Effects Of Cucurbit Chlorotic Yellows Virus On The Biological Characteristics Of Its Vector Bemisia Tabaci

Tobacco whitefly Bemisia tabaci(Gennadius)(Hemiptera: Aleyrodidae)with host range of more than 900 plant species is a world economic pest,has brought huge damage and economic losses to global agricultural production.In addition to the direct harm to the plants,B.tabaci is also one of the most effective vectors for transmitting plant viruses.Cucurbit chlorotic yellows virus(CCYV)is transmitted specifically by B and Q biotypes of Bemisia tabaci in a semipersistent manner.In recent years,CCYV has occurred seriously on melon plants and some other plants in China.More and more evidences have proven that plant viruses can have great impacts on their vector insects,but there is no detailed report on the effects of CCYV on its vector B.tabaci.In this study,by using B.tabaci B and Q biotypes,CCYV and cucumbers as experimental materials,we investigated the effects of CCYV on the growth and reproduction of B.tabaci B and Q biotypes,including the survival rate,body size,development period and the life table parameters,and so on.In addition,we also used the real-time fluorescence quantitative method to detect the virus amount in nymphae of B.tabaci B and Q biotypes on the infected plants.This study hopefully provide a new experimental example for mechanism study of plant-vector-virus interations,and the basis for effective management of whiteflies and whitefly-transmitted viruses.The main results of this study are as follows:(1)The effects of CCYV on the survival rate of the two biotypes of B.tabaciThe overall survival rates of B or Q biotype were higher on the healthy cucumbers than those on the CCYV-infected cucumbers.The egg hatching rate and overall survival rate of B biotype were significantly higher on healthy plants than on CCYV-infected plants(P<0.05),while there were no significant difference in the survival rate of the Q biotype.On healthy cucumbers,the overall survival rate of B biotype was 86.02% and of Q biotype was 88.84%.On the CCYV-infected cucumbers,the overall survival rate of Q biotype(79.52%)was significantly higher than that of B biotype(71.21%)(P<0.01).(2)The effects of CCYV on the body size of the two biotypes of B.tabaciThe nymphae of B biotype on the healthy cucumbers had significantly longer body length,wider body width than on the CCYV-infected cucumbers(P<0.05).However,the 1st instar nymphae of Q biotype had longer body length and wider body width on the CCYV-infected cucumbers than those on healthy cucumbers.On the healthy cucumbers,B biotype was significantly larger than Q biotype(P<0.05).But on the CCYV-infected cucumbers,Q biotype was larger than B biotype in the first,second and third instars,with B biotype significantly larger than Q only in the fourth instar.For adults,whether female or male,B biotype was larger on healthy cucumbers,while Q biotype was larger on the CCYV-infected cucumbers plants.(3)The effects of CCYV on the development of the two biotypes of B.tabaciThe developmental duration of B biotype was 18.12 d on the healthy cucumbers,while on the CCYV-infected cucumbers is 20.77 d,there was significant difference between them(P<0.05).The developmental duration of Q biotype was 18.91 d on the healthy cucumbers,while on the CCYV-infected cucumbers is 22.1d,with significant difference between them(P<0.01).On the healthy cucumbers,the developmental duration of Q biotype was 4.31 d longer than B biotype(3.80d).On the CCYV-infected cucumbers,developmental period of B biotype was longer than Q biotype in 1st instar,but the overall developmental duration of B biotype was 20.77 d while that of Q biotype was 22.21 d.It can be seen that CCYV prolongs the development period of Bemisia tabaci,with and Q biotype developed slower than B biotype.(4)The effects of CCYV on the sex ratio of the two biotypes of B.tabaciBoth B and Q biotypes of B.tabaci had higher sex ratio(female/male)-onCCYV-infected cucumbers(P<0.05).On healthy cucumbers,sex ratio in B biotypewas 58.34%,while Q biotype was 50.53%.On the CCYV-infected cucumbers,sex ratioin B biotype was 66.73% while Q biotype was 66.4%.It suggested that CCYV canchange sex ratio of the vector B.tabaci,with the significant increase for Q biotype.(5)The effects of CCYV on the fecundity and longevity of the two biotypes of B.tabaciB.tabaci B Biotype laid more eggs on the healthy cucumbers than on the CCYV-infected cucumbers,while those were reverse for Q biotype.What's more,B biotype laid more eggs than Q biotype on the healthy cucumbers,but on the CCYV-infected cucumbers,Q biotype laid as many eggs as B biotype.At the same time,whether B biotype or Q biotype,the longevity had lengthened(on the healthy cucumbers: 14.11 d for Q biotype,15.89 d for B biotype;on the infected cucumbers: 16.42 d for Q biotype,16.22 d for B biotype),with significant increase of longevity in Q biotype(P<0.01).(6)The virus amount in the nymphae of B.tabaci on the CCYV-infected cucumbersOn the infected cucumbers,the CCYV amount in nymphae were significantly different between B and Q biotypes at the 2nd instar and 4th instar(P<0.01 and P<0.05).In addition,during the whole development duration,both B and Q biotypes had the highest virus amount content at the 2nd instar.In conclusion,CCYV had significant effects on the growth,development,survival and reproduction of Bemisia tabaci,and had different effects on different biotypes of Bemisia tabaci.These differences will directly affect the survival scale and quality of the populations in two biotypes of Bemisia tabacias well as the relative advantage of the offspring population.This study proved that Q biotype has better adaptability,higher virus transmission efficiency and behavioral advantages than B biotype.