| Rhopalosiphum padi L. (family Aphidae, order Homoptera) was one of the most important agricultural pests. It could cause major economic losses directly because of their feeding and indirectly by transmitting virus.The wheat yellow dwarf diseases, caused by Barely yellow dwarf viruses which were transmitted by cereal aphids including R. padi, were the most serious virus disease in cereal crops.The complex life, large amounts of host plants, wide range distributions and complicated interactions between the insect and diverse environments might bring to its high genetic structure variation, resulting in the difficulties to manage this pest. Thus, it's reasonable and important to clarify the genetic structure of R.padi populations hosting on wheat in China, analyze its relative relationship between geographic populations and obtain the regular pattern of demographic history in population expansion.In this study, using two mitochondrial (mtDNA) genes and a nucleic gene, the populations of R. padi hosting on wheat from 15 localities in China were analysed by using a series of bioinformatic methods including genetic variation parameters, systematic phylogenetic analysis and molecular biographic geography. The principal results were as follows:(1) Sequences of these three genes, i.e. two mtDNA gene (COI&Cyt b)and a nucleic gene (EF-1α), were obtained respectively by PCR from 111 individuals of R. padi from 15 localities, covering North, East, Northwest and Southwest of China. Based on 3 genes and 1 combined sequence, 22 haplotypes of COI gene, 25 haplotypes of Cyt b gene, 29 haplotypes of EF-1αgene and 67 haplotypes of combined sequence were observed.(2) The analysis of COI sequences, Cyt b sequences, EF-1αsequences and the combined sequences showed that the percentage of polymorphic sites were 3.7%, 6.0%, 5.5% and 4.7% respectively, the values of haplotype diversity (h) were 0.588, 0.615, 0.833 and 0.970 respectively, and the values of nucleic diversity (π) were 0.00153, 0.00278, 0.00305 and 0.00256 respectively. The phenomenon of high value of h and low value ofπsuggested that the population might have a fierce expansion after bottleneck effect in its history of evolution.(3) The results of 4 NJ trees and 4 networks based on the 4 kinds of haplotypes displayed that haplotypes were not clustered according to geographic distribution.(4) AMOVA analysis indicated that certain differences exsited in pairwise comparison of genetic distance by classifying the 15 populations as one group, especially significant between Sichuan population and others. Meanwhile, the results also showed gene flow existing in the population but there were not apparent unidirectional gene flows among populations along latitude or longitude over China.(5) Neutrality tests supported that R. padi was highly differentiated as well. Both all Tajiama's D and Fu's Fs of 4 genes were significant negative.The mismatch distributions of each of COI, Cyt b, EF-1αand combined sequence supported the population had an expansion in its history of evolution.
|
PDF Full Text Request