Effect of Paenibacillus alvei, strain K165, on the germination of Verticillium dahliae microsclerotia in planta

Verticillium wilt is a devastating disease of a wide range of herbaceous and woody plant hosts, incited by the soilborne fungus Verticillium dahliae. In the present study, the effect of the potential biocontrol isolate Paenibacillus alvei, strain K165, on the germination of V. dahliae microsclerotia (msc) was investigated. Strain K165 was isolated from tomato root tips and its activity against V. dahliae has been shown in glasshouse and field experiments. In the present study, the application of K165 resulted in the reduction of msc germination of V. dahliae, in the root tips and the zone of elongation, of eggplants by 50% compared to the control treatment; whereas 10 and 12 cm away from root tips and in soil without plants the percentage of msc germination was reduced by 26% and 40%, respectively. However, K165 did not significantly affect the number and length of hyphae per germinated msc. In a split-root system, K165 triggered induced systemic resistance in eggplants against V. dahliae by reducing disease severity and msc germination by 27% and 20%, respectively. In addition, K165 colonised the rhizosphere of eggplants and soil in a population density of 5 and 3 log10 cfu g−1, 7 dpi, respectively. This is the first report of evaluating the direct/indirect effect of a rhizospheric bacterium on msc germination in the rhizosphere of eggplants, indicating that strain K165 reduces msc germination.