First comprehensive evaluation of genetic variability for bacterial blight resistance in wild Punica granatum L. populations from the North-Western Himalayas

Identifying and selecting disease-resistant sources from wild germplasm pools is pivotal due to their ecological benefits and cost-effectiveness. This study encompassed the survey and collection of wild pomegranate genotypes alongside commercial cultivars, followed by screening against native pathogens. Additionally, biochemical analyses were conducted to elucidate defense mechanisms in both resistant and susceptible genotypes. Cuttings from selected germplasm across four districts were obtained, grown for one year, and assessed for pathogenicity and biochemical responses. Microscopic and molecular analyses confirmed the pathogen as Xanthomonas axonopodis pv. punicae (Xap), identified by its distinctive morphology and a 1500 bp amplicon along with phylogeny analysis. Germplasm screening via detached and attached leaf assays identified genotypes with minimal disease severity, highlighting SH-14 and SH-16 as highly resistant in the attached leaf assay. Principal component analysis categorized genotypes based on disease parameters, with PC1 explaining approximately 75 % of the variability. Agglomerative hierarchical clustering further grouped genotypes into ten clusters, emphasizing clusters IX and X for their significant resistance traits. Biochemical studies revealed that the resistant genotype SH-16 exhibited higher levels of constitutive defense components like chlorophyll and vitamin C, as well as induced defense components such as phenols, flavonoids, and antioxidants, compared to the susceptible cultivar Bhagwa. These findings underscore the critical roles of both constitutive and induced defense mechanisms in conferring pomegranate resistance to Xap. The study's comprehensive approach in evaluating genetic and biochemical resistance provides valuable insights for breeding disease-resistant pomegranate varieties, marking a significant advancement in exploring pomegranate wild relatives from the Himalayan region for their resistance to bacterial blight. • Present study identifies Himalayan wild pomegranate resist, crucial for breeding. • Molecular techniques confirmed bacterial isolate as the pomegranate bacterial blight agent in challenge inoculation. • Principal component analysis and clustering group pomegranate genotypes by disease traits, identifying resilient clusters. • Genotype SH-16 showed disease resistance with high wax, chlorophyll, vitamin C, phenols, flavonoids, and antioxidants.