Piercing-sucking Insect Pests Research Articles

Baseline of susceptibility, risk assessment, biochemical mechanism, and fitness cost of resistance to dimpropyridaz, a novel pyridazine pyrazolecarboxamide insecticide, in Bemisia tabaci from China

Bemisia tabaci is one of the most destructive agricultural insect pests around the world, and it has developed high levels of resistance to most pesticides. Dimpropyridaz, a novel insecticide developed by BASF, displays excellent activity against piercing-sucking insect pests. In this study, baseline of susceptibility showed all tested field populations of B. tabaci are susceptible to dimpropyridaz. After continuous selection with dimpropyridaz in the lab, a B. tabaci strain (F12) developed 2.2-fold higher level of resistance compared with a susceptible MED-S strain, and the realized heritability (h2) was estimated as 0.0518. The F12 strain displayed little cross-resistance to afidopyropen, cyantraniliprole, sulfoxaflor, or abamectin, and significantly increased activity of cytochrome P450 monooxygenase (P450). The fitness cost of dimpropyridaz resistance was evident in F12 strain, which had a relative fitness of 0.95 and significantly lower fecundity per female compared with MED-S strain. Taken together, B. tabaci displays high susceptibility to dimpropyridaz in the field, and low risk of developing resistance to dimpropyridaz under successive selection pressure. Little cross-resistance to popular insecticides was found, and fitness cost associated dimpropyridaz resistance was observed. Higher activity of cytochrome P450 in the F12 strain, may be involved in the process of detoxifying dimpropyridaz in whitefly.

Flowering Ocimum gratissimum intercropped in tea plantations attracts and reduces Apolygus lucorum populations.

Apolygus lucorum is one of the most important piercing-sucking insect pests of the tea plant In this study, we assessed the attractiveness of basil plants to A. lucorum and the effectiveness of Ocimum gratissimum L. in the control of A. lucorum. The control efficiency of main volatile chemicals emitted from O. gratissimum flowers was also evaluated. Among seven basil varieties, O. gratissimum was more attractive to A. lucorum adults and was selected as a trap plant to assess its attractiveness to A. lucorum and effects on natural enemies in tea plantations. The population density of A. lucorum on trap strips of O. gratissimum in tea plantations was significantly higher than that on tea at 10-20 m away from the trap strips. Intercropping O. gratissimum with tea plants, at high-density significantly reduced A. lucorum population levels. Eucalyptol, limonene, β-ocimene, and linalool were the four dominant components in the O. gratissimum flower volatiles, and their emissions showed a gradual upward trend over the sampling period. Olfactometer assays indicated that eucalyptol and dodecane showed attraction to A. lucorum. High numbers of A. lucorum were recorded on limonene, eucalyptol, and myrcene-baited yellow sticky traps in field trials in which 11 dominant volatiles emitted by O. gratissimum flowers were evaluated. Our research indicated that the aromatic plant O. gratissimum and its volatiles could attract A. lucorum and planting O. gratissimum has the potential as a pest biocontrol method to manipulate A. lucorum populations in tea plantations. © 2024 Society of Chemical Industry.

Variations in the Susceptibility of Some Potato Varieties to Infestation with Certain Piercing Sucking Insect Pests at Different Nitrogen Fertilization Levels in Assiut Area

Variations in the Susceptibility of Some Potato Varieties to Infestation with Certain Piercing Sucking Insect Pests at Different Nitrogen Fertilization Levels in Assiut Area

Influence of Nitrogen Fertilization Levels on population of the Piercing-Sucking Insect Pests in Cucumber Crop

Influence of Nitrogen Fertilization Levels on population of the Piercing-Sucking Insect Pests in Cucumber Crop

Risk assessment and resistance inheritance of triflumezopyrim resistance in Laodelphax striatellus.

Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) is one of the most important insect pests of rice, and it has been able to develop strong resistance to many insecticides. Triflumezopyrim, a new type of mesoionic insecticide developed by Corteva Agriscience, showed high biological activity in controlling piercing-sucking insect pests such as planthopper and leafhopper. In this study, we continuously selected a susceptible laboratory stain (Unsel) of L. striatellus for 16 generations by exposing it to triflumezopyrim in the laboratory. A 45.1-fold triflumezopyrim-resistant strain (Tri-sel) was established, in which cross-resistance to nitenpyram and acetamiprid was not detected. The realized heritability (h2 ) of the Tri-sel strain was estimated at 0.13. The mortalities of the testing F1 (the offspring of a cross between Unsel and Tri-sel strains) suggested that the resistance of L. striatellus to triflumezopyrim was autosomal and incompletely dominant, as well as a polygenic inheritance. In addition, the results of synergist experiment showed that P450s potentially contributed to the triflumezopyrim resistance. The activities of detoxification enzymes in the Unsel and Tri-sel strains indicated that the activity of P450s in the Tri-sel strain was significantly increased, consistent with the results of synergist experiments. Furthermore, 12 P450 genes demonstrated significant up-regulation. L. striatellus has a certain risk of resistance to triflumezopyrim after continuous selection. Triflumezopyrim resistance did not result in cross-resistance to neonicotinoid insecticides. The up-regulation of multiple P450 genes may mediate triflumezopyrim resistance in L. striatellus. © 2022 Society of Chemical Industry.

Field Evaluation of Native Fungus, Beauveria bassiana (Bals.) Vuillemin Against some Piercing-Sucking Insects on the Grapevine.

The Taify cultivar of grapevine (Vitis vinifera L.) is the second important economical fruit after pomegranate at high altitudes of the Taif region in Saudi Arabia. The grapevine trees are infested with different piercing-sucking insect pests especially aphids, whiteflies and thrips. The purpose of this study was to evaluate the ability of an indigenous endophytic entomopathogenic fungus, Beauveria bassiana to control the important piercing-sucking insect pests on grapevines. This investigation was carried out through 5, 10 and 15 day intervals between sprays for controlling Aphis illinoisensis, Bemisia tabaci and Frankliniella occidentalis with a concentration of 6×106 conidia mL-1 under field conditions. The higher infestation in the untreated control was by aphids followed by whitefly and thrips. At the end of the experiment in the treated trees, aphid and whitefly reduction percentages with 5 day intervals of sprays (98.5 and 96.12%, respectively) were not significantly different from 10 day intervals (95.17 and 91.81%, respectively) while these reductions were significantly higher than the reduction occurred by 15 day intervals of sprays (65.93 and 44.51%, respectively). Meanwhile, the 3 intervals of sprays did not differ significantly in the thrips reduction occurred by them with a range from 93.62-96.46%. This indigenous B. bassiana as 6×106 conidia mL-1 with 10 day intervals of the spray-on grapevine can suppress the piercing-sucking insect pests. This also will participate in grapevine organic production and furthermore, it could replace the chemical treatment.

Effect of Intercropping Between Garlic and Faba Bean on Yield and Infestation by Some Piercing-Sucking Insect Pests

Faba bean is an important food crop in Egypt, with seeds of 22 % protein. In addition, it is considered a land reclaiming crop, as it enriches the soil with some nitrogen fertilizer. The current study was conducted at the experimental farm of Sakha Agricultural Research station to manage some piercing-sucking insects with unconventional methods. Garlic was intercropped with faba bean to find the repellent effect of garlic, as a volatile crop, against the abovementioned insects. The solid faba bean gave the highest values of faba bean yield, number of branches, pods and seeds per plant, as well as number of seeds / pod, 100-seed weight and protein content. On the other hand, these values, except plant height, were higher in case of intercropping faba bean with Balady garlic compared to Sids-40 garlic. Concerning garlic yield attributes, Balady garlic intercropped with faba bean produced higher values of bulb diameter and bulb weight / plant, as well as number of cloves per bulb and clove weight compared to Sids-40 garlic. In 2018 / 19 season, the population density of Aphis craccivora was reduced by 55.66 and 32.47 % due to intercropping between faba bean and Balady garlic or Sids-40 garlic, respectively. Empoasca lybica population was reduced by 54.67 and 35.72%, and that of Bemisia tabaci was 59.92 and 35.26 %. Similar results were obtained in 2019/20 season. The current results show that intercropping between faba bean and garlic enhanced the total net crop income, and helped in managing these insects.

