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- Volume 35, 1997
Annual Review of Phytopathology - Volume 35, 1997
Volume 35, 1997
- Review Articles
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PHILIP HERRIES GREGORY 1907–1986: Pioneer Aerobiologist, Versatile Mycologist
Vol. 35 (1997), pp. 1–14More Less▪ AbstractPhilip Gregory pioneered aerobiology as a topic for research, drawing together inputs from many disciplines to contribute to better understanding of fungal spore dispersal, plant disease epidemiology, and allergy. In childhood, he was interested in natural history and meteorology and frequently suffered from asthma. Initially, he worked with dermatophytes in Winnipeg, where he was influenced by Buller. Returning to Britain, he investigated the epidemiology first of flower bulb diseases and then of potato virus diseases, noting the occurrence of disease gradients in crops. He developed theories of spore dispersal during wartime air-raid duties and published these in his classic paper of 1945. The remainder of his career was largely spent obtaining data in support of his theories of spore dispersal and disease gradients, on understanding splash dispersal, in identifying the cause of farmer's lung disease, and in his retirement, in elucidating the epidemiology of black pod disease of cocoa in Nigeria.
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FRANK LAMSON-SCRIBNER: Botanist and Pioneer Plant Pathologist in the United States
Vol. 35 (1997), pp. 17–26More Less▪ AbstractFrank Lamson-Scribner, in 1885, became the first scientist commissioned by the United States Department of Agriculture with the responsibility to study diseases of economic plants. His innovative approach established the foundation for applied plant pathology at the USDA. In an early international cooperative effort in plant pathology, he detailed the life history of the grape black rot pathogen. His early studies with the Bordeaux mixture introduced the American farmer to the modern era of chemical control. Scribner became the botanist and director of the University of Tennessee Agricultural Experiment Station. He published the first book written on the subject of plant diseases in the United States, and described a new nematode disease of potato. He asserted that the practical value of plant pathology to farmers would only follow meticulous studies of the life history of pathogens.
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BEVERLY T. GALLOWAY: Visionary Administrator
Vol. 35 (1997), pp. 29–43More Less▪ AbstractWith a career that began at the University of Missouri in the early 1880s and culminated at the USDA in the 1930s, Beverly Galloway devoted his life to practical botany and agriculture. He became a driving force in the movement for “New Botany” during a period that stressed an experimental approach as well as new disciplines such as plant pathology. As administrator and scientist, he was arguably the single, most influential figure involved in the early growth and development of plant pathology and the plant sciences generally in the USDA. From assistant mycologist in the Section of Mycology to Chief of the Bureau of Plant Industry to Assistant Secretary of the USDA, Galloway displayed exceptional administrative acumen. His administrative and scientific skills were instrumental in laying the foundations for the science of plant pathology during its formative period in the United States.
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THE IMPACT OF TI-PLASMID-DERIVED GENE VECTORS ON THE STUDY OF THE MECHANISM OF ACTION OF PHYTOHORMONES
Vol. 35 (1997), pp. 45–66More Less▪ AbstractThe molecular basis of tumor formation on dicotyledonous plants by Agrobacterium relies on the transfer to the plant cell of a unique segment of bacterial DNA, the T-DNA. The T-DNA contains genes that are active in the plant cell and encode hormone biosynthetic enzymes, or proteins that deregulate the cell's response to phytohormones. Study of this process has yielded not only knowledge of how alterations in phytohormone homeostasis can affect plant cell growth, but also has provided the essential tools to study phytohormone signaling in transgenic plants. Furthermore, T-DNA insertion into the plant genome forms the basis of gene tagging, a versatile method for isolating genes involved in phytohormone signal transduction and action.
