Genetic Structure Analyses Of Woolly Apple Aphid (Eriosoma Lanigerum Hausmann) Population In China Studied Using Microsatellite Markers

Woolly apple aphid, Eriosoma lanigerum (Hausmann) was a worldwide and serious pest of apple trees. It was originally found in North America, and spread to other places of the world along with the nursery stock. The woolly apple aphid invaded in our country successively in the initial period of 20th century and latter spread to some other apple growing areas of our country, and at present it distributed in more than 70 countries.We gathered the samples of 21 populations from the main apple growing regions in China and the Oregon population in America. We use 6 microsatllite loci to study the genetic structure of woolly apple aphid. Through the genetic structure and the genetic differentiation analysis of different populations, combined with the invasion and expansion condition of woolly apple aphid,we analyzed the invasion and evolve related question. Main results were summarized as follows:(1)We tried 3 methods to extract genome DNA from woolly apple aphid, there were little difference between their SSR-PCR products. According to the Marker, the size of the woolly apple aphid's genome DNA is about 23 kb.(2)Simple sequence repeats (SSR) are conserved in some extent between the close kinship species. 13 SSR primers developed from the Pemphigidae were tested, and 7 of them have band in the 60 ~ 300bp scope, and maybe they can be used in woolly apple aphid.(3)We found 31 microsatellite loci from the woolly apple aphid and the close kinship, and constructed the SSR-PCR system of apple woolly aphid using 6 microsatellite loci which have high polymorphism to woolly apple aphid populations in China. (4)Populations in China exhibited extremely high heterozygosity and the heterozygosity excess, which can be considered as the result of long-term and absolute parthenogenesis, because it has been found that ancient clonal organisms showed high heterozygosity and heterozygosity excess as consequence of accumulating mutations. High level of deviation from Hardy-Weinberg equilibrium and Linkage disequilibrium were found, which are also in line with genetic typical features of asexual aphid lineages.(5)The 15 populations from Shandong, Liaoning, Hebei, Henan, Shanxi, Shan'xi, Gansu exhibited no genetic differentiation. The populations from Shandong and Liaoning maybe have experienced a serious bottleneck effect, the genetic diversity had reduced and the population homogeneity increased, instead this made its adaptability to strengthen, this mignt be one of the molecular mechanisms that the woolly apple aphid greatly erupted once more and widely spread.Genetic differentiation between the three populations from Yunnan were remarkable, explained that the apple woolly aphid evolved quickly in Yunnan. Populations from Tibet and Xinjiang Yili exhibited little genetic differentiation. Tibet population, because of the climatic environment condition as cold, day length, high and the oxygen deficit etc., have had the big adaptability evolution, split up in a big way with other populations. The Xinjiang Yili population had possibly experienced the similar fast adaptability evolution, or its apple woolly aphid originated for Tibet population.