Ecological Studies on the Main Piercing-Sucking Insect Pests that Infesting Sweet Pea Plants in Dakahlia Governorate, Egypt

Field experiments were conducted to estimate population density of six Hemiptereous insect species thatt attacking sweet pea plants during two winter seasons of 2018 and 2019 at Dekernce region, Dakhlia Governorate. As well, to determine the impact of temperature and relative humidity on their populations. The results showed that, Myzus persica (Zeller) had two peaks during winter plantation that was recorded during 26th of November of both seasons. Data revealed that Aphis carccivora (Koch) and Acrythosiphn pisum (Koch) had only one peak for each during each season of plantation. Counts showed that Empoasca descipiens had one peak in the winter plantation during 17th of March. Three peaks during winter seasons plantations were recorded for Empoasca decedens. On the other hand, Nezara viridula had two population peaks in each of the two sweet pea seasons. The correlation between population density of the recorded insects and each of temperature or relative humidity had various degrees of significance that differed from positive to negative and from non-significant to highly significant.

Influence of Different Cucumber Varieties on the Occurrence of the Piercing-Sucking Insect Pests in Fayoum Governorate

The present experiments were conducted in a private cucumber field in Ibshwai, Fayoum governorate during the two successive years (2018 and 2019) to examine the influence of different cucumber varieties on the occurrence of the piercing-sucking insect pests in Fayoum governorate. Cucumber variety Reda F1 hybrid followed by variety Sweet Cransh F1 hybrid attracted the highest average number of the cotton aphid Aphis gossypii followed by the cotton whitefly Bemisia tabaci, the leafhopper Empoasca decedens, the green peach aphid Myzus persicae and the potato leafhopper Empoasca decipiens during the two years 2018 and 2019. Cucumber variety Hayel F1 hybrid followed variety Mayadine F1 hybrid hosted the lowest average number of the aforementioned insect pests during the two years. Cucumber variety Hayel F1 hybrid followed by Mayadine F1 hybrid, Reda F1 hybrid and Sweet Cransh F1 hybrid hosted the lowest average number of the green sting bug Nezara viridula followed by the cotton mealybug Planococcus solenopsis and the onion thrips Thrips tabaci during the two years. Cucumber variety Hayel F1 hybrid had the lowest rate of occurrence (23.3 and 23.5 %) followed by Mayadine F1 hybrid (24.6 and 23.9 %) during the two years 2018 and 2019, respectively.

Induction of defense in cereals by 4-fluorophenoxyacetic acid suppresses insect pest populations and increases crop yields in the field

Synthetic chemical elicitors, so called plant strengtheners, can protect plants from pests and pathogens. Most plant strengtheners act by modifying defense signaling pathways, and little is known about other mechanisms by which they may increase plant resistance. Moreover, whether plant strengtheners that enhance insect resistance actually enhance crop yields is often unclear. Here, we uncover how a mechanism by which 4-fluorophenoxyacetic acid (4-FPA) protects cereals from piercing-sucking insects and thereby increases rice yield in the field. Four-FPA does not stimulate hormonal signaling, but modulates the production of peroxidases, H2O2, and flavonoids and directly triggers the formation of flavonoid polymers. The increased deposition of phenolic polymers in rice parenchyma cells of 4-FPA-treated plants is associated with a decreased capacity of the white-backed planthopper (WBPH) Sogatella furcifera to reach the plant phloem. We demonstrate that application of 4-PFA in the field enhances rice yield by reducing the abundance of, and damage caused by, insect pests. We demonstrate that 4-FPA also increases the resistance of other major cereals such as wheat and barley to piercing-sucking insect pests. This study unravels a mode of action by which plant strengtheners can suppress herbivores and increase crop yield. We postulate that this represents a conserved defense mechanism of plants against piercing-sucking insect pests, at least in cereals.

