The Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) – a danger to cultivation of corn in Europe

Weltweit gesehen zählt der Westliche Maiswurzelbohrer (Diabrotica virgifera virgifera LeConte), der seit 2007 erstmalig im Süden Deutschlands aufgetreten ist, zu den wirtschaftlich bedeutendsten Maisschädlingen im intensiven Maisanbau. Er ist als Quarantäneschädling eingestuft und unterliegt entsprechenden Quarantänemaßnahmen (Meldepflicht, Ausrottungs- bzw. Eingrenzungsmaßnahmen). In den USA und Kanada verursacht er jährlich Schäden durch Ernteausfälle und Pflanzenschutzaufwendungen von mehr als einer Milliarde US-Dollar. Vor dem Hintergrund zunehmender Einschleppungen und der Etablierung der Diabrotica-Populationen in Deutschland werden zunehmend wirksame Maßnahmen benötigt, die eine weitere Ausbreitung verhindern und den Maisanbau in den betroffenen Gebieten weiterhin ermöglichen. Vorbeugende, ackerbauliche Maßnahmen, der Einsatz von chemischen Parametern wie insektizide Granulate zur Saat, Saatgutbeizen und Insektizidspritzungen, die biologische Regulierung von Diabrotica sowie Züchtungsfortschritte sind mögliche Wege, dem Maiswurzelbohrer hierzulande Einhalt zu gebieten. 2008 wurde dazu ein umfangreiches Forschungsprogramm des Bundesministeriums für Ernährung, Landwirtschaft und Verbraucherschutz (BMELV, Federführung JKI) in Absprache und in Co-Finanzierung mit dem Freistaat Bayern (Federführung LfL Bayern) ausgearbeitet, welches zum Ziel hat, vertiefende Kenntnisse zur nachhaltigen Bekämpfung von Diabrotica zu gewinnen und wissenschaftliche Empfehlungen hinsichtlich erforderlicher Eingrenzungsmaßnahmen zu erarbeiten.The Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) is economically the most important corn pest worldwide. Its first appearance in Southern Ger­many in 2007 was followed by further infestations in additional locations in the following years. Control measures on Diabrotica being a quarantine pest in Europe are carried out in Germany. In the USA and in Canada the Western Corn Rootworm causes annual losses of about one billion USD due to yield loss and expenditure on pest control. Preventive and agronomic controls, application of soil insecticides (granulates) and seed treatments, application of insecticides, biological regulation and breeding improvements will help to contain the Western Corn Rootworm. In order to improve and adapt control measures for Diabrotica including chemical and non chemical options for German conditions two substantial research programs were generated in cooperation of the German agricultural ministry (responsibility JKI) with the Free State of Bavaria (responsibility LfL)

AB-QTL analysis in winter wheat: II. Genetic analysis of seedling and field resistance against leaf rust in a wheat advanced backcross population

The present study aimed to localize exotic quantitative trait locus (QTL) alleles for the improvement of leaf rust (P.triticina) resistance in an advanced backcross (AB) population, B22, which is derived from a cross between the winter wheat cultivar Batis (Triticumaestivum) and the synthetic wheat accession Syn022L. The latter was developed from hybridization of T.turgidum ssp. dicoccoides and T.tauschii. Altogether, 250 BC2F3 lines of B22 were assessed for seedling resistance against the leaf rust isolate 77WxR under controlled conditions. In addition, field resistance against leaf rust was evaluated by assessing symptom severity under natural infestation across multiple environments. Simultaneously, population B22 was genotyped with a total of 97 SSR markers, distributed over the wheat A, B and D genomes. The phenotype and genotype data were subjected to QTL analysis by applying a 3-factorial mixed model analysis of variance including the marker genotype as a fixed effect and the environments, the lines and the marker by environment interactions as random effects. The QTL analysis revealed six putative QTLs for seedling resistance and seven for field resistance. For seedling resistance, the effects of exotic QTL alleles improved resistance at all detected loci. The maximum decrease of disease symptoms (−46.3%) was associated with marker locus Xbarc149 on chromosome 1D. For field resistance, two loci had stable main effects across environments and five loci exhibited marker by environment interaction effects. The strongest effects were detected at marker locus Xbarc149 on chromosome 1D, at which the exotic allele decreased seedling symptoms by 46.3% and field symptoms by 43.6%, respectively. Some of the detected QTLs co-localized with known resistance genes, while others appear to be as novel resistance loci. Our findings indicate, that the exotic wheat accession Syn022L may be useful for the improvement of leaf rust resistance in cultivated wheat

A subset of chemosensory genes differs between two populations of a specialized leaf beetle after host plant shift

