Search

Sucking insects are the most serious insect pests in wheat crops; the harmful effect of aphid in wheat plants is due to sucking of plant sap, honeydew excretion and causing many diseases by transport of plant viruses. The experiment was carried out at Sakha Agric. Res. Station farm during 2017-2018 on wheat Giza 171 growing season. The insecticide used is Imidacloprid (Nofedor 600 FS.) The present study was designed to evaluate comparative efficacy of imidacloprid as seed dressing formulation against sucking insects (Schizaphis graminum, Nezara viridula, Empoasca spp.) as well as their predators; Chrysoperla carena, Labidura riparia, Scymunus spp. and true spiders in two types of wheat sowing (Drill and Broadcast) in the wheat crop field. The results according to analysis of variance showed that there was a significant variation among the insect's reduction in all-season periods as a result of treatment of the wheat seeds before sowing with imidacloprid in the Broadcast and drill sowing. Whereas there is no significant effect of the treatment when comparing S. graminum in different sowing methods, also there was a non-significant effect of the treatment on S. graminum in broadcast method versus N. viridula, Empoasca spp. and predators. While, the number of seeds/spikes, Weight of 100 seeds (gm) and the Germination increasing % in Broadcast sowing were more than that in Drill sowing by 1.31,1.11 and 1.11 respectively. Thus, it could be concluded that the broadcast sowing is suitable economically for farmers than drill sowing methods when using imidacloprid as seed dressing before cultivation for sucking insect control as well as its predators. [ABSTRACT FROM AUTHOR]

Focussed searches were made across New Zealand between 2013 and 2016, for endemic aphids from the Schizaphis (Rhopalosiphina) genus, which is currently represented by two putative, undescribed species from the endemic host plants Aciphylla and Dracophyllum. Cytochrome c oxidase I (COI) gene sequences (48 in total) from the Schizaphis were analysed together with those from a broader collection of New Zealand endemic aphids that has been assembled since the year 2000. The bulk of the Schizaphis belonged to two clusters corresponding to the host plant genera. Two aphids from central North Island Dracophyllum represented a much diverged lineage without clear affiliations to other New Zealand Schizaphis. Inter-population variation in the New Zealand Schizaphis was high compared with that seen in international studies of Aphidinae and among populations of other endemic New Zealand Aphidina. Within Schizaphis from Dracophyllum, geography played an apparent role in genetic structuring, with populations from Taranaki (North Island) and especially Mt Lyford (South Island) being divergent from those on the South Island main divide. Two distinct lineages of Schizaphis, which co-occurred at some sites, were found on Aciphylla. Our sequence comparisons, including GMYC analyses, indicated up to five New Zealand Schizaphis lineages, and two newly discovered endemic Aphis species from the host plants Clematis and Hebe. [ABSTRACT FROM AUTHOR]

Greenbug, Schizaphis graminum (Rondani), is a chronic problem for small grains on the Southern Plains. Central to the pest status of greenbug is the occurrence of resistance-breaking biotypes. Rsg1 and Rsg2 are the only two genes for resistance of barley, Hordeum vulgare L., to greenbug. Only Rsg1 has been deployed in cultivars. Discovery of new resistant genes is essential as biotypes continue to shift. Five winter barley accessions, PI 499276, PI 565657, PI 566459, CI 2458, and PI 565676, 'Post 90' ( Rsg1), STARS 1501B ( Rsg2), and susceptible 'Schuyler', were evaluated in isolated cages against 14 greenbug biotypes: B, C, E, F, H, I, TX1, WY4 A, WY4 B, WY10 MC, WY10 B, WY12 MC, WY81, and WY86. Damage scores were based on a scale of 1-9 for chlorosis (1 was resistant and 9 was dead). Damage means were classified as R or S and used to construct a response matrix which indicated unique resistance genes in four lines. These new sources have potential to reduce vulnerability of barley to future outbreaks of greenbug. [ABSTRACT FROM AUTHOR]