Comparative Efficiency of Certain Products against some Piercing-Sucking Pests and their Associated Predators on Cotton Plants

The present research work aimed to evaluate the efficacy of five different products, two biocides (abamectin and protecto), two synthetic chemical products (methomyl and chlorpyrifos) and one mineral oil (Kz-oil) against some piercing-sucking insect pests attacking cotton plants and their side effects on the associated predators. The experiment was conducted during 2017 season at Kafr ElShenhab village, Mansoura district by using cotton variety Giza 94. From results were obtained, it is obvious that methomyl and chlorpyrifos were more effective as initial kill (72.2 and 68.2%), (66.4 and 51.9%) and (60.1 and 78.9%) for aphid, whitefly and predators respectively. But Kz-oil (61.4%) and abamectin (62.9%) were more effective against jassid and spider mites respectively as initial kill% (after 24 hrs. of treatment) effect, whereas a moderate or less initial kill effect ranged from 32.7 to 51.9% was recorded for the other products. In contrast, abamectin, protecto and Kz-oil were more safety against associated predators as initial kill as follows: 12.2, 9.5 and 12.5% respectively. With respect of residual mean and general mean effect, abamectin, protecto and Kz-oil were relatively highly effective against aphids (65.0, 63.3 and 61.6%) as residual mean and (61.8, 60.4,and 59.5%) as general mean effect and against jassids by moderate effect (50.3, 51.4 and 57.7%) as residual mean and (48.7, 48.3 and 58.3%) as general mean effect respectively. While other tested products recorded a weak effect as residual mean and general mean effect against all piercing sucking insects except both methomyl and chlorpyrifos were highly effective against predators (78.0 and 48.9%) and (75.0 and 53.9%) as residual mean and general mean effect respectively.

The population growth, development and metabolic enzymes of the white-backed planthopper, Sogatella furcifera (Hemiptera: Delphacidae) under the sublethal dose of triflumezopyrim

Triflumezopyrim, a new nicotinic acetylcholine receptor (nAChR) inhibition, can effectively control piercing-sucking insect pests such as white-backed planthopper (Sogatella furcifera). At present, there has been no reports on the effects of triflumezopyrim on the population growth and development of S. furcifera. In this experiment, an age-stage two-sex life table was used to evaluate the impact of triflumezopyrim on the biological parameters of S. furcifera. The results showed that the adult preoviposition period (APOP) and total preoviposition period (TPOP) of the F1 generation were significantly higher than those of the F0 and F4 generations, on the contrary the average fecundity, intrinsic rate of increase (r) and finite rate of increase (λ) of the F4 generation were higher than those of the F0 and F1 generations. The results of synergists and enzyme activities indicated that the CarE and P450 activities in the F4 generation were significantly higher than those in the F0 generation (P < 0.05). The protein contents of vitellogenin (Vg) and vitellogenin receptor (VgR) and relative expression quality of VgR in the F4 female adults were also significantly higher than those in the F0 generation (P < 0.05). These results showed that triflumezopyrim at a low concentration could promote the growth and reproduction of S. furcifera, and that may provide a reference for the rational use of triflumezopyrim in the future.

Drought Stress and Nitrogen Fertilization Affect Cereal Aphid Populations in Wheat Fields

Water stress and nitrogen deficiency are two constraints that negatively affect growth and productivity of wheat plants. Moreover, the interaction between these two stresses could affect the susceptibility of wheat plants to insect attack. In order to examine the influence of drought stress and nitrogen fertilization on piercing-sucking insect pests, the population abundance of four cereal aphid species; English grain aphid Sitobion avenae, wheat aphid Schizaphis graminum, Bird cherry-oat aphid Rhopalosiphum padi, and corn leaf aphid Rhopalosiphum maidis has been monitored in two water treatments (water stress and well-watered) and two nitrogen levels (120 and 180 kg N ha-1). Results revealed that S. graminum was the most dominant specie in all treatments, followed by S. avenae. The population of all aphids tends to increase in the second half of the season coinciding with the emergence of wheat spikes. Stressed-wheat plants attracted more aphids, especially when water deficit synchronizes with an increase in N fertilization. Aphids vigorously thrive better on stressed plants amended with high nitrogen level. Contrary, the lower infestation rate was observed in well-watered plots with lower nitrogen rate. Plant characteristics, such as days to heading, plant height, and chlorophyll content were significantly decreased in drought-stressed plants, while higher N rates increased such parameters. Grain yield and its components were reduced with drought stress and reduced nitrogen fertilization. The current study advocates avoiding severe drought concurrently with an increasing in nutritional augmentation which it might contribute in an increase in insect pest infestation and decreasing in wheat plant traits.

