Mechanism of Aspergillus niger Van Teigh Antagonism towards Fusarium oxysporum Schlect f. sp. melonis Sny.&Hans., Muskmelon Wilt Pathogen

In vitro interactions of antagonist Aspergillus niger isolate AN 27 and muskmelon wilt pathogen Fusarium oxysporum f. sp. melonis isolate MM 37 revealed three distinct growth phases of A. niger AN 27-initial normal growth with black colony colour due to sporulation, suppressed growth and sporulation followed by revived growth and sporulation. Change in medium pigmentation from violet to pink and formation of abundant thick mycelial strands and chains of chlamydospores were observed in F. oxysporum f. sp. melonis MM 37. Change in medium pigmentation of MM 37 was attributed to the change in medium pH brought by AN 27 by constitutively producing organic acids. Mechanisms involved in AN 27 antibiosis were production of organic acids, antimicrobial substances (n-butanol extract) and extra cellular enzymes - all of which inhibited microconidial germination of MM 37. Seed coating with A. niger AN 27 spores or seedling dip in its spore suspension protected muskmelon seedlings from Fusarial wilt in Rapid Pathogenicity test.