蚊幼虫病原真菌贵阳腐霉的生物学研究

为了开发灭蚊真菌贵阳腐霉Pythiumguiyangense用于蚊虫防治,对贵阳腐霉生物学特性进行了研究。采用菌丝生长率、真菌产孢情况以及对致倦库蚊Culexquinquefaciatus1龄幼虫的毒力作为评价的指标。测试了7种人工培养基、7种单糖、7种氮源、真菌生长所需的pH范围和温度范围、以及4种光-暗比的光照程序对真菌的影响。结果证明该真菌生长的适合温度为5℃～35℃,最佳温度为25℃～30℃;适合pH范围是5～12;在pH9～11范围内菌丝和游动孢子生长最好;测试的人工培养基中,按照菌丝生长速度从高到低排列,依次为Czapek’SFE、PYG、KPYG2、SDAY、CMA和PDA。其中从真菌的游动孢子形成量和对蚊幼虫的毒力来看,最佳培养基为SFE;葡萄糖、果糖、乳糖、蔗糖、麦芽糖、甘露糖和可溶性淀粉都是本真菌的合适碳氢营养源;含有机氮的培养基比含无机氮的培养基好;不同的光照程序没有表现明显的影响,但是观察到紫外光对本真菌有明显的抑制作用。

Biological studies on Pythium guiyangense, a fungal pathogen of mosquito larvae

Biological characteristics of Pythiun guiyangense (Pythiaceae, Peronosporales, Oomycota), a species of mosquito-killing fungus, were studied. Hyphal growth rate, sporulation and virulence to the first instar larvae of Culex quinquefaciatus were used as assessing indexes. Seven kinds of artificial media with different carbon and nitrogen sources were used in the study. The effect of different pH values and temperature, and different light-dark alternation treatments on the fungal growth were investigated. The results showed that 5℃～35℃ was the suitable temperature range for the fungal growth, with optimal temperatures of 25℃～30℃; suitable pH values were 5～12, with optimal pH range of 9～11 for development of both hyphae and zoospores; the media ranked by favorite for fungus growth were Czapek's, SFE, PYG, KPYG2, SDAY, CMA, PDA, while SFE was the best medium for fungal sporulation and increase of pathogenicity to mosquitoes; glucose, fructose, lactose,sucrose, maltose, mannose and soluble starch were suitable hydrocarbon sources; media containing organic nitrogen were much better than those containing inorganic nitrogen; light-dark alternation treatments did not show influence on the fungal growth, but ultraviolet illumination has obviously inhibitory effect.