Effects Of Secondary Symbiotic Bacteria Regiella Insecticola And Tempertature On The Biological Traits Of Sitobionavenae

The symbiotic bacteria are widespread in insects which impact on the ecological fitness of host insects.How does the secondary symbiotic Regiella insecticola affect the biology characteristics of wheat aphids Sitobion avenae populations which are not clear.In this paper,species of the secondary symbiotic bacteria and their infection rates in wheat aphids in NanJing were monitored for during 2015 and 2016,and the effects of the secondary symbiotic Regiella insecticola and temperature on the biological characteristics of S.avenaewere studied.The main results are as followings:Using the method of diagnostic polymerase chain reaction(PCR),these endosymbionts Regiella insecticola,Hamiltonella defense,Serratia symbiotica and Rickettsiain S.avenaepopulation of Nanjing were detected.The results showed that S.avenae in every year from December to February were mainly infected with Serratia symbiotica and Rickettsia,and almost no infection of Regiella insecticola was detected,but it was mainly infected with Regiella insecticola from March to May.S.avenae populations infected with R.insecticola were reared at different temperatures,and the infection rate of R.insecticola in their offspring was significantly lower at high temperatures than that at the low temperatures.With the increase of generations under different temperatures,the infection rates of offspring rose and kept a high level.Short-term high temperature environment can lead to the R.insecticola of Sitobion avenae losing.Life tables of S.avenae infected with R.insecticola were established at 25?,28 ?,and 31 ?.The results showed that as the temperature increasesed,net reproductive rate and intrinsic rate of growth were decreased and average life span was shorter.Life tables of different strains of S.avenae infected and uninfected R.insecticola were built at 25?,28?,and 31?.The results show that infection of R.insecticola resulted in lower net reproductive rate and intrinsic rate of increase of S.avenaein the medium and low density and at an optimum temperature.But at 31? high temperature and high density,infection of R.insecticola was not affected the net reproductive rate and intrinsic rate of increase,or significantly increased these values in some genotypes of S.avenae populations.Temperature,population density,and infection of R.insecticola together affected the biological traits of S.avenae.The winged aphids in different population densities 5,10,15,20 and 25 aphids per dish of S.avenae which infected or uninfected R.insecticola were studied.The results showed that winged aphid ratio was smaller in S.avenae infected with R.insecticola under low temperature and population density,but under the conditions of high density and high temperature,winged aphid ratio was not significant between infected and removed R.insecticola strains.Ability of producing winged aphids of S.avenae was controlled by R.insecticola infection,population density and temperature,but the aphid genotype did not affect the ratio.In sum,secondary symbiont R.insecticola has adverse effects on biological characteristics of S.avenae populations and this effects were also regulated by aphid host genotype,population density and temperature.