| There are more than7000species of scale insects (Insecta:Hemiptera: Coccoidea), which is a group of the most destructive pests in fruit orchards, forests, and ornamental plants in the world. It is difficult to control scale insects due to the scale insects protected by their waxy substances secreted from a various of wax pores on the body surface. The objective of this research is to study the role of the entomopathogenic fungi and wax-phage bacteria in decomposing and invading the wax substances of the Ceroplastes japonicus. The results may provide a base for developing entomogenous fungi into the high-powered bio-insecticide to control scale insects.The contents are as follows:1. The entomogenous fungi decomposing the wax subtance of the Ceroplastes japonicus1.1After inoculation with the conidial suspensions of the four strains (2×107spore/mL), the infection symptoms of adult females of C. japonicus were observed. We found that a large number of mycelia appeared on wax covering, the scale insect became dead and the body shriveled. In the control group without fungal infection, cultured for15days, the wax shell and body of the scale insect generally kept well, and insect was still alive. After15days, the mortalities of the scale insects in the infected groups with four strains were TSL0(670.56±0.04%)> V3.4504(68.33±0.06%)> FDB01(67.22±0.07%)>V3.4505(65.00±0.05%).1.2A special WTC medium was prepared by puting wax substance that is "wax covering" or "wax covering+insect body" of C. japonicus into medium in the rate of0.4g/50mL. The wax substance was as sole carbon source for the strians. Experiment showed that the4strains all were able to grow and reproduce. The strains V3.4504and V3.4505existed mostly as mycelia, twhile strains FDB01and TSL06existed mostly as spores. This means that entomogenous fungi invade the wax covering probably by different ways. 1.3The lipsae is the important enzymes when fungi decompose the wax subtance of C. japonicus. The experiments showed that in decomposing the wax subtance of C. japonicus, the lipase activity of the four strains displayed a different change trend. In decomposing the wax covering groups, The highest activity of lipase of the four strains were TSL06(0.535±0.009U/mL)> V3.4504(0.433±0.015U/mL)> FDB01(0.426±0.082U/mL)> V3.4505(0.289±0.003U/mL). In decomposing "wax covering+insect body" groups, The highest activity of lipase of the four strains were TSL06(O.535±0.009U/mL)> V3.4504(0.433±0.015U/mL)> FDB01(0.426±0.082U/mL)> V3.4505(0.289±0.003U/mL)。The highest lipase activity of the strains TSL06, V3.4504and FDBO were higher than V3.4505. Then The first three strians probably had more ability than V3.4505in decomposing the wax suntance of C. Japonicus.1.4The microbes produce dehydrogenase to decompose the long carbon of wax subtance. In metabolism, the dehydrogenase activate hydrogen atoms in the petroleum hydrocarbons and transfer them to the specific hydrogen acceptor, that resulted in a realization of oxidation and conversion of petroleum hydrocarbons. Our experiments showed that in decomposing the wax subtance of C. japonicus, the dehydrogenase activity of the four strains changed in different trends. In decomposing wax covering groups, the highest activity of dehydrogenase of the four strains were V3.4504(0.075±0.003U/mL)> V3.4505(0.074±0.002U/mL)> TSL06(0.066±0.002U/mL)>FDB01(0.061±0.004U/mL). In decomposing "wax covering+insect body" groups, the highest activity of dehydrogenase of the four strains were V3.4505(0.075±0.002U/mL)>V3.4504(0.070±0.006U/mL)>FDB01(0.074±0.004U/mL)>TSL06(0.069±0.002U/mL)1.5Morphological changes of the insect wax caused by degradation of strians. By using scanning electron microscope and stereomicroscope, we found that in decomposing wax covering groups, the structure of the wax became crisp, some mycelia conglutinated on the