Detection of Botrytis cinerea in strawberry transplants imported into Brazil and fungicide sensitivity characterization of the isolates

Most strawberry growers in Brazil use imported transplants due to their higher quality in terms of plant health and productivity. However, there is a risk of entry of quiescently infecting pathogens such as Botrytis species and/or isolates resistant to different fungicides. In this work, we investigated the incidence of Botrytis in imported transplants, and identified the species. In addition, isolates were characterized for their pathogenicity in fruit and sensitivity to seven fungicides (procymidone, fludioxonil, iprodione, cyprodinil, pyrimethanil, boscalid and fluazinam). The average incidence of Botrytis spp. in transplants imported from Chile, Argentina, and Spain was 43.5%. A total of 79 isolates were identified molecularly as B. cinerea and the pathogenicity in fruit was confirmed for a subsample of 14 isolates. To evaluate sensitivity to fungicides, the following discriminatory doses were used: procymidone (P) (10 µg/mL), fludioxonil (F) (0.5 µg/mL), iprodione (I) (10 µg/mL), cyprodinil (C) (10 µg/mL), pyrimethanil (PY) (10 µg/mL), boscalid (B) (50 µg/mL) and fluazinam (FL) (1 µg/mL). As a result, 24 resistant phenotypes were identified with the most frequent being the phenotype with resistance to three fungicides (C-PY-B). The isolates with low sensitivity to cyprodinil and pyrimethanil fungicides, which are not yet widely used in Brazil, represent a risk for strawberry production and should be considered in disease management and future fungicide monitoring programs.