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103-450: Most phytopathogenic fungi are Ascomycetes or Basidiomycetes . They reproduce both sexually and asexually via the production of spores and other structures. Spores may be spread long distances by air or water, or they may be soil borne. Many soil inhabiting fungi are capable of living saprotrophically , carrying out the role of their life cycle in the soil . These are facultative saprotrophs. Fungal diseases may be controlled through

206-506: A root hair they produce a plasmodium which invades the roots . Some abiotic disorders can be confused with pathogen-induced disorders. Abiotic causes include natural processes such as drought , frost , snow and hail ; flooding and poor drainage; nutrient deficiency ; deposition of mineral salts such as sodium chloride and gypsum ; windburn and breakage by storms; and wildfires . Plants are subject to disease epidemics. The introduction of harmful non native organisms into

309-1196: A thallus usually referred to as the mycelium , which—when visible to the naked eye (macroscopic)—is commonly called mold . During sexual reproduction, many Ascomycota typically produce large numbers of asci . The ascus is often contained in a multicellular, occasionally readily visible fruiting structure, the ascocarp (also called an ascoma ). Ascocarps come in a very large variety of shapes: cup-shaped, club-shaped, potato-like, spongy, seed-like, oozing and pimple-like, coral-like, nit-like, golf-ball-shaped, perforated tennis ball-like, cushion-shaped, plated and feathered in miniature ( Laboulbeniales ), microscopic classic Greek shield-shaped, stalked or sessile. They can appear solitary or clustered. Their texture can likewise be very variable, including fleshy, like charcoal (carbonaceous), leathery, rubbery, gelatinous, slimy, powdery, or cob-web-like. Ascocarps come in multiple colors such as red, orange, yellow, brown, black, or, more rarely, green or blue. Some ascomyceous fungi, such as Saccharomyces cerevisiae , grow as single-celled yeasts, which—during sexual reproduction—develop into an ascus, and do not form fruiting bodies. In lichenized species,

412-472: A bottle shaped cell called a phialide , from which the spores are produced. Not all of these asexual structures are a single hypha. In some groups, the conidiophores (the structures that bear the conidia) are aggregated to form a thick structure. E.g. In the order Moniliales, all of them are single hyphae with the exception of the aggregations, termed as coremia or synnema. These produce structures rather like corn-stokes, with many conidia being produced in

515-519: A country can be reduced by controlling human traffic (e.g., the Australian Quarantine and Inspection Service ). Global trade provides unprecedented opportunities for the introduction of plant pests. In the United States , even to get a better estimate of the number of such introductions would require a substantial increase in inspections. In Australia a similar shortcoming of understanding has

618-653: A different origin: Port inspections are not very useful because inspectors know too little about taxonomy. There are often pests that the Australian Government has prioritised as harmful to be kept out of the country, but which have near taxonomic relatives that confuse the issue. X-ray and electron-beam /E-beam irradiation of food has been trialed as a quarantine treatment for fruit commodities originating from Hawaii . The US FDA ( Food and Drug Administration ), USDA APHIS ( Animal and Plant Health Inspection Service ), producers, and consumers were all accepting of

721-506: A double-dividing wall with a central lamella (layer) forms between the cells; the central layer then breaks down thereby releasing the spores. In rhexolytic dehiscence, the cell wall that joins the spores on the outside degenerates and releases the conidia. Several Ascomycota species are not known to have a sexual cycle. Such asexual species may be able to undergo genetic recombination between individuals by processes involving heterokaryosis and parasexual events. Parasexuality refers to

824-415: A few species. Nematodes are able to cause radical changes in root cells in order to facilitate their lifestyle. A few plant diseases are caused by protozoa such as Phytomonas , a kinetoplastid . They are transmitted as durable zoospores that may be able to survive in a resting state in the soil for many years. Further, they can transmit plant viruses . When the motile zoospores come into contact with

927-433: A form of pneumonia . Asci of Ascosphaera fill honey bee larvae and pupae causing mummification with a chalk-like appearance, hence the name "chalkbrood". Yeasts for small colonies in vitro and in vivo , and excessive growth of Candida species in the mouth or vagina causes "thrush", a form of candidiasis . The cell walls of the ascomycetes almost always contain chitin and β-glucans , and divisions within

1030-476: A further mitotic division that results in eight nuclei in each ascus. The nuclei along with some cytoplasma become enclosed within membranes and a cell wall to give rise to ascospores that are aligned inside the ascus like peas in a pod. Upon opening of the ascus, ascospores may be dispersed by the wind, while in some cases the spores are forcibly ejected form the ascus; certain species have evolved spore cannons, which can eject ascospores up to 30 cm. away. When

1133-737: A hypha. Vegetative hyphae of most ascomycetes contain only one nucleus per cell ( uninucleate hyphae), but multinucleate cells—especially in the apical regions of growing hyphae—can also be present. In common with other fungal phyla, the Ascomycota are heterotrophic organisms that require organic compounds as energy sources. These are obtained by feeding on a variety of organic substrates including dead matter, foodstuffs, or as symbionts in or on other living organisms. To obtain these nutrients from their surroundings, ascomycetous fungi secrete powerful digestive enzymes that break down organic substances into smaller molecules, which are then taken up into

