Dynamic of biocontrol agents against Botrytis cinerea on grape leaves

Abstract

The survival of biocontrol agents in plant tissues is an important characteristic for bioprotection against phytopathogenic organisms. In the present work, the survival of two biocontrol agents on grape leaves, Bacillus methylotrophicus FR4B12 and Metschnikowia pulcherrima NB9, was evaluated, as well as their interaction against Botrytis cinerea, a phytopathogen causing gray mold disease on grapes. To that end, grape leaves of the Cabernet Sauvignon and Syrah varieties were inoculated with 10⁴ spores of B. cinerea, followed by 10⁷ cells of each antagonist. Additionally, as a control group, individual leaves were inoculated with each of the microorganisms tested. The leaves were kept in a moist chamber, and were collected at 0, 48 and 96 h to determine the microbial populations. The results showed B. methylotrophicus to be the biocontrol agent with the best performance in terms of colonization and survival on grape leaves. B. methylotrophicus increased its population densities in a range of 2.4×10³ - 6.9×10³ CFU cm^-2 on both varieties of leaves at 96 h, which was observed on both sole inoculation and co-inoculation with B. cinerea. As a consequence, the pathogenic activity on the leaves was reduced.