Abstract
In wheat, a multi-locus genome-wide association study (ML-GWAS) was conducted for the four grain weight-related traits (days to anthesis, grain filling duration, grain number per ear, and grain weight per ear) using data recorded under irrigated (IR) and rain-fed (RF) conditions. Seven stress-related indices were estimated for these four traits: (i) drought resistance index (DI), (ii) geometric mean productivity (GMP), (iii) mean productivity index (MPI), (iv) relative drought index (RDI), (v) stress tolerance index (STI), (vi) yield index, and (vii) yield stability index (YSI). The association panel consisted of a core collection of 320 spring wheat accessions representing 28 countries. The panel was genotyped using 9,627 single nucleotide polymorphisms (SNPs). The genome-wide association (GWA) analysis provided 30 significant marker-trait associations (MTAs), distributed as follows: (i) IR (15 MTAs), (ii) RF (14 MTAs), and (iii) IR+RF (1 MTA). In addition, 153 MTAs were available for the seven stress-related indices. Five MTAs co-localized with previously reported QTLs/MTAs. Candidate genes (CGs) associated with different MTAs were also worked out. Gene ontology (GO) analysis and expression analysis together allowed the selection of the two CGs, which may be involved in response to drought stress. These two CGs included: TraesCS1A02G331000 encoding RNA helicase and TraesCS4B02G051200 encoding microtubule-associated protein 65. The results supplemented the current knowledge on genetics for drought tolerance in wheat. The results may also be used for future wheat breeding programs to develop drought-tolerant wheat cultivars.
Highlights
Wheat (Triticum aestivum L.) is one of the major cereal crops and contributes about 30% (760 million tons) of world grain production (Food Agriculture Organization of the United Nations, 2021)
An assessment by the UN’s Intergovernmental Panel on Climate Change (IPCC) predicted that the global surface temperature would increase by 1.5◦C in the 20 years, causing extreme drought in several wheat growing regions including South Asia (IPCC, 2021) which inhabits one-fourth of the global population and where wheat is a lifeline for millions
Genotype × location interactions were significant for Days to anthesis (DTA) and Grain number per ear (GNPE), while genotype × environment interactions (IR vs. RF) were significant for DTA and Grain filling duration (GFD) (Table 1)
Summary
Wheat (Triticum aestivum L.) is one of the major cereal crops and contributes about 30% (760 million tons) of world grain production (Food Agriculture Organization of the United Nations, 2021). The rate of increase in annual wheat production has recently decreased from 3% during the 1970’s and 1980’s to 0.9% in recent years causing concern. This rate must increase to ∼2% to meet the projected demand of 50–60% additional wheat. ML-GWAS Analysis in Wheat by 2050 (Ray et al, 2013) This may be challenging owing to a variety of abiotic stresses that impact wheat yield. An assessment by the UN’s Intergovernmental Panel on Climate Change (IPCC) predicted that the global surface temperature would increase by 1.5◦C in the 20 years (by 2040), causing extreme drought in several wheat growing regions including South Asia (IPCC, 2021) which inhabits one-fourth of the global population and where wheat is a lifeline for millions. Understanding the genetic systems that provide tolerance to drought stress is a priority for wheat breeding to sustain wheat production and productivity
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