Bacillus volatiles reduce gray mold in strawberries.

Volatile organic compounds produced by Bacillus velezensis CT32 reduced the growth and pathogenicity of Botrytis cinerea, the agent of gray mold in strawberries. Pre-exposure of the fungus to the volatiles decreased the incidence of the disease in the fruit by 51,35%. Mycelial growth decreased by 43,17% in in vitro assays.

Researchers identified 30 volatile compounds produced by the bacteria. Aldehydes accounted for 50,32% of the relative abundance. Alcohols totaled 24,31% and ketones, 11,28%. Dodecanal predominated in the mixture, with 48,56%.

Altered structure

The exposure altered the hyphal structure of Botrytis cinerea. Microscopy revealed rough, deformed, collapsed, and ruptured surfaces. Transcriptomic analysis detected 2.328 transcripts with differential expression. Of this total, 1.171 showed reduced expression.

The volatile compounds reduced the expression of genes associated with the pathogenicity of Botrytis cinerea. The effect affected genes linked to the synthesis of the phytotoxins botrydial and botcinic acid, as well as genes related to the degradation of the plant cell wall.

Metabolic pathways

The treatment also affected carbohydrate and amino acid metabolism pathways, the proteasome, and autophagy. All 23 autophagy-related genes evaluated showed a trend toward reduced expression. Fluorescence assays and electron microscopy did not detect autophagic structures in the exposed mycelia, even under nitrogen deprivation.

According to the study, the antifungal action involves several compounds and cellular targets. The results indicate the potential of Bacillus velezensis CT32 volatiles for future use in biofumigation for post-harvest management of gray mold in strawberries (doi 10.3390/jof12100731).