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1236-529: A large-scale specialized structure that helps to spread them. These two basic types can be further classified as follows: Sometimes the conidia are produced in structures visible to the naked eye, which help to distribute the spores. These structures are called "conidiomata" (singular: conidioma ), and may take the form of pycnidia (which are flask-shaped and arise in the fungal tissue) or acervuli (which are cushion-shaped and arise in host tissue). Dehiscence happens in two ways. In schizolytic dehiscence,

1339-468: A loss of crop yield . Therefore, it is not economically viable to try to control them, except when they infect perennial species, such as fruit trees. Most plant viruses have small, single-stranded RNA genomes . Some also have double stranded RNA or single or double stranded DNA . These may encode only three or four proteins : a replicase , a coat protein, a movement protein to facilitate cell to cell movement through plasmodesmata , and sometimes

1442-433: A mass from the aggregated conidiophores. The diverse conidia and conidiophores sometimes develop in asexual sporocarps with different characteristics (e.g. acervulus, pycnidium, sporodochium). Some species of ascomycetes form their structures within plant tissue, either as parasite or saprophytes. These fungi have evolved more complex asexual sporing structures, probably influenced by the cultural conditions of plant tissue as

1545-549: A mechanism through which insect borne plant diseases spread. So far, the beet leafhopper is the only known vector of the Beet curly top virus , which spreads through plant phloem tissues. Therefore, researchers conducted electrical penetration graph experiments of leaf hoppers in which they wired beet leafhoppers to an EPG machine and characterized the types of waveforms produced. The data showed that beet leafhoppers primarily ingested phloem sap along with xylem and mesophyll sap. What

1648-431: A microscopic sexual structure in which nonmotile spores , called ascospores , are formed. However, some species of Ascomycota are asexual and thus do not form asci or ascospores. Familiar examples of sac fungi include morels , truffles , brewers' and bakers' yeast , dead man's fingers , and cup fungi . The fungal symbionts in the majority of lichens (loosely termed "ascolichens") such as Cladonia belong to

1751-408: A period of 2 days) and later moved to their preferred choices (when observed over 20 days). Despite these differences, both species chose beet plants for laying eggs. Studies of insect feeding patterns can be conducted using electrical penetration graphs which allow researchers to match electrical waveforms to specific feeding behaviors in insects. Insects may choose to feed on different parts of

1854-401: A plant. By studying the waveforms produced for different feeding behaviors and then matching them to video images and histology of insects feeding, researchers can classify which part of a plant an insect feeds on. These waveforms may also give other valuable feeding information like the speed at which an insect feeds. For the beet leafhopper, understanding feeding is important as feeding is

1957-575: A problem in tropical and subtropical regions. Potato cyst nematodes ( Globodera pallida and G. rostochiensis ) are widely distributed in Europe and the Americas, causing $ 300 million worth of damage in Europe annually. Root knot nematodes have quite a large host range, they parasitize plant root systems and thus directly affect the uptake of water and nutrients needed for normal plant growth and reproduction, whereas cyst nematodes tend to be able to infect only

2060-481: A protein that allows transmission by a vector. Plant viruses are generally transmitted by a vector , but mechanical and seed transmission also occur. Vectors are often insects such as aphids ; others are fungi , nematodes , and protozoa . In many cases, the insect and virus are specific for virus transmission such as the beet leafhopper that transmits the curly top virus causing disease in several crop plants. Some nematodes parasitize plant roots . They are

2163-407: A result of ingesting toxins that are produced either by S. citri itself or by plants defending themselves against the pathogen. In any case, these toxins have a significant on the longevity of infected beet leafhoppers. Another study tested some of the characteristics that are important for transmission of S. citri by the beet leafhopper. Researchers tested the impacts of modes of acquisition on

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2266-545: A separate artificial phylum , the Deuteromycota (or "Fungi Imperfecti"). Where recent molecular analyses have identified close relationships with ascus-bearing taxa, anamorphic species have been grouped into the Ascomycota, despite the absence of the defining ascus. Sexual and asexual isolates of the same species commonly carry different binomial species names, as, for example, Aspergillus nidulans and Emericella nidulans , for asexual and sexual isolates, respectively, of

2369-408: A substrate. These structures are called the sporodochium . This is a cushion of conidiophores created from a pseudoparenchymatous stroma in plant tissue. The pycnidium is a globose to flask-shaped parenchymatous structure, lined on its inner wall with conidiophores. The acervulus is a flat saucer shaped bed of conidiophores produced under a plant cuticle, which eventually erupt through

2472-551: A tetraploid nucleus which divided into four diploid nuclei by meiosis and then into eight haploid nuclei by a supposed process called brachymeiosis , but this hypothesis was disproven in the 1950s. From the fertilized ascogonium, dinucleate hyphae emerge in which each cell contains two nuclei. These hyphae are called ascogenous or fertile hyphae. They are supported by the vegetative mycelium containing uni– (or mono–) nucleate hyphae, which are sterile. The mycelium containing both sterile and fertile hyphae may grow into fruiting body,

2575-423: A variety of stresses such as nutrient limitation. The sexual part of the life cycle commences when two hyphal structures mate . In the case of homothallic species, mating is enabled between hyphae of the same fungal clone , whereas in heterothallic species, the two hyphae must originate from fungal clones that differ genetically, i.e., those that are of a different mating type . Mating types are typical of

