Biological Character And Pathogenic Mechanism Of Acremonium Hansfordii To Aphid

It was studied on the biological character, host scope, virulence of Acremonium hansfordii and pathogenic mechanism to Myzus persicae. The results were as follows:1. The fungu was identified as Acremonium hansfordii by Anhui province key laboratory microbial control, Anhui agriculture university. The description is not found about the fungu's pathogenicity to insect.2. The eight carbon sources (glucose, fructose, saccharose, starch, mannite, inosite, glycerine, and maltose) and six nitrogen sources (Peptone, sodium nitrate, potassium nitrate, ammonium chloride, ammonium nitrate, urea) were examined for their effect on the growth and sporulation of Ahy1。It was turned out that glucose, saccharose and peptone were the best. The five cultures (PDA, Sarch-Agar, Czapek, SDAY, SEA cultures) was sieved. As a result, SEA csulture and SDAY culture were the optimum culture.3. The Acremonium hansfordii was bioassayed on the Myzus persicae, Acyrthosiphon possum, Therioaphis trifolii. Mythimna separate and Pieris rapae, which were exposed to the spore shower. The result showed that the Myzus persicae was the most susceptible, its final cumulative mortality was 84.07%. Then Acyrthosiphon possum, Therioaphis,trifolii and Pieris rapae were more susceptible.The final cumulative mortality were 78.18%,83.50%,73.3%,respectively. But the Ahy1 had the lowest virulence to Mythimna separata, its mortality was 63.3%. The death peak of the aphids occurred between the fourth and the fifth days, but Mythimna separata and Pieris rapae were between the sixth and the seventh days. The resulting data were fitted to a time–dose-mortality model, whose parameters were used to estimate the LD50. The LD50 of Myzus persicae was the smallest in those insecs, its LD50 on 4-5d after inoculation was 131.23, 49.23 spores/mm2,and the LD50 of Mythimna separata was about 1165.33,493.49 spores/mm2 for it.4. The invasiveness and development process of Ahy1 to the Myzus persicae was researched by pereffin wax and microtome technology.The result showed that the spores first landed on the surface of Myzus persicae, after 20~24h,they germinated on the suitable conditions(20℃,100%) and formed germ tube,then penetrated in vivo.They had finished the invasion in 36h. The fungu changed yeast and multiplied in the host, then hyphal broke through the host cuticle, the conidiophore peduncle produced the spores that began to intrude other host insects.5. Extracellular protease and extracellular chitinase were proved the existence. It was found that they produced hydrolyzation circle on the glutin culture and colloid chintinase culture. By measuring the activity of the two enzymes, the result indicated that the production of enzyme had obvious difference at different dates. The production of extracellular protease and chitinase were the lowest on the first day, only 9.73 U/mL and...