Search

Vitellogenin (Vg) is a glycolipid complex protein produced by the fat body of female insects. It plays vital roles in oocyte development and helps regulate reproductive development. In this study, we determined the grading criteria for ovarian development and identified a Vg gene (designated TaVg) from the devastating invasive pest, Tuta absoluta (Meyrick). TaVg contains a 5208 bp open reading frame encoding a protein of 1735 amino acids that includes conserved domain structures of insect Vg. Phylogenetic analysis indicated that TaVg was clustered into a clade with the Vg of other Lepidoptera species, suggesting this gene has been conserved during evolution. Spatiotemporal expression analyses showed that TaVg was highly expressed in the female pupae and adults. There was increased expression during sexual maturation, and the high expression level was found in the ovary and fat body. RNAi-mediated silencing of TaVg resulted in significant downregulation of vitellogenin contents and severely affected ovarian development. Females injected with dsTaVg had shorter ovarian tubes and fewer oocytes compared with the untreated individuals. The number of oocytes and the amount of yolk deposition in the egg chambers also reduced. Depletion of TaVg significantly reduced the number of eggs laid and the hatching rate. Co-silencing of TaVg and TaVgR had a more significant effect on inhibiting the ovarian development and reducing female fecundity of T. absoluta, showing that the two genes play important role in regulating the reproduction. Our results provide potential targets for developing RNAi-based pest management tractic on T. absoluta.

Tuta absoluta(Meyrick) originated in South America and is one of the most serious pests of tomatoes. It is also known to attack other solanaceous crops, including potato, eggplant, pepper, tobacco, and weedy species such as black nightshade. After accidental introduction into Spain in 2006, this pest spread rapidly throughout Afro-Eurasia and has become a major threat to tomato production worldwide. Here, we report the first record of T. absolutaas an invasive pest in China. It was found in tomato fields in Ili Kazakg Autonomous Prefecture, Xinjiang Uygur Autonomous Region (Ili, Xinjiang), China, and its occurrence was confirmed by both morphological and molecular approaches. In Ili, T. absolutahas been found to attack eggplant, potato, and black nightshade. We found the larvae generally mining and feeding on leaves and boring into tomato fruits, with multiple larvae sometimes observed in a single fruit. Its infestation levels differ among the tomato fields and host species. In all of the surveyed tomato fields, T. absolutainfested 100% of plants. In some of the fields, up to 90% of the eggplant and 100% of the potato plants were infested. Since no natural enemies were found under field conditions, suitable management practices are urgently needed to stop the further spread of this destructive pest in China.

The globally invasive cotton mealybug Phenacoccus solenopsisTinsley, has recently invaded several Chinese regions, and continues to expand its range. This mealybug is a polyphagous insect pest, with at least 200 host plants from 63 families, including cotton, food crops, fruits, ornamental plants, tobacco, and vegetables. Here, we describe the first finding of P. solenopsisin Shandong Province, and investigate the abundances of its natural enemies (predator Coccinella septempunctataL. and parasitoid Aenasius bambawaleiHayat). All three species were detected from ornamental and weed species in Linyi, Shandong, in September 2018, and were positively identified using DNA barcoding. BLAST analysis revealed significant identity (99.38–100%) between sequences of P. solenopsisobtained in this study and those published in the past. This invasive pest represents a major potential threat to agri-horticulture in Shandong, which is a key province of China for production and export of many vegetables, flowers, fruits, and other crops. This mealybug species has a wide range of potential distribution in Shandong and is easily dispersed with agricultural and horticultural transport products. Further monitoring and management strategies are required to limit the spread of this pest species.

The globally invasive cassava mealybug Phenacoccus manihotiMatile-Ferrero is a pernicious pest of cassava, and its recent introduction into Asia has raised considerable alarm. To slow or prevent further invasion, an accurate, simple, and developmental-stage-independent detection method for P. manihotiis required. In the present study, a PCR method based on a species-specific mitochondrial DNA cytochrome oxidase I (SS-COI) marker was developed for rapid identification of P. manihoti. One pair of SS-COI primers (PMSSZW-1F and PMSSZW-1R) was designed based on sequence variations in the COI gene among P. manihotiand related mealybug species. Specificity of the primer pair was validated on 21 closely related species. Sensitivity tests were performed on four immature developmental stages and female adults. Efficacy tests demonstrated that at the relatively low concentration of (135.2±14.7) pg μL−1resuspended DNA, the specific fragment was detected in all replicates. Furthermore, the SS-COI primer pair was assayed on three populations of P. manihotifrom major exporting countries of cassava. The PCR assay was proved to be a rapid, simple, and reliable molecular measure for the identification of P. manihoti. This tool will be useful for quarantine, monitoring, and management of this invasive pest.

The Jack Beardsley mealybug, Pseudococcus jackbeardsleyiGimpel & Miller (Hemiptera: Pseudococcidae), a globally devastating, invasive polyphagous insect, causes great damage to many fruits, ornamentals, vegetables, and food crops worldwide. It is of Neotropical origin and has invaded throughout America and in parts of Asia, Africa and Oceania, and is still expanding its invasion ranges. Therefore, a method for quick and correct identification of this invasive species is crucial for quarantine and spreading interruption of it. In present study, we report the first record of P. jackbeardsleyion the Chinese mainland, which would cause great damage to many crops. The identification of P. jackbeardsleyiwas verified via morphological characters and DNA barcoding. One pair of species-specific polymerase chain reaction (SS-PCR) primers was designed based on variations in the sequences of the mitochondrial cytochromecoxidasesubunitIgene among P. jackbeardsleyiand 28 other mealybug species. No cross-reaction was detected among 21 closely related species using this SS-PCR assay, demonstrating the specificity of this marker. Furthermore, this method was successfully applied to detect individuals from different developmental stages and adult debris across four geographic populations of P. jackbeardsleyi, showing the high stability of the assay. Additionally, the detection limit of the marker was 55.94 ± 5.05 pg/µl of P. jackbeardsleyiDNA, illustrating the high sensitivity of the assay. The SS-PCR assay developed in this study provides a rapid, simple and reliable method for the identification of P. jackbeardsleyi, which should be crucial in the plant quarantine, early detection and sustainable management of this globally invasive pest.