Expression Profiling of MAPK1 , PR‐1 and HSP 70 Genes in Capsicum annuum Genotypes During Infection With Sclerotium rolfsii

Chilli ( Capsicum annuum ) is an economically important vegetable crop in Pakistan, with productivity severely constrained by wilt disease caused by the soil‐borne fungus Sclerotium rolfsii . This study aimed to characterise the pathogenicity of S. rolfsii and investigate molecular defence responses in local C. annuum varieties. Field surveys in Tehsil Haroon Abad, District Bahawalnagar, confirmed S. rolfsii as the causal agent of leaf spot and wilt. Pathogenicity assays on different C. annuum genotypes revealed infection rates of up to 65% in the most susceptible variety. Controlled pot experiments combined with RT‐qPCR analysis demonstrated differential expressions of defence‐related genes, including MAP kinase 1 ( MAPK1 ), pathogenesis‐related protein 1 ( PR‐1 ) and heat shock protein 70 ( HSP70 ). The Green Queen variety exhibited consistent MAPK1 upregulation, correlating with enhanced resistance, whereas HSP70 showed constitutive expression across all varieties. The Zenia variety displayed delayed and inconsistent PR‐1 and MAPK1 expressions, corresponding to higher susceptibility. KEGG pathway analysis identified MAPK and PR‐1 as central components of the defence signalling cascade. In silico docking indicated strong interactions between PR‐1 and fungal cell wall‐degrading enzymes, suggesting a potential inhibitory effect on pathogen virulence. These findings elucidate key molecular mechanisms underlying resistance to S. rolfsii in C. annuum , identifying MAPK1 and PR‐1 as pivotal inducible defence factors, while HSP70 may serve a constitutive protective role. The study provides valuable targets for breeding or transgenic strategies to develop disease‐resistant C. annuum cultivars, contributing to sustainable crop protection and improved yield.