Study On Subspecies Differentiation For Myzus Persicae (Sulzer) On Different Host Plants

Myzus persicae (Sulzer) is one kind of euryphagous pests. Its host range is very extensive, but it mostly endanger peach and plum belonged to Rosaceae, cabbage and rape belonged to Cruciferae, tobacco belonged to Solanaceae. In the long-term coevolution with host plants, green peach aphids have produced a series of phenomenon of host specialization, and then have formed host biotypes. But the study on its host biotypes has been controversial. In this study, the aphids were collected from peach, cabbage and tobacco in Shanxi province. In order to explore subspecies differentiation of Myzus persicae (Sulzer), we studied the selective behavior of aphids to different host plants, the effects of host plants on the suivival rate, morphological differentiation and enzyme activity, as well as the level of DNA differentiation of aphids from different host plants. So that it not only provides more evidences for host biotypes of green peach aphid,but also provides a theoretical basis for the study on the species diversity. The main results are as follows.The results of host selective adaptability showed that green peach aphids from different host plants have different selective adaptability after host switching. In this study, green peach aphids had the highest survival after switched host and had significant selectivity and palatability on tobacco. Green peach aphids on cabbage showed some tendency choice on original host, but its survival leave were relatively high on the cabbage, which also indicated that green peach aphids on cabbage adephagia cabbage. Green peach aphids on Peach on the original host didn’t show obvious preference, and had low survival rate on peach leaf.Morphological index test showed that the length of segment Ⅰ, Ⅱ asexual parthenogenetic adult peach had no significant difference on peach, tobacco and cabbage,but it had obvious difference on body length, metapodium femur, antennal length and the flagella of tentacles details. Among them, the body length of peach aphid on tobacco is the longest, the minimum on peach and green peach aphid had the longest body length and metapodium femur on cabbage. For other morphological indicators on three kinds of green peach aphid host, although their morphologically similar, but the difference still remained.. This showed that the morphological characteristics of the three kinds of green peach aphid host in certain kinds of variation.Analysis of enzyme activity test showed that the activity of degestive enzymes and detoxifying enzymes subject to changes in original host after host switching, it illustrated that green peach aphid had strong physiological plasticity. From the influence of degestive enzymes on host, the variation trend was active-inhibition- active after the host species changed; while the detoxifying enzymes was significantly inhibited from tobacco switched to peach and cabbage. From the detoxifying enzymes aspects, When aphids from peach switched to tobacco and cabbage, the activity of CarE was activity type, the activity of AChE was inhibition-inhibition- active type; When aphids from tobacco switched to peach and cabbage, the activity of CarE was inhibited, the AChE and GST transferase had been activated. When aphids from cabbage switched to tobacco and peach, the change on detoxifying enzymes were varied different.Sequence alignment analysis found that the average content of A+T of the mitochondrial COI,12S rRNA and Cytb gene in aphids on three kinds of host was higher than C+G, this was the common trait of insects Mt Dna. Compared the aberration of three gene, the mutation of COI gene was the highest, which was 1.9% and was available for species indentification; While the mutation in Cytb and the 12S rRNA gene was the lowest, which was 0.65% and 0.52%, was unsuitable for polarization.. In addition, based on the study of the COI genetic distance and NJ contribution found that green peach aphid on cabbage and peach first assembled, the genetic distance was 0.7%, and then gathered with peach aphid, hosts and kale, genetic distance of green peach aphid on peach, cabbage and tobacco were 1.5%, suggesting that the genetic relationship of green peach aphid on winter hosts and summer hosts was farther than that on cabbage and tobaccoIn conclusion, peach aphid had not only the differentiation on the host, but also the seasonal differentiation was probably a differentiation species because of the host selection pressure.