The greenbug, Schizaphis graminum (Rondani), is a major pest of cereals in some parts of the world and is of particular concern because it can be resistant to some insecticides and overcome the resistance of crops. In the UK, it has never been found on crops, but two rather little-known and closely-related species (Schizaphis holci and Schizaphis agrostis) are associated with the wild grasses, Holcus lanatus and Agrostis stolonifera. Since 1987, winged (alate) aphids morphologically resembling the greenbug have been found in increasing numbers in 12.2 m high suction-trap samples of the Rothamsted Insect Survey (RIS); hence, studies were undertaken to establish their identity. Clones (=asexual lineages) established from populations collected from H. lanatus in southern England showed strong preference for Holcus over Agrostis and Hordeum in laboratory tests and produced sexual morphs when transferred to short-day conditions, the males being apterous, as expected for S. holci. Multivariate morphometric comparisons of alatae caught in UK RIS suction traps in 2007 and 2011 with named specimens from museum collections, including S. graminum from many countries, indicated that the suction-trapped alatae were mostly S. agrostis and S. holci. Cytochrome c oxidase subunit I (COI) mtDNA obtained from 62 UK specimens from suction-traps had 95.4–100% sequence identity with US specimens of S. graminum. Two of the UK specimens had identical COI sequence to the US sorghum-adapted form of S. graminum, and these specimens also had 100% identity with a 640 bp fragment of nDNA CytC, indicating that this form of S. graminum may already be present in the UK. Present and future economic implications of these results are discussed. [ABSTRACT FROM AUTHOR]

The status of host-plant resistance was evaluated in pearl millet (Pennisetum glaucum L.) against aphid species greenbug, Schizaphis graminum (Rondani). It was determined by the ability of seedlings to resist for plant stunting caused by aphid's feeding at seedling stage. The results indicated that out of 135 pearl millet entries tested, 21 were resistant, 69 were moderately resistant and 45 were susceptible to greenbug feeding. The resistant entries were: C-591, Pak-75211, Pak-75212, Pak-75219, Pak-75194, Pak-75227, Pak-75238 Pak-75272, Pak-75276, WCA-78, C-47, Pak-75322, Pak-75323, Pak-75329, Pak-75331, Pak-75334, Pak-75337, Pak-75338, Pak- 75339, Pak-75353 and Pak-75359. The entries resistant or moderately resistant with damage rating< 4 in the present studies may be used in any breeding programme to reduce greenbug damage, whereas the susceptible entries should be avoided. [ABSTRACT FROM AUTHOR]

Buchnera aphidicola is an obligate symbiotic bacterium that sustains the physiology of aphids by complementing their exclusive phloem sap diet. In this study, we reappraised the transport function of different Buchnera strains, from the aphids Acyrthosiphon pisum, Schizaphis graminum, Baizongia pistaciae and Cinara cedri, using the re-annotation of their transmembrane proteins coupled with an exploration of their metabolic networks. Although metabolic analyses revealed high interdependencies between the host and the bacteria, we demonstrate here that transport in Buchnera is assured by low transporter diversity, when compared to free-living bacteria, being mostly based on a few general transporters, some of which probably have lost their substrate specificity. Moreover, in the four strains studied, an astonishing lack of innermembrane importers was observed. In Buchnera, the transport function has been shaped by the distinct selective constraints occurring in the Aphididae lineages. Buchnera from A. pisum and S. graminum have a three-membraned system and similar sets of transporters corresponding to most compound classes. Transmission electronic microscopic observations and confocal microscopic analysis of intracellular pH fields revealed that Buchnera does not show any of the typical structures and properties observed in integrated organelles. Buchnera from B. pistaciae seem to possess a unique double membrane system and has, accordingly, lost all of its outer-membrane integral proteins. Lastly, Buchnera from C. cedri revealed an extremely poor repertoire of transporters, with almost no ATP-driven active transport left, despite the clear persistence of the ancestral three-membraned system. [ABSTRACT FROM AUTHOR]

