Journal of Advances in Biology & Biotechnology

Wilt complex disease is a major constraint in ginger cultivation, leading to severe reductions in both yield and rhizome quality. The disease is primarily caused by a combination of soil-borne pathogens, including Fusarium spp. and root-knot nematodes (Meloidogyne spp.). The study of biochemical alterations in infected tissues provides valuable information on host-pathogen interactions and the mechanisms involved in disease progression. Therefore, the present investigation was undertaken to study the biochemical changes in ginger rhizomes infected with wilt complex disease and to compare the biochemical constituents of healthy and diseased rhizomes. The study was conducted in the Department of Plant Pathology, College of Agriculture, V.C. Farm, Mandya, Karnataka, India, using four ginger cultivars under greenhouse and laboratory conditions. Biochemical analyses of ginger rhizomes from four cultivars — IISR Varada, IISR Mahima, IISR Rejatha, and Rio-de-Janeiro — were conducted to assess enzymatic activities (peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase) and biochemical constituents (total phenols, total sugars, reducing sugars, and condensed tannins) in healthy and wilt complex-infected plants at 30 and 60 days post-inoculation. The results revealed that infection by Fusarium sp., Meloidogyne incognita, and especially their combined inoculation significantly altered the biochemical constituents of ginger rhizomes, with the combined inoculation consistently inducing the highest levels of defense-related enzymes and metabolites, indicating a synergistic effect of the wilt complex pathogens. Among the cultivars evaluated, IISR Varada exhibited the highest activities of peroxidase, polyphenol oxidase, and phenylalanine ammonia lyase, along with greater accumulation of tannins and total phenols following pathogen challenge. IISR Mahima also showed a strong biochemical response, whereas IISR Rejatha and Rio-de-Janeiro exhibited comparatively lower levels of enzyme activity and phenolic accumulation. Pathogen inoculation also influenced carbohydrate metabolism, resulting in increased reducing and total sugar contents in infected rhizomes. Overall, the study revealed a clear association between cultivar identity and the magnitude of biochemical defense responses. IISR Varada and IISR Mahima exhibited consistently stronger activation of defense enzymes and accumulation of secondary metabolites than IISR Rejatha and Rio-de-Janeiro, suggesting that PO, PPO, PAL, total phenols, and tannins may serve as useful biochemical indicators for evaluating ginger germplasm against wilt complex pathogens.