Abstract
Poor understanding of the genetic and molecular basis of heat tolerance component traits is a major bottleneck in designing heat tolerant wheat cultivars. The impact of terminal heat stress is generally reported in the case of late sown wheat. In this study, our aim was to identify genomic regions for various agronomic traits under late sown conditions by using genome-wide association approach. An association mapping panel of 205 wheat accessions was evaluated under late sown conditions at three different locations in India. Genotyping of the association panel revealed 15,886 SNPs, out of which 11,911 SNPs with exact physical locations on the wheat reference genome were used in association analysis. A total of 69 QTLs (10 significantly associated and 59 suggestive) were identified for ten different traits including productive tiller number (17), grain yield (14), plant height (12), grain filling rate (6), grain filling duration (5), days to physiological maturity (4), grain number (3), thousand grain weight (3), harvest index (3), and biomass (2). Out of these associated QTLs, 17 were novel for traits, namely PTL (3), GY (2), GFR (6), HI (3) and GNM (3). Moreover, five consistent QTLs across environments were identified for GY (4) and TGW (1). Also, 11 multi-trait SNPs and three hot spot regions on Chr1Ds, Chr2BS, Chr2DS harboring many QTLs for many traits were identified. In addition, identification of heat tolerant germplasm lines based on favorable alleles HD2888, IC611071, IC611273, IC75240, IC321906, IC416188, and J31-170 would facilitate their targeted introgression into popular wheat cultivars. The significantly associated QTLs identified in the present study can be further validated to identify robust markers for utilization in marker-assisted selection (MAS) for development of heat tolerant wheat cultivars.
Highlights
Wheat is an important staple food crop supplying about 20% of the calories needed by the world population (Lobell and Gourdji, 2012; Shiferaw et al, 2013)
The present analysis was conducted to map QTLs and identify SNP markers associated with agronomical traits under very late sown wheat in order to accelerate marker-assisted selection (MAS) for development of heat tolerance wheat varieties
The wheat association mapping (AM) panel used in this study showed large phenotypic variation for the majority of analyzed traits related to phenology and yield attributes
Summary
Wheat is an important staple food crop supplying about 20% of the calories needed by the world population (Lobell and Gourdji, 2012; Shiferaw et al, 2013). Heat stress refers to plants exposed to high temperature during the grain filling period. January sown crop is exposed to high temperatures within one week of flowering and experiences stress for the most period of grain filling. Yield losses are caused by long periods of high temperatures as well as short heat waves during heading and grain filling stages (Wardlaw and Wrigley, 1994). The reproductive stages of wheat (flowering and grain filling) are highly sensitive to heat stress, and rises in temperature during this period can result in a complete loss of grain production (Zinn et al, 2010). Average wheat yield losses in India due to a 1°C increase in temperature have been estimated at 9.1 ± 5.4% (Zhao et al, 2017), while global yield reduction caused by the same 1°C increase is estimated at 5.5%, signifying a total loss of 35 M tons (Lobell and Gourdji, 2012)
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