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Gene-for-gene
The gene-for-gene relationship was discovered by Harold Henry Flor who was working with rust (''Melampsora lini'') of flax (''Linum usitatissimum''). Flor showed that the inheritance of both resistance in the host and parasite ability to cause disease is controlled by pairs of matching genes. One is a plant gene called the resistance (''R'') gene. The other is a parasite gene called the avirulence (''Avr'') gene. Plants producing a specific R gene product are resistant towards a pathogen that produces the corresponding ''Avr'' gene product. Gene-for-gene relationships are a widespread and very important aspect of plant disease resistance. Another example can be seen with ''Lactuca serriola'' versus '' Bremia lactucae''. Clayton Oscar Person was the first scientist to study plant pathosystem ratios rather than genetics ratios in host-parasite systems. In doing so, he discovered the differential interaction that is common to all gene-for-gene relationships and that is now known as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pathosystem
A pathosystem is a subsystem of an ecosystem and is defined by the phenomenon of parasitism. A plant pathosystem is one in which the host species is a plant. The parasite is any species in which the individual spends a significant part of its lifespan inhabiting one host individual and obtaining nutrients from it. The parasite may thus be an insect, mite, nematode, parasitic Angiosperm, fungus, bacterium, mycoplasma, virus or viroid. Other consumers, however, such as mammalian and avian herbivores, which graze populations of plants, are normally considered to be outside the conceptual boundaries of the plant pathosystem. A host has the property of resistance to a parasite. And a parasite has the property of parasitic ability on a host. Parasitism is the interaction of these two properties. The main feature of the pathosystem concept is that it concerns parasitism, and it is not concerned with the study of either the host or parasite on its own. Another feature of the pathosystem con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melampsora Lini
''Melampsora lini'' is a species of fungus and plant pathogen found in Ireland and commonly known as flax rust. Life cycle The pathogen is an obligate biotroph meaning that each stage of its cycle is dependent on having a living host. The direction between reproducing sexually or asexually is dependent on the availability of a host. Sexually, the life cycle starts when basidiospores land on flax leaves and form pycnium during December and through January. Aecium are then formed from the pycnium after being fertilized with a pycniospore that is of a different mating type. Urediniospores and aeciospores then form pustules on the leaves that release more spores leading to further infection on neighboring leaves. Teliospores are then formed on the plants stem and undergo meiosis. Afterward, the teliospores shed haploid basidiospores repeating the cycle. Asexually, the pathogen cycles between forming pustules and infecting surrounding leaves and plants. The pathogen is autoeci ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lactuca Serriola
''Lactuca serriola'', also called prickly lettuce, milk thistle (not to be confused with ''Silybum marianum'', also called milk thistle), compass plant, and scarole, is an annual or biennial plant in the tribe Cichorieae within the family Asteraceae. It has a slightly fetid odor and is commonly considered a weed of orchards, roadsides and field crops. It is the closest wild relative of cultivated lettuce (''Lactuca sativa'' L.). ''Lactuca serriola'' is known as the compass plant because in the sun the upper leaves twist round to hold their margins upright. ''Lactuca serriola'' is native to Europe, Asia, and north Africa, and has become naturalized elsewhere. Description ''Lactuca serriola'' has a spineless reddish stem, containing a milky latex, growing up to . The leaves get progressively smaller as they reach its top. They are oblong or lanceolate, often pinnately lobed and (especially for the lower leaves), waxy grey green. Fine spines are present along the veins and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clayton Oscar Person
Clayton Oscar Person, (May 16, 1922 – September 1, 1990) was recognized internationally as an authority on the genetics of host-parasite relations. He was born and raised in Aylesbury, Saskatchewan, Canada and died in Vancouver, British Columbia, Canada. His writings have made a major contribution to the development of a rigorous theoretical basis for our understanding of how the genetic structure of parasitic populations interacts with that of their host populations. This was known as the gene-for-gene relationship. His theoretical methods have been applied widely in the practical management of parasitic diseases in agriculture and forestry. Biography Education After service overseas in the Royal Canadian Navy from 1941-1945, he returned to enroll at the University of Saskatchewan where he was awarded Honours in Biology in 1950 and the MA in 1951. He studied for the Ph.D. at the University of Alberta, then spent two post-doctoral years abroad — one at the University ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harold Henry Flor