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PRESENTATION OF HETEROLOGOUS PEPTIDES ON PLANT VIRUSES: Genetics, Structure, and Function
J. Johnson, T. Lin, and G. LomonossoffVol. 35 (1997), pp. 67–86More LessCapsid proteins of a number of plant viruses are permissive to genetic modifications in which foreign polypeptides are inserted in exposed loops or at their C termini. Plant viruses with these genetic alterations often grow at wild-type levels, providing gram quantities of modified viruses. Presented polypeptides studied most extensively correspond to antigenic epitopes of animal viruses and in some cases appropriately altered plant viruses generate neutralizing antibodies to the cognate animal virus when the plant virus is used as a vaccine. Structure-based analyses of these animal-plant virus chimeras have led to rational alterations to the presentation in efforts to increase the efficacy of the presented peptide.
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WHITE PINE BLISTER RUST CONTROL IN NORTH AMERICA:
A Case HistoryVol. 35 (1997), pp. 87–109More Less▪ AbstractWhite pine blister rust was introduced into North America at the turn of the twentieth century, threatening valuable white pine resources. Measures to eliminate, contain, or control this disease constitute the most extensive forest disease control effort in time, money, men, and materiel in the history of US forestry. The major thrust was protection of pine stands by eliminating currant and gooseberry (ribes) alternate hosts from within and around these stands. Failures with ribes eradication resulted in application of antibiotic fungicides without adequate testing. These failures, coupled with lower dependence on white pines and reduced need for a large reserve of men for fire fighting, led to sudden termination of the program in 1967. The chronology of events and interactions between agencies and personnel responsible for the program provide an interesting case history and, it is hoped, valuable lessons for the future.
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THE EVOLUTIONARY BIOLOGY OF FUSARIUM OXYSPORUM
T. R. Gordon, and R. D. MartynVol. 35 (1997), pp. 111–128More Less▪ AbstractFusarium oxysporum is an anamorphic species that includes both pathogenic and nonpathogenic strains. Plant pathogenic forms cause a wilt disease and are grouped into formae speciales based on their host range; some are further subdivided into pathogenic races. Many formae speciales are comprised of multiple clonal lineages and, in some cases, a pathogenic race is associated with more than one clonal lineage, suggesting independent origins. Although some evidence suggests one pathogenic race may give rise to another, recent derivation of a pathogen from a nonpathogen has not been documented. Most new occurrences of Fusarium wilt appear to be the result of a recent introduction rather than an independent local origin of the pathotype. Asexual propagation is the dominant influence on population structure in F. oxysporum and the absence of sexual reproduction is not likely to prevent this pathogen from continuing to inflict significant damage on susceptible crop hosts.
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THE ROLE OF hrp GENES DURING PLANT-BACTERIAL INTERACTIONS
Vol. 35 (1997), pp. 129–152More Less▪ Abstracthrp genes control the ability of phytopathogenic bacteria to cause disease and to elicit hypersensitive reactions on resistant plants. Genetic and biochemical studies have demonstrated that Hrp proteins are components of Type III secretion systems, regulatory proteins, proteinaceous elicitors of the hypersensitive reaction, and enzymes needed for synthesis of periplasmic glucans. Significantly, Type III secretion systems are involved with the secretion of pathogenicity proteins in bacterial pathogens of animals. The transcriptional activation of a number of bacterial avirulence (avr) genes is controlled by Hrp regulatory proteins, and recent experimental evidence suggests that Avr proteins may be transported by Hrp secretion systems. It has also been hypothesized that pathogenicity and/or virulence gene products exit bacterial phytopathogens via Hrp pathways. Thus, hrp genes may be one of the most important groups of genes found in phytopathogenic bacteria in relationship to pathogenicity and host range.
