Koehl, J.; Fokkema, N. J.

Sixty isolates of saprophytic microorganisms were screened for their ability to reduce the severity of grey mould (Botrytis cinerea) infection and sporulation. Isolates of the bacteria Xanthomonas maltophilia, Bacillus pumilus, Lactobacillus sp., and Pseudomonas sp. and the fungus Gliocladium catenulatum reduced germination of conidia of the pathogen and controlled disease on bean and tomato plants. Their activity under growth room conditions was good, consistent, and similar to the activity of the known biocontrol agent, Trichoderma harzianum T39 (non-formulated). Although the tested isolates may for nutrients with the germinating conidia of B. cinerea, resistance induced in the host by live or dead cells were also found to be involved. Inhibitory compounds were not detected on treated leaves. Sporulation of B. cinerea after its establishment on leaves was also reduced by the above mentioned isolates and by Penicillium sp., Arthrinium montagnei, At. phaeospermum, Sesquicillium candelabrum, Chaetomium globosum, Alternaria alternata, Ulocladium atrum, and T. viride. These sporulation-inhibiting fungi did not reduce the infection of leaves by B. cinerea. Most of these selected fungi and bacteria were capable of reducing lesion expansion.