Temperature-responded biological fitness of carbendazim-resistance Fusarium graminearum mutants conferring the F167Y, E198K and E198L substitutions
Understanding the effects of temperature on Fusarium graminearum infection can provide the theoretical guidance for chemical control of Fusarium head blight (FHB).Here, we evaluated the effects of various temperatures on biological fitness development of wild-type sensitive strain 2021 and carbendazim-resistance mutants conferring β2-tubulin substitutions F167Y, E198K and E198L. The results showed that mycelial growth and conidiation of four strains increased with the increase of the temperature between 10°C and 25°C. Conidia of F167Y displayed strong adaptability to low temperature. The virulence of the four strains was largely similar at the same temperature, showing an upward trend between 10°C and 25°C. At 10°C, the hyphal growth of all strains was significantly inhibited, and metabolism slowed down and the accumulation of secondary metabolites decreased. Subsequently, the production of deoxynivalenol (DON) and its intermediate, pyruvate and aurofusarin decreased at low temperature, and the expression of DON biosynthesis-related genes Tri5, FgPK and AUR decreased accordingly. At the same temperature, the aurofusarin production of the strains F167Y and E198K was higher than that of strains 2021 and E198L. The contents of DON and pyruvic acid in carbendazim-resistance mutants were higher than that of the wild-type strain 2021. The sensitivity of four strains to different fungicides changed at various temperatures. The sensitivity to most fungicides increased with the temperature decreasing. The carbendazim-resistance mutants appeared positive cross-resistance with other benzimidazoles. But there was no cross-resistance to pyraclostrobin and azoles. These results would direct us to use fungicide preventing the infection of F. graminearum with changeable atmospheric temperature at wheat flower stage.