2678-469: A week. There were also differences noticed in mortality on plants that were preferred for settling: insects were more likely to die on carrot plants as compared to beets, potato and radish. Experiments on oviposition also showed that the insects had a preference to lay eggs on beet, potato and radish plants where nymphs hatched from eggs and continued providing generations of beet leafhoppers. Carrot, bean and tomato plants were also rejected for oviposition by

2781-566: A year, with generally 3 different generations produced in Idaho in a year. The insects are active in mustard and flixweed plants over winter and females begin laying eggs in March. The adults from this generation mature by May when they may migrate to beet fields to mate and lay eggs for the second annual generation to be born. The third generation matures to adulthood by early September or October when these insects migrate back to their winter habitats. There

2884-417: Is a dictyospore . In staurospores ray-like arms radiate from a central body; in others ( helicospores ) the entire spore is wound up in a spiral like a spring. Very long worm-like spores with a length-to-diameter ratio of more than 15:1, are called scolecospores . Important characteristics of the anamorphs of the Ascomycota are conidiogenesis , which includes spore formation and dehiscence (separation from

2987-442: Is a species of leafhopper which belongs to the family Cicadellidae in the order Hemiptera . A lot of morphological diversity has been reported among populations of the beet leafhopper in the United States . Morphological descriptions of two different populations of beet leafhoppers from California and Mexico are presented here. The leaf hopper is described as a small insect, 3–3.5 mm (0.12–0.14 in) in length, that

3090-484: Is a tube-shaped vessel, a meiosporangium , which contains the sexual spores produced by meiosis and which are called ascospores . Apart from a few exceptions, such as Candida albicans , most ascomycetes are haploid , i.e., they contain one set of chromosomes per nucleus. During sexual reproduction there is a diploid phase, which commonly is very short, and meiosis restores the haploid state. The sexual cycle of one well-studied representative species of Ascomycota

3193-451: Is described in greater detail in Neurospora crassa . Also, the adaptive basis for the maintenance of sexual reproduction in the Ascomycota fungi was reviewed by Wallen and Perlin. They concluded that the most plausible reason for the maintenance of this capability is the benefit of repairing DNA damage by using recombination that occurs during meiosis . DNA damage can be caused by

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3296-400: Is different from adults that mature in the winter which generally show darker markings on their wings and pronotum. These changes in colouration may be due to changes in seasonal temperatures as sometimes leafhoppers who mature in colder spring temperatures also show darker colouration like that of winter leafhoppers. Some researchers believe that these changes in colouration occur according to

3399-399: Is evidence that this migration may be related to seasonal temperatures as leafhoppers migrated to beet fields later during colder seasons. Researchers proposed that these later migrations can decrease damage to beet fields as the leafhoppers stay on the fields for shorter periods of time overall. The study showed that temperature had a significant impact on the growth rate and development of

3502-554: Is often greenish yellow, tan or olive in colour. The leaf hopper may have darker markings on its wings, pronotum, abdomen and head if it has developed during colder temperatures. The general shape of the body has been described as "wedge shaped" with the body tapering off at the posterior end of the insect. The head of the insect is wider than the pronotum with distinct eyes and a curved anterior margin. The mouth parts, like that of all hemipterans, have stylets used for penetration into plants and sucking. The seta , or hair present on

3605-522: Is only found on Nothofagus (Southern Beech) in the Southern Hemisphere . Asexual reproduction is the dominant form of propagation in the Ascomycota, and is responsible for the rapid spread of these fungi into new areas. It occurs through vegetative reproductive spores, the conidia . The conidiospores commonly contain one nucleus and are products of mitotic cell divisions and thus are sometimes called mitospores, which are genetically identical to

3708-475: Is the causal agent of the Citrus Stubborn Disease . The bacterium S. citri is initially acquired by the leafhopper through feeding on a plant that has already been infected. Through feeding, the prokaryote enters the gut of the beet leafhopper where most of its cells are killed, but some do survive. These surviving organisms then enter the epithelial cells of the intestine and multiply. Eventually

3811-440: Is the lone insect vector of the beet curly top virus (BCTV) which causes disease in many important crops like beans , sugar beet , cantaloupe , cucumber , peppers , spinach , squash , tomato , watermelon and other important plants. The beet leafhopper is also responsible for transmission of two other strains of the Beet curly top virus , which according to literature are now considered separate species. These strains are

3914-463: Is usually inconspicuous because it is commonly embedded in the substrate, such as soil, or grows on or inside a living host, and only the ascoma may be seen when fruiting. Pigmentation , such as melanin in hyphal walls, along with prolific growth on surfaces can result in visible mold colonies; examples include Cladosporium species, which form black spots on bathroom caulking and other moist areas. Many ascomycetes cause food spoilage, and, therefore,

4017-416: The ascocarp , which may contain millions of fertile hyphae. An ascocarp is the fruiting body of the sexual phase in Ascomycota. There are five morphologically different types of ascocarp, namely: The sexual structures are formed in the fruiting layer of the ascocarp, the hymenium . At one end of ascogenous hyphae, characteristic U-shaped hooks develop, which curve back opposite to the growth direction of

