Email: rrmir@skuastkashmir.ac.in ; imrouf2006@gmail.com

Bread wheat is one of the most important cereal crops in the world. The production and productivity of wheat is significantly reduced by various unpredictable biotic and abiotic stresses. Among biotic stresses, diseases like stripe rust is the most important diseases posing threat to its production and productivity both locally and globally.

Therefore, we have made efforts to screen a core set of >4500 diverse wheat genotypes from Indian gene bank harboring whole world wheat diversity for stripe rust resistance in six (06)diverse environments in India. Based on trait data of stripe rust resistance, a core set of 400 genotypes showing varying degree of response to stripe rust was selected for further trait characterization. This mini core set was used for physio-biochemical characterization for Ascorbic peroxidase, Catalase, Peroxidase, Superoxide dismutase, Polyphenol oxidase, Lipid peroxidation and Hydrogen peroxidation.

The analysis underscored heightened antioxidant activity in the resistant genotypes, indicating a stronger defense mechanism against oxidative stress. The same mini-core set was also characterized for different already known stripe rust resistance gene linked markers.

The trait data on stripe rust collected over six (06) environments across three different locations in India was used along with 35K SNP genotyping data for validation of already known and discovery of several new genes/QTLs for stripe rust resistance.

GWAS analysis identified 108 significant associations for stripe rust resistance using six GWAS models across six environments E1, E2, E3, E4, E5, E6 and data pooled over environments (E7). Among them, 20 marker-trait associations (MTAs) were found stable and promising and detected across all seven environments using multiple GWAS models.

In addition, based on trait evaluation for stripe rust, we have selected two candidate genotypes for stripe rust resistance (one highly resistant and one highly susceptible) and used them for metabolomics study.

The analysis of metabolomics data from contrasting wheat genotypes for stripe rust resistance led to the identification of several important metabolites including defense phytohormones, flavonoids and Anthocyanidins. Metabolomic profiling unveiled a notable increase in arginine biosynthesis, aldarate metabolism, and amino acid and nucleotide metabolism in the resistant genotype, fortifying its defense system against stripe rust.

Comparative analysis of phytohormones revealed the role of key regulators like salicylic acid jasmonic acid signaling cascade that activates defense genes, leading to the production of antimicrobial proteins, pathogenesis-related (PR) proteins and phytoalexins. Comparative flavonoid analysis revealed key secondary metabolites like rutin, malvidin and epigallocatechin in conferring resistance against stripe rust by providing antioxidant protection and antiomicrobial activity. We have also tried to study inheritance pattern and selection of promising segregants for stripe rust resistance using 9 bi-parental F2 mapping populations for stripe rust.

This study will lead us to identify new sources of stripe rust resistance under Kashmir conditions, the candidate genotypes and candidate genes/QTLs/markers for stripe rust, key candidate metabolites induced by stripe rust and important segregants for future wheat breeding programs.

Key words: Wheat, mini-core set, stripe rust, biochemical, gene/QTLs, metabolomics, genomics, GWAS.