Evaluation in vitro and in vivo of biocontrol agents against tomato gray mold in postharvest

Tomatoes for fresh market have a short shelf life in most part caused by mechanical injuries that result in fruit infections by plant pathogens. Botrytis cinerea, is worldwide one of the most important etiological agents of postharvest rot of this type of tomatoes. Biocontrol agents provide new alternatives for the prevention and treatment of this disease being safe for humans and friendly to the environment.This study evaluated the efficacy of two commercial formulations (Sonata® and Biorestore flow), having Bacillus spp., as active ingredient, towards gray mold in vitro and on tomato fruits. Antifungal activity of the two formulations at different concentrations (1, 10, 100, and 1000 ppm) were evaluated into Potato Dextrose Agar (PDA) medium by in vitro test and compared to untreated sample. A 5-mm diameter plug of B. cinerea of 5-days old mycelial culture was placed at the center of a 55 mm fresh PDA plate. Furthermore, the concentrations of the two formulations that completely inhibited in vitro B. cinerea growth were evaluated on tomato fruits in vivo. For this purpose, surface of cherry tomato fruits were dipped in the solutions of two formulates at the dose of complete inhibition of mycelial growth. After the surfaces of fruits dried, 5µL of B. cinerea conidial suspension (1,6 x 105 conidia mL-1) was inoculated near the wounds. Fruits were incubated at 4°C and 25°C and 95% relative humidity were maintained for 48 hours. The two tested Bacillus spp.-based formulates inhibited the mycelial growth and reduced the activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) in B. cinerea mycelium, conversely malondialdehyde levels, an oxidative product of the cell membrane, considerably increased at sub-lethal dose. Bacillus spp. applied to tomato fruit surfaces reduced gray mold development and could be used as a friendly alternative solution to increase shelf life of tomato fruits.