4120-402: The ascogonium , and merges with a gametangium (the antheridium ) of the other fungal isolate. The nuclei in the antheridium then migrate into the ascogonium, and plasmogamy —the mixing of the cytoplasm —occurs. Unlike in animals and plants, plasmogamy is not immediately followed by the merging of the nuclei (called karyogamy ). Instead, the nuclei from the two hyphae form pairs, initiating

4223-473: The Beet severe curly top virus (BSCTV) and Beet mild curly top virus (BMCTV). So far, the methods of transmission for all three strains seem to be the same. In order to understand the movement of the MBCTV inside its hosts, experiments have been conducted using PCR analysis which allow for the detection and quantification of MBCTV particles inside leafhoppers. One such study measured the amounts of MBCTV found in

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4326-441: The S. citri pathogen may be using cell mediated endocytosis as a predominant way to enter gut and salivary cells and may be travelling directly though the cells rather than travelling in the spaces between cell membranes of individual cells through a process called diacytosis. They also observed damage to muscle cells in the gut and salivary glands of insects infected with S. citri which is evidence that S. citri causes damage to

4429-749: The Stramenopiles . They include some of the most destructive plant pathogens, such as the causal agents of potato late blight root rot , and sudden oak death . Despite not being closely related to the fungi, the oomycetes have developed similar infection strategies, using effector proteins to turn off a plant's defenses. Some slime molds in Phytomyxea cause important diseases, including clubroot in cabbage and its relatives and powdery scab in potatoes. These are caused by species of Plasmodiophora and Spongospora , respectively. Most bacteria associated with plants are saprotrophic and do no harm to

4532-452: The conidia . The asexual, non-motile haploid spores of a fungus, which are named after the Greek word for dust (conia), are hence also known as conidiospores . The conidiospores commonly contain one nucleus and are products of mitotic cell divisions and thus are sometimes called mitospores , which are genetically identical to the mycelium from which they originate. They are typically formed at

4635-627: The detritivores (animals that feed on decomposing material) to obtain their nutrients. Ascomycetes, along with other fungi, can break down large molecules such as cellulose or lignin , and thus have important roles in nutrient cycling such as the carbon cycle . The fruiting bodies of the Ascomycota provide food for many animals ranging from insects and slugs and snails ( Gastropoda ) to rodents and larger mammals such as deer and wild boars . Many ascomycetes also form symbiotic relationships with other organisms, including plants and animals. Probably since early in their evolutionary history,

4738-401: The dikaryophase of the sexual cycle, during which time the pairs of nuclei synchronously divide. Fusion of the paired nuclei leads to mixing of the genetic material and recombination and is followed by meiosis . A similar sexual cycle is present in the red algae (Rhodophyta). A discarded hypothesis held that a second karyogamy event occurred in the ascogonium prior to ascogeny, resulting in

4841-685: The ergot fungi, black knot , and the powdery mildews . The members of the genus Cordyceps are entomopathogenic fungi , meaning that they parasitise and kill insects. Other entomopathogenic ascomycetes have been used successfully in biological pest control , such as Beauveria . Several species of ascomycetes are biological model organisms in laboratory research. Most famously, Neurospora crassa , several species of yeasts , and Aspergillus species are used in many genetics and cell biology studies. Ascomycetes are 'spore shooters'. They are fungi which produce microscopic spores inside special, elongated cells or sacs, known as 'asci', which give

4944-426: The mycoplasmas , which are human pathogens, they belong to the class Mollicutes . Their cells are extremely small, 1 to 2 micrometres across. They tend to have small genomes (roughly between 0.5 and 2 Mb). They are normally transmitted by leafhoppers (cicadellids) and psyllids , both sap-sucking insect vectors. These inject the bacteria into the plant's phloem , where it reproduces. Many plant viruses cause only

5047-449: The photoautotrophic algal partner generates metabolic energy through photosynthesis, the fungus offers a stable, supportive matrix and protects cells from radiation and dehydration. Around 42% of the Ascomycota (about 18,000 species) form lichens, and almost all the fungal partners of lichens belong to the Ascomycota. Beet leafhopper The beet leafhopper ( Circulifer tenellus ), also sometimes known as Neoaliturus tenellus ,

5150-533: The Ascomycota have formed symbiotic associations with green algae ( Chlorophyta ), and other types of algae and cyanobacteria . These mutualistic associations are commonly known as lichens , and can grow and persist in terrestrial regions of the earth that are inhospitable to other organisms and characterized by extremes in temperature and humidity, including the Arctic , the Antarctic , deserts , and mountaintops. While

5253-1126: The Ascomycota. Ascomycota is a monophyletic group (containing all of the descendants of a common ancestor). Previously placed in the Basidiomycota along with asexual species from other fungal taxa, asexual (or anamorphic ) ascomycetes are now identified and classified based on morphological or physiological similarities to ascus-bearing taxa , and by phylogenetic analyses of DNA sequences. Ascomycetes are of particular use to humans as sources of medicinally important compounds such as antibiotics , as well as for fermenting bread, alcoholic beverages, and cheese. Examples of ascomycetes include Penicillium species on cheeses and those producing antibiotics for treating bacterial infectious diseases . Many ascomycetes are pathogens , both of animals, including humans, and of plants. Examples of ascomycetes that can cause infections in humans include Candida albicans , Aspergillus niger and several tens of species that cause skin infections . The many plant-pathogenic ascomycetes include apple scab , rice blast ,

