Antagonistic activity of bacteria from the chickpea rhizosphere against Fusarium oxysporum f.sp. ciceris.

Abstract

The antagonistic activity against in vitro growth of Fusarium oxysporum f.sp. ciceris was determined for 74 bacterial isolates obtained from the rhizosphere of chickpeas grown in two field soils with different histories of Fusarium wilt, and for seven isolates of Pseudomonas spp. from culture collections. Twenty-four isolates of Bacillus spp. and Pseudomonas chlororaphis 30-84 showed a strong antagonism against three races (0, 1 and 5) of F.o. ciceris tested. Three selected Bacillus isolates and P. chlororaphis 30-84 were further tested against 30 isolates of races 0, 1 and 5 of F.o ciceris, races 0,1 and 2 of F.o. melonis, F.o. Phaseoli and nonpathogenic F. oxysporum. Bacillus isolates differed in their antagonistic activity and were less inhibitory to myce lial growth of F.o. ciceris than to that of other fungal isolates. Furthermore, the extent of growth inhibition of F.o. ciceris was influenced both by bacterial isolates and by race of the pathogen. Cell-free culture filtrates of four Bacillus isolates inhibited conidial germination and hyphal growth of F.o. ciceris and nonpathogenic F. oxysporum. Joint seed+soil treatment with some selected antagonistic Bacillus spp. isolates suppressed disease caused by the highly virulent F.o. ciceris race-5 in cv. ICCV 4 and cv. PV 61 chickpeas. However, the degree of protection was influenced by the host genotype and the inoculum concentration of pathogen