The oriental aphid Schizaphis piricola (Matsumura) is recorded for the first time in Europe, on the ornamental pear tree Pyrus calleryana in landscaped areas in Madrid (Spain). Data on the morphology of the forms on primary host (apterous and alate fundatrigeniae and fundatrices), and their biology and distribution are given. The keys for identifying species of Schizaphis (Schizaphis) in the Iberian Peninsula are updated. Two species of aphids are also recorded for the first time on Pyrus calleryana: S. piricola and Aphis pomi. [ABSTRACT FROM AUTHOR]

The cytochrome c oxidase subunit I (COI) gene of the mitochondrial DNA was sequenced in eight holocyclic monoecious aphids (Hemiptera: Aphididae) that occur on wheat, Triticum aestivum L.; barley, Hordeum vulgare L.; oat, Arena sativa L.: and sorghum, Sorghum bicolor (L.) Moench in the United States. The first 640 bp of the 5' end were considered as a DNA barcoding technique for species identification. DNA barcoding successfully differentiated Schizaphis graminum (Rondani), Diruaphis noxia (Kurdjumov), Diruaphis tritici (Gillette), Diruaphis frequens (Walker), Diruaphis mexicana (McVicar Baker), Sipha tiara (Forbes), Sipha elegans del Guercio, and Sitobion avenae (F.). In addition to the above-mentioned monoecious species, the common cereal aphids Rhopalosiphum padi (L.) and Rhopalosiphum maidis (Fitch) were included and successfully differentiated. DNA barcoding is a reliable alternative to traditional morphology in the identification of cereal aphids and their various life stages and morphs, including eggs. The application of DNA barcoding to aphid eggs found on grasses will be able to confirm whether D. noxia is now reproducing sexually in the United States after 20 yr of sexual reproduction. [ABSTRACT FROM AUTHOR]

Background: Plants are affected by several aspects of the soil, which have the potential to exert cascading effects on the performance of herbivorous insects. The effects of biotic and abiotic soil characteristics have however mostly been investigated in isolation, leaving their relative importance largely unexplored. Such is the case for the dune grass Ammophila, whose decline under decreasing sand accretion is argued to be caused by either biotic or abiotic soil properties. Methodology/Principal Findings: By manipulating dune soils from three different regions, we decoupled the contributions of region, the abiotic and biotic soil component to the variation in characteristics of Ammophila arenaria seedlings and Schizaphis rufula aphid populations. Root mass fraction and total dry biomass of plants were affected by soil biota, although the latter effect was not consistent across regions. None of the measured plant properties were significantly affected by the abiotic soil component. Aphid population characteristics all differed between regions, irrespective of whether soil biota were present or absent. Hence these effects were due to differences in abiotic soil properties between regions. Although several chemical properties of the soil mixtures were measured, none of these were consistent with results for plant or aphid traits. Conclusions/Significance: Plants were affected more strongly by soil biota than by abiotic soil properties, whereas the opposite was true for aphids. Our results thus demonstrate that the relative importance of the abiotic and biotic component of soils can differ for plants and their herbivores. The fact that not all effects of soil properties could be detected across regions moreover emphasizes the need for spatial replication in order to make sound conclusions about the generality of aboveground-belowground interactions. [ABSTRACT FROM AUTHOR]

Abstract  We report the effects of some bisorbicillinoids isolated from biomass of the fungus Trichoderma citrinoviride on settling and feeding preference of the aphid Schizaphis graminum. Purification of the fungal metabolites was carried out by a combination of column chromatography and thin-layer chromatography using direct and reverse phases. Chemical identification was performed by spectroscopic methods including nuclear magnetic resonance and mass spectrometry. The identified bisorbicillinoids appeared to be bislongiquinolide, its 16,17-dihydro derivative, trichodimerol, and dihydrotrichodimerol. A feeding preference test with alate morphs of S. graminum was used to identify the active fractions. Among the four bisorbicillinoids, dihydrotrichodimerol and bislongiquinolide influenced aphid feeding preference, restraining specimens from settling on leaves treated with metabolites. Taste neurons sensitive to these compounds, particularly to bislongiquinolide, were located on tarsi of the S. graminum alate morphs. [ABSTRACT FROM AUTHOR]