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5356-410: The Ascomycota. The most frequent types are the single-celled spores, which are designated amerospores . If the spore is divided into two by a cross-wall ( septum ), it is called a didymospore . When there are two or more cross-walls, the classification depends on spore shape. If the septae are transversal , like the rungs of a ladder, it is a phragmospore , and if they possess a net-like structure it

5459-629: The Ascomycota. These include the following sexual ( teleomorphic ) groups, defined by the structures of their sexual fruiting bodies : the Discomycetes , which included all species forming apothecia ; the Pyrenomycetes , which included all sac fungi that formed perithecia or pseudothecia , or any structure resembling these morphological structures; and the Plectomycetes, which included those species that form cleistothecia . Hemiascomycetes included

5562-648: The CT1 cell line. They used this cell line to study how leafhopper cells interacted with S. citri cells in vivo . After incubation of beet leafhopper cells with S. citri cells , researchers used an electron microscope to see how cell lines interact. They found that S. citri cells were pressed against the cell membranes of C. tenellus cells, and they also observed invaginations of the cell membrane. They concluded that these sighting were consistent with previous studies which suggested that S. citri cells are taken up by beet leafhopper cells by endocytosis. The beet leafhopper

5665-449: The atmosphere and freshwater environments, as well as ocean beaches and tidal zones. The distribution of species is variable; while some are found on all continents, others, as for example the white truffle Tuber magnatum , only occur in isolated locations in Italy and Eastern Europe. The distribution of plant-parasitic species is often restricted by host distributions; for example, Cyttaria

5768-560: The beet leafhopper, researchers inoculated insects with the pathogen and then observed the locations of S. citri inside the leafhoppers using electron microscopy. They observed S. citri in the gut as well as the salivary glands of the insects which further proves that the pathogen may be transmitted by the mechanisms described in the studies above. In particular, researchers observed that S. citri were often found within gut epithelial and salivary gland cells on infected hosts within small membrane bound vesicles. This led them to believe that

5871-427: The beet leafhoppers when it uses them as vectors. However the authors also noted how this damage was not as significant as seen in other insects which may suggest that the beet leafhopper may be co-evolving to reduce harm by S. citri pathogens. In a follow-up study to understand the exact mechanism of uptake of S. citri cells by beet leafhopper gut cells, researchers developed a line of beet leafhopper cells called

5974-456: The body are uniseriate, meaning that they are arranged in a row are present on the hind tibia of the insect. One of the distinguishing feature of this species is also the presence of plates on males. For general information on insect anatomy see: Insect morphology . Beet leafhoppers are polyphagous generalists which means that they are able to feed on various different types of host (biology) plants. The fact that these insects migrate during

6077-470: The body. Another important finding of this study was showing that individual insects can maintain MBCTV in their bodies for up to a 30 days after getting infected by it, even though the amount of virus detected does not increase in this period. The authors propose that this indicates that MBCTV is unable to replicate within its vector. It was also found that the virus is not transmitted between generations of beet leafhoppers from adults to nymphs, proposing that

6180-755: The cell. Many species live on dead plant material such as leaves, twigs, or logs. Several species colonize plants, animals, or other fungi as parasites or mutualistic symbionts and derive all their metabolic energy in form of nutrients from the tissues of their hosts. Owing to their long evolutionary history, the Ascomycota have evolved the capacity to break down almost every organic substance. Unlike most organisms, they are able to use their own enzymes to digest plant biopolymers such as cellulose or lignin . Collagen , an abundant structural protein in animals, and keratin —a protein that forms hair and nails—, can also serve as food sources. Unusual examples include Aureobasidium pullulans , which feeds on wall paint, and

6283-417: The cuticle for dispersal. Asexual reproduction process in ascomycetes also involves the budding which we clearly observe in yeast. This is termed a "blastic process". It involves the blowing out or blebbing of the hyphal tip wall. The blastic process can involve all wall layers, or there can be a new cell wall synthesized which is extruded from within the old wall. The initial events of budding can be seen as

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6386-605: The development of a ring of chitin around the point where the bud is about to appear. This reinforces and stabilizes the cell wall. Enzymatic activity and turgor pressure act to weaken and extrude the cell wall. New cell wall material is incorporated during this phase. Cell contents are forced into the progeny cell, and as the final phase of mitosis ends a cell plate, the point at which a new cell wall will grow inwards from, forms. There are three subphyla that are described and accepted: Several outdated taxon names—based on morphological features—are still occasionally used for species of

6489-408: The disease to uninfected plants. These findings suggest that the insects become virulent very shortly after feeding on infected plants. The study also found that as time of feeding on infected plants increased, the numbers of viral particles in the gut, hemocoel and salivary glands of the insects also increased, even though there were individual differences in the amounts of BMCTV particles detected in

6592-433: The embryo within the leafhopper egg, with higher temperatures generally being proportionally related to quicker development. The optimal range of temperatures for the development of these insects is between 65 and 95 °F (18 and 35 °C). This means that development takes longer over winter for these insects as compared to spring and summer times. Since development is very closely related to temperature, researchers in

