Russian Wheat Aphid

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Development and Characterization of Wheat Germplasm with Combined Resistance to Russian Wheat Aphid and Stem Rust (Race “Ug99”) in Kenya

Development and Characterization of Wheat Germplasm with Combined Resistance to Russian Wheat Aphid and Stem Rust (Race “Ug99”) in Kenya

Wheat is the second most important cereal in Kenya. However, production is severely constrained by both abiotic and biotic stresses. Of the biotic stresses a devastating pest (Russian wheat aphid (RWA)) and a serious disease (stem rust race TTKS (“Ug99”)) are currently the biggest problem for wheat producers in Kenya. Severe infestations by RWA may result in yield losses of up to 90% while “Ug99” infected fields may suffer 100% crop loss. The two pests com- bined are seriously affecting wheat farmers’ incomes because of the heavy reliance on pesticides that increase the cost of production. This study attempted to develop and characterize wheat lines that are resistant to both RWA and “Ug99” by pyramiding two major resistance genes. Three wheat varieties: “Kwale”, a Kenyan high yielding variety but suscep- tible to both RWA and “Ug99”; “Cook”, an Australian variety carrying stem rust resistance gene Sr36 conferring im- munity to “Ug99”; and “KRWA9”, a Kenyan line with resistance to RWA but of poor agronomic attributes were used. A double cross F 1 (DC F 1 ) was obtained by crossing the F 1 of “Kwale × Cook” and the F 1 of “Kwale × KRWA9”. The

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Evaluation of Dryland Wheat Cultivars on the Market in South Africa for Resistance against Four Known Russian Wheat Aphid, Diuraphis noxia, Biotypes in South Africa

Evaluation of Dryland Wheat Cultivars on the Market in South Africa for Resistance against Four Known Russian Wheat Aphid, Diuraphis noxia, Biotypes in South Africa

An increased wheat yield potential under changing environmental conditions is a challenge in agriculture. Resistant wheat lines can yield more than sus- ceptible wheat lines in the presence of Russian wheat aphid infestation. There are currently four Russian wheat aphid (RWA) biotypes known in South Africa with different virulence against different wheat cultivars. To keep up with the ever-changing patterns it is necessary to screen the cultivars for re- sistance against these Russian wheat aphid (RWA) biotypes. All the dryland wheat cultivars on the market were evaluated for resistance against the four known Russian wheat aphid (RWA) biotypes in South Africa. Through this evaluation, the status of Russian wheat aphid (RWA) resistance in South African dryland wheat cultivars can be updated to adapt to environmental changes and the wheat industry can adapt to changes in virulence of Russian wheat aphid (RWA) biotypes that may cause damage to Russian wheat aphid (RWA) resistant cultivars, subsequently affecting yield. Evaluations were done in the glasshouse by screening wheat cultivars against four different South African Russian wheat aphid (RWA) biotypes, RWASA1-RWASA4, under controlled conditions. The glasshouse evaluations showed that out of the 19 dryland wheat cultivars currently on the market in South Africa 16 are resistant against RWASA1, 7 are resistant against RWASA2, 7 are resistant against RWASA3 and 5 are resistant against RWASA4. Dryland wheat culti- vars were also evaluated under field conditions at four different field locali- ties. In the field, 5 cultivars were resistant to RWASA3 at two localities, re- spectively, and 3 and 5 cultivars were resistant to RWASA4 at two localities, respectively. Since Russian wheat aphid (RWA) damage can influence the fi- nal yield of a wheat cultivar significantly, changing conditions can influence How to cite this paper: Jankielsohn, A.

