紫外光诱导苎麻疫霉抗甲霜灵突变及对苎麻疫霉生物学特性的影响

作者研究了紫外光对苎麻疫霉的抗甲霜灵诱变效应及对苎麻疫霉生物学特性的影响。结果表明,供试6个苎麻疫霉野生型菌株经菌丝块紫外光药剂诱变和菌丝块药剂驯化3周后,均获得抗甲霜灵突变体,且紫外光药剂诱变处理角变区出现频率明显高于药剂驯化处理,说明紫外光对苎麻疫霉抗甲霜灵突变有一定促进效应。紫外光显著地抑制苎麻疫霉游动孢子的萌发和菌丝的生长,在一定范围内,处理时间愈长,抑制率愈高。苎麻疫霉耐紫外光菌株(经亚致死剂量的紫外光照射处理后存活的游动孢子所形成的菌株)与野生型亲本相比,对温度和pH的敏感性大致相同,但菌落形态有一定变异,菌丝生长速率、卵孢子产生量均显著下降,表明紫外光对苎麻疫霉的菌丝生长和卵孢子产生量有明显的抑制作用。苎麻疫霉耐紫外光菌株EC50值比野生型亲本菌株EC50值提高了23.21%-56.70%,即耐紫外光菌株对甲霜灵敏感性比野生亲本菌株显著下降,这与紫外光诱变试验结果是相一致的。

Effects of ultraviolet irradiation on metalaxyl-resistance mutagenization and biological characteristics of Phytophthora boehmeriae

The effects of ultraviolet light (UV) on mutagenizing metalaxyl resistance and the biological characteristics of Phytophthora boehmeriae were studied. The results indicated that the metalaxyl-resistant mutants were obtained from each of the six wide-type isolates in P. boehmeriae after mutagenizing for 3 weeks by mycelium-block-UV-drug method and by drug taming method, respectively. The frequency of mutation sectors in mycelium-block-UV-drug mutagenization was obviously higher than that in drug taming treatment, suggesting that UV played a cooperative or improving role in mutagenizing metalaxyl resistance of P. boehmeriae. UV obviously inhibited the germination of the zoospores and the mycelium growth, and in a certain range, the inhibitive rates increased with the lengthening of the UV irradiation time. Compared with the wide-type parental isolates, the ultraviolet-patient isolates (originated from the survivals of zoospores treated by sublethal UV irradiation) displayed similar adaptability to temperature and pH, but were obviously different in colony morphology, mycelial growth rates and oospore production. The mycelial growth rates and oospore production of the ultraviolet-patient isolates were all significantly decreased, suggesting that UV had significant inhibitory effects on the mycelial growth rates and oospore production of P. boehmeriae. The EC50 values of the ultraviolet-patient isolates were increased by 23.21% to 56.70% as compared with the wide-type parental isolate, that is to say the metalaxyl sensitivities of the ultraviolet-patient isolates decreased, suggesting that UV irradiation had an improving effect on the formation and development of metalaxyl resistance of P. boehmeriae.