6695-407: The ends of specialized hyphae, the conidiophores. Depending on the species they may be dispersed by wind or water, or by animals. Conidiophores may simply branch off from the mycelia or they may be formed in fruiting bodies. The hypha that creates the sporing (conidiating) tip can be very similar to the normal hyphal tip, or it can be differentiated. The most common differentiation is the formation of

6798-663: The fungal symbiont directly obtains products of photosynthesis . In common with many basidiomycetes and Glomeromycota , some ascomycetes form symbioses with plants by colonizing the roots to form mycorrhizal associations. The Ascomycota also represents several carnivorous fungi , which have developed hyphal traps to capture small protists such as amoebae , as well as roundworms ( Nematoda ), rotifers , tardigrades , and small arthropods such as springtails ( Collembola ). The Ascomycota are represented in all land ecosystems worldwide, occurring on all continents including Antarctica . Spores and hyphal fragments are dispersed through

6901-428: The fungi and correspond roughly to the sexes in plants and animals; however one species may have more than two mating types, resulting in sometimes complex vegetative incompatibility systems. The adaptive function of mating type is discussed in Neurospora crassa . Gametangia are sexual structures formed from hyphae, and are the generative cells. A very fine hypha, called trichogyne emerges from one gametangium,

7004-662: The ground to take root. Plant diseases cause major economic losses for farmers worldwide. Across large regions and many crop species, it is estimated that diseases typically reduce plant yields by 10% every year in more developed settings, but yield loss to diseases often exceeds 20% in less developed settings. The Food and Agriculture Organization estimates that pests and diseases are responsible for about 25% of crop loss. To solve this, new methods are needed to detect diseases and pests early, such as novel sensors that detect plant odours and spectroscopy and biophotonics that are able to diagnose plant health and metabolism . As of 2018

7107-517: The group its name. Asexual reproduction is the dominant form of propagation in the Ascomycota, and is responsible for the rapid spread of these fungi into new areas. Asexual reproduction of ascomycetes is very diverse from both structural and functional points of view. The most important and general is production of conidia, but chlamydospores are also frequently produced. Furthermore, Ascomycota also reproduce asexually through budding. Asexual reproduction may occur through vegetative reproductive spores,

7210-423: The gut, hemocoel and salivary glands of beet leafhoppers and found that the virus was present in all those regions suggesting that the virus may use a circulative transmission mechanism inside its host. A circulative transmission mechanism refers to a transmission mechanism in which the vector ingests a pathogen during feeding from an infected host, the pathogen is absorbed in the vector’s gut and then travels through

7313-615: The hemocoel into the salivary glands. When the vector then bites into an uninfected host, the pathogen enters the new host. This mechanism is similar to the transmission mechanism used by "Spiroplasma citri" in transmitting the Stubborn citrus disease which also uses the beet leafhopper as a vector. In the same study, researchers were able to detect viral particles of MBCTV in beet leafhopper guts after as soon as an hour of feeding on infected plants. Furthermore, they found that insects that had fed on an infected plant for an hour were able to spread

7416-518: The hook with one nucleus, one at the basal of the original hypha that contains one nucleus, and one that separates the U-shaped part, which contains the other two nuclei. Fusion of the nuclei (karyogamy) takes place in the U-shaped cells in the hymenium, and results in the formation of a diploid zygote . The zygote grows into the ascus , an elongated tube-shaped or cylinder-shaped capsule. Meiosis then gives rise to four haploid nuclei, usually followed by

7519-446: The hyphae, called " septa ", are the internal boundaries of individual cells (or compartments). The cell wall and septa give stability and rigidity to the hyphae and may prevent loss of cytoplasm in case of local damage to cell wall and cell membrane . The septa commonly have a small opening in the center, which functions as a cytoplasmic connection between adjacent cells, also sometimes allowing cell-to-cell movement of nuclei within

7622-416: The hyphae. The two nuclei contained in the apical part of each hypha divide in such a way that the threads of their mitotic spindles run parallel, creating two pairs of genetically different nuclei. One daughter nucleus migrates close to the hook, while the other daughter nucleus locates to the basal part of the hypha. The formation of two parallel cross-walls then divides the hypha into three sections: one at

7725-478: The insects prefer to settle and lay eggs on and which plants were good for insect survival. These studies are important as factors like host preference may impact which species of plants the BCTV is transmitted to. It is also important to understand the complex interactions that take place between the beet leafhopper and non-host plants to understand how disease may be spread. Tests of settling behaviors showed that although

7828-436: The insects settled similarly on all plants in the beginning, the numbers of beet leafhoppers on bean and tomato plants declined significantly after a period of four hours. Instead, the insects preferred to settle on sugar beets, radish, potato and carrot plants. These results were similar to studies of insect mortality on the same plants, which showed that the majority of insects confined to bean and tomato plants had died within

7931-516: The insects where no eggs were laid on these plants. Even though bean and tomato plants proved to be in-hostile hosts for the beet leafhopper, research shows that the insects still transmit the BCTV to these plants. A major implication of this study is that it shows that plants which are inappropriate hosts of the beet leafhopper insect can also be transmitted with the Beet Curly Top Virus. The authors propose that these findings may suggest that

