Temperature adaptability of different types Monilinia fructicola isolates and their cross-resistance between methyl benzimidazole carbamates and diethofencarb

Monilinia fructicola is an economically important pathogen, causing brown rot on many fruit trees. Previous studies revealed that the resistance in this pathogen to thiophanate-methyl was associated with multiple amino acid variations in the Tub2 protein. To understand the temperature adapatability and the activity of diethofencarb in differrent types of isolates, the sensitivities to thiophanate-methyl, carbendazim and diethofencarb were investigated in the sensitive type isolates S and three types of resistant isolates including R_(E198A), R_(E198Q) and R_(F200Y), among which the cross-resistance of different types to MBCs and diethofencarb were analyzed. The results showed that the optimum growth temperature of the four types was ranged from 21 to 22 ℃, among which the R_(E198Q) isolates had the lowest optimum growth temperature, and its growth rate was significantly smaller than the other three types under the conditions of 13 ℃ and 28 ℃. While no significant difference was observed in the growth rate of S, R_(E198A) and R_(F200Y) isolates under all temperature conditions. The three resistant types showed different sensitivities to thiophanate-methyl, among which the R_(E198Q) type was least resistant, and the R_(F200Y) type was no difference from the R_(E198A) type at low concentration but significantly less resistant under high concentration of thiophanate. The difference in sensitivity of three resistant types to carbendazim was similar to that of thiophanate-methyl, only in which the R_(E198Q) and R_(F200Y) types were more sensitive to carbendazim than thiophanate-methyl. The sensitivity test to diethofencarb showed that the R_(E198A) isolates were sensitive, and S isolates were insensitive, while the other two types of R_(E198Q) and R_(F200Y) showed resistance with little difference. The results of linear correlation analysis showed a significant negative correlation between the sensitivity to benzimidazole fungicides and diethofencarb only in R_(E198A) type and S type, (thiophanate-methyl and diethofencarb: r =−0.992, p = 0.000; carbendazim and diethofencarb: r = −0.982, p = 0.001). All the results mentioned above showed that only the R_(E198A) type had negative cross-resistance to methyl-benzimidazole carbamates (MBCs) and diethofencarb among the three types of resistant isolates.