Mineral dynamics in cauliflower (Brassica oleracea var. botrytis) genotypes under Alternaria brassicicola infection: A multivariate approach

Among many diseases effecting cauliflower (Brassica oleracea var. botrytis L.), Alternaria leaf spot (ALS) disease caused by Alternaria brassicicola (Schw.) impacts the most, with yield reduction upto 50% under favourable condition. The present study was carried out during 2024 at ICAR-Indian Agricultural Research Institute, New Delhi to evaluate the role of mineral nutrients in disease resistance. Six genotypes [DCF-14, DC-309, VV, Pusa Meghna (PM), Pusa Kartiki (PK) and Pusa Deepali (PD)] were assessed pre- and post-infection conditions artificially challenged by pathogen. The disease severity-index (DSI) showed that genotypes DCF14 and VV were resistant (6.67%), while Pusa Kartiki and Pusa Deepali as moderately resistant (20%), and Pusa Meghna and DC309 as susceptible (33.33%) at 9th day. ANOVA revealed significant genotypic interactions for essential macro- (N, P, K), secondary- (Ca, Mg, S), and micro- (Fe, Cu) nutrients. Resistant genotypes exhibited substantial post-inoculation increase in K, Ca, S, and Fe nutrients compared to others. Principal Component Analysis (PCA) explained 92.56% of total phenotypic variance (PC1-71.99%, PC2-20.57%), with minerals N, P, K, S and Ca aligning negatively with DSI. PCA-biplot distinguished susceptible, moderate and resistant genotypes based on nutrient profile. Heatmap showed distinct clustering of genotypes where resistant genotypes having higher nutrients with lower DSI and susceptible genotypes grouped with lower nutrient profile and higher DSI. Partial correlation network (PCN) identified P, Mg, and Cu are negatively correlated with DSI, highlighting their potential roles in resistance against ALS. These outcomes revealed that coordinated mobilization of key nutrients K, Ca, S, and Fe, is pivotal for resistance against A. brassicicola, which provides solid foundation for genotype improvement and integrated nutrient management strategies in cauliflower.