玉米大斑病菌有性杂交后代的交配型与寄生适合度分化

【目的】了解玉米大斑病菌有性杂交后代交配型和致病性分化情况，明确有性杂交与菌株变异间的关系。【方法】以01-12和01-15为出发菌株，人工诱导玉米大斑病菌的有性后代，获得F1代菌株，再以F1代菌株40和42为亲本，获得有性杂交F2代菌株；对有性后代进行交配型和寄生适合度测定；采用毛细管电泳技术分析不同致病类型菌株的毒素含量。【结果】在室内条件下连续诱导产生玉米大斑病菌的2个有性世代，获得了79个F1代菌株和32个F2代菌株；后代菌株的交配型发生了明显分化，出现了A、a、Aa和中性菌株，其中F1代A、a分离比例明显偏离1﹕1；寄生适合度测定结果表明，F1代和F2代菌株较亲本均发生了寄生适合度分化，其中F1代中较亲本寄生适合度增强的菌株占30.00%，减弱的菌株占50.00%；F2代中较亲本寄生适合度增强的菌株占21.87%，减弱的菌株占31.25%；毛细管电泳结果表明，强致病力菌株的毒性组分含量明显高于弱致病力菌株。【结论】有性杂交是导致菌株交配型及致病性发生分化变异的主要因素之一，菌株的致病力强弱与其毒素含量呈一致关系。

Analysis on Mating Type and Parasitic Fitness Diversity in Sexual Hybridization Offsprings of Setosphaeria turcica

【Objective】The objective of this study is to analyze the diversity of mating type and pathogenicity in sexual hybridization offsprings of Setosphaeria turcica and investigate the relationship between sexual hybridization and variation of S. turcica.【Method】Using isolates 01-12 and 01-15 of S. turcica as parents, the sexual hybridization F1 generations were obtained by artificial induction, and F2 generation isolates were got by the same method when isolates 40 and 42 coming from F1 generation were used as parents. The mating type and parasitic fitness of sexual hybridization offsprings were tested with Huangzaosi. The toxin of different pathogenic isolates was analyzed by capillary electrophoresis. 【Result】Two sexual generations were induced continuously. Seventy-nine sexual hybridization F1 and thirty-two F2 isolates were obtained in this experiment. The mating types were A, a, Aa and neutral isolates, which appeared obvious diversity, but the ratio of A and a in F1 generations was far away from 1:1. The result of parasitic fitness showed that F1 and F2 isolates generated diversity. The percentages of strong parasitic fitness and feeble parasitic fitness in F1 generations were 30.00% and 50.00%, respectively, and those in F2 generations were 21.87% and 31.25%, respectively. The results of capillary electrophoresis suggested that the toxin content of stronger pathogenic isolates were higher than that of lower pathogenic isolates. 【Conclusion】 The sexual hybridization is one of the chief elements resulting in mat type and pathogenic diversity. The toxin content of an isolate is positively correlated with its pathogenicity.