RNA Sequencing Analysis of Metopolophium dirhodum (Walker) (Hemiptera: Aphididae) Reveals the Mechanism Underlying Insecticide Resistance

Xinjiang (XJ) and Ningxia (NX) provinces are important agricultural regions in western China. Aphids are one kind of the most devastating pests in both the provinces. Aphids are typical phloem-feeding insects distributed worldwide and can severely damage crops. In this study, two representative Metopolophium dirhodum (Walker) (Hemiptera: Aphididae) populations were collected from the typical agricultural regions of XJ and NX, respectively for a high-throughput transcriptome sequencing analysis. A total of 5,265 differentially expressed genes (DEGs) were identified. The functional annotation of DEGs and the identification of enriched pathways indicated many of the DEGs are involved in processes related to energy metabolism, development, and insecticide resistance. Furthermore, an investigation of insecticide toxicity revealed the NX population is more resistant to insecticide treatments than the XJ population. Thus, the transcriptome data generated in present study can be used for functional gene characterization relevant to aphid development, metabolism, environmental adaptation, and insecticide resistance.

Phenology and Development of the Yellow Rose Aphid, Acythrosiphon porosum (Sanderson), in Northern Florida and Southern Georgia

The yellow rose aphid, Acythrosiphon porosum (Sanderson), is a cosmopolitan pest of roses and strawberries. Acythrosiphon porosum is one of only a few arthropod pests of roses occurring in northern Florida and southern Georgia. Hybrid roses are widely planted around the city of Thomasville, GA, which is known as the Rose City. Three ‘Grandiflora’ rose cultivars ‘Queen Elizabeth’, ‘Roundelay’ and ‘Spartan’ were used to determine cultivar and location effects on A. porosum seasonal abundance and natural enemies. Developmental rate, longevity and nymph production of A. porosum were also investigated at 4 temperatures, 10.0, 15.5, 21.1, and 26.7°C, in environmental chambers using cut leaf discs of ‘Queen Elizabeth’ on agar plates. Acythrosiphon porosum occurred throughout much of the year except for the coldest winter and warmest summer months and reached highest populations during the cooler weather of spring and fall. Cultivar differences were statistically significant at all locations where ‘Queen Elizabeth’ averaged higher aphids per leaf than ‘Roundelay’, which averaged higher aphids than ‘Spartan’. Aphid numbers did not significantly differ in comparisons of leaves sampled from the bottom, middle or top third of the plant's canopy height. Developmental rate calculated as the time from nymph to nymph was most rapid (x̄ = 10.3 d) at 21.1 °C, but no aphid development was observed at 26.7°C. Total egg production was highest (x̄ = 27.5 nymphs per aphid) at 10.0°C as was longevity of 60.1 d. Highest nymph production (1.5 per d) was observed at 21.1 °C. Many generalist predators and two parasitoid species were found in low numbers attacking A. porosum: Syrphophagous aphidovorus (Mayr) (Hymenoptera: Encyrticidae) and Ephedius sp. (Hymenoptera: Aphidiidae).