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THE PINEWOOD NEMATODE:Regulation and Mitigation
Vol. 35 (1997), pp. 153–166More Less▪ AbstractIn North America, the native pinewood nematode (PWN), Bursaphelenchus xylophilus, kills exotic pines. When inadvertently introduced to Japan and other Asian countries, PWN became a destructive pest of pines. The PWN has been intercepted in pine shipments from North America to Europe, where there is concern that it may also kill pines and other conifers. To protect their forests from the PWN and other pests, the European Union and other countries now regulate the import of all coniferous chips, sawn wood, and logs. Several species of Bursaphelenchus have a phoretic relationship with Monochamus spp., which carry them to recently felled logs and dead or dying conifers, particularly pines. As a result, species of Monochamus, Bursaphelenchus, or both may be found in chips, unseasoned lumber, and logs. During the past decade, procedures to disinfest transported unprocessed wood have been investigated. These mitigation measures include prevention, host selection, and treatment by fumigation, irradiation, chemical dips, and elevated temperatures.
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Barley Yellow Dwarf Viruses
Vol. 35 (1997), pp. 167–190More LessBarley yellow dwarf viruses represent one of the most economically important and ubiquitous groups of plant viruses. This review focuses primarily on four research areas in which progress has been most rapid. These include (a) evidence supporting reclassification of BYDVs into two genera; (b) elucidation of gene function and novel mechanisms controlling gene expression; (c) initial forays into understanding the complex interactions between BYDV virions and their aphid vectors; and (d ) replication of a BYDV satellite RNA. Economic losses, symptomatology, and means of control of BYD are also discussed.
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MECHANISMS OF PLANT
VIRUS EVOLUTIONVol. 35 (1997), pp. 191–209More Less▪ AbstractPlant viruses utilize several mechanisms to generate the large amount of genetic diversity found both within and between species. Plant RNA viruses and pararetroviruses probably have highly error prone replication mechanisms, that result in numerous mutations and a quasispecies nature. The plant DNA viruses also exhibit diversity, but the source of this is less clear. Plant viruses frequently use recombination and reassortment as driving forces in evolution, and, occasionally, other mechanisms such as gene duplication and overprinting. The amount of variation found in different species of plant viruses is remarkably different, even though there is no evidence that the mutation rate varies.
The origin of plant viruses is uncertain, but several possible theories are proposed. The relationships between some plant and animal viruses suggests a common origin, possibly an insect virus. The propensity for rapid adaptation makes tracing the evolutionary history of viruses difficult, and long term control of virus disease nearly impossible, but it provides an excellent model system for studying general mechansims of molecular evolution.
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SIGNAL PATHWAYS AND APPRESSORIUM MORPHOGENESIS
Vol. 35 (1997), pp. 211–234More Less▪ AbstractFungal pathogens have evolved elaborate strategies to gain access to plant tissues. For many pathogens, following attachment of spores to the leaf surface, germ tubes emerge and grow across the surface, often in response to particular environmental cues and to a specific location. At an appropriate site, polar elongation of the germ tube ceases, the tip attaches to the surface and swells to form an appressorium, a uniquely organized infection structure. Following a period of maturation, a hypha then emerges at the plant interface and penetrates into the plant tissues. This chapter discusses recent developments that provide new insight into the molecular mechanism regulating induction and function of appressoria. Topics include attachment to the leaf surface; environmental cues that signal germ-tube growth and appressorium formation; mechanisms for sensing environmental cues; endogenous signaling pathways; and mechanisms of penetration from the appressorium.
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SYSTEMIC ACQUIRED RESISTANCE
Vol. 35 (1997), pp. 235–270More Less▪ AbstractThis paper examines induced resistance (SAR) in plants against various insect and pathogenic invaders. SAR confers quantitative protection against a broad spectrum of microorganisms in a manner comparable to immunization in mammals, although the underlying mechanisms differ. Discussed here are the molecular events underlying SAR: the mechanisms involved in SAR, including lignification and other structural barriers, pathogenesis-related proteins and their expression, and the signals for SAR including salicylic acid. Recent findings on the biological role of systemin, ethylene, jasmonates, and electrical signals are reviewed. Chemical activators of SAR comprise inorganic compounds, natural compounds, and synthetic compounds. Plants known to exhibit SAR and induced systemic resistance are listed.