We investigated the life history consequences of changes in diet between larval and adult life stages in the polyphagous lady beetle Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae). Beetles were reared on three larval diets: greenbug, Schizaphis graminum Rondani (Homoptera: Aphididae), eggs of the flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), and bee pollen. The reproductive performance of females was then evaluated on an adult diet of either greenbug or moth eggs. Moth eggs appeared to be the most suitable diet for larvae, yielding the largest adults, and pollen the least suitable, resulting in the smallest adults and greatly extended developmental time. Pollen-reared beetles tended to have lower fecundity and fertility than those reared on animal protein, regardless of adult diet. Female fitness was generally increased by a change in diet upon emergence to the alternative source of animal protein, suggesting that dietary complementation occurred across life stages. Among females reared on greenbug, a change of diet to moth eggs reduced the period required for production of 12 clutches and increased egg fertility compared to continued feeding on greenbug. Among females reared on moth eggs, a change of diet to greenbug increased fecundity compared to continued feeding on moth eggs. Among females fed an adult diet of greenbug, those fed moth eggs as larvae had faster production of 12 clutches and higher fecundity. We discuss these novel results in the context of coccinellid life history and ecology and their potential implications for other insects that are predatory as both larvae and adults. [ABSTRACT FROM AUTHOR]

The Russian wheat aphid (RWA) [Diuraphis noxia (Kurdjumov)] is an economically significant insect pest of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in the USA. Since 1986, only one biotype existed in the USA. In 2003, a new biotype appeared which was virulent to all known resistance genes in wheat, with the exception of Dn7. Dn7 is a rye gene transferred into a wheat background via 1RS/1BL translocation. It was previously mapped; however no PCR-based markers were developed for marker-assisted selection (MAS) and the map was sparse. This study presents a higher density map of Dn7 containing 19 markers. The markers spanning Dn7 are XHor2 and Xscb24l at distances of 1.4 and 1 cM, respectively, from Dn7. PCR markers were developed and tested on 19 wheat cultivars. Two markers which amplified rye-specific fragments proved to be useful for MAS. Xrems1303 amplified a 320-bp band only in cultivars with high-level resistance to biotype 2 and is effective for MAS of Dn7. Xib267 is linked to the susceptible locus and amplified a fragment specific for rye Petkus 1RS and would be a good marker for selecting against the susceptible locus. The value of Dn7 as a source of resistance has increased because of the broad spectrum resistance it provides against several biotypes. The markers developed in this study will be useful for facilitating the transfer of Dn7 into wheat cultivars with or without translocation chromosomes containing 1RS. [ABSTRACT FROM AUTHOR]

Functional responses by Lysiphiebus testaceipes (Cresson), a common parasitoid of small grain aphids, on greenbug, Schizaphis graminum (Rondani), were measured at seven temperatures (14, 12, 10, 8, 6, 4, and 2°C) during a 24-h period (12-h light: 12-h dark), Oviposition by L. testaceipes ceased at temperatures <4°C. At all experimental temperatures, a type I, rather than a type II or type III, functional response was determined to be the best fit based on coefficient of determination (r²) values. L. testaceipes was observed to oviposit in greenbugs at temperatures below the developmental temperature of both the greenbug host (5.8°C) and the parasitoid itself (6.6°C). This ability to oviposit at subdevelopmental temperatures enables the parasitoid to increase the percentage of greenbugs that are parasitized while the greenbugs are unable to reproduce. The implications of these findings regarding population suppression of greenbugs are discussed. [ABSTRACT FROM AUTHOR]

The greenbug, Schizaphis graminum (Rondani), and bird cherry-oat aphid, Rhopalosiphum padi L., are aphid pests of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), sorghum (Sorghum bicolor L.), oat (Avena sativa L.), and other cereals worldwide. Greenbug and bird cherry-oat aphid infestation in crops is unpredictable over space and time. From these 2 aphids, greenbug infestation causes significant reduction in yield, and consequently large amounts of insecticides are used to control greenbug populations. Therefore, a repeatable and rapid method is necessary for monitoring aphid populations. Remote sensing appears promising for the monitoring of aphid density in crops. The present research examined the potential use of spectral data to quantify aphid density (greenbug and bird cherry-oat aphid) in 3 winter wheat field experiments and 1 greenhouse experiment. A multispectral ground radiometer and a hyperspectral hand-held spectrometer were used to record reflectance data. In order to quantify the relationship between reflectance data and aphid density, 2 spectral indices were used in regression. The coefficients of determination (r²) ranged from 0.48 to 0.76 for the hyperspectral-derived index and from 0.43 to 0.67 for the multispectral-derived index. The results indicate that multispectral and hyperspectral remote sensing appears functional to monitor aphid population density in production winter wheat fields. [ABSTRACT FROM AUTHOR]