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Yield Evaluation of a Wheat Line with Combined Resistance to Russian Wheat Aphid and Stem Rust  Race “Ug99” in Kenya

Yield Evaluation of a Wheat Line with Combined Resistance to Russian Wheat Aphid and Stem Rust Race “Ug99” in Kenya

In Kenya, Russian wheat aphid (RWA) and stem rust race TTKS (“Ug99”) are the most devastating pests of wheat. Se- vere infestations by RWA result in yield losses of up to 90% while epidemics of “Ug99” can cause up to 100% loss. The two pests combined have seriously affected farmer incomes forcing them to rely heavily on pesticides and increas- ing the cost of production. This study sought to evaluate a wheat line that has been developed to be resistant to both RWA and “Ug99” by pyramiding two major resistance genes. Three varieties were used in this study: “Kwale”, a Ken- yan high yielding commercial variety but susceptible to both RWA and “Ug99”; “Cook”, an Australian variety carrying stem rust resistance gene Sr36 conferring immunity to “Ug99”; and “KRWA9”, a Kenyan line resistant to RWA but with poor agronomic attributes. The F 1 of the double cross (DC F 1 ) was obtained by crossing the F 1 of “Kwale × Cook”

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Compatibility of entomopathogenic fungi and botanical extracts against the wheat aphid, Sitobion avenae (Fab.) (Hemiptera: Aphididae)

Compatibility of entomopathogenic fungi and botanical extracts against the wheat aphid, Sitobion avenae (Fab.) (Hemiptera: Aphididae)

when S. avenae exposed to them in the study although variations were observed under different treatments. Treated aphids reproduced at slower rate than un- treated ones, except when they were exposed to neem and B. bassiana binary mixture. Neem and eucalyptus extracts negatively affected the longevity as well as fe- cundity of cotton aphids (Bayhan et al. 2006). Similarly, Pavela et al. (2004) reported the lowest fecundity in cabbage aphids after exposure to systemic neem ex- tract. Citrus aphids also produced lowered number of nymphs after they were exposed to neem seed extracts (Tang et al. 2002). The negative effects of fungal infec- tions on fecundity and egg fertility were also reported, using fungal species B. bassiana and M. anisopliae on Russian wheat aphid (Wang and Knudsen 1993).

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Aphid resistance in wheat varieties

Aphid resistance in wheat varieties

In the fecundity test, aphids had no choice but to feed on the test plants and substantial differences in the rate of reproduction of R. padi between varieties was seen. All the A genome diploid species varieties tested showed significantly reduced intrinsic rate of population increase, both in the development time and in the size of the aphids. As with the settling test the insect resistant plants showed the same effect as the ordinary hexaploid varieties and did not reduce the reproduction of the R. padi. Thus these results have been unable to show any antixenosis or antibiosis efficacy of the Russian wheat aphid, greenbug or orange blossom midge resistance sources against R. padi.

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Flight muscles degenerate by programmed cell death after migration in the wheat aphid, Sitobion avenae

Flight muscles degenerate by programmed cell death after migration in the wheat aphid, Sitobion avenae

A trade-off has been proposed between IFM degenera- tion and reproduction with regard to energy allocation [26]. IFM degeneration is regulated in many insects, and the products are reallocated to reproduction [24–30]. Here, we identified two groups of genes that differen- tially expressed pre-/post- aphid migration (Additional file  6: Table  S3). First group included apoptotic genes, like Ras-related Rab-29b, p53, and RPS27a, which sug- gested that aphid IFM degeneration is an active PCD. The second group included metabolic genes. Some of those genes are involved in the metabolism of energy building blocks (e.g. amino acids, sugars, and vitamins), while other genes are involved in energy transport (e.g. exocyst complex component-3). The differentially expressed genes indicated that aphid IFM degeneration is an active process that involves a trigger of PCD fol- lowed by a systematic reallocation of energies (e.g. from migration to reproduction) [5, 29, 31, 32].