wax surface and many small holes appeared on the wax surface. The degradation rates of the wax covering were TSL06(23.10±0.031%)>V3.4504(18.20±0.019%)>FDB01(15.4±0.017%)>V3.4505(11.00±0.011%). In decomposing "wax covering+insect body" groups, the wax coverings changed their color to luteotestaceous and wax structure became loose and crisp. In the strains V3.4504and V3.4505experiment groups, some mycelia conglutinated on the wax surface and many small holes appeared on the wax surface; comparably, in the strain FDB01and TSL06treated groups, many spores adhering to the wax were observed and many small holes also were visible. The degradation rates of the wax covering were TSL06(32.50±0.03%)> V3.4504(31.50±0.01%)> FDB01(30.40±0.03)>V3.4505(26.90±0.05). This result was consistent with the highest activity of lipase.1.6By using linear regression, the relativity between the enzymes activity of the four strains and wax degradation rate of C. Japonicus was analysed. In decomposing the wax covering groups, the maximum lipase activity was significantly relative (r=0.9014) to the wax degradation of the scale insect, but the correlation coefficent between the highest activity of dehydrogenase and the wax degradation was only0.1789. In decomposing "wax covering+insect body" groups, the maximum lipase activity was significantly relative to the wax degradation with the correlation coefficent0.9332. But the maximum dehydrogenase activity was without correlation relative to the wax degradation with the correlation coefficent0.8525.2. The wax-phage bacteria decomposing the wax of the Ceroplastes japonicus2.1The concentration (OD)、CSH、lipase activity of the wax-phage bacteria were determined during decomposing the wax of C. Japonicus. On the groups of solid salt medium, the wax covering melted down. In decomposing the wax covering groups, the structure of the wax beceme crisp, some mycelia conglutinated on the wax surface and many small holes appeared on the wax. The highest rates of wax degradation by wax-phage bacteria action was23.50±0.042%. In decomposing "wax covering+insect body" groups, the wax shells changed their color to luteotestaceous and wax structure became loose and crisp. The highest rates of wax degradation by wax-phage bacteria action was41.82±0.0024%.2.2The lipase activity and wax degradation rates by wax-phage bacteria action with different concentrations was determined. In decomposing wax covering groups, the highest lipase of the wax-phage bacteria were OD1(0.172±0.0035U/mL)>OD3(0.161±0.0093U/mL)>OD2(0.150±0.0015U/mL)> OD4(0.087±0.0031U/mL)> OD5(0.062±0.0070U/mL); The wax degradation rates were OD5(34.29±4.93%)>OD4(26.45±1.73%)> OD3(23.43±3.75%)> OD2(17.56±3.01%)> OD1(17.20±0.55%). In decomposing "wax covering+insect body" groups, the highest lipase of the wax-phage bacteria were OD,(0.172±0.0035U/mL)>OD3(0.161±0.0093U/mL)>OD2(0.150±0.0015U/mL)>OD4(0.087±0.0031U/mL)>OD5(0.062±0.0070U/mL); The wax degradation rates were OD4(60.35±1.78%)> OD5(57.60±0.73%)> OD3(57.24±2.29%)>OD2(53.47±2.21%)>OD,(35.47±3.87%)2.3The effect of the wax-phage bacteria on the entomogenous fungi in decomposing the wax subtance of C. Japonicus. It was found that the wax-phage bacteria restrained growth of the V3.4504on PDA medium. In salt medium, the wax-phage bacteria also restrained growth of the V3.4504. In decomposing wax covering groups, mixed with bacteria, the lipase less than the fungi as follows V3.4504(0.282±0.0055U/mL)> OD3+V4(0.229±0.0100U/mL)> OD4+V4(0.225±0.0040U/mL);The wax degradation rate were V3.4504(18.01±2.93%)> OD3+V4(16.39±1.26%)> OD4+V4(14.42±0.41%)In decomposing "wax covering+insect body" groups, the lipase were V3.4504(0.427±0.0072U/mL)> OD3+V4(0.259±0.0055U/mL)> OD4+V4(0.250±0.0026U/mL); The wax degradation rate were OD4+V4(49.30±3.74%)>OD3+V4(31.17±6.25%)>V3.4504(30.76±6.11%)... |
PDF Full Text Request