Although spectral remote sensing techniques have been used to study many ecological variables and biotic and abiotic stresses to agricultural crops over decades, the potential use of these techniques for greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) infestations and damage to wheat, Triticum aestivum L., under field conditions is unknown. Hence, this research was conducted to investigate: 1) the applicability and feasibility of using a portable narrow-banded (hyperspectral) remote sensing instrument to identify and discern differences in spectral reflection patterns (spectral signatures) of winter wheat canopies with and without greenbug damage; and 2) the relationship between miscellaneous spectral vegetation indices and greenbug density in wheat canopies growing in two fields and under greenhouse conditions. Both greenbug and reflectance data were collected from 0.25-, 0.37-, and 1-m² plots in one of the fields, greenhouse, and the other field, respectively. Regardless of the growth conditions, greenbug-damaged wheat canopies had higher reflectance in the visible range and less in the near infrared regions of the spectrum when compared with undamaged canopies. In addition to percentage of reflectance comparison, a large number of spectral vegetation indices drawn from the literature were calculated and correlated with greenbug density. Linear regression analyses revealed high relationships (R² ranged from 0.62 to 0.85) between greenbug density and spectral vegetation indices. These results indicate that hyperspectral remotely sensed data with an appropriate pixel size have the potential to portray greenbug density and discriminate its damage to wheat with repeated accuracy and precision. [ABSTRACT FROM AUTHOR]

Biotypic diversity of the greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), was assessed among populations collected from cultivated wheat, Triticum aestivum L., and sorghum, Sorghum bicolor (L.) Moench, and their associated noncultivated grass hosts. Greenbugs were collected during May through August 2002 from 30 counties of Kansas, Nebraska, Oklahoma, and Texas. Discounting the presumptive biotype A, five of the remaining nine letter-designated greenbug biotypes were collected; however, biotypes C, F, J, and K were not detected. Biotypes E and I exhibited the greatest host range and were the only biotypes collected in all four states. Sixteen greenbug clones, collected from eight plant species, exhibited unique biotype profiles. Eleven were collected from noncultivated grasses, three from wheat, and two from sorghum. The most virulent biotypes were collected from noncultivated hosts. The great degree of biotypic diversity among noncultivated grasses supports the contention that the greenbug species complex is composed of host-adapted races that diverged on grass species independently of, and well before, the advent of modern agriculture. [ABSTRACT FROM AUTHOR]

Sorghum, Sorghum bicolor (L.) Moench, is the fifth most important cereal crop grown worldwide and the fourth in the United States. Greenbug, Schizaphis graminum (Rondani), is a major insect pest of sorghum with several biotypes reported to date. Greenbug biotype I is currently the most prevalent and most virulent on sorghum plants. Breeding for resistance is an effective way to control greenbug damage. A successful breeding program relies in part upon a clear understanding of breeding materials. However, the genetic diversity and relatedness among the greenbug biotype I resistant accessions collected from different geographic origins have not been well characterized, although a rich germplasm collection is available. In this study, 26 sorghum accessions from 12 countries were evaluated for both resistance to greenbug biotype I and genetic diversity using fluorescence-labeled amplified fragment length polymorphism (AFLP). Twenty-six AFLP primer combinations produced 819 polymorphic fragments indicating a relatively high level of polymorphism among the accessions. Genetic similarity coefficients among the sorghum accessions ranged from 0.69 to 0.90. Cluster analysis indicated that there were two major groups based on polymorphic bands. This study has led to the identification of new genetic sources of sorghum with substantial genetic variation and distinct groupings of resistant accessions that have the potential for use in the development of durable greenbug resistant sorghum. [ABSTRACT FROM AUTHOR]

