Mineral Dynamics of Cauliflower (Brassica oleracea var. botrytis L.) under Alternaria Leaf Spot Infection: A Multivariate Approach

Abstract

Alternaria brassicicola (Schw.) causal organism of Alternaria leaf spot, severely impacts cauliflower, with yield losses exceeding 50% under conducive conditions. This study, conducted at ICAR-IARI, New Delhi, assessed six genotypes (DCF14, VV, PK, PD, PM, and DC309) under pre- and post-inoculation conditions to explore the role of mineral nutrients in disease resistance. Disease severity index (DSI) revealed DCF14 and VV as resistant (6.67%), PK and PD as moderately resistant (20%), and PM and DC309 as susceptible (33.33%). ANOVA for CRD showed significant genotype interactions for key macro- (N, P, K), secondary (Ca, Mg, S), and micro- (Fe, Cu) nutrients. Resistant genotypes displayed substantial post-inoculation increases in K, Ca, S, and Fe nutrients critical for structural reinforcement, oxidative defense, and immune signaling. Principal Component Analysis (PCA) captured 92.56% of total variance (PC1: 71.99%, PC2: 20.57%), with resistance-associated minerals (N, P, K, S, Ca) aligning negatively with DSI. The PCA biplot distinguished resistant, intermediate, and susceptible genotypes based on mineral profiles. Heatmap analysis revealed distinct clustering of genotypes: resistant genotypes (DCF14, VV) grouped with higher nutrient levels and lower DSI, while susceptible genotypes (PM, DC309) clustered with nutrient depletion and higher disease indices. Partial-correlation network (PCN) analysis identified P, Mg, and Cu as negative correlates of disease score, highlighting their potential roles in resistance. Collectively, these findings demonstrate that coordinated nutrient mobilization, particularly of K, Ca, S, and Fe, is integral to resistance against A. brassicicola, offering a basis for breeding and integrated nutrient management strategies in cauliflower.