Genetic Diversity Within And Among Populations Of Acarus Siro Linnaeus Revealed By Inter Simple Sequence Repeats

Acarus siro Linnaeus,a common acaroid mite in China,is one of the main pest mites damaging the stored products,economic crops and edible fungi.The mite is widely studied due to its economic importance.In this paper,the genetic structure and genetic diversity of A.siro in different area of China were studied by using ISSR marker.The main results were as follows:(1)The discussion and establishment of the optimum protocol extracting DNA of A. siro:SDS(10%m/v) 40μl,proteinase K(10mg/mL) 6μl,STE 204μl,total 250μl of digesting system,and the samples each consisting of 50 individuals were digested at 45℃for 10-12h.(2)Optimization of ISSR-PCR reaction system:the optimal ISSR-PCR reaction system was established with L₁₆(4⁵) orthogonal design:10×PCR Buffer 2.5mmol/L, Mg²⁺ 2.0mmol/L,dNTPs 0.25μmol/L,ISSR primers 0.3μmol/L,DNA 20ng,Taq DNA polymerase 0.75U,total 25μl.(3)The results of amplification:18 primers were selected for their ability to produce clear and reproducible patterns of polymorphic bands.Those primers were then used for analysing genetic diversity within and among populations of A.siro collected in Nanchang,Jiujiang and another two populations sampled in two sorts of feedstuff in Anhui province(NC,JJ,AH-1,AH-2).A total of 136 DNA bands were yielded,107 of which were polymorphic and the percentage of polymorphic bands(PPB) was 78.68%.(4)Evaluation of genetic diversity:At population level,the value of expected heterozygosity(He) was 0.1302,Shannon information index(I) 0.1875 and the percentage of polymorphic bands(PPB) 30.15%;at species level,the values of He,I, PPB were 0.3586 0.5314 and 78.68%,respectively.The levels of genetic diversity could be ordered in abundance as JJ＞NC＞AH-1＞AH-2 and the JJ population possessed the highest level.(5) Analysis to genetic variation:the value of Gst(coefficient of gene differentiation) was 0.6283,which was consistent with AMOVA analysis(Fst=0.5824,P＜0.001), indicating high level of genetic differentiation among populations.Nei's genetic diversity analysis showed that the level of gene flow(Nm=0.3717) was low between populations.Dendrogram constructed using the UPMGA method and Nei's unbias genetic distance showed the relationships between two Anhui populations was closest. And the populations of A.siro strongly differentiated between Jiujiang and others. The results indicated that there was a certain genetic differentiation between these different populations;Geographic difference caused stronger differentiation than habitat difference.Moreover,there was no significant correlation between the genetic distance and geographic distance,indicating that geographic isolation was not the main factors inducing genetic difference.