Identification of candidate genes for late leaf spot resistance in previous QTL regions for late leaf spot and rust resistance in groundnut.

Late leaf spot (LLS) and rust are major biotic constraints in Arachis hypogaea, governed by complex polygenic resistance largely mapped to QTL-rich regions on chromosomes A02 and A03. This review synthesizes recent advancements in the identification, mapping, and deployment of candidate resistance genes within these loci. Resistance is underpinned by key gene families including NBS-LRRs, RLKs, serine/threonine kinases, and PPR proteins, identified through integrative approaches combining QTL-seq, transcriptomics, metabolomics, and high-density SNP genotyping. Functional validation using RNAi, CRISPR/Cas9, and overexpression has confirmed the regulatory roles of genes such as LLSR1, LLSR2, and LR1 in mediating defense via ROS homeostasis, PTI/ETI signaling, and secondary metabolism. The development of diagnostic KASP markers has enabled marker- assisted selection (MAS) and early-generation pyramiding of non-allelic loci, accelerating the release of resistant cultivars like Girnar 4 and GG 39. Cross-species synteny and comparative QTL analysis further reveal conserved defense networks across legumes and cereals, supporting translational breeding strategies. Collectively, this genomics-driven framework underscores a shift toward precision resistance breeding, integrating functional gene discovery with high-throughput marker deployment for durable, broad-spectrum foliar disease resistance in groundnut.