烟草赤星病菌嘧菌酯抗性突变体的诱导及其生物学特性

Induction and Characterization of Laboratory Mutants of Alternaria alternata Resistant to Azoxystrobin

为探究烟草赤星病菌对嘧菌酯的抗药性风险水平,通过对烟草赤星病菌在室内含药平板上的菌丝药剂驯服和分生孢子紫外诱变,进行突变体的生物学特性的研究,并对突变体靶标基因细胞色素b进行了测序分析。获得了4株嘧菌酯抗药性突变体。其中,菌丝药剂驯服未获得突变体;孢子紫外诱变获得4株突变体,突变率约为0.004%,突变体抗性倍数分别为42.50、282.50、515和107.50。4株突变体均降低了对嘧菌酯的敏感性。适合度研究表明,抗药性突变体具有同敏感菌株同样的分生孢子萌发能力和致病能力;菌丝生长速率较敏感菌株有所降低,3株突变体的分生孢子产量较敏感菌株增强,1株突变体较敏感菌株减弱。抗药性靶基因细胞色素b基因部分序列分析表明,突变体在129位和143位的碱基与敏感菌株完全相同,未发生任何突变。初步认为烟草赤星病菌对嘧菌酯的抗性风险水平较低。

This study was conducted to analyze the risk of resistance of Alternaria alternata to azoxystrobin. Resistant mutants wereinduced by incubating mycelial plugs and mutating conidia on poisoned agar plates. Mutant characterization and mechanism ofresistance were also studied and the target gene cyt b was analyzed using partial sequence analysis. Four mutants of A. alternata withresistance to azoxystrobin were isolated. No mutant was obtained through mycelial plug incubation while four mutants were isolatedthrough conidia mutation, with a frequency of around 0.004%. The resistance factors for the four mutants were 42.50, 282.50, 515 and107.50, respectively. All resistant strains displayed a highly reduced sensitivity to azoxystrobin. Studies of fitness parameters in thewild-type and mutant strains of A. alternata showed that all resistant isolates had equal abilities on conidia germination and virulence,and less ability in mycelial growth. Three mutants showed enhanced ability of conidia production, while the other one decreased its’conidia production. Sequence analysis of the target gene cyt b showed that there was no point mutation at position 129 or 143 on neitherthe four mutants or the sensitive isolate of A. alternata. This is believed to be the first report of different levels of azoxystrobin resistancein A. alternata. These studies suggested that the risk of resistance development in A. alternata was low for azoxystrobin.