 2018).…”