Toxoptera Aurantii Boyer De Fonscolombe Research Articles

Physiological and metabolomic analyses reveal the resistance response mechanism to tea aphid infestation in new shoots of tea plants (Camellia sinensis)

The tea plant (Camellia sinensis (L.) O. Kuntze) is an important woody economic crop and often attacked by various insect pests such as tea aphids (Toxoptera aurantii Boyer de Fonscolombe). To reveal tea plant responses to tea aphid infestation, tea aphid-resistant cultivar ‘Taicha13’ and -susceptible one ‘Jingfeng’ were first screened, and then widely targeted metabolomics profiling, biochemical parameter and RT-qPCR analyses were performed in three samples, TCN (tea aphid non-infested ‘Taicha13’), JFN (tea aphid non-infested ‘Jingfeng’) and JFA (tea aphid-infested ‘Jingfeng’). The results showed amnio acid (plus proline) and protein content, and amnio acid: sucrose ratio were significantly less abundant in TCN relative to JFN, suggesting TCN is low nutritional quality for tea aphids. Metabolite profiling revealed that flavonoids and JA-isoleucine (JA-Ile) were more enriched in TCN and JFA compared to JFN, proposing effective roles of flavonoids and JA-Ile in tea plant defense against tea aphid infestation. RT-qPCR results demonstrated that five JA biosynthesis genes (CsLOX2, CsLOX3, CsOPR, CsAOC and CsJAR) in exception of CsAOS, and six flavonoid biosynthesis genes (CsPAL, CsC4H, CsCHS1, CsCHS2, CsFL and CsDFR) shared similarly higher abundance in TCN than in JFN, and exhibited elevated expression levels in JFA relative to JFN, further suggesting flavonoids and JA confer tea plant resistance against tea aphid feeding. Overall, our findings uncovered that tea aphid-infestation activated defensive responses and highlighted involvement of nutritional quality, flavonoids and JA-Ile in tea plant resistance against tea aphid infestation.

The genetic adaptations of Toxoptera aurantii facilitated its rapid multiple plant hosts dispersal and invasion

Toxoptera aurantii Boyer de Fonscolombe (Hemiptera: Aphididae) can attack many plant hosts, including tea (Camellia sinensis L.), citrus (Citrus spp.), lychee (Litchi chinensis Sonn.), banana (Musa spp.), and pineapple (Ananas comasus L.) among others. It is a widely distributed hexapod and one of the most destructive pests in tea plantations, causing enormous economic losses in tea production each year. A high-quality reference genome is important to study the phylogenetics and evolution of T. aurantii because its genome is highly heterozygous and repetitive. We obtained a de novo genome assembly of T. aurantii at the chromosome level using a combination of long Nanopore reads from sequencing with high-throughput chromosome conformation capture technology. When finally assembled, the genome was 318.95 Mb on four chromosomes with a 15.19 Mb scaffold N50. A total of 12,162 genes encoded proteins, while there were 22.01% repetitive sequences that totaled 67.73 Mb. Phylogenetic analyses revealed that T. aurantii and Aphis gossypii parted ways approximately 7.6 million years ago (Mya). We used a combination of long-read single-molecule sequencing with Hi-C–based chromatin interaction maps that resulted in a reference chromosomal level reference genome of T. aurantii that was high quality. Our results will enable the exploration of the genetics behind the special biological features of T. aurantii and also provide a source of data that should be useful to compare the compare genome among the Hemiptera.

Control of tea aphids via attracting the parasitic wasp, Aphelinus sp. with synthetic semiochemicals

The tea aphid (Toxoptera aurantii Boyer de Fonscolombe) is an important tea plant pest insect worldwide. The parasitoid wasp, Aphelinus sp., is one of the most important natural enemies of the tea aphid in China. Unfortunately, Aphelinus sp. alone cannot effectively control the outbreaks of the aphid under natural conditions. In this study, 27 volatile compounds from tea aphid-injured tea shoots, tea flowers, aphid sex pheromones, or body rinses were selected and tested in Y-tube olfactometer assays to find potential attractants of the parasitoid wasp, Aphelinus sp. Based on the Y-tube assay results, the following three attractant mixtures were formulated and further tested in the field. Attractant-1 (HIPV-based) included trans-2-hexenal (10−6 g/ml), β-ionone (10−6 g/ml), allyl isothiocyanate (10−4 g/ml), trans-2-pentenal (10−2 g/ml), and jasmone (10−2 g/ml) at equal loading volume of their solutions. Attractant-2 (with aphid sex-pheromone and body rinse compounds) included nepetalactone (10−6 g/ml), 2,5-hexanedione (10−4 g/ml), benzaldehyde (10−2 g/ml), eicosane (10−2 g/ml), and heptadecane (10−2 g/ml) at equal loading volume of their solutions. Attractant-3 (partial combination of Attractant-1 and Attractant-2) included nepetalactone (10−4 g/ml), benzaldehyde (10−2 g/ml), jasmone (10−2 g/ml), trans-2-hexenal (10−6 g/ml), eicosane (10−2 g/ml), and heptadecane (10−2 g/ml) at equal loading volume of their solutions. Field trials showed that Attractant-3 was much more attractive to the parasitic wasps than Attractant-1 and Attractant-2. From late August to late September the controlled release of Attractant-3 effectively attracted Aphelinus sp. to parasitize and colonize the aphid populations in the treated tea plantations, resulting in a progressive decrease of the tea aphid abundances/populations in the fall. The continued enhanced parasitism of overwintered aphids by Aphelinus sp. further reduced this population during the next spring tea harvest season. This approach may present an environmentally sound, non-insecticidal control tactic against tea aphids using synthetic semiochemicals.

