Studies On The Activity Of Isaria Fumosorosea To B-biotype Bemisia Tabaci And Its Transmission Of TYLCV

Isaria fumosorosea,is a common entomogenous fungi,is widely distributed and is used in the biological control of pests.It has the advantages of safety,no pollution and resistance to resistance.In our previous study,we found that the IfB01 strain of I.fumosorosea was highly active to B-biotype and reduced the efficiency of its transmission of Tomato yellow leaf curl virus（TYLCV）.This study will further study the effect of IfB01strain and its fermentation products on the accumulation of TYLCV in plants and Bemisia tabaci,and to explore the mechanism of the strain affecting the spread of TYLCV virus,and the inheritance of 16 plants from Guangdong,Fujian and Qinghai.Geographical difference analysis and bioassay of Bemisia tabaci were mainly studied as follows:（1）The effect of IfB01 strain on the accumulation of TYLCV in tomato plant.After spray treatment of tomato plants that had been poisoned by spore suspension of 10⁸mL^-1of I.fumosorosea.In the 4 days,21 days and 28 days after treatment,the quantitative analysis of TYLCV virus in tomato plants was carried out by qPCR method.The results showed that there was no significant difference in the accumulation of TYLCV virus in the tomato plant of the treatment group and the control group,indicating that the IfB01 strain of the I.fumosorosea could not affect the accumulation of TYLCV through the tomato.（2）Investigating preliminarily the mechanism of transmission efficiency of TYLCV by whiteflies as a result of the extracted of the strain IfB01 fermented liquid.Using the dichloromethane extract of the fermentation broth of IfB01 strain to treat the plant with poisonous tomato,the amount of TYLCV in the plant was detected by qPCR 14 days after treatment.The results showed that there was a significant difference between the control group and the virus in the tomato plants of the extract 500μg/ml and 250μg/ml treatment group,and the higher the concentration,the more the virus was.However,when treated with extracts of 125μg/ml concentration,there was no significant difference in viral load between the two groups.In the tomato plant with TYLCV,inoculated with B type of Bemisia tabaci to spawn,when it was developed to second-instar nymphs,the extract of IfB01 strain was treated by impregnation.The results showed that the percentage of the control group was 80.18%,38.59%,52.57%,70.31%,respectively,and the extracts of the extract,500μg/ml,250μg/ml,and 125μg/ml treatment group.It showed that the eclosion rate of B.tabaci was significantly reduced by the extract treatment,indicating that the extract had insecticidal effect on B.tabaci.Then,inoculating B.tabaci adults on the healthy tomato plants,the results of tomato infection TYLCV were investigated.The results showed that after 3 days treatment,the rate of tomato was 30%,46.67%and 80%in the 500g/ml,250g/ml and 125g/ml treatment group,respectively,which were lower than that of the control group 90%.After 10 days,the rate of tomato was 83.33%,90%and 93.33%in the 500g/ml,250g/ml and 125g/ml treatment group.There was no significant difference between the treatment group and the control group.The detection of TYLCV virus was carried out by extracts of 500μg/ml,250μg/ml and125μg/ml treatment group and control group.The results showed that the toxicity rate was96.67%,90%,100%,and the rate of virus was 100%in the control group,but the quantitative detection of virus in the body of B.tabaci showed that the virus content in the treatment group was obvious.Lower control group.It can be seen that the IfB01 strain can reduce the accumulation of TYLCV in tomato plant on the one hand,on the other hand,it can reduce the emergence rate of B.tabaci,and reduce the accumulation of TYLCV in the body of B.tabaci,thus reducing the toxic ability of B.tabaci.（3）Genetic geography of Isaria fumosorosea and its pathogenicity against B-biotype of Bemisia tabaci.In current research,the genetic geographical difference of the 16 strains of I.fumosorosea isolated from the soils of Guangdong,Fujian,and Qinghai Provinces,were surveyed by comparing the similarity of ITS sequences.Meanwhile,their insecticidal activities against the second-instar nymphs of B-biotype B.tabaci were evaluated.The ITSs similarities of the 16 I.fumosorosea strains with the reference strain（KX057375.1）were more than 97.7%.But,the 9 strains from Guangdong and 6 strains from Fujian had no geographic difference.The strain IfTS01 of Qinghai was almost the same as the reference strain（KX057375.1）,and was highly closest with the strains,IfFJ02/06 of Fujian and IfGD17 of Guangdong.Furthermore,the pathogenicitiesof all strains against B-biotype B.tabaci ranged from 47%to 86%after 10 days treatment.The most effective strains,IfFJ06,IfGD02 and IfTS01,had more than 80%pathogenicity.There is no obvious differences of genetic geography in I.fumosorosea strains isolated from Guangdong and Fujian.Meanwhile,the pathogenicity of I.fumosorosea strains to B.tabaci is not related its geographical distribution and ITS sequence similarity.