CHITINOLYTIC BACILLUS spp ISOLATES ANTAGONISTIC TO FUSARIUM MONILIFORME IN MAIZE
W. Bressan, J.E. Fontes Figueiredo
Six isolates of Bacillus spp. (BM1, BM2, BM3, BM4, BM5 and BM6) were evaluated to determine their antagonistic activity towards Fusarium moniliforme in maize seeds. A preliminary survey detected F. moniliforme (Giberella fujikuroi) in all subsamples of maize seeds apparently free from disease. The fungus incidence in the seeds ranged from 26.7% to 61.4%. All Bacillus spp. isolates suppressed the growth of F. moniliforme in vitro and in maize seed trials. The highest disease control in seeds was given by isolate BM2 (79.6%) and the lowest by isolate BM5 (54.2%). In soil trials, the reduction in diseased plants ranged from 65% to 78% and no significant differences (p=0,05) were observed among Bacillus spp. isolates in controlling the pathogen. All Bacillus spp. isolates produced chitinase, but isolates BM2 and BM3 had the highest chitinase activity. These results indicate that Bacillus spp. isolates have antagonist activity towards F. moniliforme and have a potential to be used as a biocontrol agent. The possible role of chitinase secreted by Bacillus spp. isolates in the suppression of the fungal infection is discussed.