Due to its fundamental role in shaping host selection behavior, we have analyzed thechemosensory repertoire of Chrysomela lapponica. This specialized leaf beetleevolved distinct populations which shifted from the ancestral host plant, willow (Salixsp. Salicaceae), to birch (Betula rotundifolia, Betulaceae). We identified 114 chemosensory candidate genes in adult C. lapponica: 41 olfactory receptors (ORs), eightgustatory receptors, 17 ionotropic receptors, four sensory neuron membrane proteins, 32 odorant binding proteins (OBPs), and 12 chemosensory proteins (CSP) byRNA-seq. Differential expression analyses in the antennae revealed significant upregulation of one minus-C OBP (ClapOBP27) and one CSP (ClapCSP12) in the willowfeeders. In contrast, one OR (ClapOR17), four minus-C OBPs (ClapOBP02, 07, 13, 20),and one plus-C OBP (ClapOBP32) were significantly upregulated in birch feeders.The differential expression pattern in the legs was more complex. To narrow downputative ligands acting as cues for host discrimination, the relative abundanceand diversity of volatiles of the two host plant species were analyzed. In additionto salicylaldehyde (willow-specific), both plant species differed mainly in theiremission rate of terpenoids such as (E,E)-a-farnesene (high in willow) or4,8-dimethylnona-1,3,7-triene (high in birch). Qualitatively, the volatiles were similarbetween willow and birch leaves constituting an "olfactory bridge" for the beetles.Subsequent structural modeling of the three most differentially expressed OBPs anddocking studies using 22 host volatiles indicated that ligands bind with varying affinity. We suggest that the evolution of particularly minus-C OBPs and ORs in C. lapponica facilitated its host plant shift via chemosensation of the phytochemicals frombirch as novel host plant.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Barley yellow dwarf virus Infection Leads to Higher Chemical Defense Signals and Lower Electrophysiological Reactions in Susceptible Compared to Tolerant Barley Genotypes

Barley yellow dwarf virus (BYDV) is a phloem limited virus that is persistently transmitted by aphids. Due to huge yield losses in agriculture, the virus is of high economic relevance. Since the control of the virus itself is not possible, tolerant barley genotypes are considered as the most effective approach to avoid yield losses. Although several genes and quantitative trait loci are known and used in barley breeding for virus tolerance, little is known about molecular and physiological backgrounds of this trait. Therefore, we compared the anatomy and early defence responses of a virus susceptible to those of a virus-tolerant cultivar. One of the very early defence responses is the transmission of electrophysiological reactions. Electrophysiological reactions to BYDV infection might differ between susceptible and tolerant cultivars, since BYDV causes disintegration of sieve elements in susceptible cultivars. The structure of vascular bundles, xylem vessels and sieve elements was examined using microscopy. All three were significantly decreased in size in infected susceptible plants where the virus causes disintegration of sieve elements. This could be associated with an uncontrolled ion exchange between the sieve-element lumen and apoplast. Further, a potential reduced electrophysiological isolation would negatively affect the propagation of electrophysiological reactions. To test the influence of BYDV infection on electrophysiological reactions, electropotential waves (EPWs) induced by leaf-tip burning were recorded using aphids as bioelectrodes. EPWs in infected susceptible plants disappeared already after 10 cm in contrast to those in healthy susceptible or infected tolerant or healthy tolerant plants. Another early plant defence reaction is an increase in reactive oxygen species (ROS). Using a fluorescent dye, we found a significant increase in ROS content in infected susceptible plants but not in infected tolerant plants. Similar results were found for the phytohormones abscisic acid and three jasmonates. Salicylic acid levels were generally higher after BYDV infection compared to uninfected plants. Heat stimulation caused an increase in jasmonates. By shedding light on the plant defence mechanisms against BYDV, this study, provides further knowledge for breeding viral tolerant plants

Data_Sheet_1.DOCX

<p>Barley yellow dwarf virus (BYDV) is a phloem limited virus that is persistently transmitted by aphids. Due to huge yield losses in agriculture, the virus is of high economic relevance. Since the control of the virus itself is not possible, tolerant barley genotypes are considered as the most effective approach to avoid yield losses. Although several genes and quantitative trait loci are known and used in barley breeding for virus tolerance, little is known about molecular and physiological backgrounds of this trait. Therefore, we compared the anatomy and early defense responses of a virus susceptible to those of a virus-tolerant cultivar. One of the very early defense responses is the transmission of electrophysiological reactions. Electrophysiological reactions to BYDV infection might differ between susceptible and tolerant cultivars, since BYDV causes disintegration of sieve elements in susceptible cultivars. The structure of vascular bundles, xylem vessels and sieve elements was examined using microscopy. All three were significantly decreased in size in infected susceptible plants where the virus causes disintegration of sieve elements. This could be associated with an uncontrolled ion exchange between the sieve-element lumen and apoplast. Further, a reduced electrophysiological isolation would negatively affect the propagation of electrophysiological reactions. To test the influence of BYDV infection on electrophysiological reactions, electropotential waves (EPWs) induced by leaf-tip burning were recorded using aphids as bioelectrodes. EPWs in infected susceptible plants disappeared already after 10 cm in contrast to those in healthy susceptible or infected tolerant or healthy tolerant plants. Another early plant defense reaction is an increase in reactive oxygen species (ROS). Using a fluorescent dye, we found a significant increase in ROS content in infected susceptible plants but not in infected tolerant plants. Similar results were found for the phytohormones abscisic acid and three jasmonates. Salicylic acid levels were generally higher after BYDV infection compared to uninfected plants. Heat stimulation caused an increase in jasmonates. By shedding light on the plant defense mechanisms against BYDV, this study, provides further knowledge for breeding virus tolerant plants.</p

