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Pythium Marinum
''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but '' Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequently a vector for their transmission. Morphology ;Hyphae: ''Pythium'' species, like others in the family Pythiaceae, are usually characterized by their production of coenocytic hyphae without septations. ;Oogonia: Generally contain a single oospore. ;Antheridia: Contain an elongated and club-shaped antheridium. Ecological importance ''Pythium''-induced root rot is a common crop disease. When the organism kills newly emerged or emerging seedlings, it is known as damping off, and is a very common problem in fields and greenhouses. Thus there is tremendous interest in genetic host resistance, but no crop has ever developed adequate resistance to ''Pythium''. This disease complex usually involves other pathogens such as ''Phytophthora'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phase-contrast Microscopy
__NOTOC__ Phase-contrast microscopy (PCM) is an optical microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image. Phase shifts themselves are invisible, but become visible when shown as brightness variations. When light waves travel through a medium other than a vacuum, interaction with the medium causes the wave amplitude and phase to change in a manner dependent on properties of the medium. Changes in amplitude (brightness) arise from the scattering and absorption of light, which is often wavelength-dependent and may give rise to colors. Photographic equipment and the human eye are only sensitive to amplitude variations. Without special arrangements, phase changes are therefore invisible. Yet, phase changes often convey important information. Phase-contrast microscopy is particularly important in biology. It reveals many cellular structures that are invisible with a bright-field microscope, as exem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antheridium
An antheridium is a haploid structure or organ producing and containing male gametes (called ''antherozoids'' or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an androecium. The androecium is also the collective term for the stamens of flowering plants. Antheridia are present in the gametophyte phase of cryptogams like bryophytes and ferns. Many algae and some fungi, for example, ascomycetes and water moulds, also have antheridia during their reproductive stages. In gymnosperms and angiosperms, the male gametophytes have been reduced to pollen grains, and in most of these, the antheridia have been reduced to a single generative cell within the pollen grain. During pollination, this generative cell divides and gives rise to sperm cells. The female counterpart to the antheridium in cryptogams is the archegonium, and in flowering plants is the gynoecium. An antheridium typically consists of sterile cells and spermatogenous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant Pathology
Plant pathology or phytopathology is the scientific study of plant diseases caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Plant pathology involves the study of pathogen identification, disease etiology, disease cycles, economic impact, plant disease epidemiology, plant disease resistance, how plant diseases affect humans and animals, pathosystem genetics, and management of plant diseases. Plant pathogenicity Plant pathogens, organisms that cause infectious plant diseases, include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants. In most plant pathosystems, virulence depends on hydrolases and enzymes that degrade the cell wall. The vast majority of these act on pectins (for example, pectinesterase, pectate lyase, and pectinases). For microbes, the cell wall polysaccharides are both a food source and a barrier to be overcome. Many path ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Pretoria
The University of Pretoria (, ) is a multi-campus public university, public research university in Pretoria, the administrative and ''de facto'' capital of South Africa. The university was established in 1908 as the Pretoria campus of the Johannesburg-based Transvaal University College and is the fourth South African institution in continuous operation to be awarded university status. The university has grown from the original 32 students in a single late Victorian house to approximately 53,000 in 2019. The university was built on seven suburban campuses on . The university is organised into nine faculties and a business school. Established in 1920, the University of Pretoria Faculty of Veterinary Science is the second oldest veterinary school in Africa and the only veterinary school in South Africa. In 1949, the university launched the first MBA programme outside North America, and the university's Gordon Institute of Business Science (GIBS) has consistently been ranked the top ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Guelph
The University of Guelph (abbreviated U of G) is a comprehensive Public university, public research university in Guelph, Ontario, Canada. It was established in 1964 after the amalgamation of Ontario Agricultural College (1874), the MacDonald Institute (1903), and the Ontario Veterinary College (1922), and has since grown to an institution of almost 30,000 students (including those at the Humber campus, Ridgetown campus, off-campus degree enrolments, diploma enrolments and part-time students) and employs 830 full-time faculty (academic staff) as of fall 2019. It offers 94 undergraduate degrees, 48 graduate programs, and 6 associate degrees in many different disciplines. The university conducts a significant degree of research and offers a wide range of undergraduate, graduate, and professional degrees. According to the ''Journal of Hospitality & Tourism Research'', the university's Hospitality and Tourism Management program has Canada's highest research index. The faculty at t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are infectious and transmittable, such as '' Batrachochytrium dendrobatidis'', a fungal zoospore that causes high rates of mortality in amphibians. Diversity General morphology Zoospores are composed of a microtubular cytoskeleton base which extends from the base of the flagellum. The complexity and structure of this cytoskeleton is variable and is largely dependent on volume and size. One common feature of zoospores is their asymmetrical shape; a result of the ventral grove housing the flagella base. Certain zoospores progress through different phases, the first phase commonly referred to as 'the initial'. Others form cysts that vary tremendously in volume (14-4905 cubic micrometers) and shape, each with distinctive hair structures. Flag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhizoctonia Solani
