Effects Of Nutrition In Diet On Host Range Of The Host-Specialized Aphid,Aphis Gossypii Glover

In the long-term evolution of phytophagous insects,host specialization is often formed to adapt to different environments or host plants.Aphis gossypii Glover is a typical polyphagous insect,with 285 species of host plants in 35 families.However,the populations of cotton aphid on different host plants have obvious host specialization.The cucurbit-specialized aphid can’t use cotton plants,while the cotton-specialized aphid can’t use cucumber plants.Some studies have shown that the special feeding experience can change the host range of the specialized aphid,for example,the feeding on zucchini,cowpea and artificial diet can change the host specialization of this aphid.But it is still unclear why the specific host plants and feeding experience can cause the change in host range of the host-specialized aphids.Therefore,this experiment studied on survival and reproduction of six genotypes of cotton-and cucurbit-specialized aphids on the nutrient-controlled artificial diet,as well as the ability to use cotton and cucumber hosts of these aphids after feeding on different artificial diet,and studied on the influence of nutrients in diet on the host range of the specialized A.gossypii Glover.The main results are as follows:(1)The feeding experience on artificial diet caused the change in host range of the host-specialized aphidsThe life table parameters of three genotypes from cucumber(CU1,CU2,CU3)and three genotypes from cotton(CO1,CO2,CO3)of gossypii Glover on two kinds of artificial diet(diet Ⅰ and Ⅱ)were determined.The results showed that the net growth rate and intrinsic growth rate of all genotypes fed on feed diet Ⅰ were higher than those fed on feed diet Ⅱ,indicating that the diet Ⅰ was more suitable for the survival and reproduction of A.gossypii Glover populations than the diet II.The utilization ability of different genotypes of A.gossypii Glover to artificial diet was different.The propagation ability of.4phis gossypii Glover on artificial diet varied with aphid genotype and diet.The population of CO2 genotype could survive 23 generations on diet Ⅰ,2 generations on diet Ⅱ and 2-3 generations on both diets.The results showed that there were different nutritional requirements among different genotypes of aphid.The feeding experience on artificial diet changed the host range of host-specialized aphid,but this change was related to the aphid genotype and diet type.After feeding on dietⅠ,the host range of six genotypes did not change.However,the cucurbit-specialized aphids CU3 population fed on diet Ⅱ acquired the ability to utilize the leaves of cotton,and the cotton-specialized aphid CO2 and CO3 genotypes acquired the ability to utilize the leaves of cucurbit,while the host utilization ability of other genotypes fed on diet Ⅱ did not change.(2)The duration of feeding experience affected the host use of the specialized aphidThe population growth of CO2 aphids on cotton and cucumber was observed after their nymph and adults feeding on artificial diet Ⅱ for different days.The results showed that the adult CO2 aphid fed on the diet Ⅱ for one and three days could not use the cucumber leaves,while the adult aphid fed on diet Ⅱ for five and seven days could establish populations on cucumber leaves.However,the new-born aphids fed on the diet Ⅱ for 1-7 days and then transferred onto cucumber leaves could establish populations.No matter how long aphids CO2 took to feed on the artificial diet Ⅱ,they did not change the utilization ability to the original host.The CO2 population still could use the original host cotton leaves when they fed on the cucumber leaves for 5 generations via feeding experience on diet Ⅱ,but it lost the utilization ability of the original host cotton leaves when it fed on the cucumber leaves for more than 50 generations.However,these aphids lost ability to use original host could recover after feeding on the diet Ⅰ or Ⅱ.There was no genetic differentiation in the population of A.gossypii which had been kept on other hosts for a long time.The change of host utilization ability caused by feeding experience is a phenotypic plasticity.(3)The feeding nutrition affected the survival,reproduction and host selection of the specialized aphidThe results showed that the removal of riboflavin and p-aminobenzoic acid in the dietⅡ significantly increased the reproduction rate of the specialized aphid;the removal of cystine and y-aminobutyric acid had no significant effect on the reproduction rate of aphids:after the removal of Na,the reproduction rate of the cucurbit-specialized aphids increased.but that of the cotton-specialized aphids decreased or unchanged.The feeding experience on artificial diet Ⅱ improved the selection ability of cotton-specialized aphids to cucumber leaves and cucurbit-specialized aphids to cotton leaves.However,the cotton-specialized and cucurbit-specialized aphids still changed their host range after feeding on diet Ⅱremoved the riboflavin,p-aminobenzoic acid,cystine,γ-aminobutyric acid or Na elements.Therefore,these nutrients in diet are not the main factor that causes the host range change of the specialized aphids.