High Virulence To Chilo Suppressalis's Fungus For Biology And Solid-phase Culture Technique

Chilo suppressalis is one of the most significant pests of rice in Asia,which have great impact on the yield of rice of China.In recent years,the harm of the incidence of C.suppressalis on rice crops are more and more serious.Its characteristics have borer hazards,their prevention and treatment has been relatively difficult.Currently prevention and management mostly rely on chemical control.But long-term,the single use of highly toxic organophosphate,carbonate and other chemicals,exacerbated by the development of C.suppressalis resistance.Control effect decreased significantly,which made the prevention increasing difficult.Therefore,to carry out research on C.suppressalis resistance mechanism,the development of new formulations of pesticides has important implications for resistance to C.suppressalis of governance.The article states the processing of screening insecticidal fungus,insect fungus virulence determination of C.suppressalis,and molecular identification of insecticidal fungi.It screened the high virulence Beauveria bassiana on C.suppressali and systematic evaluation of bassiana the effect on the application of C.suppressalis.,which provided soliad evidence for biological control and theoretical basis of the application of bassiana.The main results of the experiment were as follows:1.The insecticidal fungal's purification and biological characteristics.We collected naturally diseased 500 of C.suppressalis cadaver in fileds.Using tissue separation method and isolated 36 insecticidal fungus from C.suppressalis bugs stiff body,after that we carried on the purification fungus and stored backup samples.From isolated and purified 36 insecticidal fungus,we screened 10 pairs of pests fungal virulence,measured a number of biological indicators of the diameter of colony growth,the initial production of sporing time,speculation and spore germination rate.It's characters culture results show: after 7d medium,the strain Bbr14,Bbr84,YQ147 and QING strains on SDAY culture,its colony diameter are more than 1.4cm,the highest reached 1.89 cm,which showed good growth features.Initial speculation timeof strains Bbr84,QING,YQ147 and Bbr14 were 2.83 d,3.03 d,3.22 d and 3.49 d,compared with other six strains,its time are shorter;The speculation were 3.28 ×108,3.12×108,3.01×108 and 2.85 ×108 spores / cm²,speculation is relatively high;And this four strains germination rates were 96.14%,95.24%,92.12% and 90.11%,exceeding 90%.2.The test of virulence of strains on C.suppressalisthe study used rice pests C.suppressalis as sample,under same conditions?including same concentrations,temperature and humidity?,the virulence of 10 insecticidal fungus on C.suppressalis larvae were measured indoor with a method of spraying.The results show that: the virulence instars of different strains for the effects of different C.suppressalis significant differences.At a concentration below 1.0 × 108 spores / m L,fungus YQ147,QING,Bbr14,Bbr84 on C.suppressalis larvae have strong virulence,after treatment 10 d,including fungi YQ147 on C.suppressalis the first three larvae cumulative correction mortality rate of 78.4%,LT50 for 5.8d,for C.suppressalis egg masses cumulative corrected mortality rate of 99.7%,LT50 is 3.54 d,results significantly higher than other strains.To toxicity tests on C.suppressalis showed higher cumulative corrected mortality strains,LT50 smaller,the better effect of strain.3.Invasion mechanism and molecular identification of highly virulent strains.Virulence by screening out the most virulent strain,the use of scanning electron microscopy insecticidal fungus spores on C.suppressalis infestation process.According to the biological characteristics of the strain,the use of Beauveria sp.18 S rDNA ITS sequences were amplified by PCR,agarose gel electrophoresis and sequence analysis.It used to homology sequence alignment in the nucleic acid sequence database,and building systems to determine their tree branch to determine their species.The results show that the strain is Beauveria bassiana.4.Response surface methodology bassiana nutrition.Choose inexpensive and readily available experimental material as solid fermentation medium to experiment univariate basis,Response surface composite design parameters of experimental conditions on Beauveria bassiana proportion ofsolid fermentation medium was optimized.It's speculation volume of fermentation for recipe quality standards after 7d.Experimental results show that: when solid medium proportion of rice,peanut shells and rice husk as 5.00g: 1.00g: 0.65 g,measured unit weight medium YQ147's conciliation highest,reaching 4.0723 × 10¹⁰ spores / g.Than the single factor experiment highest value 3.858 × 10¹⁰ spores / g higher than 5.49%,basically consistent with theoretical predictions.