玉米大斑病菌两性交配型菌株的出现频率及其育性分析

The occurrence and fertility analysis of bisexual strains of Setosphaeria turcica

玉米大斑病菌属于异宗配合真菌,在自然界中存在A、a交配型菌株和Aa两性交配型菌株,为明确两性菌株的出现频率及其对有性生殖的影响,采用有性态诱导和交配型PCR鉴定的方法,对2011—2014年采集的野生菌株及室内诱导产生的有性杂交后代F1、F2代进行交配型组成鉴定,通过检测两性菌株子囊壳和子囊孢子的发育情况明确其有性生殖能力,结合RT-PCR技术对有性生殖过程中MAT1和MAT2基因的表达情况进行分析。结果表明,野生菌株和有性杂交后代中均存在两性交配型菌株,且出现频率相当,介于2.09%和6.25%之间;Aa两性菌株的育性与杂交时对应菌株的交配型组成相关,两性菌株与A交配型菌株或a交配型菌株杂交均可育,能产生成熟的子囊壳和子囊孢子,但其自交时败育,只产生子囊壳,不产生子囊孢子。两性菌株Aa自交和两性菌株Aa与A交配型或与a交配型菌株杂交时,Aa菌株中MAT1和MAT2基因表达量无明显差异,推测MAT基因在有性生殖产生子囊壳的过程中发挥了重要作用。

There were mating type A,a and Aa bisexual strains of heterothallic fungus Setosphaeria turcica in the nature. By inducing sexual reproduction,mating type of the wild type strains collected from2011 to 2014 and sexual hybridization offspring F1 and F2in the laboratory were tested,and mating type genes were identified by polymerase chain reaction technology. The fertility of the bisexual strains was analyzed by identifying the ascus and ascospore development during the hybridization. The expression level of the MAT1 and MAT2 which were related to sexual reproduction was detected by quantitative realtime PCR. The results showed that the occurrence of the bisexual strains in the wild type and the offspring of bisexual strains were identical,accounting for 2. 09%- 6. 25%. The fertility of the bisexual strain Aa was related to the mating type of the hybridization were confirmed. Bisexual strain Aa could produce ascus and ascospores when it hybridized with the A or a,but it did not give ascospores when bisexual strain selfing. Further, the gene expression level of MAT1 and MAT2 in Aa showed no obvious difference,indicating that the MAT gene played a pivotal role in the development of the ascus during the sexual reproduction of S. turcica.