Spatial Distribution and Sampling Plans With Fixed Level of Precision for Citrus Aphids (Hom., Aphididae) on Two Orange Species.

Aphis spiraecola Patch, Aphis gossypii Glover, and Toxoptera aurantii Boyer de Fonscolombe are three important aphid pests of citrus orchards. In this study, spatial distributions of the aphids on two orange species, Satsuma mandarin and Thomson navel, were evaluated using Taylor's power law and Iwao's patchiness. In addition, a fixed-precision sequential sampling plant was developed for each species on the host plant by Green's model at precision levels of 0.25 and 0.1. The results revealed that spatial distribution parameters and therefore the sampling plan were significantly different according to aphid and host plant species. Taylor's power law provides a better fit for the data than Iwao's patchiness regression. Except T. aurantii on Thomson navel orange, spatial distribution patterns of the aphids were aggregative on both citrus. T. aurantii had regular dispersion pattern on Thomson navel orange. Optimum sample size of the aphids varied from 30-2061 and 1-1622 shoots on Satsuma mandarin and Thomson navel orange based on aphid species and desired precision level. Calculated stop lines of the aphid species on Satsuma mandarin and Thomson navel orange ranged from 0.48 to 19 and 0.19 to 80.4 aphids per 24 shoots according to aphid species and desired precision level. The performance of the sampling plan was validated by resampling analysis using resampling for validation of sampling plans (RVSP) software. This sampling program is useful for IPM program of the aphids in citrus orchards.

An evaluation of the effect of botanical insecticide, palizin in comparison with chemical insecticide, imidacloprid on the black citrus aphid, Toxoptera aurantii Boyer de Fonscolombe and its natural enemy, Aphidius colemani Viereck

AbstractThe black citrus aphid,Toxoptera aurantiiBoyer de Fonscolombe (Hemiptera: Aphididae), an important pest of citrus species, feeds by sucking sap from plant leaves. It causes some leaf distortion and malformation of growing leaves and shoot tips. In this study, the effects of the botanical insecticide, palizin onT. aurantiiand its parasitoid,Aphidius colemaniViereck (Hymenoptera: Brachonidae) were compared with the chemical insecticide, imidacloprid. The compounds were evaluated at maximum recommended field concentrations: palizin 2,000 ppm, imidacloprid 500 ppm, water (as control) on adult aphids. Spraying was done with a 100-l engine Honda sprayer (GX120T1, 160T1, 200T) until run-off. The number of dead aphids was recorded 24, 48 and 72 hours after treatment. According to the results, statistically significant differences were found between treatments (p ≤ 0.05). Twenty-four hours after treatment, imidacloprid was more effective than palizin in reducing theT. aurantiipopulation. Palizin showed high efficiency (95% mortality) 72 hours after treatment. However, at that time, there was no statistically significant difference between the mean mortality percentages of imidacloprid and palizin. This shows that botanical insecticide, palizin can effectively controlT. aurantii. Also, palizin caused low mortality (10.86%) onA. colemaniwhile imidacloprid was more toxic (31.1% mortality). The results of the present study indicated that palizin can be used instead of chemical insecticide, imidacloprid in control programs ofT. aurantii.

Oviposition behaviour of the polyphagous aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiidae)

A population of Aphidius colemani Viereck imported from La Réunion successfully parasitized Aphis gossypii Glover, Myzus persicae Sulzer, Rhopalosiphum padi L., and Toxoptera aurantii Boyer de Fonscolombe in the laboratory. The parasitoid stung, but did not complete development in five other common aphid species. The La Réunion population thus showed a similar host range to Brazilian and other tropical populations of this species, in contrast to the much narrower host range of indigenous Mediterranean populations. In laboratory host-choice tests, a cohort of a Brazilian population of Aphidius colemani reared on Myzus persicae and a cohort reared on Aphis gossypii both preferred to oviposit on Aphis gossypii, indicating an innate genetic preference for this host. However, the cohort reared on Myzus persicae showed a lower degree of preference for Aphis gossypii than the one reared from Aphis gossypii, indicating that epigenetic (conditioning) factors can alter the genetic predisposition to some extent.