The wheat lines (cultivars) 'Largo', 'TAM110', 'KS89WGRC4', and 'KSU97-85-3' conferring resistance to greenbug, Schizaphis graminum (Rondani), biotypes E, I, and K were evaluated to determine the categories of resistance in each line to greenbug biotype K. Our results indicated that Largo, TAM110, KS89WGRC4, and KSU97-85-3 expressed both antibiosis and tolerance to biotype K. Largo, KS89WGRC4, and KSU97-85-3, which express antixenosis to biotype I, did not demonstrate antixenosis to biotype K. The results indicate that the same wheat lines may possess different categories of resistance to different greenbug biotypes. A new cage procedure for measuring greenbug intrinsic rate of increase (rm) was developed, by using both drinking straw and petri dish cages, to improve the efficiency and accuracy of rm-based antibiosis measurements. [ABSTRACT FROM AUTHOR]

Coccinella septempunctata L. (Coleoptera: Coccinellidae) larvae were supplied daily with 4 or 16mg of biotype-E Schizaphis graminum Rondani (Homoptera: Aphididae) reared on either resistant TAM-lb (TAM 105*4/Amigo*5//Largo), TAM-107 (TAM 105*4/Amigo), or the susceptible isoline TAM-105 winter wheat cultivars. No significant differences in survival ratios or developmental times were observed among C. septempunctata larvae supplied with increasing daily levels of greenbugs from each winter wheat cultivar. However, among cultivars small but significant differences in adult dry weight were observed. At the 16 mg daily prey level individuals supplied with greenbugs reared on TAM-105 were ≥2.5 mg heavier than those supplied with greenbugs reared on TAM-107 or TAM-110. Results from our study indicated that winter wheat cultivars with Amigo and Largo resistance genes would have little effect on the nutritional value of S. graminum for C. septempunctata. [ABSTRACT FROM AUTHOR]

Interactions of the parasitoid Lysiphlebus testaceipes (Cresson) and the greenbug, Schizaphis graminum (Rondani), on greenbug-resistant 'Cargill 607E' (antibiosis), 'Cargill 797' (primarily tolerance), and -susceptible 'Golden Harvest 510B' sorghum, Sorghum bicolor (L.) Moench, were tested using three levels of biotype I greenbug infestation. The parasitoid infestation rate was 0.5 female and 1.0 male L. testaceipes per plant. For all three greenbug infestation levels, the parasitoid brought the greenbug under control (i.e., prevented the greenbugs from killing the plants) on both resistant hybrids, but it did not prevent heavy leaf damage at the higher greenbug infestation rates. At the low greenbug infestation rate (50 greenbugs per resistant plant when parasitoids were introduced), greenbugs damaged 5 and 18% of the total leaf area on 'Cargill 797' and 'Cargill 607E', respectively, before greenbugs were eliminated. Leaf damage was higher for the intermediate infestation study (120 greenbugs per plant), 21% and 30% leaf area were damaged on the resistant sorghum hybrids 'Cargill 797' and 'Cargill 607E', respectively. At the high greenbug infestation rate (300 greenbugs per plant), heavy damage occurred: 61% on 'Cargill 607E' and 75% on 'Cargill 797'. The parasitoids did not control greenbugs on the susceptible sorghum hybrid 'Golden Harvest 510B'. L. testaceipes provided comparable control on both greenbug-resistant hybrids. This study supports previous studies indicating that L. testaceipes is effective in controlling greenbugs on sorghum with antibiosis resistance to greenbugs. Furthermore, new information is provided indicating that L. testaceipes is also effective in controlling greenbugs on a greenbug-tolerant hybrid. [ABSTRACT FROM AUTHOR]

