Population Genetic Diversity of Two Blue Oat Mite Species on Triticum Hosts in China

Simple Summary Blue oat mite species mainly include Penthaleus major, P. falcatus, P. tectus, and P. minor. Among them, P. major, P. falcatus and P. tectus are important pest mites on gramineous crops, which often occur in low-temperature and high-humidity environments. These three mites are difficult to distinguish in the field due to their small size and similar shape. Furthermore, they exhibit different resistance to chemical pesticides, making it challenging to control their outbreak. Worryingly, we only saw reports of frequent occurrence of P. major in winter wheat regions in China, and no other species of blue oat mites were found. Understanding the distribution pattern, genetic diversity, and genetic differentiation among populations of blue oat mite species in winter wheat regions of China is essential for developing effective control programs. In this study, we evaluated the distribution of blue oat mites in the major wheat regions in China and assessed the level of genetic diversity and genetic structure of blue oat mites from winter wheat regions of China using mitochondrial cytochrome c oxidase I (COI) sequences. Blue oat mite species, including Penthaleus major and P. tectus, are pests widely distributed across China that cause damage to winter wheat. This study evaluated the genetic diversity of P. major and P. tectus on Triticum hosts collected from 23 geographic locations based on mitochondrial cytochrome c oxidase subunit I (COI) sequences. We identified nine haplotypes in 438 P. major individuals from 21 geographic locations and five haplotypes in 139 P. tectus individuals from 11 geographic locations. Meanwhile, P. major exhibits high values of haplotype diversity (Hd) and nucleotide diversity (Pi) (Hd = 0.534 > 0.5 and Pi = 0.012 > 0.005), representing a large stable population with a long evolutionary history. P. tectus shows low values of Hd and Pi (Hd = 0.112 < 0.5 and Pi = 0 < 0.005), which suggest recent founder events. Moreover, demographic analysis suggested that P. major and P. tectus have not undergone a recent population expansion. The lowest genetic variation was observed in Xiangzhou (XZ-HB), Zaoyang (ZY-HB), Siyang (SY-JS), and Rongxian (RX-SC), with only one species and one haplotype identified in over 30 individuals. Robust genetic differentiation was found in P. major compared to P. tectus, which provides a theoretical basis for the widespread distribution of P. major in China.