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microRNA 92a regulates the expression of aphid bacteriocyte specific secreted protein 1

microRNA 92a regulates the expression of aphid bacteriocyte specific secreted protein 1

Objective: Aphids harbor a nutritional obligate endosymbiont in specialized cells called bacteriocytes, which aggregate to form an organ known as the bacteriome. Aphid bacteriomes display distinct gene expression profiles that facilitate the symbiotic relationship. Currently, the mechanisms that regulate these patterns of gene expression are unknown. Recently using computational pipelines, we identified miRNAs that are conserved in expression in the bacteriomes of two aphid species and proposed that they function as important regulators of bacteriocyte gene expression. Here using a dual luciferase assay in mouse NIH/3T3 cell culture, we aimed to experimentally validate the computationally predicted interaction between Myzus persicae miR-92a and the predicted target region of M. persicae bacteriocyte-specific secreted protein 1 (SP1) mRNA.

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Aphid alarm pheromone produced by transgenic plants affects aphid and parasitoid behavior

Aphid alarm pheromone produced by transgenic plants affects aphid and parasitoid behavior

Manipulation of parasitic wasps (parasitoids) presents an alternative, or at least an additional, approach to aphid control (29). Because E ␤ f is known to act as a kairomone in attracting aphid parasitoids (4, 5), the effect of transgenic plants on the foraging behavior of Diaeretiella rapae (Hymenoptera: Bra- conidae) (6) was also tested. D. rapae is a parasitoid specialized for aphids feeding on members of the Brassicaceae and hence is appropriate for use with A. thaliana. We first confirmed that antennae of D. rapae were physiologically able to respond to the E ␤ f produced by transgenic A. thaliana plants (Fig. 1C). The behavioral response was then investigated by releasing individual D. rapae directly onto plants and recording the time spent before the parasitoid flew away (30, 31). Our results showed a highly significant increase in time spent by foraging parasitoids on the transgenic A. thaliana plants (Fig. 4). Most of this increase was in the time spent remaining still on the plant, suggesting an arrestment or ‘‘sit and wait’’ response in the absence of aphid prey. The practical implication of this finding, and the influence of learning behavior, remain to be investigated in field simula- tion studies.

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Influence of host plant on susceptibility of the aphid Acyrthosiphon pisum (Hemiptera: Aphididae) to the fungal pathogen Pandora neoaphidis (Zygomycetes: Entomophthorales)

Influence of host plant on susceptibility of the aphid Acyrthosiphon pisum (Hemiptera: Aphididae) to the fungal pathogen Pandora neoaphidis (Zygomycetes: Entomophthorales)

described, with the greatest species numbers and abun- dances occurring in temperate regions of the world, where approximately 25% of plant species are food resources for aphids (Dixon, 1998). Adaptation by many aphid species to marked seasonality and ephemeral summer host resources includes polyphenism (sexual, asexual forms) and telescoping of generations in parthe- nogenic summer females (Dixon, 1998). Alternation between different host plant species is a necessary strategy for population survival within and between sea- sons. In general, the feeding strategies and gut physiology of aphids, as with other sap-sucking Hemiptera, are con- sidered to have adapted to evade plant defence and wounding responses involving the polyphenol oxidase metabolic pathway (Gatehouse, 2002).

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Competition and Niche-Partitioning in Two Species of Walnut Aphids

Competition and Niche-Partitioning in Two Species of Walnut Aphids

Walnut trees are susceptible to pests and diseases such as walnut weevil (Alcides Porrectirostris Marsha), walnut blue beetle (Monolepta erythrecephale), Sanjose scale (Quadraspidiotus pernicious Comst), Dusky veined aphid (Panaphis juglandis Goeze) 1 and walnut green aphid (Chromaphis juglandicola Kalt). Among the different pests prevalent in the walnut-producing areas, walnut aphids’ viz. P. juglandis and C. juglandicola damage walnut orchards most seriously. 1,2 Their feeding reduces tree vigour, nut size, yield, and quality. In addition to direct feeding damage, they excrete copious amounts of honey-dew that falls onto nuts, leaves and shoots. Honey-dew supports growth of the black sooty mould fungus. This fungus reduces light penetration to the leaf surface reducing its photosynthetic capacity. Being black, it also absorbs heat to predispose nuts to sunburn and subsequent kernel quality loss due to high temperatures 2 . High populations of aphids may also cause leaf drop, exposing more nuts to sunburn. If heavy populations are allowed to develop (i.e. > 15 aphids per walnut leaflet) and remain for as little as 14 days uncontrolled, current season’s nut quality is reduced along with a substantial reduction in the following season’s crop 3 .

