Rapid assay using recombinase polymerase amplification and lateral flow dipstick for identifying Agrilus mali (Coleoptera: Buprestidae), a serious wood-boring beetle of the western Tianshan Mountains in China.

Agrilus mali stands as a significant wood-boring pest prevalent in Northeast Asia. Identifying this pest beetle is often hindered by insufficient efficient, rapid, on-site discrimination methods beyond examining adult morphological features. As a result, an urgent need arises for developing and implementing a rapid and accurate molecular technique to distinguish and manage the beetle. This study presents a straightforward, swift, highly specific, and sensitive method built upon recombinase polymerase amplification combined with a lateral flow dipstick (RPA-LFD). This method demonstrates the capability to promptly identify the beetle, even during its larval stage. RPA primers and probes were designed using the internal transcribed spacer 1 region. Through probe optimization, false-positive signals were successfully eliminated, with an accompanying discussion on the underlying causes of such signals. The RPA-LFD assays exhibited remarkable specificity and sensitivity, requiring as little as 10-3 ng of purified DNA. Furthermore, the extraction of crude DNA was achieved through immersion in sterile distilled water, thus streamlining the assay process. Achievable at temperatures ranging from 30 to 50 °C, the RPA-LFD assay can be executed manually without specialized equipment. By merging the RPA-LFD assay with DNA coarse extraction, A. mali can be detected within just 30 min. This current study effectively demonstrates the immense potential of RPA-LFD in quarantine and pest management. Additionally, it presents a universal technique for the rapid on-site diagnosis of insects, showcasing the wide applicability of this method.

Genetic Variation May Have Promoted the Successful Colonization of the Invasive Gall Midge, Obolodiplosis robiniae, in China.

Invasive species often cause serious economic and ecological damage. Despite decades of extensive impacts of invasives on bio-diversity and agroforestry, the mechanisms underlying the genetic adaptation and rapid evolution of invading populations remain poorly understood. The black locust gall midge, Obolodiplosis robiniae, a highly invasive species that originated in North America, spread widely throughout Asia and Europe in the past decade. Here, we used 11 microsatellite DNA markers to analyze the genetic variation of 22 O. robiniae populations in China (the introduced region) and two additional US populations (the native region). A relatively high level of genetic diversity was detected among the introduced populations, even though they exhibited lower diversity than the native US populations. Evidence for genetic differentiation among the introduced Chinese populations was also found based on the high Fst value compared to the relatively low among the native US populations. Phylogenetic trees, structure graphical output, and principal coordinate analysis plots suggested that the Chinese O. robiniae populations (separated by up to 2,540 km) cluster into two main groups independent of geographical distance. Genetic variation has been observed to increase rapidly during adaptation to a new environment, possibly contributing to population establishment and spread. Our results provide insights into the genetic mechanisms underlying successful invasion, and identify factors that have contributed to colonization by an economically important pest species in China. In addition, the findings improve our understanding of the role that genetic structure plays during invasion by O. robiniae.