Biocontrol of Botrytis cinerea the causal agent of gray mold of strawberry by antagonistic fungi

Abstract

Gray mold of strawberry fruits, caused by Botrytis cinerea Pers, is an important disease in Iran. Traditionally the disease has been controlled by fungicides whose residues are considered dangerous to environment. Experiments were carried out with four isolates of Trichoderma speces (T. koningii, T. viride and T. harzianum) and two isolates of Gliocladium virens. These isolates were used to investigate their biocontrol traits in vitro and ability to suppress the gray mold strawberry fruits in vivo. The antagonistic mechanism occurred through branching of hyphal tips of B.cinerea, hyphal contact, coiling, vacuolation and lysis. Volatile metabolites of T. koningii and non-volatile metabolites of G. virens and T. koningii caused maximum inhibition of the fungal growth. Greenhouse studies were carried out by using sprays of the antagonistic fungal and B.cinerea spores with 48-hour intervals on the plants. Each treatment was studied with five replicates and each replicate consisted of a single plant. Disease severity was assessed 15 days after treatment. The results suggested that the application of fungal antagonists reduced the gray mold disease severity between 5-42%. The isolate of T. koningii caused a maximum reduction of disease severity. Trichoderma isolates survived on strawberry foliage much better than Gliocladium isolates did. T. koningii and T. viride were persisted on the plants after two months.