Sensibilidade e adaptabilidade de espécies de Botryosphaeriaceae de mangueira a fungicidas MBC

Abstract

Dieback and stem-end rot caused by Botryosphaeriaceae species are an important mango disease in Brazil. Thiabendazole and thiophanate-methyl (both belonging to methyl benzimidazole carbamate group - MBC) are common fungicides used in mango orchards in northeastern Brazil. There are no data available on the sensitivity to these fungicides, stability of sensitivity, molecular mechanisms of resistance and fitness-related variables on Botryosphaeriaceae to these fungicides. Thus, evaluate the sensitivity to fungicides thiophanate-methyl and thiabendazole in Botryosphaeriaceae isolates collected from different commercial mango orchards in the Brazilian Northeastern. Thus, the effective concentration that results in 50% of mycelial growth inhibition (EC50) of 154 isolates were established. Ten isolates with lower (sensitive, S) and high (less-sensitive, LS) values of EC50 values for thiabendazole and thiophanate-methyl were evaluated for sensitivity, stability of sensitivity, molecular mechanisms of resistance, components of fitness (mycelial growth rate, osmotic sensitivity and virulence) and effectiveness to disease control in mango fruits .The mean EC50 value for the LS isolates (2.48 μg ml-1) and (7.65 μg ml-1 was significantly higher (P≤0.05) than that for the S isolates (0.12 μg ml-1) and (0.05 μg ml-1) for thiabendazole and thiophanate-methyl, respectively. Despite this, no mutation was found in codon 198 of the β-tubulin gene when compared LS and S isolates. Significant and positive correlation (P<0.01; r=0.81) was detected between the sensitivity of the isolates to thiabendazole and thiophanate-methyl. No significant difference was observed in stability of sensitivity for the S and LS. No significant difference was found (P0.05) between S and LS isolates for mycelial growth and virulence on mango fruits for both fungicides. In contrast, LS isolates showed an increased capacity of growing under salt stress. The fungicides were able to control both S e LS isolates showed control efficacy in mango fruits. This is the first study about the sensitivity to the fungicides thiabendazole and thiophanate-methyl in isolates of Botryosphaeriaceae from mango orchards.The results demonstrate that these fungicides can be used in mango orchards, although with caution due to the imminent risk of increasing the insensitivity in the population.