POPULATION FLUCTUATION OF SOME PIERCING-SUCKING INSECTS AND ITS RELATION TO ASSOCIATED PREDATORS AND THE PREVAILING WEATHER FACTORS IN SOYBEAN FIELDS AT KAFR EL-SHEIKH GOVERNORATE

In Egypt, aphids, Aphis spp.; leafhoppers, Empoasca spp. and whitefly, Bemisia tabaci (Genn.) are the most important piercing-sucking insect pests infesting soybean plants and a good understanding of their population dynamics is essential to develop an integrated pest management strategy. Therefore, the population densities of these insects and its relation to the common associated predators and the prevailing weather factors were investigated in soybean fields at Kafr El-Sheikh Governorate for 2016 and 2017 seasons. Weekly counts of the considered insects per 15 leaves indicated that whitefly was the most abundant species followed by leafhoppers, while aphids were the least one. Whitefly and leafhoppers appeared on soybean plants all over the growing season. The maximum density of whitefly took place from mid-June to late July in the first season and from the second half of July to the first half of August in the second season. The high number of leafhoppers occurred in the period from mid-July to mid-August for the first season and during August in the second season. Aphid population appeared only in two periods with very low numbers for every season. In the first season, the first period occurred in the second half of June, while the second period took place in the first half of September. In the second season, the population appeared from late June to mid-July and from late August to mid-September. Also, three predaceous insect species: Chrysoperla carnea (Steph.); Coccinella undecimpun ctata L. and Orius spp. were observed on soybean plants. Ch . carnea was the most abundant predator, while C . undecimpunctata was the least one. The total of the predaceous insects attained the highest numbers during July in the first season and during July and August in the second one. The weather factors (temperature, relative humidity and wind speed) had insignificant effect on the cotton whitefly population in the two study seasons. As for leafhoppers, wind speed only had significant effect on the population activity in the second season. Temperature and wind speed in the first season and wind speed in the second season had highly significant effect on aphids activity in the first season. The effect of the predators on the insects was insignificant during the two seasons except effect of the predaceous insects on the leafhoppers which it was significant. The combined effect of both predators and the prevailing weather factors was more pronounced only on aphids in the first season and on leafhoppers in the second season. However, the gained results may provide valuable information for comprehensive integrated insect management of soybean.

Influence of Different Plantations on the Main Piercing-Sucking Insect Pests Attacking Faba Bean and Soybean Plants

The present investigation was conducted in the farm of Sakha Agricultural Research Station, Kafr El-Sheikh Governorate during 2015/ 16 and 2016/ 17 to determine the influence of sowing dates on the major piercing-sucking insect pests which infested faba bean and soybean plants. On faba bean plants, Emposca spp. ranked in the first category with the highest average number in October cultivated (60.35 ± 12.08 and 89.55 ± 11.29 indiv.) followed by M. persicae (37.30 ± 12.08 and 61.85 ± 12.74 indiv.) in both seasons, respectively. Meanwhile, in November implanted A. craccoivora was recorded the highest average number (72.85 ± 23.86 and 270.45 ± 80.49 indiv.) followed by Emposca spp. (51.15 ± 7.76 and 69.25 ± 12.73 indiv.) in the two successive seasons, respectively. While, in December grown Emposca spp. came in the first category (53.30 ± 10.90 indiv.) in the first season and M. persicae observed the first category (63.35 ± 10.95 indiv.) during the second season. P. solenopsis was found the lowest average number in the different planting dates at the two successive seasons. On the other side, on soybean plants, A. gossypii arranged in the first category in the three plantations and observed the highest average number in the June plantation with values (248.80 ± 48.58and 332.45 ± 67.77 indiv.) followed by April plantation(149.05± 36.08 and 172.10 ± 38.93 indiv.) and May plantation (117.35 ± 26.67 and 167.4 ± 34.44 indiv.)in both seasons, respectively. Number of B. tabaci came in the second category in the three cultivated with the highest values in the June plantation with (216.50 ± 45.11 and232.5 ± 53.36 indiv.) followed by April plantation(143.85 ± 30.77 and 172.00 ± 32.97 indiv.) and May plantation (63.05 ± 15.69 and 87.05 ± 19.10 indiv.) during the two successive seasons, respectively.

