Heat and drought adaptive QTL in a wheat population designed to minimize confounding agronomic effects

Abstract

A restricted range in height and phenology of the elite Seri/Babax recombinant inbred line (RIL) population makes it ideal for physiological and genetic studies. Previous research has shown differential expression for yield under water deficit associated with canopy temperature (CT). In the current study, 167 RILs plus parents were phenotyped under drought (DRT), hot irrigated (HOT), and temperate irrigated (IRR) environments to identify the genomic regions associated with stress-adaptive traits. In total, 104 QTL were identified across a combination of 115 traits × 3 environments × 2 years, of which 14, 16, and 10 QTL were associated exclusively with DRT, HOT, and IRR, respectively. Six genomic regions were related to a large number of traits, namely 1B-a, 2B-a, 3B-b, 4A-a, 4A-b, and 5A-a. A yield QTL located on 4A-a explained 27 and 17% of variation under drought and heat stress, respectively. At the same location, a QTL explained 28% of the variation in CT under heat, while 14% of CT variation under drought was explained by a QTL on 3B-b. The T1BL.1RS (rye) translocation donated by the Seri parent was associated with decreased yield in this population. There was no co-location of consistent yield and phenology or height-related QTL, highlighting the utility of using a population with a restricted range in anthesis to facilitate QTL studies. Common QTL for drought and heat stress traits were identified on 1B-a, 2B-a, 3B-b, 4A-a, 4B-b, and 7A-a confirming their generic value across stresses. Yield QTL were shown to be associated with components of other traits, supporting the prospects for dissecting crop performance into its physiological and genetic components in order to facilitate a more strategic approach to breeding.

Fig. 1

Trait association for yield across all six trials of the Seri/Babax population grown between 2002 and 2006. The diagonal contains the yield histogram for each trial, the lower diagonal a scatter plot and loess smoothing line between all trials, and the upper diagonal contains the phenotypic correlations

Fig. 2

Main genomic regions associated with yield, grain number (GM⁻²), and canopy temperature (CT) under drought (D), heat (H), and irrigated (I) environments. Blue and red colors are used to distinguish between Babax (red) and Seri (blue) LOD scores. On both sides of the figure is indicated the corresponding trial × year, canopy temperature (CT) is additionally labeled with the date of measurement given in number of days after emergence

Fig. 3

QTL effects for agronomic traits in the six trials. Positive (+) and negative (−) values are used to distinguish between additive effects of Babax and Seri alleles in each linkage group. Only effects where LOD > 2 are shown

Fig. 4

QTL effects for the phenological traits. Positive (+) and negative (−) values are used to distinguish between additive effects of Babax and Seri alleles in each linkage group. Only effects where LOD > 2 are shown

Fig. 5

QTL effects for the physiological traits. Positive (+) and negative (−) values are used to distinguish between additive effects of Babax and Seri alleles in each linkage group. Only effects where LOD > 2 are shown

Fig. 6

Dissection of yield QTL into agronomy- and physiology-related QTL. a QTL for yield (single lined curve) dissected into QTL related to agronomic traits, QTL for GM⁻² (dotted circle) QTL for TGW (double lined circle); b QTL for yield dissected into physiological traits, QTL for CT (double lined circle); QTL for NDVI (dotted circle); QTL for CHL(single lined curve); Big fonts are robust QTL for yield while small fonts are suggestive QTL for yield