Abstract: 【Aim】 The eulophid wasp Neochrysocharis formosa (Westwood) is an important dominant parasitoid against vegetable agromyzid leafminers all over the world. In June 2015, we found the thelytokous strain of N. formosa in Beijing, which was its first discovery in China. It is difficult to distinguish thelytokous strain from arrhenotokous strain because of no distinct morphological differentiation. In this study molecular methods were adopted to identify these two strains so as to provide a basis for future research and application of the thelytokous strain of N. formosa. 【Methods】 The genetic differentiation between the thelytokous strain TH-China and the arrhenotokous strain AR-China of N. formosa reared for several generations indoor was analyzed by multiple molecular markers (COⅠ gene, ITS-1 gene and 28S rDNA). The 16S rDNA sequence was amplified from the endosymbiont Rickettsia of the two strains using the specific primers NforRick1/NforRick2, sequenced and blasted against NCBI database. The existence of Rickettsia which can induce thelytoky was detected in ovarioles, larvae, pupae and adults of TH-China, and adults of AR-China. 【Results】 Phylogenetic trees constructed based on two fragments of COⅠ gene amplified with the primer pairs LCO1490/HCO2198 and COⅠ1/COⅠ2 showed that the thelytokous and arrhenotokous strains of N. formosa diverged into two distinct clades and their genetic distance is 0.039 and 0.023, respectively. Using the ITS-1 gene and 28S rDNA as the molecular markers, there are 21 and 0 discrepant sites between the two strains, respectively, and the genetic distance of the two strains based on ITS-1 gene is 0.008. The 16S rDNA sequence amplified from Rickettsia in TH-China strain has 100% identity with that from Rickettsia in the thelytokous strain in Japan (GenBank accession no.: AB185963). Rickettsia was detected in ovarioles, larvae, pupae and adults of the thelytokous strain, but absent in adults of the arrhenotokous strain, suggesting that Rickettsia might contribute to the thelytoky. 【Conclusion】 The thelytokous and arrhenotokous strains of N. formosa are easily differentiated by COⅠ gene sequences, while no genetic variation is found based on 28S rDNA and almost no genetic divergence based on ITS-1 gene.

Key words: Neochrysocharis formosa; thelytokous strain, arrhenotokous strain, molecular identification, Rickettsia, COⅠ, ITS-1, 28S rDNA