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Biochemical Characterization of the Helper Component of Cauliflower Mosaic Virus

Biochemical Characterization of the Helper Component of Cauliflower Mosaic Virus

The helper component of Cauliflower mosaic virus is encoded by viral gene II. This protein (P2) is dispensable for virus replication but required for aphid transmission. The purification of P2 has never been reported, and hence its biochemical properties are largely unknown. We produced the P2 protein via a recombinant bacu- lovirus with a His tag fused at the N terminus. The fusion protein was purified by affinity chromatography in a soluble and biologically active form. Matrix-assisted laser desorption time-of-flight mass spectrometry demon- strated that P2 is not posttranslationally modified. UV circular dichroism revealed the secondary structure of P2 to be 23% ␣ -helical. Most ␣ -helices are suggested to be located in the C-terminal domain. Using size exclusion chromatography and aphid transmission testing, we established that the active form of P2 assembles as a huge soluble oligomer containing 200 to 300 subunits. We further showed that P2 can also polymerize as long paracrystalline filaments. We mapped P2 domains involved in P2 self-interaction, presumably through coiled-coil structures, one of which is proposed to form a parallel trimer. These regions have previously been reported to also interact with viral P3, another protein involved in aphid transmission. Possible interference between the two types of interaction is discussed with regard to the biological activity of P2.

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Chemical Compositions of Ligusticum chuanxiong Oil and Lemongrass Oil and Their Joint Action against Aphis citricola van der Goot (Hemiptera: Aphididae)

Chemical Compositions of Ligusticum chuanxiong Oil and Lemongrass Oil and Their Joint Action against Aphis citricola van der Goot (Hemiptera: Aphididae)

in several countries confirmed that some plant essential oils not only repel insects, but also have contact and fumigant activities against specific pests, and fungicidal actions against some important plant pathogens [14]. Essential oils of cumin (Cuminum cyminum L.), anise (Pimpinella ansium L.), oregano (Origanum syriacum L.) and eucalyptus (Eucalyptus dives) were confirmed to be effective as fumigants against two greenhouse pests, the cotton aphid (Aphis gossypii) and carmine spider mite (Tetranychus cinnabarinus)[15].

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Cross habitat usage by crop aphids and their parasitoids in the cropnoncrop interface in an organic vegetable farm

Cross habitat usage by crop aphids and their parasitoids in the cropnoncrop interface in an organic vegetable farm

Interestingly, a few host plants in the non- cultivated habitat hosted parasitized aphids that do not cause damage to crops (BLACKMAN and EASTOP, 2000), which make these plants highly suitable for biological control. This was the case of Chaptalia sp., Carduus sp. and A. abrotanum (hosting the parasitized aphids C. elaeagni, U. aeneus and M. artemisiae respectively). Therefore, these plants could act as reservoirs of L. testaceipes, A. ervi, D. rapae, A. polygonaphis and Aphidius sp. These parasitoids are all potential controllers of many aphid species.

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Herbivory by a Phloem-Feeding Insect Inhibits Floral Volatile Production

Herbivory by a Phloem-Feeding Insect Inhibits Floral Volatile Production

We tested whether aphid-induced changes in floral volatile production affects olfactory orientation by two important aphid natural enemies, both of which use aphid-induced volatiles in host location [23,38] and can use flower resources as food. The experiments were designed to test the relative importance of volatile cues from flowering and vegetative plant parts, and comparative responses to plants infested with the different aphids species. Plants used as odour sources were enclosed in transparent polyester (PET) bags (Melitta Scandinavia, Sweden) (35 643 cm). For whole plant sources, a plant including its plastic pot and soil were enclosed in a bag sealed with a metal twist-tie above the soil. Where flower heads or green parts were separated, bags were sealed carefully around the stem using rubber foam and a twist-tie. A small hole was made through which a Teflon tube was inserted, sealed with labfilm (Parafilm) and connected to the olfactometer arm. A second hole was made in the opposite end of the bag with a Teflon tube connected through which air could enter and flow over the plant. The tube was 50 cm long to avoid re-collecting air in the direct vicinity of the odour sources. Aphid-damaged plants were infested with 200 aphids 72 h prior to the bioassays and aphids were not removed from the plant before the tests.