The Resource Availability Hypothesis (RAH) states that plants with a low Relative Growth Rate (RGR) and high levels of defence against herbivores or pathogens are favoured in habitats with low resource availability, whereas plants with a high potential RGR and low levels of defence are favoured in environments with high resource availability. High levels of defence are expected to result in lower reproduction and/or growth of the herbivores or pathogens. To test this hypothesis, four accessions of each of nine natural Hordeum spontaneum (wild barley) populations were grown in a climate chamber under two levels of nutrient supply. Susceptibility to Schizaphis graminum (greenbug) was quantified by placing a single adult greenbug on each plant and measuring its realised fecundity after 8 days. Data on potential RGR were available from a previous experiment. No support for the RAH was found. The correlation between potential RGR and greenbug reproduction was not significant, neither at the high nor at the low level of nutrient supply. Furthermore, on average plants grown under high and low nutrients did not differ in susceptibility. However, accessions-within-populations differed in the way susceptibility was affected by nutrient supply, and most accessions had a higher susceptibility under nutrient-poor conditions. It could be that these accessions differed in the spectrum of secondary metabolites they produced. Whatever the cause, the genetic variation for the reaction in susceptibility to nutrient supply suggests that selection could act in favour of more or less plasticity in plants without any apparent change in potential RGR. [ABSTRACT FROM AUTHOR]

Ninety three recombinant inbreds of Sorghum bicolor (L. Moench) were derived from a cross between two sorghum lines GBIK and Redlan. This population was used to identify quantitative trait loci (QTLs) for resistance and tolerance to greenbug (Schizaphids graminum Rondani) Biotypes I and K. One hundred and thirteen loci (38 SSRs and 75 RAPDs) were mapped in 12 linkage groups covering 1,530 cM. In general, nine QTLs were detected affecting both resistance and tolerance to greenbug (GB) Biotypes I and K. The phenotypic variance explained by each QTL ranged from 5.6% to 38.4%. Four SSRs and one RAPD marker were associated with the expression of all resistance and tolerance traits. These markers appear to be linked to biotype non-specific resistance and tolerance genes. Four additional markers were associated with biotype-specific resistance or tolerance traits. The detection of more than one locus for each biotype supports the hypothesis that several regions, which represent different genes, control the expression of resistance and tolerance to greenbug in sorghum. The results can be used for marker-assisted selection and the breeding of greenbug-tolerant sorghum cultivars. [ABSTRACT FROM AUTHOR]

Categories of resistance to greenbug, Schizaphis graminum (Rondani), biotype I, were determined in goatgrass, Aegilops tauschii (Coss.) Schmal., accession 1675 (resistant donor parent), ‘Wichita’ wheat, Triticum aestivum L., (susceptible parent), and an Ae. tauschii-derived resistant line, ‘97-85-3’. Antibiosis was assessed using the intrinsic rate of increase (rm) of greenbugs confined to each of the three genotypes. Neither parent nor the resistant progeny expressed antibiosis. Mean rm values for greenbug I on Wichita (0.0956), and Ae. tauschii (0.10543) were not significantly different. Mean rm values for Wichita and 97-85-3 were also not significantly different. Antixenosis was determined by allowing aphids a choice to feed on plants of each of the three genotypes. Ae. tauschii 1675 exhibited antixenosis, but this resistance was not inherited and expressed in 97-85-3. In experiments comparing Wichita and Ae. tauschii 1675, greenbug I population distributions were not significantly different on Wichita at 24 h, but were shifted toward Wichita at 48 h. In the second antixenosis experiment, there were no significant differences in greenbug I population distributions on 97-85-3 or Wichita at 24 or 48 h. When all three lines were compared, there were no significant differences in greenbug biotype I populations at 24 or 48 h after infestation. Comparisons of proportional dry plant weight loss (DWT) and SPAD meter readings were used to determine tolerance to greenbug I feeding. Ae. tauschii 1675 and 97-85-3 were highly tolerant compared with Wichita. Infested and uninfested Ae. tauschii 1675 DWT was nonsignificant, and infested Wichita plants weighed significantly less than uninfested plants. When Wichita and 97-85-3 were contrasted, DWT of infested and uninfested Wichita plants were significantly different, but those of 97-85-3 were not. Mean percent leaf chlorophyll losses for the three genotypes, as measured by the SPAD chlorophyll meter, were as follows: Wichita = 65%; Ae. tauschii 1675 = 25%; and 97-85-3 = 39%. Percent leaf chlorophyll losses caused by greenbug feeding was significantly different in comparisons between Wichita and Ae. tauschii 1675, and comparisons between Wichita and 97-85-3, although feeding damage was not significantly different in comparisons between Ae. tauschii 1675 and 97-85-3. These data provided further evidence of the expression of tolerance to greenbug feeding in Ae. tauschii 1675 and 97-85-3. [ABSTRACT FROM PUBLISHER]

