The Relation Between Symbionts And Resistance Of Rice Planthoppers To Serratia Smarcescens,and Effects Of Bismerthiazol On Symbionts

Insects commonly harbor endosymbionts,and the infections are affected by a variety of exogenous and endogenous factors.Symbionts can help insects improve their ecological adaptability and resistance to pathogenic microorganisms and so on.In nature,insect pests often face with stress of lethal pathgenic microorganisms,other than this,they also have chance to be exposed to bactericides.The influence of pathgenic microorganisms and fungicides on the endosymbiont infection in insect pests are far from known.Planthoppers are important insect pests in rice,there are various endosymbionts in the pests.And apart from yeast-like fungus which are fungal symbionts,there are bacteria symbionts such as Arsenophonus,Wolbachia,Serratia and Acinetobacter in rice planthoppers.Based on the isolation of a new strain of Serratia marcescens from brown planthopper(BPH),Nilaparvata lugens(Stal),we studied the relation between symbionts and S.marcescens.In addition,we also studied the impact of bactericide bismerthiazol on the symbionts in BPH.Our findings will enrich the study of symbionts and be beneficial to the rational use of S.marcescens.The main results are as follows:(1)The diversity of secondary symbionts in BPH and the relation between insecticidal bacterium S.marcescens and symbionts were studied.We established six isofemale lines of BPH from Anhui Hexian population,and then we detected the infection rate of the symbionts in all the six lines.We also compared the sensitivity of the six lines to S.marcescens.It was found that,only in line 4 and 6,there was no Wolbachia infection,whereas in the other four lines,they all harbored Wolbachia.Arsenophonus,Serratia,and Acinetobacter were present in all the six lines.Within the same line,there is significantly difference in the infection rates of the different symbionts,and the difference varied with symbiont infection,no infection of Arsenophonus was found in male BPH in all the six lines.There are significant differences in the sensitivity to S.marcescens among the six lines.We analyzed the relationship between the mortality of BPH caused by S.marcescens and the infection rate of symbionts,and found that Arsenophonus infection had correlation with sensitivity to S.marcescens.(2)The impact of bactericides bismerthiazol on symbionts of rice planthoppers was also investigated.The results showed that,there are significant differences in Wolbachia quantity among different populations of small brown planthopper(SBPH),Laodelphax striatellus(Fallen).The Fengxian population of SBPH had the highest quantity of Wolbachia,and the quantity of Wolbachia in female and male of Fengxian population were all significantly higher than that of Nantong population.We also found that whether there was impact of bismerthiazol on symbiont infection depended on the population of SBPH,only the quantity of Wolbachia in the males of Nanjing population decreased after bismerthiazol treatment.Our studies on BPH showed that,bismerthiazol could affect the bacterial symbionts,and the impact was associated with the species of symbionts.The infection rate of Serratia significantly decreased after bismerthiazol treatment,but the infection rate of Arsenophonus,Wolbachia and Acinetobacter were not affected.