8034-612: The kerosene fungus Amorphotheca resinae , which feeds on aircraft fuel (causing occasional problems for the airline industry), and may sometimes block fuel pipes. Other species can resist high osmotic stress and grow, for example, on salted fish, and a few ascomycetes are aquatic. The Ascomycota is characterized by a high degree of specialization; for instance, certain species of Laboulbeniales attack only one particular leg of one particular insect species. Many Ascomycota engage in symbiotic relationships such as in lichens—symbiotic associations with green algae or cyanobacteria —in which

8137-495: The latent period of S. citri within the leafhopper and found that insects that had been injected directly with the prokaryote in their gut had the lowest latency period of 10 days followed by leafhoppers who had ingested the pathogen from an infected plant (16 days). In testing the time taken for the insects to acquire S. citri , the acquisition access period, researchers found that a time period of at least 6 hours of feeding on S. citri cultures were required for insects to acquire

8240-600: The local ecosystem. From an economic standpoint, all but the simplest natural additives may disqualify a product from "organic" status, potentially reducing the value of the yield. Crop rotation is a traditional and sometimes effective means of preventing pests and diseases from becoming well-established, alongside other benefits. Other biological methods include inoculation. Protection against infection by Agrobacterium tumefaciens , which causes gall diseases in many plants, can be provided by dipping cuttings in suspensions of Agrobacterium radiobacter before inserting them in

8343-486: The most costly diseases of the most produced crops worldwide are: Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota , forms the subkingdom Dikarya . Its members are commonly known as the sac fungi or ascomycetes . It is the largest phylum of Fungi, with over 64,000 species . The defining feature of this fungal group is the " ascus " (from Ancient Greek ἀσκός ( askós )  'sac, wineskin'),

8446-402: The mycelium from which they originate. They are typically formed at the ends of specialized hyphae , the conidiophores . Depending on the species they may be dispersed by wind or water, or by animals. Different types of asexual spores can be identified by colour, shape, and how they are released as individual spores. Spore types can be used as taxonomic characters in the classification within

8549-523: The organisms are able to make their way into the hemocoel of the insect through which they are transferred to the insect’s salivary glands. When the insect then feeds on healthy plants, the prokaryotes enter the phloem of the plant and thus infect the new plant. One study has shown that this process of transmission also has negative effects on the leafhopper itself, where significant numbers of leafhoppers may die after being infected with S. citri . The researchers suggest that this increased mortality may be as

8652-436: The original parent nuclei. Alternatively, nuclei may lose some chromosomes, resulting in aneuploid cells. Candida albicans (class Saccharomycetes) is an example of a fungus that has a parasexual cycle (see Candida albicans and Parasexual cycle ). Sexual reproduction in the Ascomycota leads to the formation of the ascus , the structure that defines this fungal group and distinguishes it from other fungal phyla. The ascus

8755-413: The parent structure). Conidiogenesis corresponds to Embryology in animals and plants and can be divided into two fundamental forms of development: blastic conidiogenesis, where the spore is already evident before it separates from the conidiogenic hypha, and thallic conidiogenesis, during which a cross-wall forms and the newly created cell develops into a spore. The spores may or may not be generated in

8858-456: The pathogen. However this study should be viewed critically as insects were membrane fed a culture of the organism to determine this time period and actual results may vary when insects feed on an infected plants. The study also found that the numbers of host plants that were infected with S. citri increased with the numbers of infected leafhoppers that were feeding on these plants. In an experiment to understand how S. citri cells move within

8961-472: The pellicles or moldy layers that develop on jams, juices, and other foods are the mycelia of these species or occasionally Mucoromycotina and almost never Basidiomycota . Sooty molds that develop on plants, especially in the tropics are the thalli of many species. Large masses of yeast cells, asci or ascus-like cells, or conidia can also form macroscopic structures. For example. Pneumocystis species can colonize lung cavities (visible in x-rays), causing

9064-516: The plant itself. However, a small number, around 100 known species, cause disease, especially in subtropical and tropical regions of the world. Most plant pathogenic bacteria are bacilli . Erwinia uses cell wall–degrading enzymes to cause soft rot . Agrobacterium changes the level of auxins to cause tumours with phytohormones. Significant bacterial plant pathogens include: Phytoplasma and Spiroplasma are obligate intracellular parasites , bacteria that lack cell walls and, like

9167-533: The plant with BCTV. This waveform is also the same waveform which is produced during phloem ingestion by beet leafhoppers. Thus, this study further lends credibility to the transmission model that suggests that beet leafhoppers transmit the BCTV when they feed on the phloem sap of healthy plants. A previous study of oviposition in the beet leafhopper has shown that the insects prefer to lay eggs on beet plants even when they prefer different host plants for feeding. In another study, researchers tried to study which plants

9270-656: The process of heterokaryosis, caused by merging of two hyphae belonging to different individuals, by a process called anastomosis , followed by a series of events resulting in genetically different cell nuclei in the mycelium . The merging of nuclei is not followed by meiotic events , such as gamete formation and results in an increased number of chromosomes per nuclei. Mitotic crossover may enable recombination , i.e., an exchange of genetic material between homologous chromosomes . The chromosome number may then be restored to its haploid state by nuclear division , with each daughter nuclei being genetically different from

9373-668: The results - more thorough pest eradication and lesser taste degradation than heat treatment. The International Plant Protection Convention (IPPC) anticipates that molecular diagnostics for inspections will continue to improve. Between 2020 and 2030, IPPC expects continued technological improvement to lower costs and improve performance, albeit not for less developed countries unless funding changes. Many natural and synthetic compounds can be employed to combat plant diseases. This method works by directly eliminating disease-causing organisms or curbing their spread; however, it has been shown to have too broad an effect, typically, to be good for

