QTL on wheat (Triticum aestivum L.) chromosomes 1B, 3D and 5A are associated with constitutive production of leaf cuticular wax and may contribute to lower leaf temperatures under heat stress

Abstract

Cooler canopy temperatures and glaucousness have both been identified as adaptive traits for improving abiotic stress tolerance in wheat. The objective of this study was to determine if glaucousness resulting from the constitutive production of leaf cuticular waxes was associated with cooler leaf and spike temperatures under heat stress and to identify associated quantitative trait loci (QTL). A set of 121 recombinant inbred lines (RILs) derived by crossing the heat tolerant wheat cultivar ‘Halberd’ and heat susceptible wheat cultivar ‘Karl92’ was utilized for QTL mapping. Flag leaf cuticular wax was extracted and quantified using a colorimetric technique at 10 days after pollination prior to initiation of the heat stress. The parental cultivars and RIL population were then subjected to a heat treatment of 38 °C and temperature depression of both leaf and spike was measured. The parental cultivar Halberd had high flag leaf wax content, and cooler leaf and spike temperatures compared to Karl92, with the RIL population showing significant genetic variation for these traits. QTL identified for leaf and spike temperature depression and leaf waxes explained 8–12 % of the phenotypic variation. Stable QTL for leaf wax content were located on chromosomes 1B and 5A with the 5A QTL region showing localization with QTL for leaf and spike temperature depression, indicating a genetic link between these traits. The results suggest that common genetic loci may influence both of these adaptive traits and could be targeted to improve adaptation to high temperature stress.