Genome Wide Association Study Uncovers the QTLome for Osmotic Adjustment and Related Drought Adaptive Traits in Durum Wheat

Abstract

Osmotic adjustment (OA) is a major component of drought resistance in crops. The genetic basis of OA in wheat and other crops remains largely unknown. In this study, 248 field-grown durum wheat elite accessions grown under well-watered conditions, underwent a progressively severe drought treatment started at heading. Leaf samples were collected at heading and 17 days later. The following traits were considered: flowering time (FT), leaf relative water content (RWC), osmotic potential (ψs), OA, chlorophyll content (SPAD), and leaf rolling (LR). The high variability (3.89-fold) in OA among drought-stressed accessions resulted in high repeatability of the trait (h2 = 72.3%). Notably, a high positive correlation (r = 0.78) between OA and RWC was found under severe drought conditions. A genome-wide association study (GWAS) revealed 15 significant QTLs (Quantitative Trait Loci) for OA (global R2 = 63.6%), as well as eight major QTL hotspots/clusters on chromosome arms 1BL, 2BL, 4AL, 5AL, 6AL, 6BL, and 7BS, where a higher OA capacity was positively associated with RWC and/or SPAD, and negatively with LR, indicating a beneficial effect of OA on the water status of the plant. The comparative analysis with the results of 15 previous field trials conducted under varying water regimes showed concurrent effects of five OA QTL cluster hotspots on normalized difference vegetation index (NDVI), thousand-kernel weight (TKW), and/or grain yield (GY). Gene content analysis of the cluster regions revealed the presence of several candidate genes, including bidirectional sugar transporter SWEET, rhomboid-like protein, and S-adenosyl-L-methionine-dependent methyltransferases superfamily protein, as well as DREB1. Our results support OA as a valuable proxy for marker-assisted selection (MAS) aimed at enhancing drought resistance in wheat.

Dosage differences in 12-OXOPHYTODIENOATE REDUCTASE genes modulate wheat root growth

“…We then recorded the dry-weight (DW) after the samples were dried at 60 °C for 5 days. The RWC was calculated based on the following formula: RWC = 100* ((FW-DW)/(FWS-DW)) 43 .…”

Time for a drought experiment: Do you know your plants’ water status?

“…We anticipate that joining new high-throughput tools for measuring water status and ‘omics responses to stress will drive many new discoveries. For example, Condorelli et al (2022) recently used genome wide association (GWA) studies of a Durum wheat diversity panel to identify candidate genes underlying osmotic adjustment.…”

Improving Drought Resistance by Introduction of the Proline Synthesis Gene P5CSA into Inbred Rice Lines as a New Genetic Resource for Breeding Programs

“…The range of organisms from bacteria to maize, shows a strong correlation between increased levels of cellular proline and survival under water-deprived and high-salinity conditions (Chakraborty and Roychoudhury 2022). Some positive evidence associating osmotic adjustment with biomass production or yield under drought stress has been reported for wheat (Mehmood et al 2020;Condorell et al 2022), sorghum (Wagaw 2019;Ngugi et al 2022), chickpeas (Singh et al 2021), Brassica species (Xiong and Ma 2022) and barley (Shrestha et al 2022).…”