The rate of loss of infectivity for greenbugs, Schizaphis graminum Rondani, carrying maize dwarf mosaic virus (MDMV) was similar for adult apterae and alates regardless of the acquisition access period (AAP) given. The rate was rapid during the first 2 hours post-acquisition and then decreased. Weighted least squares linear regression of log % transmission were plotted against retention-time intervals to obtain regression slopes for each of the AAP groups tested (1, 3, 17, and 30 min). There were no significant differences among the regression slopes using F-test comparisons. In serial transmission trials, transmission frequencies among aphids allowed 1-min or 30-min timed acquisition probes followed by 30-sec or 1-min timed inoculation probes were not significantly different when statistical tests that quantify categorical data were applied. This suggests little difference in the amount of virus obtained by these groups of aphids. Transmission and retention data are discussed in relation to the two principal theories of the mechanism of non-persistent virus transmission by aphids. Transmission of MDMV by the greenbug by a two mechanism process (stylet-borne and ingestion-egestion) is not confirmed. [ABSTRACT FROM AUTHOR]

The reproductive potential of insecticide-resistant green bugs, Schizo phis germanium (Ronni), was investigated. Several clones each of the 3 est erase phenotypes associated with insecticide resistance and designated susceptible (S), pattern 1 (R1), and pattern 2 (R2) collected from Colorado, Kansas, and Texas were induced into the sexual phase (when possible) and inbred or out crossed to S clones to identify clones which may be used in inheritance studies. Most of the R2 clones could not be induced into the sexual cycle; only oviparae were produced from clones that entered the sexual phase. Seven of 10 of the S clones, 5 of 10 of the R1 clones, and 6 of 30 R2 clones tested entered the sexual cycle. Three green bug clones, one each of S, RI, and R2, were induced into the sexual cycle and inbred or crossbred to determine their reproductive capacity. Crosses with susceptible females averaged the highest number of eggs per cross, followed by RI females, and then by R2 females. This study further substantiates that fecundity in the green bug is variable, and suggests that insecticide resistance may be associated with reduced fecundity in certain insecticide-resistant green bug clones. [ABSTRACT FROM PUBLISHER]

Switchgrass (Panicum virgatum L.) is an important crop for biofuel production but it also serves as host for greenbugs (Schizaphis graminum Rondani; GB). Although transcriptomic studies have been done to infer the molecular mechanisms of plant defense against GB, little is known about the effect of GB infestation on the switchgrass protein expression and phosphorylation regulation. The global response of the switchgrass cultivar Summer proteome and phosphoproteome was monitored by label-free proteomics shotgun in GB-infested and uninfested control plants at 10 days post infestation. Peptides matching a total of 3,594 proteins were identified and 429 were differentially expressed proteins in GB-infested plants relative to uninfested control plants. Among these, 291 and 138 were up and downregulated by GB infestation, respectively. Phosphoproteome analysis identified 310 differentially phosphorylated proteins (DP) from 350 phosphopeptides with a total of 399 phosphorylated sites. These phosphopeptides had more serine phosphorylated residues (79%), compared to threonine phosphorylated sites (21%). Overall, KEGG pathway analysis revealed that GB feeding led to the enriched accumulation of proteins important for biosynthesis of plant defense secondary metabolites and repressed the accumulation of proteins involved in photosynthesis. Interestingly, defense modulators such as terpene synthase, papain-like cysteine protease, serine carboxypeptidase, and lipoxygenase2 were upregulated at the proteome level, corroborating previously published transcriptomic data. [ABSTRACT FROM AUTHOR]