Annals of Plant Protection Sciences

Pseudomonas fluorescens, Streptomyces spp. and Trichoderma spp., isolated from the rhizosphere soils of various crops, were screened by dual culture and cell free culture filtrate techniques against Fusarium oxysporum f. sp. dianthi and F oxysporum f. sp. gladioli, causing wilt in carnation and gladiolus, respectively. Several isolates effectively inhibited mycelial growth of Fusarium in vitro. Pseudomonas, Streptomyces and Tricoderma exhibited considerable difference in their antagonism against Fusarium. The antagonistic efficacy of various isolates also differed markedly within Pseudomonas, Streptomyces and Trichoderma and their effect on the pathogen isolates from carnation and gladiolus. Among P. fluorescens isolates, PAPF-Nagrota exerted the maximum inhibition against F.o. f. sp. gladioli. Streptomyces isolate CAAC-Banuri exerted the maximum inhibition against F.o. f. sp. dianthi and GLAC-Kotli was found to be highly effective in inhibiting the growth of F.o. f. sp. gladioli. Among the isolates of Trichoderma, CATR-Darang and GLTR-Chauntra were equally effective against F.o. f. sp. dianthi, while GLTR-Kotli was effective against F.o. f. sp. gladioli. Similar trend of inhibition obtained in dual culture and cell free culture filtrate assay indicated the involvement of secondary metabolites in antagonism by the biological control agents. The antagonistic effects were elucidated in terms of antibiotic equivalence in respect of fluconazole and carbendazim for the isolates exhibiting high antagonistic potential.