Screen Of Thermo-tolerable Strains Of Lecanicillium Lecanli And Their Thermo-tolerance Mechanism Preliminary Analysis

To search for more potential candidates for formulations adaptable to pest control during hot summer and to study the stress biology for Lecanicillium lecanii, the conidial thermo-tolerance mechanism of L. lecanii were analyzed based on the thermo-tolerable strains screening. Results of this research as follow1. Conidial thermo-tolerance evaluation and thermo-tolerable strains screening. To evaluate the conidial thermo-tolerance, an assay protocol was developed by exposing fungal conidia of25strains to the thermal stress of48℃using water bathing, for different time periods. An index Is was used to define the ratio of conidial viability, measured as germinate rate, after a given period of thermal stress, compared to the blank control (unstressed conidia). A Logistic equation Is=l[l+exp (a+bt)](r2≥0.970) fitted well the relations of the index Is and the stress time. The results showed that strain V3861is the highest thermo-tolerable strain with the LT50value of10.56min; strain V6888LT50is the lowest of thermo-tolerable strain with the LT50value of0.06960min. The average value of LT50of these25strains is4.647min.2. Comparison of virulence of thermo-tolerance-different strains. Virulence of strain V6791, Vp28and V62against Myzus persicae and Gynaikothrips ficorum were biassayed at the high temperature stress in experimental laboratory. The results showed that strain V6791is the highest virulent strain against M. persicae, G. ficorum with the values of LT50of2.362d and3.453d, respectively; strain V62, the lowest virulent strain against M. persicae, G. ficorum with the values of LT50of3.482d and3.913d, respectively.3. Hydrophobin extract from spore wall. Cell wall proteins hydrophobin were extracted from9thermo-tolerance-different strains, with the protocol of BCA of Jeff s. Protein extracts were analyzed by SDS-PAGE and mass spectrum. The results showed that, strain V6791has the highest value of the content of cell wall protein hydrophobin, round at21.71829+3.33165ug/mg; strain Vp28, the lowest value of the content of cell wall protein hydrophobin, round at15.00607+0.820643ug/mg. There are two protein stripes each strain, with molecule as11.3and2.7kD, respectively. Nevertheless, the matching proteins of two different proteins are identical, so it is concluded that2.7kD protein stripe is subunit of11.3kD, inferred that the hydrophobin of Lecanicillium lecanii contains disulfide linkage.