Role of botrydial in the interaction between Botrytis cinerea and antagonistic microorganisms

VIGNATTI, P; GONZALEZ ME; ROMERO FM; JOFRÉ E; BOLIVAR-ANILLO H; IZQUIERDO-BUENO I; GONZÁLEZ COLLADO I; VIAUD M; PIECKENSTAIN FL

Simposio; XXVII International Botrytis Symposium; 2016

Botrytis cinerea produces several phytotoxins, such as the sesquiterpene botrydial and related compounds. The relevance of botrydial as a virulence factor is well known, but its role in the interaction between B. cinerea and other microorganisms has not been studied in depth. This work aimed to determine if botrydial confers B. cinerea a competitive advantage during the interaction with antagonistic bacteria (Bacillus methylotrophicus and Bacillus amyloliquefaciens) and fungi (Trichoderma spp.) with potential as biological control agents (BCAs). For this purpose, wild-type (WT) B. cinerea and mutant strains (Bcbot-) unable to synthesize botrydial were confronted with the above-mentioned microorganisms in dual cultures. All B. methylotrophicus and B. amyloliquefaciens strains tested inhibited B. cinerea growth in confrontation assays in which both partners were spot-inoculated on potato dextrose agar (PDA). Conversely, B. cinerea was able to inhibit Bacillus strains when a disc of mycelium was inoculated on a bacterial lawn grown on tryptein soybean agar. As opposed to WT strains, Bcbot? mutants were unable to inhibit Bacillus strains under these conditions. In addition, when added to B. methylotrophicus cultures, botrydial was found to inhibit bacterial growth. Trichoderma spp. strains susceptible to inhibition by B. cinerea were identified within a fungal culture collection. Bcbot? mutants did not show a reduction of its inhibitory effects towards these Trichoderma strains. However, botrydial inhibited the germination of conidia of Trichoderma strains. In addition, botrydial release to the culture medium by WT B. cinerea was strongly enhanced in colonies confronted with Trichoderma strains, as compared to control B. cinerea colonies. However, botrydial accumulation in the periphery of B. cinerea colonies was less intense in the vicinity of Trichoderma colonies than in distal parts. Results demonstrate that botrydial production confers B. cinerea the ability to inhibit antagonistic Bacillus strains, an issue that could affect the potential of these bacteria as BCAs of B. cinerea diseases. On the other hand, clear evidences about a role of botrydial in the inhibition of Trichoderma were not obtained. However, the modulation of botrydial production by the presence of Trichoderma suggests that this sesquiterpene is part of the response of B. cinerea to the presence of antagonistic fungi.