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2. Control of rhizomania in sugar beet—A success story made possible by resistance breeding.

Author

Benjes, Kristin, Varrelmann, Mark, and Liebe, Sebastian

Subjects
VIRAL mutation, MOLECULAR cloning, PHYTOPLASMAS, FARMERS, BEETS
Abstract

The economic success of sugar beet production depends largely on the control of various pathogens and pests. Beet necrotic yellow vein virus (BNYVV) has historically been a major threat to sugar beet growers because of the high yield losses and the fact that the virus is transmitted by a soilborne protist vector that cannot be controlled. Resistance breeding began after the disease was first described in 1959 and led to the identification of two monogenic resistance genes. Rz1 was the first resistance gene to be introduced into all varieties, enabling sugar beet production under high disease pressure. However, the widespread use of a single resistance gene resulted in high selection pressure on the virus population. As a result, resistance‐breaking of Rz1 was first reported in the early 2000s in the United States and later in many other countries. The mechanism of resistance‐breaking is based on mutations in the viral pathogenicity factor P25 and the presence of an additional RNA5 species. The second resistance gene being used in breeding is Rz2, which is based on a different resistance mechanism and is highly effective at sites where Rz1 has been overcome by the virus. In addition, Rz2 was the first rhizomania resistance gene to be cloned, and the triple gene block I of BNYVV was identified as the corresponding avirulence gene. This article highlights that resistance breeding has been key to the control of rhizomania, but history also shows that re‐emergence of the disease due to resistance‐breaking remains a permanent threat. [ABSTRACT FROM AUTHOR]

Published
2024
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6. Intermolecular base‐pairing interactions, a unique topology and exoribonuclease‐resistant noncoding RNAs drive formation of viral chimeric RNAs in plants.

Author

Nemes, Katalin, Gil, Jose F., Liebe, Sebastian, Mansi, Mansi, Poimenopoulou, Efstratia, Lennefors, Britt‐Louise, Varrelmann, Mark, and Savenkov, Eugene I.

Subjects
NON-coding RNA, PLANT RNA, INTERMOLECULAR interactions, HAIRPIN (Genetics), SITE-specific mutagenesis, CHIMERIC proteins
Abstract

Summary: In plants, exoribonuclease‐resistant RNAs (xrRNAs) are produced by many viruses. Whereas xrRNAs contribute to the pathogenicity of these viruses, the role of xrRNAs in the virus infectious cycle remains elusive.Here, we show that xrRNAs produced by a benyvirus (a multipartite RNA virus with four genomic segments) in plants are involved in the formation of monocistronic coat protein (CP)‐encoding chimeric RNAs. Naturally occurring chimeric RNAs, we discovered, are composed of 5′‐end of RNA 2 and 3′‐end of either RNA 3 or RNA 4 bearing conservative exoribonuclease‐resistant 'coremin' region.Using computational tools and site‐directed mutagenesis, we show that de novo formation of chimeric RNAs requires intermolecular base‐pairing interaction between 'coremin' and 3′‐proximal part of the CP gene of RNA 2 as well as a stem‐loop structure immediately adjacent to the CP gene. Moreover, knockdown of the expression of the XRN4 gene, encoding 5′→3′ exoribonuclease, inhibits biogenesis of both xrRNAs and chimeric RNAs.Our findings suggest a novel mechanism involving a unique tropology of the intermolecular base‐pairing complex between xrRNAs and RNA2 to promote formation of chimeric RNAs in plants. XrRNAs, essential for chimeric RNA biogenesis, are generated through the action of cytoplasmic Xrn 4 5′→3′ exoribonuclease conserved in all plant species. [ABSTRACT FROM AUTHOR]

Published
2024
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7. The arms race between beet necrotic yellow vein virus and host resistance in sugar beet

Author

Liebe, Sebastian, Maiss, Edgar, Varrelmann, Mark, Liebe, Sebastian, Maiss, Edgar, and Varrelmann, Mark

Abstract

Beet necrotic yellow vein virus (BNYVV) causes rhizomania disease in sugar beet (Beta vulgaris), which is controlled since more than two decades by cultivars harboring the Rz1 resistance gene. The development of resistance-breaking strains has been favored by a high selection pressure on the soil-borne virus population. Resistance-breaking is associated with mutations at amino acid positions 67-70 (tetrad) in the RNA3 encoded pathogenicity factor P25 and the presence of an additional RNA component (RNA5). However, natural BNYVV populations are highly diverse making investigations on the resistance-breaking mechanism rather difficult. Therefore, we applied a reverse genetic system for BNYVV (A type) to study Rz1 resistance-breaking by direct agroinoculation of sugar beet seedlings. The bioassay allowed a clear discrimination between susceptible and Rz1 resistant plants already four weeks after infection, and resistance-breaking was independent of the sugar beet Rz1 genotype. A comprehensive screen of natural tetrads for resistance-breaking revealed several new mutations allowing BNYVV to overcome Rz1. The supplementation of an additional RNA5 encoding the pathogenicity factor P26 allowed virus accumulation in the Rz1 genotype independent of the P25 tetrad. This suggests the presence of two distinct resistance-breaking mechanisms allowing BNYVV to overcome Rz1. Finally, we showed that the resistance-breaking effect of the tetrad and the RNA5 is specific to Rz1 and has no effect on the stability of the second resistance gene Rz2. Consequently, double resistant cultivars (Rz1+Rz2) should provide effective control of Rz1 resistance-breaking strains. Our study highlights the flexibility of the viral genome allowing BNYVV to overcome host resistance, which underlines the need for a continuous search for alternative resistance genes.

