Biodiversity And Genetic Structure Of North China Population Of Beauveria Bassiana

Beauveria bassiana is an important entomopathogenic fungus for natural populationregulation and has been developed into fungal insecticides widely used in biologicalcontrol. It has broad host range and wide geographic distribution, and hence complicatedpopulation genetic structure. In order to clarify the genetic differentiation of B. bassianapopulation in north China, and to further reveal the nature of the genetic variation,genetic diversity and population genetic structure of B. bassiana of north China werestudied by ISSR（inter-simple sequence repeat）technique in the present dissertation. Theimpacts of gene flow and other estimates on genetic differentiation of B. bassianapopulation were analyzed with the theories of molecular ecology.Six hundred and twenty-two isolates of B. bassiana collected in13provinces innorth China were divided into13provincial subpopulations and568among them dividedinto9subpopulations including8insect orders and Araneida. The major results are listedas follows:1. The polymorphism analysis of ISSR primers: a total of216fragments wereamplified by9primers，the percentage of polymorphic loci (PPL) of the9primers were100%, and showed good reproducibility, indicating that the ISSRs are good markers toevaluate the genetic diversity of B. bassiana.2. Genetic diversity analysis: the total PPL of all isolates in north China was100%,Nei’s gene diversity index (He) was0.361, Shannon’s information index (Is) was0.538.But subpopulation-wised diversity indices varied very differently. The provincialsubpopulations of B. bassiana: the PPL varied within70.83%~99.54%, the Hevariedwithin0.197~0.360, the Isvaried within0.309~0.537; while the different insect ordersubpopulations of B. bassiana: the PPL varied very differently within66.20%~100%, theHevaried within0.257~0.394, the Isvaried within0.382~0.575. All diversity indicesshowed high level genetic diversity and revealed a highly heterogenous population.Among them, Inner Mongolia Subpopulation and Lepidoptera Subpopulation showedhighest genetic diversity and highest populational heterogeneity, respectively, whileHenan Subpopulation and Araneida Subpopulation showed the lowest.3. the intersubpopulational genetic differentiation: The provincial subpopulations ofB. bassiana: the total gene diversity (Ht) was0.378, the intrasubpopulational genediversity (Hs) was0.290, the mean genetic differentiation coefficient (Gst) was0.233, thegene flow (Nm) was0.824; while the different insect order subpopulations of B. bassiana: the total gene diversity (Ht) was0.347, the intrasubpopulational gene diversity (Hs) was0.312, the mean genetic differentiation coefficient (Gst) was0.100, the gene flow (Nm)was2.245. The genetic differentiation indices between Henan and LiaoningSubpopulations and between Mantodea and Araneida Subpopulations were the highest,while that between Ningxia and Shaanxi Subpopulations and between Coleoptera andHymenoptera Subpopulations were the lowest: and the genetic differentiation amongdifferent insect order subpopulations was small, so there was no strong hostspecialization of B. bassiana.4. Genetic identity (I) and genetic distance (D): the mean genetic identity (I) of theprovincial subpopulations was0.867, genetic distance (D) was0.145; while the meangenetic identity (I) of the different insect order subpopulations was0.945, geneticdistance (D) was0.057. The genetic distances between Henan and LiaoningSubpopulations and between Mantodea and Araneida Subpopulations were the highest,while that between Ningxia and Shaanxi Subpopulations and between Coleoptera andHymenoptera Subpopulations were the lowest. Mean genetic differentiation indices andgenetic distances between host order subpopulations were both lower than those of theprovincial subpopulations.5. UPGMA clustering analysis: the clustering dendrogram of13provincialsubpopulations showed that: several far apart provinces were clustered together, whilecertain neighboring provinces were not clustered together, therefore there was no obviouscorrelation between genetic lineage and geographic distance; the clustering dendrogramof9host order subpopulations showed that: the Araneida Subpopulation, which was notbelong to the insecta, has nearer sibship than the Mantodea Subpopulation to the other7insect order subpopulations, all the subpopulations clustered together besides theMantodea Subpopulation, so there was also no obvious correlation between geneticlineage and host origin; the clustering dendrogram of single provincial subpopulationshowed that: the genetic lineages of all the provincial subpopulations were heterogenous,B. bassiana lineage distribution of geographic and host origin was random, so the geneticlineage of B. bassiana in north China had no clear relationship with geographic originand host origin; the clustering dendrogram of all isolates in north China showed that thedistribution of genetic lineage had certain geographical characteristics: the isolatescollected from the northeast (including Inner Mongolia) and the vast majority ofShandong Subpopulation isolates clustered together formed the Northeast-ShandongClade, the vast majority of isolates collected from the northwest clustered together formed the Northwest Clade, while among the subpopulations of Huanghuai region, theisolates of Anhui Subpopulation (Huaibei region) clustered to one clade independently,the isolates of Hebei, Henan and Shanxi Subpopulations, which were mixed into thelineages of the northwest, were the components of the Northwest Clade. However, thesegeographical characteristic distribution still could not prove the correlation of geneticdistance and geographic distance.These results suggest that: although the genetic differentiation of B. bassiana innorth China had some degree of geographical characteristics, but there was no significantrelationship with geographic distance and host variation; differentiation is the result ofselection pressure, the variation of B. bassiana in north China was mainly caused byvariation between families and genera of hosts, and also caused by variation betweendifferent collection sites and microhabitats inside them.