Screening Of Highly Effective Beauveria Bassiana Against Toxopteru Auruntii And Optimization Of Oil Formulations For Storage

At present,Toxopteru auruntii are still one of the main pests of tea trees.In this paper,a strain of Beauveria bassiana with high temperature resistance and high efficiency of killing Toxopteru auruntii was screened from 5 strains of Beauveria bassiana isolated from hemiptera to study its biological characteristics.Furthermore,five solvent oils,three kinds of antioxidants and three kinds of desiccants were selected,and the optimal oil formulation for the high-temperature resistant storage of Beauveria bassiana was screened by calculating the spore germination rate,so as to improve the preservation ability of Beauveria bassiana.The effects of water content of spores,main nutrient sources and ultraviolet on oil storage of Beauveria bassiana Bb2488 were investigated.The main research results are as below:1.After the same treatment for the five strains of Beauveria bassiana,the germination rate of the spores of Beauveria bassiana Bb2488 was the highest in the temperature segment above 35℃.The suspension of five strains of Beauveria bassiana treated at 35℃was sprayed on the surface of Toxopteru auruntii.The infection rate and the accumulated death rate of Beauveria bassiana Bb2488 for seven days were the highest,90.0%and 96.7%,respectively.The LT50 of Bb2488 was the smallest(2.763d),followed by that of Bb2535.The spores germination rate of Beauveria bassiana Bb2488 at different temperatures,and the mycelia growth rate and spore production amount cultured on five media for 10 days were measured.The results showed that the spores germination rate of Beauveria bassiana Bb2488 was higher when the temperature was about 35℃,and significantly decreased when the temperature was 40℃,and the transition temperature of spores germination was between 40℃and 45℃.Mycelial growth of Beauveria bassiana Bb2488 was the fastest on 1/4 of the SDAY and the slowest on SDA.The best culture medium for sporulation was 1/4 SDAY,and the culture reached 2.32×10~7/cm on 10d.The sporulation sequence on the five media was 1/4 SDAY>PDA>SDAY>SMAY>SDA.Under laboratory conditions,Beauveria bassiana Bb2488 can be cultured using1/4 SDAY medium.2.Formulation optimization for extending the storage period of the efficient Beauveria bassiana under high temperature condition.The optimal solvent oil was selected from five kinds oil of No.7 white oil,No.15 white oil,No.50 white oil,palm oil and salad oil.The results showed that the higher spores germination rate of Beauveria bassiana was stored in No.15 white oil under high temperature condition.The most suitable oil desiccant formulation was selected from montmorillonite desiccant,discoloration silica gel desiccant and calcium oxide.The results showed that the spores germination rate was 52.64%and the appropriate concentration was1.2%.3.The factors affecting the storage period of oil formulation of Beauveria bassiana.The results showed that the spores germination rate of Beauveria bassiana was62.88%,and that of the strain with water content of 12.54%was 63.57%of germination rates.The average germination rates of the spores of Beauveria bassiana in carbon and nitrogen limited medium were merely 37.92%and 43.36%after storage in oil.The spores germination rate of the control group without ultraviolet irradiation was 85.94%,while the spores germination rate of the control group after 1h under ultraviolet irradiation decreased to 29.41%.With the addition of the oil agent of Beauveria bassiana with the optimal formulation,the spores germination rate of the culture after 1h under ultraviolet irradiation was 44.59%,which was higher than that of the control group.