| The entomophthorales fungi resources of Gansu province were investigated, at the same time the biological characters, pathogenicity, compatibility and organizing pathology to Brevicorvne brassicae also were reported in this paper. The results were as follows: 1. Through the investigation of the entomophthorales fungi resources in Gansu province, the results showed that 8 species of entomophthorales fungi were obtained from Lanzhou, Tianshui, Yongjing, Tianzhu and Yuzhong in Gansu province, and they were as follows: T.atrospermum Petch, Pandora humber, C.obscurus, Zoophthora radicansm, F.shandomgensis, T.cyrtoneurae Giard, and Neozygites Witlaczil. And pathogenicity of them to aphids was tested, and the results showed the pathogenicity rates of Z.radicansm and C.obscurus were 40.32% and 46% respectively, and it proved that there were some entomophthorales fungi resources in Gansu province. 2. The C.obscurus belongs to Zygomycota and Zygomycetes. It was obligate to aphid in nature. Through the purification and culture on PDA and SEMA media, the biological characteristics of C.obscurus were studied systematically. The results showed that the C. obscurus could produce from 20℃to 30℃and it was inhibited by high and low temperature. It easily produced on long illumination. The C.obscurus conidia germinated faster on the relative humidity (RH) changing from 95% to 100%, and the optimum range of pH was 9~10. The results also showed that the ultraviolet could strongly kill the conidia. The germination rate was 63% when the illumination time was 5 minutes by ultraviolet, while illumination time was 20 minutes, it reduced to 5%. The longer illumination time was, the lower germination rate was. 3. Through some bioassay about C. obscurus against B. brassicae, it was concluded that C. obscurus had efficacy on Brevicorvne brassicae by using "spore shower"(12L/12D). Seven spore dosages were used to inoculate among 71~143 B.brassicae. The added morality rate was 64% at seventh day. The result was analyzed by time-dose-mortality (TDM) modeling technique and obtained the parameters of time and dose effect. In the end, it could draw the conclusion that the C. obscurus killed the aphids was not because of the toxin that produced itself, but because of the infection of compatibility. 4. Using pereffin wax microtome technology,the infection mechanism of C.obscurus to B. brassicae was studied. During this period, the tissue pathology of host was changed as well as the body color and other characters. The germ tube of conidium was germinated on the surface of the aphid and could infect it. C. obscurus was multiplied rapidly using host nutrition in the form of protoplasts. As soon as the protoplasts filled with the host haemocoel completely, they began to form cell wall and shaped compatibility, as a result the host died. After being inoculated 36h, died aphids could find, and the morality rate was 5%, and the surviving ones behaved sluggishly. The morality rate was 10% after 48h and 43% after 144h. The color of host was grey at first, but as the time went on, it turned into white, and the surface of host covered with gray fluff. 5. This paper mainly discussed on the compatibility of chemical insecticide and fungus, and will provide reference and basis for applying insectcidel during epidemic of entomophthoralos. Through experience, the results showed that all of the 23 insecticides, fungcides and herbicides had dramaticly effected on the growth of C.obscurus. Among the 10 pesticides, the restrain of phoxim to C.obscurus was 39.3%.On the contrary, the restrain rate of inlinling was 0. Among the 6 fungcides, the restrain rate of Trazodone to C. obscurus was 50%, and the restrain rate of Pisum sativum was the lowest, it was 5.6%. All of the seven herbicides had controlled on the growth of C.obscurus. And among them, the restrain rate of pendimethalin to C. obscurus was the lowest, it was 4.6%.
|
PDF Full Text Request