Mapping the genetic loci regulating leaf epicuticular wax, canopy temperature, and drought susceptibility index in Triticum aestivum

Earlier studies have shown the significant impact of leaf glaucousness and cooler canopies on wheat (Triticum aestivum L.) yield. However, breeding for drought adaptive traits and potential yield as responses to heat or water deficit were poor. The genetic basis for drought-adaptive traits and yield potential were assessed using quantitative trait locus (QTL) analysis. The 180 recombinant inbred lines (RILs) were derived from a cross between 'Len' (USA) and 'Halberd' (Australian) wheat lines. The RIL population and the parents were genotyped with a 90K Infinium single nucleotide polymorphism (SNP) library to construct 22 linkage groups. The QTLs segregating for leaf epicuticular wax (EW), cooler canopies, drought susceptibility index (DSI), and grain attributes were identified in the population across five environments. The QTLs associated with leaf EW, cooler canopies, DSI-mean single head weight (MSHW), DSI-thousand-kernel weight (TKW), and grain attributes co-localized on chromosomes 1A, 2B, 3B, 6B, 7A, and 7B. Gene ontology of the leaf EW QTLs on chromosomes 2B and 3B indicated that their sequences were similar to an Arabidopsis ABC transporter gene, and the leaf EW QTL on chromosome 7B was similar to the sorghum [Sorghum bicolor (L.) Moench] ethylene-insensitive gene. The favorable alleles associated with moisture stress tolerance were associated with the Halberd parent. The genetic loci (QWax.tam-3B and QCTP.tam-2B, QDSIM.tam-2B.1) with higher logarithm of odds (LOD) and R-2 values could be important potential tools in breeding to improve. The chromosomal regions identified in this study can provide breeders with additional tools to develop drought- and heat-tolerant cultivars through breeding.

Automated summary

Previous studies have pointed out the significance of leaf glaucousness and cool canopies on wheat yield, but the improvement in drought adaptive traits and potential yield in response to heat or water deficit was lacking. QTL analysis was conducted to assess the genetic basis of drought-adaptive traits and yield potential in a population of 180 recombinant inbred lines (RILs) derived from a cross between 'Len' (USA) and 'Halberd' (Australian) wheat lines. The study identified QTLs associated with leaf epicuticular wax, cooler canopies, drought susceptibility index, and grain attributes on various chromosomes, providing potential tools for breeding drought- and heat-tolerant wheat cultivars.