Screening Of Aphid Kaburagia Rhusicola Strains Forming High Quality Egg-Like Galls

Egg-like galls are endemic to China and formed by the aphid,Kaburagia rhusicola(Hemiptera:Aphididae:Eriosomatinae:Fordini)on Rhus plants.The galls are rich in tannin content and among the economically important insect products of China.The products of egg-like galls are widely used in fields,such as chemistry-industry,medicines,and foods etc.However,the galls have not been brought into cultivation and their natural production cannot meet market demands.Moreover,naturally produced galls are undesirably of non-uniform sizes and tannin content.In this study,we investigated the genetic diversity and biochemistry of populations of gall aphids,K.rhusicola,as a step towards human-mediated selection and cultivation.We analyzed the population demographics of K.rhusicola populations representing 11 localities and 170 individuals using the mtDNA genes,COI and Cytb,and the nuclear gene,EF-1?.We also screened the tannin acid contents of egg-like galls for high quality,commercially-viable phenotypes.The main results are as following:1)We used PCR to obtain mtDNA sequences that were 1,691 bp in length with Cytb of 434bp and COI of 1,257bp.EF-1? sequences were 857 bp in length.The combined mtDNA sequences included 171 variable sites(about 10.11%)and the EF-1? coding sequences included 73 variable sites(about 10.49%).The sequences of K.rhusicola in this study had high A-T content,which is not uncommon among insects.We found that transitions occurred more often than transversions within all genetic markers used in this study.2)We found that the mtDNA sequences of K.rhusicolas possessed 92 haplotypes while the EF-1? sequences had 60 haplotypes.The haplotypes of populations from Shanxi,Sichuan and Hubei of K.rhusicola were the most common.3)Populations in Bazhong,Guangyuan,Ankang and Chenggu had the highest genetic diversity,while the populations of Yuncheng and Sangzhi had the lowest.All the 11 populations can be divided as five groups according to their geographic distributions,and the Chenggu,Bazhong and Guangyuan populations of K.rhusicola can be identified as Group Two.The populations of Group Two showed the highest genetic diversity and,therefore,represents a good source for developing cultivars.4)The analysis molecular variance analysis(AMOVA)of K.rhusicola mtDNA sequences showed that the genetic variation between populations was much higher than within populations.Specifically,the AMOVA of K.rhusicola EF-1? gene sequences showed 37.64%of variation is between populations and 62.36%is within populations.Therefore,the gene flow between populations is limited.Limited gene flow may be caused by different evolutionary rates between mtDNA and nuclear genes.Group Two haplotypes showed the highest genetic distance and Fst.5)Our NJ/MP phylogenetic trees and TCS network indicated that there were three main clusters of haplotypes.The Bazhong,Ankang,Guangyuan and Zhushan populations that belong to Qinba Mountains area could be center of origin of K.rhusicola.The population at Shuifu was isolated from other groups,and we speculate that it may represent a previously-unknown species of Kaburagia.6)Our analyses of DNA sequences and tannin acid contents showed that K.rhusicola populations in the Qinba Mountains have potential for cultivation development and already produce galls of relatively high chemical quality.