Antagonistic Gluconobacter sp induces abnormal morphodifferentiation to Fusarium oxysporum f. sp lycopersici hyphae

A total of 541 rhizoplane bacteria, isolated from 41 different plant species, were screened for their growth inhibition against hyphae of Fusarium oxysporum f. sp. lycopersici in a dual culture assay. Among the bacterial isolates, only 4 (0.7%) showed remarkable growth inhibition of the test fungus, in which one genus, Gluconobacter sp. 71F, isolated from Erigeron annuus (Asteraceae), was most active. The characteristic morphophysiological effects of the active isolate on Fusarium were excessive lateral hyphal branching and cytoplasmic extrusion from the affected hyphal tips. According to fluorescent staining for nuclei, the affected hyphal nuclei either partly disintegrated in extruded cell matter or divided into portions on the lateral side of the hyphal cells. Nuclei disintegration at the severely affected hyphal tip eventually led to cell death. (C) Pesticide Science Society of Japan.