Comparing the genetic diversity and structure of indigenous Korean and Chinese populations of Laodelphax striatellus Fallén using mitochondrial haplotypes

Abstract

The small brown planthopper, Laodelphax striatellus Fallén, is a major migratory pest from China to Korea and transmits viral diseases of rice plants. In this study, we compared the genetic structures of overwintered indigenous Korean and Chinese populations. The eight Korean populations consisted of 33 haplotypes, and 16 of these were newly identified. The genetic diversity of the Korean population revealed high haplotype diversity (Hd) and low nucleotide diversity (π) of 0.86±0.017 and 0.0024±0.0001 on average, respectively. These values for the Chinese population were Hd=0.92±0.016 and π=0.0026±0.0002. Overall, genetic distances by pairwise FST were generally low, ranging from −0.022 to 0.089. Moreover, the Korean population revealed its ongoing population expansion by showing negative values in the neutrality test (Tajima's D=−1.4, Fu's Fs=−15.8) and a unimodal pattern in the mismatch distribution analysis. The genetic structures and population relationships were determined using 8 indigenous Korean and 30 Chinese populations by Bayesian approaches and population tree construction, respectively. The genetic structure was inferred as five (K=5), and all indigenous Korean populations as well as 10 Chinese populations from the Shanghai city, Anhui, Henan, Jiangsu, Liaoning, Shandong, and Zhejiang provinces were grouped into ‘G3’. These results provide partial support for unidirectional gene flow by migratory Chinese populations into Korea. Further analysis conducted using specimens from China and Korea collected in similar periods is necessary to clarify the migration population's origin and its effect on the genetic structure of the indigenous populations.