QTL mapping and loci dissection for leaf epicuticular wax load and canopy temperature depression and their association with QTL for staygreen in Sorghum bicolor under stress

Abstract

Plant waxes and staygreen are distinct phenotypic traits that have been independently implicated in heat and drought tolerance among grasses. The association between these two traits has not been fully explored, which makes the exploitation of synergy between them difficult. This study assessed the association between QTL regulating the staygreen (Stg) trait in sorghum and those regulating epicuticular wax load (WL) and associated canopy temperature depression (TD). Using a recombinant inbred line (RIL) population derived from Tx642 and Tx7000, phenotypic data were collected in three replicated field trials and one greenhouse trial. High absolute TD generally corresponded to high WL. The r 2 of TD against WL was highest under non-stress conditions in the greenhouse while it was much larger in the cooler and irrigated field conditions compared to hotter, drier field trials. The genetic correlations between the two traits also followed this pattern. Composite interval mapping identified a total of 28 QTL, 15 of which had significant overlaps between different traits. Most of the wax QTL were associated with pre-anthesis drought tolerant Tx7000. However, one QTL for WL overlapped with a QTL for staygreen (Stg2) and was represented by a single, isolated marker near the centromeric region on the short arm of SBI-01. The marker is identified by a Cis-acting regulatory module and is part of a 2-kb multifunctional motif-rich region which includes core promoter and enhancer regions and transcription elements, including a droughtresponsive MYB binding site. We suggest that this QTL may be pleiotropic for important stress tolerance mechanisms regulating both staygreen and leaf wax in sorghum.

Correlation and co-localization of QTL for stomatal density and canopy temperature under drought stress in Setaria

“…The magnitude of variation in canopy temperature across the Setaria RIL population was similar to that observed for sorghum (Awika et al, 2017) and wheat (Mason et al, 2013) RIL populations. Variation in canopy temperature among the RIL population were similar on 30 DAS (wet 3.1 ˚C, dry 8.3 ˚C) and 32 DAS (wet 3.3 ˚C, dry 8.8 ˚C) and canopy temperature was correlated across the two dates sampled for both the wet (r = 0.78) and dry treatments (r = 0.66).…”

“…Therefore, improved methods for acquiring and analyzing images of stomatal guard cell complexes and other cell types in the epidermis are an area of active research (Haus et al, 2015;Dittberner et al, 2018;Fetter et al, 2019;Li et al, 2019). In addition, alternative approaches to rapidly screen stomatal conductance or rates of transpiration at the leaf and canopy scales (including temperature as a proxy) have also been developed and used to reveal genetic variation in traits related to drought stress and WUE (Liu et al, 2011;Bennett et al, 2012;Awika et al, 2017;Prado et al, 2018;Deery et al, 2019;Vialet-Chabrand and Lawson, 2019). However, the expected links between genetic variation in stomatal density and measures of water use, which would be expected in theory, are rarely tested and when tested, the results are inconsistent (e.g.…”

Identification and Characterization of Contrasting Genotypes/Cultivars for Developing Heat Tolerance in Agricultural Crops: Current Status and Prospects

“…Yield potential and the metabolic fitness of crop plants under specific environmental conditions are determined by CTD (Kumari et al, 2013). A study on barley revealed a strong link between epicuticular leaf wax QTL and CTD, and that wax load influences plant canopy temperature (Awika et al, 2017). Based on phenotypic variation, CTD can act as a desirable criterion for heat-tolerant genotype selection (Mason and Singh, 2014).…”

Developing Growth‐Associated Molecular Markers Via High‐Throughput Phenotyping in Spinach

“…For example, the DAS CC -associated SNP 36324_127 is located in Spo15232, which belongs to the basic leucine zipper transcription factor family proteins, members of which are involved in light and stress signaling influencing plant growth and development (Xiang et al, 2008). The marker 44291_137 (chr6, Position 45,352,029) resides in an intronic segment of the gene Spo11400, which codes for cytochrome P450 family protein, whose orthologs have been implicated in stay-green, photosynthesis, defense, and plant development (Cooper, 2000;Xu et al, 2015;Awika et al, 2017).…”