9476-759: The same species. Species of the Deuteromycota were classified as Coelomycetes if they produced their conidia in minute flask- or saucer-shaped conidiomata, known technically as pycnidia and acervuli . The Hyphomycetes were those species where the conidiophores ( i.e. , the hyphal structures that carry conidia-forming cells at the end) are free or loosely organized. They are mostly isolated but sometimes also appear as bundles of cells aligned in parallel (described as synnematal ) or as cushion-shaped masses (described as sporodochial ). Most species grow as filamentous, microscopic structures called hyphae or as budding single cells (yeasts). Many interconnected hyphae form

9579-423: The size of the instars follow a sigmoidal curve which means that there is greatest increase in size among younger instars and the rate of growth decreases as the instars reach adulthood. Beet leafhoppers may show different coloration based on the time of year that they mature in. Generally, adults that mature during warmer temperatures in the spring and summer time show light green or yellowish colouration. This

9682-514: The spores reach a suitable substrate, they germinate, form new hyphae, which restarts the fungal life cycle. The form of the ascus is important for classification and is divided into four basic types: unitunicate-operculate, unitunicate-inoperculate, bitunicate, or prototunicate. See the article on asci for further details. The Ascomycota fulfil a central role in most land-based ecosystems . They are important decomposers , breaking down organic materials, such as dead leaves and animals, and helping

9785-864: The spring and summer time to cultivated fields also means that they show a lot of variation in their host plant choices by season: feeding on desert weeds in the winter and feeding on cultivated fields in the summer. They also show incredible variation in food choices between populations in different states, and these choices may change depending on host plant diversity, availability, defenses, etc. In one study on host plant preferences of beet leafhoppers from California and New Mexico , researchers found that beet leafhoppers from California preferred to feed on sugar beet plants while those from New Mexico preferred to feed on kochia, Russian thistle and redwood pigweed plants. The study also found differences in short term and long term feeding preferences where both kinds of leaf hoppers initially settled on beet plants (when observed over

9888-453: The study also concluded that the number of leafhopper generations produced in a year may be related to the seasonal temperatures of their habitat. They found that under lab conditions, where the leafhoppers were raised in optimal temperatures of 95 °F (35 °C), as many as 15–16 generations of leafhoppers could be produced per year. However they cited that actual numbers of generations per year may be limited to up to eight generations in

9991-483: The surrounding temperatures of the last leaf hopper instars as this is the stage during which wings develop. This may also be backed by the fact that adult leaf hopper do not change colour once they have matured regardless of the temperature of their environment. Several studies conducted in the 1970s and 1980s have showed that the beet leafhopper is a vector (epidemiology) of the Spiroplasma citri prokaryote which

10094-409: The thallus of the fungus defines the shape of the symbiotic colony. Some dimorphic species, such as Candida albicans , can switch between growth as single cells and as filamentous, multicellular hyphae. Other species are pleomorphic , exhibiting asexual (anamorphic) as well as a sexual (teleomorphic) growth forms. Except for lichens, the non-reproductive (vegetative) mycelium of most ascomycetes

10197-454: The use of fungicides and other agricultural practices. However, new races of fungi often evolve that are resistant to various fungicides. Biotrophic fungal pathogens colonize living plant tissue and obtain nutrients from living host cells. Necrotrophic fungal pathogens infect and kill host tissue and extract nutrients from the dead host cells. Significant fungal plant pathogens include: The oomycetes are fungus-like organisms among

10300-453: The virus does not use transovarial transmission . In another study, waveforms from electrical penetration graphs (EPG) were used to understand which waveforms coincided with the inoculation of plants with BCTV. As insects feed on different parts of the plant, they produce different EPG waves which can be measured using probes wired to the insects. Researchers found that D waveforms were most likely to coincide with successful inoculation of

10403-664: The warmer parts of the Southern United States. This may be partly because other factors like the seasonal availability of beet plants as food, may also impact the number of generations in a year. Generally beet plants are harvested in October which would limit food resources for the beet leafhopper in the fall. The life cycle of the beet leafhopper consists of three stages: eggs, nymphs and adults. The insects grow through 5 different molts during development which provides 5 instars before they reach adulthood. The growth patterns in

10506-822: The yeasts and yeast-like fungi that have now been placed into the Saccharomycotina or Taphrinomycotina , while the Euascomycetes included the remaining species of the Ascomycota, which are now in the Pezizomycotina , and the Neolecta , which are in the Taphrinomycotina. Some ascomycetes do not reproduce sexually or are not known to produce asci and are therefore anamorphic species. Those anamorphs that produce conidia (mitospores) were previously described as mitosporic Ascomycota . Some taxonomists placed this group into

10609-509: Was surprising however was that the rate of phloem ingestion in beet leafhoppers is significantly lower than that in other sap feeding insects. This leads researchers to believe that beet leafhoppers are unable to use the natural turgor pressure of phloem sap in order to ingest fluid and may need to use muscles to actively draw sap from phloem. A study of beet leafhoppers in Idaho showed that they are capable of producing multiple generations within

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