Effect Of Endosymbionts On Formation And Development Of Two Invasive Whitefly Species In China

The sweet potato whitefly,Bemisia tabaci(Gennadius)(Hemiptera:Aleyrodidae),is an important cosmopolitan insect pest all over the world.B.tabaci is a species complex composed of numerous biotypes,which are morphologically indistinguishable.Among the numerous B.tabaci biotypes,B and Q biotypes are widely distributed and well-studied.Many researches proved that B.tabaci Q biotype has better survival than B biotype due to higher tolerance to extreme temperature and greater resistance to insecticides,and Q biotype has spread worldwidely.In addition to the essential intracellular symbiotic bacterium Portiera,several facultative secondary symbionts(S-symbionts)including Hamiltonella,Rickettsia,Wolbachia,Cardinium,Fritschea,and Arsenophonus have been identified from B.tabaci.To verify the correlation between the geographical distribution of S-symbiont communities and population proportions of B and Q biotypes,S-symbiont infection frequencies of 86 Chinese geographical populations of B and Q biotypes were determined by a specific PCR detection technique.The main results and conclusion were as follows,1.At 2008 year,the frequencies of S.tabaci B biotype and Q biotype were almost equal,which were balancing distribution.During 2012 and 2015,S.tabcrci Q biotype was gruadually becoming predominant whitefly,and distributed most of the investigated province and regions,of which the frequency was respectively up to 81.05%for 2012(308/380)and 83.31%for 2015(594/713).Meanwhile,we confirmed most B.tabaci Q biotype in our country was classified into Q2 subclade.2.Both of two main whitefly species(B biotype and Q biotype)harboured primary symbiont.However,the predominant secondary symbiont of B biotype was Hamiltonella and Rickettsia,of which the frequencies were up to 90%and 65%.Besides,Wolbachia,Cardinium,Fritschea and Arsenophonus was rare,the frequencies were less than 5%.The predominant S-symbiont of Q biotype was Hamiltonella,the infected rate was more than 90%,after then Rickettisa and Cardinium.Meanwhile,the frequency of Rickettsia was increased with the invasive time.Also,both of two biotype whitefly have coinfection situation,and the main type of coinfection of S-symbiont was Hamiltonella+Rickettsia.3.No genetic variation was found among two mainly S-symbiont Hamiltonella and Rickettsia,either interspecific or intraspecific.