QTL associated with heat susceptibility index in wheat (Triticum aestivum L.) under short-term reproductive stage heat stress

Abstract

Heat stress adversely affects wheat production in many regions of the world and is particularly detrimental during reproductive development and grainfilling. The objective of this study was to identify quantitative trait loci (QTL) associated with heat susceptibility index (HSI) of yield components in response to a short-term heat shock during early grainfilling in wheat. The HSI was used as an indicator of yield stability and a proxy for heat tolerance. A recombinant inbred line (RIL) population derived from the heat tolerant cultivar 'Halberd' and heat sensitive cultivar 'Cutter' was evaluated for heat tolerance over 2 years in a controlled environment. The RILs and parental lines were grown in the greenhouse and at 10 days after pollination (DAP) half the plants for each RIL received a three-day heat stress treatment at 38°C/ 18°C day/night, while half were kept at control conditions of 20°C/18°C day/night. At maturity, the main spike was harvested and used to determine yield components. A significant treatment effect was observed for most yield components and a HSI was calculated for individual components and used for QTL mapping. QTL analysis identified 15 and 12 QTL associated with HSI in 2005 and 2006, respectively. Five QTL regions were detected in both years, including QTL on chromosomes 1A, 2A, 2B, and 3B. These same regions were commonly associated with QTL for flag leaf length, width, and visual wax content, but not with days to flowering. Pleiotropic trade-offs between the maintenance of kernel number versus increasing single kernel weight under heat stress were present at some QTL regions. The results of this study validate the use of the main spike for detection of QTL for heat tolerance and identify genomic regions associated with improved heat tolerance that can be targeted for future studies.

Heat Tolerance in Wheat - A Key Strategy to Combat Climate Change through Molecular Markers

“…It is therefore recommended to design a breedingled approach to adapting wheat to elevated temperature environments (Reynolds et al, 2007;. The genetic basis of high temperature tolerance in wheat is not very well understood; to date it has been assessed largely by monitoring the response of grain yield (Yang et al, 2002;Pinto et al, 2010), grain filling duration (Yang et al, 2002), grain size, canopy temperature depression (Reynolds et al, 1994;Ayeneh et al, 2002), a heat sensitivity index (Mohammadi et al, 2008;Mason et al, 2010;Paliwal et al, 2012) or various senescence-related traits (Vijayalakshmi et al, 2010) to exposure to high temperature.…”

“…Patil et al, (2008) evaluated wheat genotypes for terminal and continual heat stress tolerance and reported that the reduction in grain number in terminal heat stress environment was due to sudden increase in temperature during grain growth period. Mason et al, (2010) identified QTL associated with heat susceptibility index (HSI) of yield components in response to a short term heat shock during early grain filling in wheat. The HSI was used as an indicator of yield stability and a proxy for heat tolerance.…”

Wheat physiology: a review of recent developments

“…Looking specifically at a susceptible (Karl 92) and a tolerant cultivar (Halberd) grown at 20/188C, exposed to 1-2 days of heat (38/258C) at 10 days after pollination, Hays et al (2007) found 25% grain abortion and 10% GW reduction in cultivar Karl, but no response whatsoever in Halberd, responses which were associated with a large increase in ethylene production in grains and leaves with heat in the susceptible cultivar. These researchers have gone on to identify, in a RIL population of Halberd  Susceptible, several QTLs significantly associated with heat tolerance (Mason et al 2010), but they are still some way from gene identification.…”

Genetic Parameters of Variability and Path Analysis in Wheat under Timely and Late Sown Conditions

“…Among abiotic factors heat stress is a major production constraint for bread wheat grown in non-temperate environments (Mason et al, 2010;Pinto et al, 2010). High temperature is affecting about 65 to 70 mha in the World (Reynolds et al, 1994), around 13.5 mha area in India (Joshi et al, 2007).…”