Abstract:

【Aim】 Atrijuglans hetaohei, an important fruit pest of Juglans regia, is widely distributed among the main producing areas (Beijing, Shandong, Shanxi, Shaanxi, Sichuang, etc.) of J. regia inChina, seriously affecting the yield and quality of J. regia and causing serious economic losses. This study aims to investigate the genetic differentiation and geographic distribution characteristics of A. hetaohei, clarify its genetic structure among different geographical populations, understand the population dispersal pattern, and provide theoretical guidance for the prevention and control of this pest insect. 【Methods】 Based on the transcriptome sequencing result of A. hetaohei, the polymorphic microsatellite markers were selected using polyacrylamide gel electrophoresis and capillary electrophoresis typing methods to analyze the population genetic diversity of319 A. hetaohei individual samples from 16 populations in eight provinces/city (Beijing, Hebei, Henan, Shandong, Shanxi, Shaanxi, Gansu and Sichuan). Population genetic structure of A. hetaohei was analyzed using STRUCTURE and BAPS software, and the factors that affect the geographical distribution of A. hetaohei were also explored. 【Results】 Nine SSR loci of A. hetaohei exhibited high polymorphism, most of them did not deviate from Hardy-Weinberg equilibrium. The genetic diversity of A. hetaohei geographical populations was medium low (effective number of alleles Ne: 1.334－1.824; expected heterozygosity He: 0.203－0.342), the genetic differentiation between populations was small (genetic differentiation coefficient F_ST<0.142), and the gene flow among populations was significantly different (Nm: 1.518－23.800). There was a significant correlation (R²=0.226) between the degree of genetic differentiation and geographical distance among the populations. Sixteen geographical populations of A. hetaohei could be divided into two lineages (eastern and western lineages). AMOVA analysis showed a relatively small genetic variation among A. hetaohei populations, and population variation mainly originated from that within populations. The values of the fixation indice F_CT within A. hetaohei populations ranged from 0.03941 to 0.06449, indicating that geographical barriers and climatic differences were not the main factors affecting the genetic structure and geographical distribution pattern of A. hetaohei populations.【Conclusion】 A. hetaohei populations have a medium low genetic diversity, and a low level of genetic differentiation and a significantly different gene flow between populations. In view of the special life history and unique biological characteristics of A. hetaohei, combining with the population genetic structure analysis result, we speculate that rivers form a stronger blocking effect on the gene flow of the geographical populations of A. hetaohei than mountains. As a major pest of economic tree, human activities are possibly the main factor which affects the geographical distribution of A. hetaohei populations.

Key words: Atrijuglans hetaohei, geographical population, microsatellite marker, genetic diversity, population genetic structure, gene flow