Harold Henry Flor known as H. H. Flor (1900–1991) was a plant pathologist famous for proposing the Gene-for-gene relationship, gene for gene hypothesis of plant-pathogen genetic interaction whilst working on rust (Melampsora lini var. lini, ''Melampsora lini'') of flax (''Linum usitatissimum''). Life and career Harold Henry Flor completed his B.S. at the University of Minnesota in 1922, and continued on to an M.S. degree there for the following two years. He received his M.S. degree in June 1924 for his research work entitled ''Control of covered smuts of small grains''. Between January 1924 and May 1925 he worked at Iowa State College as a Research Fellow and completed his work on the ''Fungicidal activity of furfural'' there. For a year between September 1925 to September 1926 he worked as a Research Fellow at the graduate school of the University of Minnesota, following which he completed a research work on root rot in sugarcane supervised by E.G. Edgerton at the State Univ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amino Acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha amino acids appear in the genetic code. Amino acids can be classified according to the locations of the core structural functional groups, as Alpha and beta carbon, alpha- , beta- , gamma- or delta- amino acids; other categories relate to Chemical polarity, polarity, ionization, and side chain group type (aliphatic, Open-chain compound, acyclic, aromatic, containing hydroxyl or sulfur, etc.). In the form of proteins, amino acid '' residues'' form the second-largest component (water being the largest) of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis. It is thought that they played a key role in enabling life ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladosporium
''Cladosporium'' is a genus of fungi including some of the most common indoor and outdoor molds. Species produce olive-green to brown or black colonies, and have dark-pigmented conidia that are formed in simple or branching chains. Many species of ''Cladosporium'' are commonly found on living and dead plant material. Some species are endophytes or plant pathogens, while others parasitize fungi. ''Cladosporium'' spores are wind-dispersed and they are often extremely abundant in outdoor air. Indoors ''Cladosporium'' species may grow on surfaces when moisture is present. '' Cladosporium fulvum'', cause of tomato leaf mould, has been an important genetic model, in that the genetics of host resistance are understood. In the 1960s, it was estimated that the genus ''Cladosporium'' contained around 500 plant-pathogenic and saprotrophic species, but this number has since been increased to over 772 species. The genus ''Cladosporium'' is very closely related to black yeasts in the order Do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudomonas
''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able to colonize a wide range of niches. Their ease of culture ''in vitro'' and availability of an increasing number of ''Pseudomonas'' strain genome sequences has made the genus an excellent focus for scientific research; the best studied species include ''P. aeruginosa'' in its role as an opportunistic human pathogen, the plant pathogen '' P. syringae'', the soil bacterium '' P. putida'', and the plant growth-promoting ''P. fluorescens, P. lini, P. migulae'', and ''P. graminis''. Because of their widespread occurrence in water and plant seeds such as dicots, the pseudomonads were observed early in the history of microbiology. The generic name ''Pseudomonas'' created for these organisms was defined in rather vague terms by Walter Migula i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leucine
Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain isobutyl group, making it a non-polar aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it: it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, and beans and other legumes. It is encoded by the codons UUA, UUG, CUU, CUC, CUA, and CUG. Like valine and isoleucine, leucine is a branched-chain amino acid. The primary metabolic end products of leucine metabolism are acetyl-CoA and acetoacetate; consequently, it is one of the two exclusively ketogenic amino acids, with lysine being the other. It is the most import ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arginine
Arginine is the amino acid with the formula (H2N)(HN)CN(H)(CH2)3CH(NH2)CO2H. The molecule features a guanidino group appended to a standard amino acid framework. At physiological pH, the carboxylic acid is deprotonated (−CO2−) and both the amino and guanidino groups are protonated, resulting in a cation. Only the -arginine (symbol Arg or R) enantiomer is found naturally. Arg residues are common components of proteins. It is encoded by the codons CGU, CGC, CGA, CGG, AGA, and AGG. The guanidine group in arginine is the precursor for the biosynthesis of nitric oxide. Like all amino acids, it is a white, water-soluble solid. History Arginine was first isolated in 1886 from yellow lupin seedlings by the German chemist Ernst Schulze and his assistant Ernst Steiger. He named it from the Greek ''árgyros'' (ἄργυρος) meaning "silver" due to the silver-white appearance of arginine nitrate crystals. In 1897, Schulze and Ernst Winterstein (1865–1949) determined the structure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobic
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds. Hydrophobic is often used interchangeably with lipophilic, "fat-loving". However, the two terms are not synonymous. While hydrophobic substances are usually lipophilic, there are exceptions, suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