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ADVANCES IN THE MOLECULAR GENETIC ANALYSIS OF THE FLAX-FLAX RUST INTERACTION
Vol. 35 (1997), pp. 271–291More Less▪ AbstractThe L6 and M rust-resistance genes, representing two of the five rust-resistance gene loci in flax (Linum usitatissimum), have been cloned. The molecular data are fully consistent with earlier genetic data: the L locus is a single gene with multiple alleles expressing different rust resistance specificities, and the M locus is complex, containing an array of about 15 similar genes. Thus, while L6 and M resistance genes have 86% nucleotide identity, their locus structure is very different. These genes encode products belonging to the nucleotide binding site–leucine-rich repeat class of disease-resistance proteins. Analysis of alleles from the L locus and chimeric genes is providing evidence suggesting that important specificity determinants occur in the C-terminal half of the proteins, the region containing the leucine-rich repeats. The isolation and characterization of the rust (Melampsora lini) avirulence genes that correspond to the cloned rust-resistance genes is one of the major challenges remaining to the understanding of this system.
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STRUCTURE AND EVOLUTION OF THE rp1 COMPLEX CONFERRING RUST RESISTANCE IN MAIZE
Vol. 35 (1997), pp. 293–310More Less▪ AbstractGenetic analyses of the rp1 rust resistance complex of maize have demonstrated that recombination plays a central role in the creation of genetic diversity at the locus. The generation of rp1 diversity is promoted by a high rate of intragenic recombination coupled with a tendency for genes in the complex to mispair in meiosis. Among the novel rp1 genes that have been identified include genes with novel race-specificities and genes conferring lesion mimic phenotypes. Recombinants have also been identified that confer partial resistance which is apparently non-race-specific and may be useful in controlling maize rusts in a durable manner.
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ANTICIPATORY BREEDING FOR RESISTANCE TO RUST DISEASES IN WHEAT
Vol. 35 (1997), pp. 311–326More LessAnticipatory resistance breeding is the process of predicting future pathotypes and producing resistant germplasm to avert future losses. It is made possible by a national pathotype surveillance program and knowledge that new pathotypes arise predominantly from mutation in existing pathotypes. This is supported by genetic analyses to catalogue the identity and distribution of resistance genes in current cultivars. A national germplasm enhancement program ensuring that both currently effective and potentially new sources of resistance are available in a wide range of adapted genotypes enables rapid cultivar replacement before or soon after the occurrence of new pathotypes. The policy of recommending only rust-resistant cultivars in the more rust-prone areas has resulted in significant reductions in pathogen population size and variability. With increased and more rapid international human travel and transport, there is an increased threat of exotic pathotypes, the effects of which are more difficult to predict. As the frequency and magnitude of epidemics decline, public awareness programs will be required to achieve and maintain the use of rust resistance by the entire wheat industry.
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MICROBIAL POPULATION DYNAMICS ON LEAVES
Vol. 35 (1997), pp. 327–347More Less▪ AbstractMicrobial population dynamics on leaves in time and space are a function of immigration, emigration, growth, and death. Insight into the relative significance of each population process to the generation of specific dynamics for individual microorganisms is necessary to understanding the ecology and life history strategy of the microorganism and to developing effective control strategies. Additionally, information on the significance of within-leaf versus extra-leaf processes to the generation of phyllosphere dynamics is important to determining the range of spatial scales over which a population should be studied. Unfortunately, such information is difficult to obtain due to the lack of effective methodologies for distinguishing these processes within phyllosphere populations. Future research efforts should focus on the quantification of immigration, emigration, growth, and death relative to the population dynamics of phyllosphere microorganisms.
