| Presently Beauveria bassiana(Balsamo)Vuillemin is one of the most widely applied entomopathogenic fungi at home and abroad, to effectively control pest. It could infect more than 700 insects species of 149 families in 15 orders. In this paper, biological characteristics,Germinated spores characteristics, interspecies relation and esterase isoenzyme characteristic of Beauveria bassiana samples isolated from 15 different host species were studied; random amplifier polymorphic DNA(RAPD) was applied in the study of genetic diversity;Beauveria bassiana HFW-05 Colonization on phylloplane of tomato,cabbage and cucumber, and soil; and the HFW-05 strains influence on bacterium and actinomycetes of native environment were also studied.To explicitly show biological characteristic and taxonomic status,fifteen Beauveria strains, were assayed on ITS nucleotides sequence, growth rate of colony, sporulation, spore germination rate, length of germ tube and ratio of single tube spores were also looked at. Results showed that they were Beauveria bassiana.There was no significant difference in colony growth rates.The ratio of single germ tube spores of these strains was 11.91-96.03%. The average length of single germ tube and double germ tube were 6.28-21.43μm and 10.34-19.90μm, respectively. The spore germination rate was 22.09%- 86.32%. No significant correlation was observed between the micro-germinated spores characteristics and macro-cultivate characteristics (p=0.341).There was significantly correlation between the spore germination rate and the ratio of single germ tube germination spores, and the growth rate of colony was found to be significantly correlated with average length of longer germ tube.In this study, the esterase isozyme zymogram and RAPD technology for genetic analysis was used to study the genetic diversity of the 15 strains. Based on esterase isozyme zymogram, clustering analysis showed that the genetic similarity coefficients among different strains ranged from 0.125 to 1.000, the examined isolates were clustered into 10 groups at a similarity coefficient level of 0.7. RAPD fingerprint quality, forty-seven 10nt-primers were selected from 160 examined RAPD primers, which produced clear fingerprints by PCR amplification. In total, 497 DNA fragments were amplified ranging from 100 to 2200 bp in size,among which 416 were polymorphic bands,reaching a percentage of 83.70%.Clustering analysis showed that the genetic similarity coefficients among different strains ranged from 0.4848 to 0.8848, suggesting that there was abundant DNA polymorphism among the isolates. The examined isolates were clustered into 6 groups at a similarity coefficient level of 0.7. Comparison of the origins of strains within and between groups indicates that much of the DNA polymorphism was’t associated with either geographical origin or insect host species.Beauveria bassiana HFW-05 Colonization on phylloplane of tomato, cabbage and cucumber, and soil was studied as well. The results showed that population of strain HFW-05 for greenhouse and field conditions at phylloplane and mesophyll of tomato were 29.25±6.50×105cfu/g fresh weight and 9.20±1.06×103 cfu/g fresh weight respectively,whereas that phylloplane and mesophyll population of cabbage under greenhouse and field conditions were 21.45±2.30×105 cfu/g resh weight and 5.94±1.15×103 cfu/g resh weight respectively. The research on the survival ability of Beauveria bassiana HFW-05 shows that the CFUs could be monitered at a level of 53.1±5.16×106cfu/g in sterilized soil and 28.04±5.34×106cfu/g in natural soil. The HFW-05 strains can colonize in natural and sterilized soil. The numbers in the natural soil were less than those in the sterilized soil. And also, Beauveria bassiana was found to be beneficial to bacterium and actinomycetes in the soli. The result showed the survival ability of Beauveria bassiana HFW-05 at phylloplane and mesophyll of tomato and cabbage and also in the natural soil. |
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