''Rhizoctonia solani'' is a species of fungus in the order Cantharellales. Basidiocarps (fruit bodies) are thin, effused, and web-like, but the fungus is more typically encountered in its anamorphic state, as hyphae and sclerotia. The name ''Rhizoctonia solani'' is currently applied to a complex of related species that await further research. In its wide sense, ''Rhizoctonia solani'' is a facultative plant pathogen with a wide host range and worldwide distribution. It causes various plant diseases such as root rot, damping off, and wire stem. It can also form mycorrhizal associations with orchids. Taxonomy In 1858, the German plant pathologist Julius Kühn observed and described a fungus on diseased potato tubers and named it ''Rhizoctonia solani'', the species epithet referring to '' Solanum tuberosum'' (potato). The disease caused was well known before the discovery and description of the fungus. In 1956, Dutch mycologist M.A. Donk published the new name ''Thanatephoru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phytophthora
''Phytophthora'' (from Greek (''phytón''), "plant" and (), "destruction"; "the plant-destroyer") is a genus of plant-damaging oomycetes (water molds), whose member species cause economic losses on crops worldwide, as well as environmental damage in natural ecosystems. The cell wall of ''Phytophthora'' is made up of cellulose. The genus was first described by Heinrich Anton de Bary in 1875. Approximately 210 species have been described, although 100–500 undiscovered ''Phytophthora'' species are estimated to exist. Pathogenicity ''Phytophthora'' spp. are mostly pathogens of dicotyledons, and many are relatively host-specific parasites. '' P. cinnamomi'', though, infects thousands of species ranging from club mosses, ferns, cycads, conifers, grasses, lilies, to members of many dicotyledonous families. Many species of ''Phytophthora'' are plant pathogens of considerable economic importance. '' P. infestans'' was the infective agent of the potato blight that caused the Gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Summa Phytopathologica
Summa and its diminutive summula (plural ''summae'' and ''summulae'', respectively) was a medieval didactics literary genre written in Latin, born during the 12th century, and popularized in 13th century Europe. In its simplest sense, they might be considered texts that 'sum up' knowledge in a field, such as the compendiums of theology, philosophy and canon law. Their function during the Middle Ages was largely as manuals or handbooks of necessary knowledge used by individuals who would not advance their studies any further. Features It was a kind of encyclopedia that developed a matter about Law, Theology or Philosophy most of all. Matters were divided in a more detailed way as it was in the ''tractatus'' (treatise), since they were divided into ''quaestiones'' (questions) and these ones were also divided into ''articles''. The articles had the following structure: #Title of the article as a question and showing two different positions (''disputatio''). #Objections or arguments a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant Disease Resistance
Plant disease resistance protects plants from pathogens in two ways: by pre-formed structures and chemicals, and by infection-induced responses of the immune system. Relative to a susceptible plant, disease resistance is the reduction of pathogen growth on or in the plant (and hence a reduction of disease), while the term disease tolerance describes plants that exhibit little disease damage despite substantial pathogen levels. Disease outcome is determined by the three-way interaction of the pathogen, the plant, and the environmental conditions (an interaction known as the disease triangle). Defense-activating compounds can move cell-to-cell and systematically through the plant's vascular system. However, plants do not have circulating immune cells, so most cell types exhibit a broad suite of antimicrobial defenses. Although obvious ''qualitative'' differences in disease resistance can be observed when multiple specimens are compared (allowing classification as "resistant" or "su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Breeding For Resistance
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together. Domesticated animals are known as breeds, normally bred by a professional breeder, while domesticated plants are known as varieties, cultigens, cultivars, or breeds. Two purebred animals of different breeds produce a crossbreed, and crossbred plants are called hybrids. Flowers, vegetables and fruit-trees may be bred by amateurs and commercial or non-commercial professionals: major crops are usually the provenance of the professionals. In animal breeding artificial selection is often combined with techniques such as inbreeding, linebreeding, and outcrossing. In plant breeding, similar methods are used. Charles Darwin discussed how selective breeding had been successful in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saint Paul, Minnesota
Saint Paul (often abbreviated St. Paul) is the List of capitals in the United States, capital city of the U.S. state of Minnesota and the county seat of Ramsey County, Minnesota, Ramsey County. As of the 2020 United States census, 2020 census, the city had a population of 311,527, making it Minnesota's List of cities in Minnesota, second-most populous city and the List of United States cities by population, 63rd-most populous in the United States. Saint Paul and neighboring Minneapolis form the core of the Minneapolis–Saint Paul, Twin Cities metropolitan area, the third most populous in the Midwestern United States, Midwest with around 3.7 million residents. The Minnesota State Capitol and the state government offices sit on a hill next to downtown Saint Paul overlooking a bend in the Mississippi River. Local cultural offerings include the Science Museum of Minnesota, the Ordway Center for the Performing Arts, and the Minnesota History Center. Three of the region's profession ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