Published
2023

13. Timing of fungicide application against Cercosporaleaf spot disease based on aerial spore dispersal of Cercospora beticolain sugar beet

Author

Liebe, Sebastian, Imbusch, Frederike, Erven, Tobias, and Varrelmann, Mark

Abstract

Cercospora leaf spot is an important foliar disease in sugar beet caused by Cercospora beticola. Tolerant cultivars are available, but application of fungicides is still mandatory for disease control. The timing of the fungicide application is crucial as it determines the outcome of disease epidemiology. A disease incidence (DI) of 5% is widely used as a threshold for fungicide application. Recently a method was developed that allows the quantification of aerial spore dispersal of C. beticolafor measuring spore flight intensity. It was aimed in this study to prove if fungicide application based on spore flight might improve disease control compared to DI. In a field trial with artificial inoculation, a single fungicide application at the onset of spore flight slowed down disease development as indicated by reduced disease severity and aerial spore dispersal. However, it did not provide sufficient control in terms of sugar yield. Only a second fungicide application based on spore flight detection achieved an efficacy similar to two fungicide applications based on DI. In contrast, a single fungicide application based either on spore flight or DI was sufficient in two on-farm trials under natural infection with moderate disease pressure. This highlights the necessity of an early timed first fungicide application followed by a second application under high disease pressure induced by artificial inoculation. Although fungicide application based on spore flight achieved sufficient control success in on-farm trials, it seems not to improve disease control compared to the usage of DI as threshold.

Published
2023
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16. Application of a Reverse Genetic System for Beet Necrotic Yellow Vein Virus to Study Rz1 Resistance Response in Sugar Beet

Author

Liebe, Sebastian, Wibberg, Daniel, Maiss, Edgar, Varrelmann, Mark, Liebe, Sebastian, Wibberg, Daniel, Maiss, Edgar, and Varrelmann, Mark

Abstract

Beet necrotic yellow vein virus (BNYVV) is causal agent of rhizomania disease, which is the most devastating viral disease in sugar beet production leading to a dramatic reduction in beet yield and sugar content. The virus is transmitted by the ubiquitous distributed soil-borne plasmodiophoromycete Polymyxa betae that infects the root tissue of young sugar beet plants. Rz1 is the major resistance gene widely used in most sugar beet varieties to control BNYVV. The strong selection pressure on the virus population promoted the development of strains that can overcome Rz1 resistance. Resistance-breaking has been associated with mutations in the RNA3-encoded pathogenicity factor P25 at amino acid positions 67–70 (tetrad) as well as with the presence of an additional RNA component (RNA5). However, respective studies investigating the resistance-breaking mechanism by a reverse genetic system are rather scarce. Therefore, we studied Rz1 resistance-breaking in sugar beet using a recently developed infectious clone of BNYVV A-type. A vector free infection system for the inoculation of young sugar beet seedlings was established. This assay allowed a clear separation between a susceptible and a Rz1 resistant genotype by measuring the virus content in lateral roots at 52 dpi. However, mechanical inoculation of sugar beet leaves led to the occurrence of genotype independent local lesions, suggesting that Rz1 mediates a root specific resistance toward BNYVV that is not active in leaves. Mutation analysis demonstrated that different motifs within the P25 tetrad enable increased virus replication in roots of the resistant genotype. The resistance-breaking ability was further confirmed by the visualization of BNYVV in lateral roots and leaves using a fluorescent-labeled complementary DNA clone of RNA2. Apart from that, reassortment experiments evidenced that RNA5 enables Rz1 resistance-breaking independent of the P25 tetrad motif. Finally, we could identify a new resistance-breaking

Published
2020

20. Einfluss von blattaktiven Herbizidwirkstoffen auf die Unkrautkontrolle in Zuckerrüben.

Author

Laufer, Daniel and Liebe, Sebastian

Subjects
RAPESEED, WEED control, PLANT protection, VOLUNTEERS, WEEDS, VOLUNTEER service, HERBICIDES, SUGAR beets
Abstract

Copyright of Julius-Kühn-Archiv is the property of Julius Kuehn Institut and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2024
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23. Impact of Environment, Genotype and Storage Temperature on the Microbial Community, Rot Development and Root Quality of Stored Sugar Beets

