ChileanJAR

In order to identify a molecular marker able to detect dicarboximide-resistant strains of Botrytis cinerea, genetic variability in two populations of the pathogen was analyzed. One group of strains was isolated from grapes and a second one from tomato. In both groups, sensitive (EC₅₀ <2 mg/L), low-level resistant (EC₅₀ 2 a 10 mg/L), and highly resistant strains (EC₅₀ > 10 mg/L) to dicarboximides were detected. Resistance to iprodione correlated positively with resistance to procymidone although osmotic sensitivity, a component of fungal colonizing ability, did not correlate with the observed degrees of resistance. Genetic variability was assessed by RAPDs. Ten primers were selected which provided 56 polymorphic bands. High genetic variability was found in this species with similarity coefficients varying between 0.55 and 0.98. Bands tightly linked to dicarboximide resistance could not be identified, and a cluster analyses using UPGMA could not cluster apart resistant and sensitive strains. Unexpectedly, this later analysis showed that strains isolated from grapes are different from those isolated from tomato. We conclude that due to the high genetic variability of B. cinerea the use of fungal populations is not the most appropriate approach to identify a molecular marker associated with resistance to dicarboximides. Alternative approaches are suggested for this later purpose and sorne aspects regarding the population structure of this pathogen in Chile are discussed.