The Screening Of The Strains Of The High Pathological Beauveria Bassiana On Soybean Pod Borers And The Biophysical And Biochemical Effects On Their Hosts

To utilize Beauveria bassiana to prevent and control soybean pod borers(Leguminivora glycinivorella), this paper first studied the biological characters of the8strains of the pathological Beauveria bassiana, screened the high pathological strain:Bb02, which has good biological characters, and applied this strain to theexperiments of infection on soybean pod borers, recording the infecting symptoms ofthe hosts both in the room condition and in the fielding condition respectively andstudying the immune effect of the hosts on the strain, the results are as follows:1. From the comprehensive analysis of the biological characters of the8strains,such as growing speed, sporulation yield, rate of spore germination and level ofextracellular proteinase, the strains: Bb02, Bb03and Bb06had the best biologicalcharacters, being suitable for the experiments of preventing and controlling soybeanpod borers. Based on the measurement of the virulence of the strains on soybean podborers, the strain: Bb02had the highest edited mortality rate:90.5%, and the LT50wasjust5.8d, so the strain: Bb02was chose to be the tested one.2. The room experiments demonstrated that the appearances of the infectedlarvas of soybean pod borers had not any obvious change after48h, and showed twoperceivable disease spots at the sides of the bodies after72h, but no larvas died. After96h, there were many disease spots on the bodies, at the meantime, larvas began todie. Between108h and120h, black spots covered the whole bodies of the larvas,many had died. The fielding experiments illustrated that the larvas of soybean podborers of different races had deviation in susceptibility of the same strain ofBeauveria bassiana, the larvas from Jinong14was more susceptible that the larvasfrom Jinong23.3. The amounts of water, glycogen and protein in the infected soybean podborers demonstrated obvious declining trend. The amount of fat in the infected larvasfrom Jinong14and Jinong23first declined then rose, in the cases of the larvas fromJiyu45and Jiyu89, the amounts of fat were declining. The same indicators in thecontrolled healthy larvas kept stable or declined slightly.4. The number of blood cells and the activity of polyphenol oxidase in theinfected larvas of soybean pod borers by Beauveria bassiana reached the prime after7d, then declined progressively. The larvas of soybean pod borers of different races had manifest deviation in the number of blood cells and in the activity of polyphenoloxidase, the larvas from Jinong14displayed a better immune capacity.