The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is an agricultural pest that seriously infests many crops worldwide. This study used electrical penetration graphs (EPGs) and life table parameters to estimate the sublethal effects of cyantraniliprole and imidacloprid on the feeding behavior and hormesis of M. persicae The sublethal concentrations (LC30) of cyantraniliprole and imidacloprid against adult M. persicae were 4.933 and 0.541 mg L(-1), respectively. The feeding data obtained from EPG analysis indicated that the count probes and number of short probes (<3 min) were significantly increased when aphids were exposed to LC30 of imidacloprid-treated plants. In addition, the phloem-feeding behavior of M persicae was significantly impaired on fed tobacco plants treated with cyantraniliprole and imidacloprid at LC30 Analysis of life table parameters indicated that the growth and reproduction of F1 generation aphids were significantly affected when initial adults were exposed to LC30 of cyantraniliprole and imidacloprid. The nymphal period, female longevity, total preoviposition period, and mean generation time were significantly prolonged when initial adults were exposed to LC30 of imidacloprid. By comparison, these parameters were prolonged but not significantly in the cyantraniliprole treatment. The fecundity and gross reproductive rate were significantly increased in the treated groups. Similarly, the net reproductive rate was greater in the treated group than the control group. Our results indicate that treatment with LC30 of imidacloprid and cyantraniliprole would lead to a hormetic response of M. persicae, with higher likelihood of occurrence when initial adults were exposed to LC30 of cyantraniliprole.
Background Tea plants originated in southwestern China. Guizhou Plateau is an original center of tea plants, and is rich in germplasm resources. However, the genetic diversity, population structure and distribution characteristics of cultivated-type tea plants in the region are unknown. In this study, we explored the genetic diversity and geographical distribution of cultivated-type tea accessions in Guizhou Plateau. Results We used 112,072 high-quality genotyping-by-sequencing to analyze the genetic diversity, principal components, phylogeny, population structure, and linkage disequilibrium, and develop a core collection of 253 cultivated-type tea plant accessions from Guizhou Plateau. The results showed Genetic diversity of the cultivated-type tea accessions of the Pearl River Basin was significantly higher than that of the cultivated-type tea accessions of the Yangtze River Basin. Three inferred pure groups (CG-1, CG-2 and CG-3) and one inferred admixture group (CG-4), were identified by a population structure analysis, and verified by principal component and phylogenetic analyses. The highest genetic distance and differentiation coefficients were determined for CG-2 vs CG-3. The lower genetic distance and differentiation coefficients were determined for CG-4 vs CG-2 and CG-4 vs CG-3, respectively. We developed a core set and a primary set. The primary and core sets contained 77.0 and 33.6% of all individuals in the initial set, respectively. The primary set may serve as the primary population in genome-wide association studies, while the core collection may serve as the core population in multiple treatment setting studies. Conclusions The present study demonstrated the genetic diversity and geographical distribution characteristics of cultivated-type tea plants in Guizhou Plateau. Significant differences in genetic diversity and evolutionary direction were detected between the ancient landraces of the Pearl River Basin and the those of the Yangtze River Basin. Major rivers and ancient hubs were largely responsible for the genetic exchange between the Pearl River Basin and the Yangtze River Basin ancient landraces as well as the formation of the ancient hubs evolutionary group. Genetic diversity, population structure and core collection elucidated by this study will facilitate further genetic studies, germplasm protection, and breeding of tea plants.
With the purpose of studying the feeding behavior of the brown citrus aphid pest, Toxoptera citricida (Kirkaldy) (Hemiptera: Aphididae), we compared stylet probing behaviors of third and fourth instars and adults on Citrus unshiu Marc (Rutaceae) seedlings using the electrical penetration graph (EPG) technique. EPG waveforms exhibited the full suite of stylet behaviors – stylet pathway, intracellular stylet puncture, phloem salivation (E1), sieve ingestion (E2), and xylem sap ingestion activities, plus the non‐penetration (Np) waveform. Before the phloem phase, the number of probes was significantly higher for third‐instar nymphs than for adults. Overall duration of Np events by adults was significantly lower than the duration of third and fourth instars. The number of short probes of the fourth instars was significantly higher than that of the adults. In the phloem phase, adults made more frequent and longer E1 events than the third and fourth instars. Third instars made more frequent but shorter E2 events, whereas adults made fewer but longer events. These results showed adults gained nutrients by increasing feeding time during phloem ingestion. Thus, the probability of phloem‐associated virus acquisition and transmission of T. citricida was higher in adults than in nymphs.
Piercing–sucking insects are prominent phloem-feeding insect pests and understanding their feeding behavior and life characteristics plays a crucial role in studying insect host adaptability. The green peach aphid, Myzus persicae (Hemiptera: Aphididae), is one of the most prominent pests in tobacco-growing areas around the world. This study evaluated the adaptability of M. persicae to five host plants: tobacco, radish, Chinese cabbage, Brassica oleracea, and rape using the electropenetrography, age-stage, two-sex life table and population dynamics. The results demonstrated that the feeding behavior of M. persicae differed significantly according to the target hosts. M. persicae exhibited reduced pathway activities and increased phloem sap ingestion on radish, whereas the opposite was observed on Chinese cabbage. Additionally, the mechanical difficulties of M. persicae mouthparts in the probe pathway phase were significantly lower on tobacco and radish than on other host plants. Life table parameters indicated that for M. persicae reared on radish, preadult duration, longevity, and total preoviposition increased significantly and the fecundity was the highest. Furthermore, the net reproductive rate (R0) increased significantly. The population number of M. persicae on radish after 15 days was significantly higher than that on other hosts, except for tobacco. Although M. persicae can successfully survive on the five plants, our results demonstrated that radish is the optimal host. These results provide significant information for understanding the population dynamics of M. persicae and on different host crops integrated management strategy.
The stylet penetration behavior of aphids when feeding on plants is associated with virus acquisition and inoculation. Aphidius gifuensis (Ashmead) is a primary endoparasitoid of Myzus persicae (Sulzer) which is the most efficient vector of plant viruses. Information about the effects of parasitoid on aphid and virus transmission can provide an essential foundation for designing effective biological control strategies. This study aimed to investigate the effects of A. gifuensis on the feeding behavior and potato virus Y (PVY) transmission ability of M. persicae. The results showed that after M. persicae was parasitized by A. gifuensis, the duration of the first probe significantly decreased. Additionally, A. gifuensis exerted remarkable effects on aphid feeding in phloem ingestion. The contribution of the E1 waveform to the phloem phase was significantly higher in all parasitized aphids than in the control group. Although the time of infestation increased for parasitized aphids, the total duration of phloem sap ingestion decreased. Interestingly, the percentage of time M. persicae spent in the xylem and phloem phases only changed significantly on day 5. The percent transmission of PVY by the aphids parasitized on day 5 was lower than that in the control, but no significant differences were detected. The significance of this work is the demonstration that A. gifuensis can impede the feeding behavior of M. persicae, which sheds light on the biological basis of A. gifuensis as a natural enemy, but unfortunately does not provide an immediate solution for disrupting the transmission of PVY.
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