Variations in the Susceptibility of some Potato (Solanum tuberosum L.) Cultivars to Infestation with Certain Piercing Sucking Insect Pests

Potato (Solanum tuberosum L.) is an economically important vegetable crop all over the world. The piercing sucking insect pests are serious pests threatening potato plantations in many countries. The present investigation contributes to the knowledge in the susceptibility of certain potato cultivars to infestation with these insects in Beheira Governorate, Egypt. Five global potato cultivars currently used in Egypt’s potato production were evaluated through two successive seasons (summer plantations) in field experiments for their susceptibility to sucking insect infestation. The experiment was designed in a completely randomized blockdesignand all data were analyzed using the SAS® program. None of the tested potato cultivars was immune or highly resistant to the tested insect pests. The cultivars Banba and Diamante were found quite resistance to piercing sucking insect pests. The cultivar Herms was found as moderately susceptible while Spunta and Cara were found to be the most susceptible cultivars. The green lacewing, Chrysoperla carnea; seven-spotted lady beetle, Coccinella septempunctata; eleven spotted lady beetle, Coccinella undecimpunctata and the pirate bug, Orius sp are the most important predators which associated with the sucking insects pests on the potato cultivars.

Sublethal effects of imidacloprid on the performance of the bird cherry-oat aphid Rhopalosiphum padi.

The bird cherry-oat aphid, Rhopalosiphum padi (L.), is a major insect pest of cereal crops in many countries. Imidacloprid has been widely used for controlling piercing-sucking insect pests worldwide, but its sublethal effects on R. padi have not been well addressed. In this study, we investigated the sublethal effects of imidacloprid on biological parameters and five enzyme activities of R. padi. The LC10, LC20, and LC25 of imidacloprid to adult aphids were 0.0053, 0.0329 and 0.0659 mg L-1, respectively. These concentrations significantly decreased pre-adult survival rate, but prolonged the development duration of 1st instar nymphs, pre-oviposition period, and adult longevity. Adult oviposition period was also extended by LC20. The intrinsic rate of increase (r), net reproductive rate (R0), and finite rate (λ) decreased at all three concentrations, whereas mean generation time (T) increased. Moreover, LC20 and LC25 significantly inhibited superoxide dismutase (SOD) activity, but increased catalase (CAT) activity. Acetylcholinesterase (AChE) activity also increased at LC20. However, cytochrome P450 enzyme and peroxidase (POD) activity did not differ between imidacloprid treatments and the control. In conclusion, the imidacloprid concentrations tested here have negative impacts on the performance of R. padi by reducing its nymphal survival, extending the development duration of some stages, decreasing the rate of population growth, and altering enzyme activities.

Comparative Morphology and Chemical Composition of Plant Leaf and their Relation with Population Density of Certain Piercing- Sucking Insect Pests

Both leaf morphology and chemistry play a potential role in predicating with the population density of organisms. The current study was conducted, at the experimental farm of Mansoura University, to examine the effect of host plant species and their morphological (trichome density, thickness, and length) and physiological ((i.e., total protein, total carbohydrates, NPK) characteristics on population density of some piercing-sucking insect pests during two successive growing seasons.The number of Aphis spp. was positively correlated with the higher ratios of total protein, total carbohydrates, and N of squash leaves. While the numbers of Bemisia spp. and N. viridula, were positively correlated with the higher ratios of P and K of eggplant leaves. In contrast, Empoasca spp. exhibited higher populations on common bean leaves that were poor in all chemical compounds. Host plant species significantly affected the population density of all insects investigated. Squash harbored the higher numbers of Aphis spp., eggplant harbored the higher numbers of Bemisia spp.and N. viridula, and common bean had the higher number of Empoasca spp. The populations of aphids, whiteflies, green bugs, and leaf hoppers varied among leaf morphological types. Whitefly and green bugs exhibited significantly higher density on eggplant with more hairiness and hair length, whereas aphids had significantly higher populations on squash leaves with higher hair thickness. Common beans, with lower magnitude of density, thickness and length had the higher populations of leafhoppers. Based on leaf features and their chemical composition, common bean seems to be more resistant against infestation with aphids and whiteflies, squash against green bugs, and eggplant against leafhoppers.