Image_1.TIF

<p>Barley yellow dwarf virus (BYDV) is a phloem limited virus that is persistently transmitted by aphids. Due to huge yield losses in agriculture, the virus is of high economic relevance. Since the control of the virus itself is not possible, tolerant barley genotypes are considered as the most effective approach to avoid yield losses. Although several genes and quantitative trait loci are known and used in barley breeding for virus tolerance, little is known about molecular and physiological backgrounds of this trait. Therefore, we compared the anatomy and early defense responses of a virus susceptible to those of a virus-tolerant cultivar. One of the very early defense responses is the transmission of electrophysiological reactions. Electrophysiological reactions to BYDV infection might differ between susceptible and tolerant cultivars, since BYDV causes disintegration of sieve elements in susceptible cultivars. The structure of vascular bundles, xylem vessels and sieve elements was examined using microscopy. All three were significantly decreased in size in infected susceptible plants where the virus causes disintegration of sieve elements. This could be associated with an uncontrolled ion exchange between the sieve-element lumen and apoplast. Further, a reduced electrophysiological isolation would negatively affect the propagation of electrophysiological reactions. To test the influence of BYDV infection on electrophysiological reactions, electropotential waves (EPWs) induced by leaf-tip burning were recorded using aphids as bioelectrodes. EPWs in infected susceptible plants disappeared already after 10 cm in contrast to those in healthy susceptible or infected tolerant or healthy tolerant plants. Another early plant defense reaction is an increase in reactive oxygen species (ROS). Using a fluorescent dye, we found a significant increase in ROS content in infected susceptible plants but not in infected tolerant plants. Similar results were found for the phytohormones abscisic acid and three jasmonates. Salicylic acid levels were generally higher after BYDV infection compared to uninfected plants. Heat stimulation caused an increase in jasmonates. By shedding light on the plant defense mechanisms against BYDV, this study, provides further knowledge for breeding virus tolerant plants.</p

Image_2.TIF

<p>Barley yellow dwarf virus (BYDV) is a phloem limited virus that is persistently transmitted by aphids. Due to huge yield losses in agriculture, the virus is of high economic relevance. Since the control of the virus itself is not possible, tolerant barley genotypes are considered as the most effective approach to avoid yield losses. Although several genes and quantitative trait loci are known and used in barley breeding for virus tolerance, little is known about molecular and physiological backgrounds of this trait. Therefore, we compared the anatomy and early defense responses of a virus susceptible to those of a virus-tolerant cultivar. One of the very early defense responses is the transmission of electrophysiological reactions. Electrophysiological reactions to BYDV infection might differ between susceptible and tolerant cultivars, since BYDV causes disintegration of sieve elements in susceptible cultivars. The structure of vascular bundles, xylem vessels and sieve elements was examined using microscopy. All three were significantly decreased in size in infected susceptible plants where the virus causes disintegration of sieve elements. This could be associated with an uncontrolled ion exchange between the sieve-element lumen and apoplast. Further, a reduced electrophysiological isolation would negatively affect the propagation of electrophysiological reactions. To test the influence of BYDV infection on electrophysiological reactions, electropotential waves (EPWs) induced by leaf-tip burning were recorded using aphids as bioelectrodes. EPWs in infected susceptible plants disappeared already after 10 cm in contrast to those in healthy susceptible or infected tolerant or healthy tolerant plants. Another early plant defense reaction is an increase in reactive oxygen species (ROS). Using a fluorescent dye, we found a significant increase in ROS content in infected susceptible plants but not in infected tolerant plants. Similar results were found for the phytohormones abscisic acid and three jasmonates. Salicylic acid levels were generally higher after BYDV infection compared to uninfected plants. Heat stimulation caused an increase in jasmonates. By shedding light on the plant defense mechanisms against BYDV, this study, provides further knowledge for breeding virus tolerant plants.</p