Occurrence Spread And Pathogenicity Of Different Beet Necrotic Yellow Vein Virus Bnyvv Isolates

Two members of the Benyviridae family, Beet soil borne mosaic virus (BSBMV) and Beet necrotic yellow vein virus (BNYVV), possess identical genome organisation, host range and high sequence similarity. To understand functional differences in molecular biology, pathogenicity mechanisms, symptom expression as well as interaction with the host and between viral species, a reverse genetic system represents a prerequisite. Infectious cDNA full length clones of both viruses were constructed by isothermal in vitro recombination. Artificial formation of BNYVV and BSBMV RNA1+2 reassortants were viable and spread long distance in N. benthamiana. Small genomic RNAs were exchangeable and systemically infected B. macrocarpa. Moreover, fluorescence labelled full length clones were achieved by replacing a part of the RNA2 encoded coat protein read through domain. Co infection experiments with labelled BSBMV and BNYVV showed that both viruses remained spatially separated after N. benthamiana agroinoculation. In contrast, a mixture of BSBMV with an unrelated virus resulted in no co infection exclusion. In super infection experiments, BSBMV and BNYVV were unable to establish a secondary infection in plants that were previously infected with BNYVV or BSBMV. In addition, a virus induced gene silencing (VIGS) system was developed. Both viruses were equipped with fragments of the magnesium chelatase subunit H and phytoene desaturase genes. Silencing phenotypes in N. benthamiana induced by both target genes, were comparable to those described in the literature.

The knowledge of ecology and epidemiology of rhizomania is particularly useful to understand the means and practices able to limit or avoid its further diffusion. Some promising methods of biological control using coexisting and non-pathogenic organisms could potentially help improve the action of the not completely effective genetic resistances. This integrated protection would be valuable, especially in the even more frequent development of resistance–breaking strains in the BNYVV, where the known types of resistance, alone or in combination, seem to have lost part of their original ability to protect the crop. Therefore, further efforts will be needed to discover new traits likely still present in the wild species of the genus Beta. The availability of large collections of germplasm stored in the International Beta gene-banks should ensure the enhanced efficiency of genetic resistance by means of conventional and marker-assisted selection methods. Some almost immune transgenic varieties seem already to be waiting for release where and when it will be possible. The introduction chapter describes briefly the sugar beet crop, the more common diseases, and the damage caused by rhizomania. The following chapters discuss biological properties of the causal virus, BNYVV, and its vector, Polymyxa betae, and their interactions with the environment and the host-plant. In particular, the great advances in research of the molecular biology of BNYVV should be noteworthy, which have been established by a wide range of the most modern methods. Recent work focused on the genetic diversity and evolution of BNYVV is moving forward our understanding of the dramatic worldwide epidemics of rhizomania. Newly developed molecular techniques also lead to practical applications, such as quantification of inoculum in ecological and epidemiological research.

Fungi enjoy great popularity in pharmaceutical, agricultural, and biotechnological applications. Recent advances in the decipherment of whole fungal genomes promise an acceleration of these trends. This timely book links scientists from different parts of the world who are interested in the molecular identification of fungi combined with the exploration of the fungal biodiversity in different ecosystems. It provides a compendium for scientists who rely on a rapid and reliable detection of fungal specimens in environmental as well as clinical resources in order to ensure the benefit of industrial and clinical applications. Chapters focus on the opportunities and limits of the molecular marker-mediated identification of fungi. Various methods, procedures and strategies are outlined. Furthermore, the book offers an update of the current progress in the development of fungal molecular techniques, and draws attention to potential and associated problems, as well as integrating theory and practice.

Concern about the environmental consequences of the widespread use of pesticides has increased, and evidence of pesticide-resistant virus vectors have continued to emerge. This volume presents a timely survey of the mechanisms of plant resistance and examines current developments in breeding for resistance, with particular emphasis on advances in genetic engineering which allow for the incorporation of viral genetic material into plants. Discusses the mechanisms of innate resistance in strains of tobacco, tomato, and cowpea; various aspects of induced resistance, including the characterization and roles of the pathogenesis-related proteins; antiviral substances and their comparison with interferon; and cross-protection between plant virus strains. Also presents several papers which evaluate the status of genetic engineering as it relates to breeding resistant plants. Among these are discussions of the potential use of plant viruses as gene vectors, gene coding for viral coat protein, satellite RNA, and antisense RNA, and practical issues such as the durability of resistant crop plants in the field.

