西瓜蔓枯病菌啶酰菌胺抗性突变体的生物学特性研究及其 Sdh B 基因位点检测

The resistance risk of Didymella bryoniae against boscalid was valuated and the resistance mechanism was investigated. By using fungicide adaptation in door, the boscalid-resistant mutants XF21-3 and YC60-1 were obtained, and their biological characteristics were investigated. The partial Sdh B gene sequences of resistant mutants were sequenced to study the molecular mechanism of resistance of D. bryoniae to boscalid. Results showed that the EC50 values of two resistant mutants, XF21-3 and YC60-1, were 108 and 124 μg/mL, with corresponding resistance ratio of 1 007 and 1 347, respectively. The mycelial growth rate and sporulation of two resistant mutants were better than that of their corresponding parents. There is no significant difference in pathogenicity between resistant mutants and their parents. However, resistant mutants showed reduced sensitivity to the high osmotic pressure compared to parental strains. Besides, the resistant mutants had cross-resistance with thifluzamid and had no cross-resistance with carboxin, diethofencrab, tebuconazole, and kresoxoimmethyl. The comparison of Sdh B gene sequencing showed that resistant mutants harbored the point mutation at position 277 in Sdh B subunit with amino acid changing from histidine to tyrosine. The findings indicated that it is easy for D. bryoniae to produce boscalid-resistance under higher selection pressure, and the in vitro fitness for resistant mutants was higher than that of sensitive strains. The results also showed that boscalid was a medium resistance risk fungicide, because the boscalid-resistant mutants showed cross-resistance between boscalid and thifluzamid. Finally, the point mutation at codon 277 (His→Tyr, CAC→TAC) in Sdh B may confer resistance of D. bryoniae to boscalid. [ABSTRACT FROM AUTHOR]