Affiliation:
1. Central South University of Forestry and Technology, 12571, Changsha, Hunan, China;
Abstract
Colletotrichum fungi could cause anthracnose, a destructive disease in tea-oil trees. The sterol demethylation inhibitor (DMI) tebuconazole has been widely used in controlling plant diseases for many years. However, the baseline sensitivity of Colletotrichum isolates on tea-oil trees to tebuconazole has not been determined. In this study, the sensitivity of 117 Colletotrichum isolates from tea-oil tree of 7 provinces in southern China to tebuconazole was tested. The mean effective concentration resulted in 50% mycelial growth inhibition (EC50) was 0.7625 μg/mL. The EC50 of 100 isolates (83%) were lower than 1 μg/mL, 20 isolates (17%) were higher than 1 μg/mL, which implied the resistance has already occurred in Colletotrichum isolates on tea-oil trees. The EC50 values of the most resistant and sensitive isolates (named Ca-R and Cc-S1 respectively) were 1.8848 and 0.1561 μg/mL respectively. The resistance mechanism was also investigated in this study. Gene replacement experiment indicated that CYP51A/B gene of resistant isolates Ca-R and Cf-R1 cannot confer Cc-S1 fully resistance to DMI fungicides, though three point mutants, Cc-S1CYP51A-T306A and Cc-S1CYP51A-R478K exhibited decreased sensitivity to DMI fungicides. This result suggested that resistance of Colletotrichum isolates was partly caused by mutations in CYP51A. Moreover, expression level of CYP51A/B was almost identical among Ca-R, Cf-R1, Cc-S1 and Cc-S1CYP51A point mutants, which indicated that the resistance was irrelevant to the expression level of CYP51A, and other non-target-based resistance mechanism may exist. Our results could help to guide the application of DMI fungicide and be useful for investigating the mechanism of resistance.
Subject
Plant Science,Agronomy and Crop Science