Abstract
Background: Stethynium empoasca is an egg parasitoid of the predominant tea pest, and is regarded as the most promising candidate for both augmentative and conservative biological control in tea plantations. However, little is presently known about its biology, ecology, and genetics. Methods: Novel microsatellite markers were developed for S. empoasca from transcriptome sequences generated using high-throughput sequencing. The identified markers were then validated and characterized using 98 individuals from five geographically distinct populations through the tests of Hardy–Weinberg equilibrium and linkage disequilibrium as well as the analyses of genetic diversity, genetic differentiation, and gene flow.Results: A total of 54,520 microsatellites were identified from 117Mb clean sequences. By assessing with five geographical populations, a total of 18 loci were demonstrated to be polymorphic, stable, and repetitive. The genetic variation over the 18 loci varied with allele number ranging from 2 to 7, polymorphism information content from 0.234 to 0.634; and observed and expected heterozygosity from 0.166 to 0.686 and 0.276 to 0.753, respectively. Meanwhile, the 18 loci showed a low frequency of null alleles (0 – 0.107), and the inbreeding coefficient revealed a range from −0.143 to 0.173, with the exception of loci Ste36 (0.4076). Based on analysis of these 18 loci, the assessed populations showed low to moderate levels of genetic differentiation, in which individuals clearly grouped into two clusters. And the recent dispersal rates between the geographically distinct populations were identified to be much lower (0.011 – 0.250) than the individual gene exchange rates within a population (0.683 – 0.939).Conclusion: The identified 18 microsatellite markers could reveal a pattern of spatial structure and gene flow in S. empoasca populations according to geographic variability. This work provides an important basis for future studies on how these markers can be used in studies of the biology, genetics, and ecology of this important parasitoid. The findings can further provide important information for the development of biological control strategies in tea plantations. Additionally, our study reaffirms the importance and efficiency of high-throughput sequencing in microsatellite marker development for non-model species lacking reference genome information.
Genetic Differentiation among Maruca vitrata F. (Lepidoptera: Crambidae) Populations on Cultivated Cowpea and Wild Host Plants: Implications for Insect Resistance Management and Biological Control Strategies