Author

Liebe, Sebastian and Liebe, Sebastian

Abstract

Zuckerrüben können während der Lagerung von verschiedenen Fäulniserregern befallen werden, die erhebliche Zuckerverluste verursachen und die Verarbeitungsqualität in der Zuckerfabrik verschlechtern. Bisher ist nur wenig über das Mikroorganismenspektrum und Faktoren, die dessen Zusammensetzung bestimmen, bekannt. Ziel der vorliegenden Arbeit war es, den Einfluss von Genotyp, Anbauumwelt und Lagerungstemperatur auf die mikrobielle Besiedlung von Zuckerrüben während der Lagerung zu beschreiben. Die Zusammensetzung des Mikrobioms gelagerter Zuckerrüben wurde mit Hilfe eines Microarray basierten Nachweisverfahrens und der Hochdurchsatzsequenzierung bestimmt. In mehreren unabhängigen Lagerungsversuchen unter kontrollierten Bedingungen konnte erstmalig gezeigt werden, dass die mikrobielle Besiedlung und damit verbunden das Auftreten von Lagerfäule entscheidend durch die Lagerungstemperatur und die Anbauumwelt beeinflusst wird. Signifikante Genotypeffekte, die auf eine Resistenz gegenüber Fäulniserregern hindeuten, ließen sich ebenso reproduzierbar nachweisen. Das Speziesspektrum wurde dominiert von den Arten Botrytis cinerea, Fusarium spp. und Penicillium spp. Die mikrobielle Besiedlung der Zuckerrüben hatte eine Reduktion des Zuckerertrages und eine Verschlechterung der Verarbeitungsqualität zur Folge. Bedeutung und Konsequenz der Ergebnisse für die praktische Zuckerrübenlagerung werden diskutiert.

Published
2016

24. Biological properties of Beet soil-borne mosaic virus and Beet necrotic yellow vein virus cDNA clones produced by isothermal in vitro recombination: Insights for reassortant appearance

Author

Laufer, Marlene, primary, Mohammad, Hamza, additional, Maiss, Edgar, additional, Richert-Pöggeler, Katja, additional, Dall'Ara, Mattia, additional, Ratti, Claudio, additional, Gilmer, David, additional, Liebe, Sebastian, additional, and Varrelmann, Mark, additional

Published
2018
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33. Biological properties of Beet soil-borne mosaic virus and Beet necrotic yellow vein virus cDNA clones produced by isothermal in vitro recombination: Insights for reassortant appearance

Author

Claudio Ratti, Edgar Maiss, Katja R. Richert-Pöggeler, Marlene Laufer, Hamza Mohammad, Sebastian Liebe, Mark Varrelmann, Mattia Dall'Ara, David Gilmer, Institut de biologie moléculaire des plantes (IBMP), Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA), Laufer, Marlene, Mohammad, Hamza, Maiss, Edgar, Richert-Pöggeler, Katja, Dall'Ara, Mattia, Ratti, Claudio, Gilmer, David, Liebe, Sebastian, and Varrelmann, Mark

Subjects
0301 basic medicine, Gene Expression Regulation, Viral, Gibson assembly, DNA, Complementary, viruses, Reassortment, Nicotiana benthamiana, Infectious cDNA full-length clone, Benyvirus, Polymyxa betae, Plant Viruses, 03 medical and health sciences, Mosaic Viruses, Complementary DNA, Virology, Beet necrotic yellow vein virus, [SDV.BV]Life Sciences [q-bio]/Vegetal Biology, RNA Viruses, Cloning, Molecular, Beet necrotic yellow vein viru, Genomic organization, Plant Diseases, Mosaic virus, biology, food and beverages, Beet soil-borne mosaic viru, biology.organism_classification, 3. Good health, Plant Leaves, 030104 developmental biology, Benyviridae, RNA, Viral, Beta vulgaris, Reassortant Viruses
Abstract

Two members of the Benyviridae family and genus Benyvirus, Beet soil-borne mosaic virus (BSBMV) and Beet necrotic yellow vein virus (BNYVV), possess identical genome organization, host range and high sequence similarity; they infect Beta vulgaris with variable symptom expression. In the US, mixed infections are described with limited information about viral interactions. Vectors suitable for agroinoculation of all genome components of both viruses were constructed by isothermal in vitro recombination. All 35S promoter-driven cDNA clones allowed production of recombinant viruses competent for Nicotiana benthamiana and Beta macrocarpa systemic infection and Polymyxa betae transmission and were compared to available BNYVV B-type clone. BNYVV and BSBMV RNA1 + 2 reassortants were viable and spread long-distance in N. benthamiana with symptoms dependent on the BNYVV type. Small genomic RNAs were exchangeable and systemically infected B. macrocarpa. These infectious clones represent a powerful tool for the identification of specific molecular host-pathogen determinants.

Published
2017

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