Physiological Characteristics, Pathogenicity And Molecular Biology Of The Entomopathogenic Fungi-Dh Strain Of Emericella Quadriclineata

In recent years, with the increasing concern about serious influence of chemicals on ecological environment, much more importance is being attached to the method of biological control in pest management. Entomopathogenic fungi, with so many merits such as safety, high efficiency, significant epidemic potential as well as high productivity, will be playing a growing role in pest biological management, among which Dh strain of Emericella quadriclineata that has a strong pathogenicity on pest of cankerworm of Lepidoptera, is believed a desirable choice and has a bright prospect in pest management of grassland and forestry ecological system.The experiment was conducted to make a systematic profound research on biological characteristics, effect of culture conditions on hyphae growing and spore germinating, exocellular enzyme activity etc., evaluate the pathogenic effectiveness of Dh strain on several different pests, also determine the variation of some protection enzymes activity level in larva of Aproaerema anthylidella on alfalfa infected by Dh strain. In addition, through RAPD and rDNA ITS analysis, the genetic relationship between Dh strain and some other kindred species was explored. The main results are as follows.1.Results of the research on Dh strain biological characters indicated that Dh strain, which prefers properly high temperature, was able to soundly grow under the conditions of temperature ranged from 15 to 45℃and pH4～8, and its spore could germinate in the temperature range of 8～45℃,and also discovered that 30℃was the optimum condition for its growth and spore germination. In addition, it was also showed that Dh strain could utilize several different types of carbon and nitrogen, and grow optimally in the media of soluble starch, mannite and maltose as carbon sources, especially had a efficient utilization of urea and NH4Cl.2. The exocellular enzyme of Dh strain could generate both in cadaver of armyworm(Leucania separatea) and glutin media. When it was incubated in glutin—agar plate medium under different given temperature conditions for three days and followed by treatment of 15% HgCl, there would appear a bright circle around every bacterial colony, which was the symbol of exocellular enzyme generating, and it was also indicated that the yield of enzyme is the greatest at 33℃in this period, subsequently comes a gradual decline. While chitinase could reach a peak in amount when Dh strain was incubated for 4～5 days.When Dh strain, the density of which was 1.5×10~6 conidia per milliliter, was incubated in PD liquid medium through shake culture of 120r/min at constant temperature of 25℃,...