Relationship between the aggressiveness of Botrytis cinerea on tomato and the efficacy of biocontrol


Abstract: The development of BCAs represents an attractive alternative to fungicides for theprotection of crops against plant pathogens but the durability of this method has not been studiedin details. The objective of the present work was to estimate the risk of loss of biocontrol efficacytowards Botrytis cinerea, by evaluating the sensibility of various isolates of the pathogen to thebiocontrol agent Microdochium dimerum. The protective efficacy of M. dimerum was evaluatedon tomato plants against 41 strains of B. cinerea differing in their geographic origin and host ofisolation. To this end, whole tomato pruning wounds and detached stem sections wereconcomitantly inoculated with B. cinerea and with M. dimerum. Lesion expansion was recordeddaily from the 3rd to the 7th day after inoculation. Due to the very high level of efficacy against alltested strains of B. cinerea when M. dimerum was used at the recommended dose, it wasnecessary to reduce the dose of application 10-fold to assess the diversity of sensitivity ofB. cinerea to this BCA. In these conditions, a wide range of sensitivities were observed amongstrains of the pathogen tested with protection levels ranging from 0 to 100% (mean = 53 ± 4%;median = 49%). A correlation was observed between the level of aggressiveness of a strain totomato and its sensitivity to the biocontrol agent (assessed by the protection level). It reveals theimportance of considering several strains of the pathogen when screening for biocontrol agents,to obtain a good representation of the pathogen population and thus take into account thepotential durability of biocontrol.

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