Differentiation of cotton and cucumber specialized aphids of Aphis gossypii Glover in capacity to produce sexuales

In order to illustrate whether host specialized aphids differentiated in their life-history tactics,inducement of sexual aphids in cotton and cucumber specialized aphids of Aphis gossypii Glover was conducted under low temperature(18℃)and short photoperiod(L:D=8:16)conditions in the laboratory.The number of alate,apterous parthenogenesis aphids,and sexuparae produced by the cotton and cucumber specialized aphids were compared.The results showed that the capacity to produce sexuparae by the cucumber and cotton specialized aphids differed significantly.The rates of alate aphids and sexuparae produced by the cotton specialized aphids were significantly higher than those by the cucumber specialized aphids.The producing time of sexuparae aphids by the cotton specialized aphids was earlier than that by the cucumber specialized aphids,whereas the apterous aphids produced by cucumber specialized aphids were significantly more than those by cotton specialized aphids.Moreover,the obligative parthenogenesis individuals had been found in the cucumber specialized aphids,but not in the cotton specialized aphids.All the two specialized aphids which produced sexuparae still kept the capacity to produce parthenogenesis offspring.There was significant interaction between host specialization and the inducement duration for producing sexual morphs.The similar results were exhibited for the wild aphids on cotton and cucumber in producing sexuparae.In the second induced generation,the rate of sexuparae produced by the aphids living on cotton was much higher than that on cucumber.Meanwhile,the rate of sexuparae was significantly higher in the third induced generation than in the second generation for the aphids on cucumber,but there was no difference for the aphids on cotton.It is inferred that there exists relationship between the formation of host specialization and differentiation of life cycle in A.gossypii.