Diversity in susceptibility of Botrytis cinerea to biocontrol products inducing plant defence mechanisms

Abstract: The development of plant defence stimulants to increase host resistance represents anattractive alternative to fungicides for the protection of crops against plant pathogens. In thisstudy we evaluated the efficiency of 14 products presumed to induce plant defence mechanismsagainst Botrytis cinerea on tomato and lettuce. Two days after the application of the products,tomato and lettuce leaves were inoculated with B. cinerea and incubated in conditions conduciveto disease development. Out of 14 products tested, Serenade Max® (Bacillus subtilis QST713)proved to have a significant protective efficacy against B. cinerea on both plants. To assess thepresence of low susceptibility to Serenade Max in populations of B. cinerea, the protectiveefficacy of this product was evaluated against 20 strains differing in their geographic origin, hostof isolation and level of aggressiveness. To this end, tomato and lettuce leaves were treated withSerenade Max two days before inoculation. The efficiency of the product was significantlyinfluenced by the isolate of B. cinerea tested with protection levels ranging from 40% to 86% ontomato leaves and 0 to 80% on lettuce leaves. No correlation was observed between the level ofaggressiveness of B. cinerea strains and the protection provided by the biocontrol agent.