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Competition and Niche-Partitioning in two Species of Walnut Aphids

Competition and Niche-Partitioning in two Species of Walnut Aphids

Walnut trees are susceptible to pests and diseases such as walnut weevil (Alcides Porrectirostris Marsha), walnut blue beetle (Monolepta erythrecephale), Sanjose scale (Quadraspidiotus pernicious Comst), Dusky veined aphid (Panaphis juglandis Goeze) 1 and walnut green aphid (Chromaphis juglandicola Kalt). Among the different pests prevalent in the walnut-producing areas, walnut aphids’ viz. P. juglandis and C. juglandicola damage walnut orchards most seriously. 1,2 Their feeding reduces tree vigour, nut size, yield, and quality. In addition to direct feeding damage, they excrete copious amounts of honey-dew that falls onto nuts, leaves and shoots. Honey-dew supports growth of the black sooty mould fungus. This fungus reduces light penetration to the leaf surface reducing its photosynthetic capacity. Being black, it also absorbs heat to predispose nuts to sunburn and subsequent kernel quality loss due to high temperatures 2 . High populations of aphids may also cause leaf drop, exposing more nuts to sunburn. If heavy populations are allowed to develop (i.e. > 15 aphids per walnut leaflet) and remain for as little as 14 days uncontrolled, current season’s nut quality is reduced along with a substantial reduction in the following season’s crop 3 .

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POPULATION DYNAMICS OF ROSE APHID MACROSIPHUM ROSAE L. ON DIFFERENT CULTIVARS OF ROSA INDICA L. IN PAKISTAN

POPULATION DYNAMICS OF ROSE APHID MACROSIPHUM ROSAE L. ON DIFFERENT CULTIVARS OF ROSA INDICA L. IN PAKISTAN

The maximum mean number of aphid nymphs, aphid winged adults and aphid wingless adults on buds by visual sampling were 7.42, 8.67 and 12.97, respectively observed on Perf- ecta as compared to Wisky Mac, Iceburg and Christen Diar varieties (Table 1). Statistical analysis for aphid nymphs, aphid winged adult and aphid wingless adults on rose plant buds showed that there were significant effects observed within varieties [F (3,311) = 25.2415, 0.3561 and 10.001,8 respectively at P<0.0000*]. Statistical analysis for aphid nym- phs, aphid winged adult and aphid

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Woolly Ash Aphid ‒ is the Alien Bug Posing a Threat to European Ash Trees? – a Review

Woolly Ash Aphid ‒ is the Alien Bug Posing a Threat to European Ash Trees? – a Review

The size of aphid populations is regulated by natural enemies, predators, and parasitoids. Among these, parasitoids, especially the specialised ones, play an effective and safe role (from the perspective of possible applications in biological control) (Raymond et al. 2016). However, despite the fact that they were detected in the native area of the woolly ash aphid, none have been found outside America yet. The data on predators is also scarce. Five species of natural predators were found in China in one of the recent studies: Harmonia axyridis (Pallas), chrysopa pallens (Rambur), Episyrphus balteata (DeGeer), deraeocoris punctulatus (Fallén), deraeocoris ater (Jakovlev) (Yu et al. 2015). But in slightly earlier research conducted in Spain, it was observed that anthocoris nemoralis (Fabricius) and also Chamaemyiidae larvae were predators of the woolly ash aphid (Pérez Hidalgo & Mier Durante 2012). In Poland, the presence of predators was found only in a few cases (25% of localities). Those were mostly representatives of Coccinellidae, Asian species H.  axyridis and native coccinella septempunctata Linnaeus and less frequently, predatory bug anthocoris nemorum (Linnaeus). The low number of predatory species and individuals (e.g. 2–3 individuals observed in all colonies on a 5-year-old tree) that do not have a significant influence on the regulation of aphid population may also be important for the quick rate of their multiplication and spreading. In some cases, the presence of ants was observed: Formica fusca (Linnaeus), Lasius niger (Linnaeus), and Myrmica rubra (Linnaeus), which also improves the safety of an aphid colony.

