Abstract
Wheat production is increasingly threatened by biotic and abiotic stresses, with stripe rust, caused by Puccinia striiformis f. sp. tritici being among the most devastating diseases. To dissect stripe rust resistance mechanisms, 329 diverse wheat genotypes were evaluated across six distinct environments in India (three locations over two years). The panel exhibited wide variation for stripe rust resistance and was genotyped using a 35K SNP-array. Genome-wide association study (GWAS) revealed 49 significant marker-trait associations (MTAs), explaining 1.58% to 29.7% of phenotypic variation, with notable quantitative-trait locus (QTL) hotspots on chromosomes 2A, 3B and 4B. Several MTAs co-localized with known resistance loci, while AX-92621629 appeared novel, suggesting new genomic region contributing to adult plant resistance. Candidate genes near significant single-nucleotide polymorphisms (SNPs) were enriched for defense-related functions, including nucleotide-binding site leucine-rich repeat (NBS-LRR) proteins, receptor-like kinases and transcription factors involved in defense signaling. To further investigate resistance mechanisms, metabolomic profiling, phytohormone and flavonoid dynamics were conducted on two contrasting wheat genotypes (resistant SKUA_415; susceptible SKUA_246) using untargeted Gas Chromatography-Mass Spectrometry (GC‒MS) and Liquid Chromatography-Mass Spectrometry (LC‒MS) approaches. Key defense-related metabolites, including myo-inositol, ketoglutaric acid, rutin and schaftoside and kaempferol derivatives were identified. These metabolites were downregulated in SKUA_246 following infection, while SKUA_415 showed up-regulation of defense phytohormones, anthocyanins and flavonoids. The two contrasting genotypes also exhibited clear allelic differentiation at key resistance-linked SNP loci, consistent with their divergent metabolomic responses. This study highlights identification of promising genes/QTLs/MTAs and metabolic markers for breeding next-generation stripe rust resistant wheat cultivars.
