Isolation And Identification Of Metarhizium Strains And Their Pathogenicity Against Brontisp Longissima (Gestro)

Metarhizium spp are important group of entomopathogenes, and can be used to control lots of pests in agriculture and forest. The biocontrol method which using Metarhizium as a biocontrol agent is an important measure to control Brontisp longissima. In order to get some high virulent strains which are fit for using in the field, and explore the efficient ways of using Metarhizium to control the pests, the listed researches below were done: Metarhizium strains were isolated from cadavers and soil samples, and then identified. In order to screening for some virulent and excellent strains, the biological characters of some strains were determined and their pathogenicity against B. longissima was also tested. The phylogenesis analysis of some strains from different hosts and geographic origins and their pathogenicity test against B. longissima were done for knowing whether there were some pathogenicity differences between different Metarhizium species strains. The covalent virulence of the mixture liquor with each of twoβ-cypermethrin pesticides and conidia of Metarhizim against the pests, were tested to evaluate the lethal efficiency. For searching for a screening method of high virulent strains, the activities of protease and chitinase of the different strains were determined, and then they were used to do cooperation analysis with the values LT 50.The results were the below:4 and 36 Metarhizium strains were isolated form cadavers and soils samples respectively, the results showed that Metarhizium strains could be efficiently isolated by using selective media with 650mg/L Dodine and 500mg/L chloromycetin as inhibitors.20 strains isolated were identified as Metarhizium anisopliae var. anisopliae, and the others were provisionally identified as Metarhizium anisopliae. The maximum parsimony tree based on the data of the rDNA regions, showed Dz01 strain was clustered together with the group of Metarhizium anisopliae var. anisopliae strains, so it provided the molecular data for the morphological identification of Dz01 strains.3 Metarhizium strains(JF86C,JF883 and JF813E) were higher virulent than other test strains in the pathogenicity against B. longissima assay, and their biological characters such as growth ratio, germination ratio and thermotolerance of condia and so on, were also excellent.There was an apparent difference between the pathogenicity of the dfferent species strains against B. longissima. The group of Metarhizium anisopliae var. anisopliae strains were higher virulent than the other groups of Metarhizium strains, some strains from the group of Metarhizium anisopliae var. acridum strains and Metarhizium flaviride var. pemphigum strains were also pathogenicity against B. longissima, but they were less pathogenicity. The cooperative lethal efficacy of the mixture liqor contain each of 2β-cypermethrin pesticides and conidia of Metarhizium against B. longissima was more excellent than single Metarhizium or pesticide solution, and both of 2 pesticides liqors on low concentration, were well compatible with conidia of Metarhizium. So these provide the useful information for controlling B. longissima using the mixture in field.The activity of protease could be used as an referenced criterion for the virulence of different strains, but it could not replace the bioassay. The activity of chitinase was not correlative with the value LT50 when the different strains against imagoes of B. longissima, but was positively correlative with the value LT50 when the different strains against larvae of B. longissima, the reason for this result should be further studied.