Optimization of Agroinfiltration in Pisum sativum Provides a New Tool for Studying the Salivary Protein Functions in the Pea Aphid Complex

Aphids are piercing-sucking insect pests and feed on phloem sap. During feeding, aphids inject a battery of salivary proteins into host plant. Some of these proteins function like effectors of microbial pathogens and influence the outcome of plant–aphid interactions. The pea aphid (Acyrthosiphon pisum) is the model aphid and encompasses multiple biotypes each specialized to one or a few legume species, providing an opportunity to investigate the underlying mechanisms of the compatibility between plants and aphid biotypes. We aim to identify the aphid factors that determine the compatibility with host plants, hence involved in the host plant specialization process, and hypothesize that salivary proteins are one of those factors. Agrobacterium-mediated transient gene expression is a powerful tool to perform functional analyses of effector (salivary) proteins in plants. However, the tool was not established for the legume species that A. pisum feeds on. Thus, we decided to optimize the method for legume plants to facilitate the functional analyses of A. pisum salivary proteins. We screened a range of cultivars of pea (Pisum sativum) and alfalfa (Medicago sativa). None of the M. sativa cultivars was suitable for agroinfiltration under the tested conditions; however, we established a protocol for efficient transient gene expression in two cultivars of P. sativum, ZP1109 and ZP1130, using A. tumefaciens AGL-1 strain and the pEAQ-HT-DEST1 vector. We confirmed that the genes are expressed from 3 to 10 days post-infiltration and that aphid lines of the pea adapted biotype fed and reproduced on these two cultivars while lines of alfalfa and clover biotypes did not. Thus, the pea biotype recognizes these two cultivars as typical pea plants. By using a combination of ZP1109 and an A. pisum line, we defined an agroinfiltration procedure to examine the effect of in planta expression of selected salivary proteins on A. pisum fitness and demonstrated that transient expression of one candidate salivary gene increased the fecundity of the aphids. This result confirms that the agroinfiltration can be used to perform functional analyses of salivary proteins in P. sativum and consequently to study the molecular mechanisms underlying host specialization in the pea aphid complex.

Cis-12-Oxo-Phytodienoic Acid Stimulates Rice Defense Response to a Piercing-Sucking Insect

The brown planthopper (BPH, Nilaparvata lugens) is a destructive, monophagous, piercing-sucking insect pest of rice. Previous studies indicated that jasmonic acid (JA) positively regulates rice defense against chewing insect pests but negatively regulates it against the piercing-sucking insect of BPH. We here demonstrated that overexpression of allene oxide cyclase (AOC) but not OPR3 (cis-12-oxo-phytodienoic acid (OPDA) reductase 3, an enzyme adjacent to AOC in the JA synthetic pathway) significantly increased rice resistance to BPH, mainly by reducing the feeding activity and survival rate. Further analysis revealed that plant response to BPH under AOC overexpression was independent of the JA pathway and that significantly higher OPDA levels stimulated rice resistance to BPH. Microarray analysis identified multiple candidate resistance-related genes under AOC overexpression. OPDA treatment stimulated the resistance of radish seedlings to green peach aphid Myzus persicae, another piercing-sucking insect. These results imply that rice resistance to chewing insects and to sucking insects can be enhanced simultaneously through AOC-mediated increases of JA and OPDA and provide direct evidence of the potential application of OPDA in stimulating plant defense responses to piercing-sucking insect pests in agriculture.