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Wheat nitrogen fertilisation effects on the performance of the cereal aphid Metopolophium dirhodum

Wheat nitrogen fertilisation effects on the performance of the cereal aphid Metopolophium dirhodum

Wheat seeds were sown individually in potting compost (Levingtons M2) in deep cell (25 mm × 80 mm) plug trays. They were vernalised for eight weeks after emergence by being held at 4 °C with 85% RH and an L8:D16 lighting regime. Plants with their root balls attached were transferred to vertical sided (150 mm diameter × 250 mm) pots with saucers in the glasshouse. The pots were filled with inert Rockwool fibre from which sections, of a sufficient size to just receive the root-balled plants, had been removed. Five plants were transferred to each pot to give a similar plant density (250/m 2 ) to those grown under field conditions. Six pots (30 plants in total) were used for each of five nitrogen treatments. Plants were initially with a nitrogen-free nutrient solution as described by Hewitt [49], which was applied to the pot surface until it just flowed into the saucer. Each pot and saucer was moved daily to a randomly determined bench position to eliminate any effects that glasshouse position may have had on aphid performance. At GS 31 pots were watered with a solution containing only NH 4 NO 3 in 250 mL distilled water, mixed to provide fertiliser amounts equivalent to field rates of 0,

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Fecundity and development rate of the bird cherry oat aphid, Rhopalosiphum padi (L) (Hom : Aphididae) on six wheat cultivars

Fecundity and development rate of the bird cherry oat aphid, Rhopalosiphum padi (L) (Hom : Aphididae) on six wheat cultivars

comprehensive pest management program for its host plant. So, a further understanding of biology and life history traits of a pest on host cultivars is essential for the development of effective man- agement strategies. These parameters provide the population growth rate of an insect pest in the current and next generations (Frel et al. 2003). Therefore, local studies on aphid biology on differ- ent cultivars are necessary to provide information in order to improve the aphid management and cultivar fitness under related environment condi- tions (Xia et al. 1999; Razmjou et al. 2006). Fur- thermore, for development of forecasting models, it is also necessary to investigate the bionomics of native populations in order to keep away from invalid data resulting from adaptation to differ- ent ecoclimatic conditions (Kersting et al. 1999; Morgan et al. 2001). Hence, we investigated the bionomics of the R. padi population collected on six wheat cultivars in the Fars province.

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Predicting aphid abundance on winter wheat using suction trap catches

Predicting aphid abundance on winter wheat using suction trap catches

Distinguishing the flight of migrants from the winter hosts (period P1) from the flight of the aphids born in the cereal stands (period P2) would require determining the presence of the migrants (moving from the primary to the secondary hosts) and the exules (moving among the secondary hostplants) in the suction trap catches. The identification of the morphs is possible (Simon et al. 1991; Taylor et al. 1994), but difficult, and is apparently impracticable during the routine aphid identification because of the necessity of using time-consuming measure- ments of aphid morphological characteristics and multivariate computation methods. The division of both periods, thus, can only be based on the indirect evidence of the existence of a sharp increase in the flight activity. Overwintering of anholocyclic aphid populations in winter cereal stands seems impossible due to the winter frosts that limit aphid survival in the cereal crop stands. For instance, in 1999–2015 at Prague-Ruzyně, the minimum temperatures at 5 cm in height ranged between 12.0 and 25.4°C

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