Studies on population dynamics of Bacillus subtilis and Fusarium oxysporum f.sp. lentis, the causal organism of lentil vascular wilt

摘要

Vascular wilt, caused by Fusarium oxysporum f.sp. lentis, is one of the most important disease of lentil (Lens culinaris Medikus) worldwide. Understanding the dynamics between a pathogen and a biological control agent (BCA) in soil is a determiningfactor in predicting the success of biological control. By studying the population density fluxes over a period of time, it can be observed how the BCA and pathogen influence each others population and how certain environmental conditions influence thisrelationship. In a growth room study, a population of Bacillus subtilis rapidly increased up to 10~7 (cfu/g soil) in the 10 days following application of 5 ml/plant (8X10~6 cfu/ml~(-1)) of bacterium to 15-days-old lentil (ILL 4605) plants and slightly decreased to 10~6 (cfu/g soil) in 5 weeks after application. In a glasshouse experiment, B. subtilis reached a population density greater than 10~9 (cfu/g) in soil 2 weeks after application either alone or in the presence of the pathogen. B. subtilis was effective at decreasing the wilt incidence by 70 percent.