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RATIONALE AND PERSPECTIVES ON THE DEVELOPMENT OF FUNGICIDES
Vol. 35 (1997), pp. 349–372More Less▪ AbstractFungicides continue to be essential for the effective control of plant diseases. New classes of fungicides with novel modes of action are being developed in the 1990s. These include the strobilurins, phenylpyrroles, anilinopyrimidines, phenoxyquinolines, and compounds that trigger defense mechanisms in the plant. For the foreseeable future, new toxophores will be identified through a process of random screening, with natural products representing a rich source of fungicide leads. Progress is being made in the development of high-throughput screens comprised of target enzyme sites or cell-based assays; these techniques will improve the probability of discovery. Following the identification of suitable leads, biorational design is used to optimize specific properties. In vivo glasshouse screens and field trials are expected to remain the dominant methods for characterizing new compounds. Low toxicity to humans and wildlife, low environmental impact, low residues in food, and compatibility with integrated pest management (IPM) programs are increasingly important considerations in the selection of fungicides for development.
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ROLE OF PLANT PATHOLOGY IN INTEGRATED PEST MANAGEMENT
Vol. 35 (1997), pp. 373–391More Less▪ AbstractIntegrated Pest Management (IPM) is a paradigm that is widely adopted by all pest control disciplines but whose early definitions and philosophical basis belong to entomologists. Plant pathology research and extension work has historically emphasized integration of several control strategies and fits both historical and modern definitions of IPM. While the term IPM has been used only sparingly in the phytopathology literature, the integrated disease management strategies emphasized are now considered to be at the forefront of ecologically based or biointensive pest management. While IPM is broadly endorsed by crop protection disciplines, farmers, other agriculturalists, and consumers, the potential for Integrated Pest Management has not been fully realized. Most IPM programs reflect a package of tools and decision aids for individual crop insect, weed, nematode, and plant disease management. IPM programs that integrate all types of pests with the agroecosystem, crop growth and loss models still await the formation of interdisciplinary teams focusing on growers needs. Lack of funding for both discipline and interdisciplinary developmental research and implementation is responsible for the paucity of comprehensive IPM programs for the majority of the U.S. crop acreage. This review explores the origins and evolution of the IPM paradigm and reviews efforts to achieve the body of knowledge and implementation structure to achieve IPM's full potential.
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Previous Volumes
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Volume 62 (2024)
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Volume 61 (2023)
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Volume 60 (2022)
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Volume 59 (2021)
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Volume 58 (2020)
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Volume 57 (2019)
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Volume 56 (2018)
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Volume 55 (2017)
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Volume 54 (2016)
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Volume 53 (2015)
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Volume 52 (2014)
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Volume 51 (2013)
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Volume 50 (2012)
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Volume 49 (2011)
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Volume 48 (2010)
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Volume 47 (2009)
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Volume 46 (2008)
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Volume 45 (2007)
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Volume 44 (2006)
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Volume 43 (2005)
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Volume 42 (2004)
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Volume 41 (2003)
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Volume 40 (2002)
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Volume 39 (2001)
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Volume 38 (2000)
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Volume 37 (1999)
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Volume 36 (1998)
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Volume 35 (1997)
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Volume 34 (1996)
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Volume 33 (1995)
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Volume 32 (1994)
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Volume 31 (1993)
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Volume 30 (1992)
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Volume 29 (1991)
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Volume 28 (1990)
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Volume 27 (1989)
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Volume 26 (1988)
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Volume 25 (1987)
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Volume 24 (1986)
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Volume 23 (1985)
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Volume 22 (1984)
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Volume 21 (1983)
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Volume 20 (1982)
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Volume 19 (1981)
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Volume 18 (1980)
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Volume 17 (1979)
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Volume 16 (1978)
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Volume 15 (1977)
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Volume 14 (1976)
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Volume 13 (1975)
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Volume 12 (1974)
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Volume 11 (1973)
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Volume 10 (1972)
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Volume 9 (1971)
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Volume 8 (1970)
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Volume 7 (1969)
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Volume 6 (1968)
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Volume 5 (1967)
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Volume 4 (1966)
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Volume 3 (1965)
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Volume 2 (1964)
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Volume 1 (1963)
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Volume 0 (1932)