Targeted Bacillus biocontrol systems for protected crops against the grey mould pathogen, Botrytis cinerea
The primary aim of this study was to isolate and investigate the biocontrol potential of natural Bacillus spp. against the causative agent of grey mould disease, Botrytis cinerea. Potential antagonists were isolated from tomato and Chinese cabbage plants. Three Bacillus isolates, two epiphytes (S15ccs and S8ts) from Chinese cabbage and tomato seeds respectively and one endophyte (M1ccst) from Chinese cabbage stems, showing the best antagonistic activities against B. cinerea were finally selected. The three selected isolates were tested in the glasshouse trial for control of tomato grey mould disease (B. cinerea). Isolates S15ccs and M1ccst significantly (P ≤ 0.05) reduced disease incidence by 40 and 35% respectively whereas S8ts showed no significant effect. A quarter strength Tryptone Soya Broth (1/4 TSB) which was used as a control treatment reduced B. cinerea infection by 55%. This surprise result was thought to be due to enhancement of the indigenous epiphytic micro-flora and was supported by the fact that leaf samples taken from the 1/4TSB treated plants had higher population levels than the other treatments. Environmental factors (air temperature, relative humidity and solar radiation) were monitored during the glasshouse trial and favourable conditions for disease development and biocontrol performance by the BCAs and 1/4TSB were specified. Persistence is often considered a problem in biocontrol so isolate S15ccs was chosen for persistence experiments under two different controlled environmental conditions. It was found to persist better under high relative humidity (90 %) and low temperature (17 °C) than under low humidity (30 %) and high temperature (25 °C).