Along the undisturbed shores, especially of the Mediterranean Sea and the European North Atlantic Ocean, is a quite widespread plant called Beta maritima by botanists, or more commonly sea beet. Nothing, for the inexperienced observer's eye, distinguishes it from surrounding wild vegetation. Despite its inconspicuous and nearly invisible flowers, the plant has had and will have invaluable economic and scientific importance. Indeed, according to Linnè, it is considered "the progenitor of the beet crops possibly born from Beta maritima in some foreign country". Recent molecular research confirmed this lineage. Selection applied after domestication has created many cultivated types with different destinations. The wild plant always has been harvested and used both for food and as a medicinal herb. Sea beet crosses easily with the cultivated types. This facilitates the transmission of genetic traits lost during domestication, which selection processes aimed only at features immediately useful to farmers and consumers may have depleted. Indeed, as with several crop wild relatives, Beta maritima has been successfully used to improve cultivated beet’s genetic resistances against many diseases and pests. In fact, sugar beet cultivation currently would be impossible in many countries without the recovery of traits preserved in the wild germplasm. Dr. Enrico Biancardi graduated from Bologna University. From 1977 until 2009, he was involved in sugar beet breeding activity by the Istituto Sperimentale per le Colture Industriali (ISCI) formerly Stazione Sperimentale di Bieticoltura (Rovigo, Italy), where he released rhizomania and cercospora resistant germplasm and collected seeds of Mediterranean sea beet populations as a genetic resource for breeding and ex situ conservation. Retired since 2009, he still collaborates with several working breeders, in particular, at the USDA Agricultural Research Stations, at the Chinese Academy of Agricultural Science (CAAS), and at the Athens University (AUA). He has edited books, books chapters and authored more than 150 papers. Dr. Lee Panella is a plant breeder and geneticist with the USDA-ARS at Fort Collins, Colorado. He earned his B.S. in Crop and Soil Science from Michigan State University, an M.S. in Plant Breeding from Texas A&M University, and a Ph.D. in genetics from the University of California at Davis. His research focus is developing disease resistant germplasm using sugar beet wild relatives. He is chairman of the USDA-ARS Sugar Beet Crop Germplasm Committee and has collected and worked extensively with sea beet. Dr. Robert T. Lewellen was raised on a ranch in Eastern Oregon and obtained a B.S. in Crop Science from Oregon State University followed by a Ph.D. from Montana State University in Genetics. From 1966 to 2008 he was a research geneticist for the USDA-ARS at Salinas, California, where he studied the genetics of sugar beet and as a plant breeder, often used sea beet as a genetic source to produce many pest and disease resistant sugar beet germplasm and parental lines, while authoring more than 100 publications.

Plants, fungi, and viruses were among the first biological objects studied with an electron microscope. One of the two first instruments built by Siemens was used by Helmut Ruska, a brother of Ernst Ruska, the pioneer in constructing electron microscopes. H. Ruska published numerous papers on different biological objects in 1939. In one of these, the pictures by G. A. Kausche, E. Pfankuch, and H. Ruska of tobacco mosaic virus opened a new age in microscopy. The main problem was then as it still is today, to obtain an appropriate preparation of the specimen for observation in the electron microscope. Beam damage and specimen thickness were the first obstacles to be met. L. Marton in Brussels not only built his own instrument, but also made considerable progress in specimen preparation by introducing the impregnation of samples with heavy metals to obtain useful contrast. His pictures of the bird nest orchid root impregnated with osmium were revolutionary when published in 1934. It is not the place here to recall the different techniques which were developed in the subsequent years to attain the modern knowledge on the fine structure of plant cells and of different plant pathogens. The tremendous progress obtained with tobacco mosaic virus is reflected in the chapter by M. Wurtz on the fine structure of viruses in this Volume. New cytochemical and immunological techniques considerably surpass the morphological information obtained from the pathogens, especially at the host-parasite interface.