Compost tea-mediated induction of resistance in biocontrol of strawberry Verticillium wilt

In vitro and in vivo trials were conducted to assess the biocontrol efficacy of the tea prepared from maize straw compost against Verticillium wilt of strawberry caused by Verticillium dahliae and the mechanisms involved in suppression of the phytopathogen. The compost tea used in the present study inhibited the mycelial growth and conidial germination of V. dahliae by 90.60% and 78.24%, respectively. However, sterilization of compost tea by autoclaving diminished the inhibitory effect, suggesting that microflora in the compost tea play a pivotal role in the prevention of Verticillium wilt. The elongation of germ tubes was suppressed by filter-sterilized compost tea and revealed the presence of thermolabile and low molecular weight antifungal substances in the compost tea. Greenhouse trials indicated that preventive application of compost tea on strawberry plants exhibited control efficacy of 41.85% against Verticillium wilt. Moreover, the compost tea treatment could induce resistance in the primed state, which led to enhanced production of defense-related enzymes in strawberry plants upon pathogen attack. Our results demonstrated that direct inhibition of V. dahliae by microorganisms and induction of plant defense response are main mechanisms involved in compost tea-based disease suppression.