Thripidae pest species community identification and population genetic diversity analyses of 2 dominant thrips in cotton fields of China.

Thrips are devastating pests for various crops, and they can rasp tender leaves, terminal buds, and flowers, which specifically causing huge economic losses to cotton production. However, there is very little knowledge about the species composition of thrips in mainland China, as well as the genetic structure of the thrips populations, particularly in the cotton-producing regions. In this study, thrips were collected from 40 geographical locations at 8 different provinces which representing majority cotton-producing belts in China, and mitochondrial cytochrome oxidase subunit I sequence was used to identify species composition and evaluate the genetic diversity of collected thrips individuals. Based on experimental results proven that overall, 10 and 8 species of thrips were identified in seedling and flowering stage respectively, which is corresponding dominant species are Thrip tabaci (Lindeman) and Frankliniella intonsa (Trybom). Genetically, 24 haplotypes were identified in 310 T. tabaci individuals from 10 locations, and 263 haplotypes were detected in 1,861 F. intonsa individuals from 40 locations. Hap1 (T. tabaci) is the most widely distributed haplotype among all the T. tabaci samples. Likewise, Hap 2 is the most widely distributed and abundant haplotype among all samples of F. intonsa. The genetic differentiation degrees of T. tabaci between SXYC population and other 9 populations were high, but its gene flow in these 10 regions was relatively low, which might be due to geographical barriers. The Mantel tests showed no correlation between genetic distance and geographic distance of the 2 thrip species. Demographic analysis results showed that both T. tabaci and F. intonsa experienced population expansion in China. Taken together, this study identifies the species composition of thrips in major cotton-producing regions at different growth periods and evaluates effects of geomorphology on the geographical distribution of haplotypes of dominant thrips T. tabaci and F. intonsa.