Research On The Difference Of Tolerance Of Extreme Temperature And Imidacloprid Between Viruliferous (RSV) And Native Laodelphax Striatellus

The damage mode of Laodelphax striatellus to rice is divided into the stinging hazard and the rice stripe disease caused by Rice stripe virus(RSV),and the latter is more serious.Rice stripe disease has caused a devastating blow to rice production in the middle and lower reaches of the Yangtze River and Southeast Asian countries.The viruliferous(RSV)L.striatellus population is the chief culprit in the occurrence of damage,and its proportion in the population of the L.striatellus,the survival status of the population and tolerance to extreme environments,etc..determine to some extent Whether rice stripe disease occurs and its severity.Therefore,the living conditions of the viruliferous L striatellus are worthy of attention.Environmental stress factors(most commonly extreme heat,extreme low temperatures,and pesticides)are critical for population development and expansion.Studies have confirmed that persistently transmitted plant viruses,including RSV,can alter the gene expression levels of host insects,directly or indirectly affecting their metabolism and some physiological and biochemical indicators.Then,if the viruliferous L.striatellus is exposed to environmental factors,its tolerance is changed.The subject of this project is the group of viruliferous L.striatellus and the native group mites,using biological and molecular biological techniques to correlate the viruliferous and native groups in extreme high temperature,low temperature and pesticide stress.The effects of cold resistance index,heat resistance index and detoxification enzyme were studied.The detailed results are as follows:(1)The cold resistance of the 4th instar larvae of the viruliferous group was significantly higher than that of the native group.The survival rate curve obtained by cold stress,different processing time at 4oC and processing time with 4 h at different temperatures,on the viruliferous and native group showed that the survival rate of the viruliferous group was higher than native group.The supercooling point and freezing point of the viruliferous group(-13.176oC,-9.868?)are lower than the native group(-10.614 C,-8.472 C).There were no significant differences of free water,total liquid and glycogen content in the viruliferous and native groups before treatment.The free water content of the native group increased with the processing time.And the free water content of viruliferous group(64.061%)was significantly lower than native group(73.244%)after cold stress for 4 d.The glycogen content of the viruliferous group increased significantly with the processing time.And the glycogen content of viruliferous group(97.295?g·mg-1)was significantly higher than native group(43.581?g·mg-1)after cold stress for 4 d.The trehalose content of the viruliferous and native group increased significantly with the processing time.And the trehalose content of viruliferous group(2d:3.97?g·mg-1,4d:4.52?g·mg-1)was significantly higher than native group(2d:2.47?g·mg-1,4d:3.15?g·mg-1)after cold stress for 2 d and 4 d.In summary,the L,striatellus infected with RSV has a low supercooling point.The accumulation rate of cold-resistant substances of viruliferous L.striatellus increased after cold stress.The cold tolerance of the viruliferous group is higher than that of the native group.(2)The heat resistance of the 4th instar larvae of the viruliferous group was significantly higher than that of the native group.The survival rate curve obtained by heat stress,different processing time at 40oC and processing time with 2 h at different temperatures,on the viruliferous and native group showed that the survival rate of the viruliferous group was higher than native group.The relative expression levels of viruliferous group of Hsp60(2.71-fold),Hsc70(1.29-fold)and Hsp90(1.43-rold)were up-regulated significantly than that of native group before treatment.The relative expression levels of viruliferous group of Hsc70(2.42-fold,1.66-fold)were up-regulated significantly than that of native group after 0.5 h and 1 h processing time.In summary,The infection of RSV up-regulated the relative expression of Hsp genes in the L.striatellus,and enhanced its tolerance to high temperature.(3)The imidacloprid tolerance of the 4tth instar larvae of the viruliferous group was significantly higher than that of the native group.The imidacloprid toxicity of the 4th instar larvae and female adults of the viruliferous and native L.striatellus was determined by the method of topical application.It was found that the survival rate of the viruliferous group was higher than native group(4th instar larvae:1.480-fold,female adult:4.276-fold).The synergistic effect of the enzyme inhibitors found that MFO plays a leading role in the detoxification metabolism of imidacloprid(synergism ratio:6.146-fold,2.265-fold).The MFO inhibition of the viruliferous group is more obvious.After treatment of the two groups with 0 h,12 h,24 h and 48 h by imidacloprid stress(320 mg·L-1),it was found that The EST activity of the viruliferous and native group increased significantly with the treatment time.And the EST activity of viruliferous group was significantly higher than native group after 12 h(1.276-fold)and 24 h(1.605-fold)of imidacloprid treatment.The MFO activity of the viruliferous and native group increased significantly with the treatment time.And the MFO activity of viruliferous group was significantly higher than native group after imidacloprid treatment for 12 h(1.277-fold)and 48 h(1.169-fold).After treatment of the two groups with 0 h,12 h and 24 h by imidacloprid stress(320 mg·L-1),it was found that the relative expression levels of viruliferous group of CYP6FU1(2.05-fold),CYP4DE1(13.65-fold)and CYP353D1v2(4.74-fold)were up-regulated significantly than that of native group before treatment.The relative expression levels of viruliferous group of CYP439A1v3(3.49-fold)and CYP353D1v2(4.82-fold)were up-regulated significantly than that of native group after 12 h of treatment.The relative expression levels of viruliferous group of CYP439A1v3(3.49-fold),CYP4DE1(2.15-fold)and CYP353D1v2(3.36-fold)were up-regulated significantly than that of native group after 24 h treatment.In summary,The infection of RSV up-regulated the relative expression of CYP450 genes in the L.striatellus,and indirectly increased the activity of MFO.The imidacloprid tolerance of the viruliferous group is higher than that of the native group.