苎麻疫霉对棉苗致病力的遗传与变异研究

ON INHERITANCE OF PATHOGENICITY OF PHYTOPHTHORA BOEHMERIAE TO COTTON SEEDLINGS

以分离自江苏省棉铃疫病病组织的苎麻疫霉（PhytophthoraboehmeriaeSawada）野生型菌株JS－5为亲本，采用菌丝块创伤接种法测定了苎麻疫霉对棉苗致病力在游动孢子无性系和卵孢子后代的遗传。结果表明，苎麻疫霉对棉苗的致病力在单游动孢子无性系连续两代稳定遗传，而在单卵孢第1代（OG1）则发生连续性变异。从OG1中选致病力强、弱2个单卵孢株为亲本，分别建立单卵孢第2代（OG2）和单游动孢子无性系，并测定其对棉苗的致病力。结果为上述2个单卵孢株的游动孢子后代对棉苗的致病力均与其各自亲本相似，而在它们的单卵孢株群体（即OG2）中对棉苗的致病力继续发生复杂的连续性变异。上述结果表明，苎麻疫霉对棉苗的致病力可能由细胞核杂合多基因控制。

The inheritance of pathogenicity of Phytophthora boehmeriae Sawada to cotton seedlings in zoospore and oospore progenies was studled. The single we zoospore isolate JS- 5 ZG0 from a wild - type isolate JS-5 of P. boehmeriae obtained from cotton boll rot tissue in Jiangsu province was selected as the parent isolate, from which the asexual and sexual monospore progenies were established. The pathogenicity was evaluated by the diameters of lesions on the wounded leaves of cotton seedllngs by culture block 1noculation. The results indicated that the pathogenicity of P. boehmeriae to cotton seeling leaves was stably inherited in two successive zoospore progenies but showed obviously variation in the first single - oospore generation (OG1). One strong and another weak pathogenic slngle -oospore cultures from OG1 were selected as parents to further establlsh second single - oospore generation (OG2). Successive variat1ons of the pathogenlcity were also observed in the both OG2 populations. However, the pathogenlcity showed no significant variation among the single-zoospore populations from the both selected single oospore cultures of OG1. The results indicated that the pathogenicity of P. boehmeriae to cotton seedlings might be controlled by nuclear heterozygous polygenes and suggested that the sexual reproduction played an important part in the differentiation of pathogenicity in the pathgenic fungus.