Functional roles of two β-tubulin isotypes in regulation of sensitivity of Colletotrichum fructicola to carbendazim

Abstract

Colletotrichum fructicola was the major pathogen of anthracnose in tea-oil trees in China. Control of anthracnose in tea-oil trees was mainly depended on application of chemical fungicides such as carbendazim. However, the current sensitivity of C. fructicola isolates in tea-oil trees to carbendazim has not been reported. Here, we tested the sensitivity of 121 C. fructicola isolates collected from Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangsu and Jiangxi provinces in China to carbendazim. 110 isolates were sensitive to carbendazim, 11 isolates were highly resistant to carbendazim. The growth rates, morphology and pathogenicity of three resistant isolates were identical with that of three sensitive isolates which indicated that these resistant isolates could from resistant population under carbendazim application. These results suggested that carbendazim should not be the unique fungicides in control of anthracnose in tea-oil trees, other fungicides with different mechanism of action or mixture fungicides could be considered. In addition, bioinformatics analysis identified two β-tubulin isotypes in C. fructicola: Cfβ1tub and Cfβ2tub. E198A mutation was discovered in Cfβ2tub of three carbendazim-resistant isolates. We also investigated the functional roles of two β-tubulin isotypes. CfΔβ1tub exhibited slightly increased sensitivity to carbendazim and normal phenotypes. Surprisingly, CfΔβ2tub was highly resistant to carbendazim and showed seriously decreased growth rate, conidial production, pathogenicity and abnormal hyphae morphology. Promoter replacement mutant CfΔβ2-2×β1 showed partly restored phenotypes, but it was still highly resistant to carbendazim, which suggested that Cfβ1tub and Cfβ2tub were functional interchangeable to a certain degree.