Ant – homopteran interactions in a tropical ecosystem. Description of an experiment on cocoa in Ghana

AbstractOver a period of six years, the presence or absence of 23 species of arboreal insects (13 Homoptera, 1 Heteroptera, 9 ants (Hymenoptera: Formicidae)) was recorded on each of 866 young Amazon and Amazon hybrid cocoa trees at the Cocoa Research Institute, Tafo, Ghana. The general form of the time-series, derived from the proportion of trees occupied by each species, is described. Analysis of 18 of these series, taken either singly or jointly, was carried out using analysis of variance and principal components analysis and the degree of spatial association between 16 of the species was also investigated. For the latter, the number of joint occurrences of pairs of species was compared with the expected number by means of a chi squared test. An index of association was derived from the proportion of occasions on which the difference was significant. For all but four species, there were highly significant differences between annual means in the analysis of variance and, in many, the overall annual trend was downward with time. For those species where significant differences were not shown between years, trends were often apparent on individual plots but were negated because of inconsistencies between plots in the direction of the trend. In the joint analysis of all 18 species by principal components, the first component accounted for approximately 33% of the total variance and could be identified as representing to a large extent the long-term upward or downward trends shown up by the analysis of variance. The second principal component, accounting for a further 13% of total variance, was interpreted as being a further manifestation of the long-term trend, representing a tendency for deviation from the trend line shown up by the first component to become less with time and to approach the trend line in a damped oscillation. This is thought to be partly caused by a drought at the start of the experiment which affected certain species adversely. The third principal component accounted for 11% of total variance and the scores followed an irregular annual cycle which was related to relative humidity. The scores on this axis were high during dry periods of the year and low during wet periods. In the analysis of variance it was found that 13 species showed significant differences in spatial distribution between seasons and, for most, there was evidence for an annual cycle. There was also some evidence of correlation between the seasonal cycles of some insects with seasonal rainfall level or morning or afternoon relative humidity. These same species are important in contributing to the third principal component scores. Spatial association analysis showed eight species to be strongly associated. These fell into three groups with positive associations between members of the same group and negative association between members of other groups. Each group featured an ant-homopteran association, Crematogaster spp. with Planococcoides njalensis (Laing) in group 1, Oecophylla longinoda (Latreille) with Stictococcus spp. in group 2, and Camponotus spp. and Polyrhachis laboriosa F. Smith with Planococcus citri (Risso) and Toxoptera aurantii Boyer de Fonscolombe in group 3. Three other coccids were loosely linked to these groups through particular members, Waxiella sp. nr zonatus (Newstead) to group 1 through Planococcoides njalensis and to group 2 through Camponotus spp. and Phenacoccus hargreavesi (Laing) and Steatococcus spp. to group 2 through Planococcus citri. Changes taking place with time in the relative abundance of members of these groups could be discerned in the trajectories of the first two principal components. The spatial re-arrangements taking place with time of the territories of the major ant species are followed in some detail, and the effect of these changes on Homoptera is discussed.

The identity and bionomics of insect vectors of tristeza and greening diseases of citrus in Ethiopia

Abstract Survey studies were carried out to determine the identity and bionomics of insect vectors of tristeza and greening diseases of citrus in citrus growing regions of Ethiopia between 1982 and 1985: Results of these studies revealed that three species of aphids: Aphis gossypii Glover, Toxoptera aurantii Boyer de Fonscolombe and T. citricidus (Kirkaldy), were implicated in tristeza, whereas the citrus psyllid, Trioza erytreae Del Guercio, was solely responsible for greening; the Asiatic psyllid, Diaphorina citri Kuwayama, was not found in this country. Among the aphids, A. gossypii was least common on citrus while T. aurantii was found in large numbers and was widely distributed throughout the country; T. citricidus was confined mainly to the middle Awash areas. Trioza erytrea was widely spread in the country above 1500 m and was more severe at higher altitudes. Host range studies indicated that A. gossypii, T. aurantii and T. erytreae are polyphagous while T. citricidus was found only on citrus. No parasitoid was reared from A. gossypii during the study while five and six species were identified from T. aurantii and T. erytreae respectively. The encyrtids, Psyllaephagus pulvinatus (Waterston) and Psyllaephagus sp. were the dominant and widely distributed primary parasitoids of T. erytreae. Eleven species of predators were recorded on one or more of the insect vectors.