Mechanism of Spread Of Pathogens

MECHANISM OF SPREAD OF PATHOGENS Active Deployment Active distribution can be divided into three parts, namely: Water gun mechanism:This mechanism is common in Ascomycetes class fungi. The ascus will swell before maturity and burst or open at the tip which directs the spores upwards. The pressure in the ascus is so high that the spores it shoots can reach a height of 100 meters at a fairly high speed. Cutting Mechanism:The upper end cells of the sporophore are suddenly cut off until the spores can be released into the air. Several species of Phycomycetes fungi have this mechanism, as do esiospores of rust pathogens Releasing Basidiospores:The basidiospoa is located symmetrically at the tip of the sterigma and when the spores ripen a drop of liquid is released from the hilum and causes the spores to be released instantly. Passive Dissemination Passive spread can be carried out by means of wind, water, animals, insects, agricultural tools and also humans. What is usually transported via this medium are pathogenic fungal spores. The dispersal of spores by any means is always preceded by a "take off" then flying along the way and finally landing somewhere.Passive dispersal of spores can occur by the following mechanisms following: Releases spores with gravity, where the dry spores collect on the spots to be released continuously due to gravity, but can also be assisted by gusts of wind. Mechanical momentum which results in the release of dry spores in large quantities. The source of this mechanical momentum is the impact of air flow and the impact of rainwater. The air flow shakes the plant parts causing the spores to be released from the fruiting bodies. Likewise, rainwater can hit plant parts causing mature spores to be released from the fruit bodies. For example, urediospores occur in rust disease which can stick to clothing, such as coffee rust disease caused by Hemileia vastatrix brought from Africa to Brazil via the jackets of coffee conference participants in 1960. Blown by the Wind, occurs in pathogenic fungi that produce dry spores. The location of the sporopores is slightly protruding above the surface so that turbulent wind currents can blow the spores away, for example conidiosporesHelminthosporium maydis. Hygroscopic Movement from conidiophores causes the release of spores. This movement is made possible by changes in the humidity of the surrounding atmosphere which often occur in the morning. Air containing mist hits tall spores that can be released from their conidiophores, for example fungal sporesBotritisspp. Water splash. Many fungal species produce spores that stick to each other. If the support is wet with water, the spores are no longer sticky and spread to cover the support in a thin layer. Raindrops that fall on this thin layer will splash everywhere and contain many spores. Furthermore, these spores can be carried by humans, insects or land, sea and air vehicles. Plant Virus diseases also spread passively in various ways as follows: Mechanical Transmission:The juice from sick plants containing the virus is rubbed on the surface of healthy plant leaves which were previously sprinkled with wound powderin the form of selite or carborundum to facilitate the entry of the virus into the plant through the wound. Transmission via Listings:Attachment is the oldest technique for artificially transferring plant parts to other plants such as: peg attachment, bud attachment, double attachment and double bud attachment and so on. Virus transmission through these listings is possible because the attack is systemic. Transmission with Taliputri (Cuscuta sp.) : Cuscuta sp. is a parasitic plant that does not have chlorophyll which has slender stems and grows wrapped around its host plant, producing haustoria which directly enter the host's vascular bundles. In this way, the parasite forms a bridge between diseased plants and healthy ones. Through this bridge the virus is transmitted from diseased plants to healthy plants. Transmission through vegetative parts:Usually plant virus infections are systemic. In this way, all parts of the plant can be entered by the virus, such as: tubers, scales, roots, wood buds and grafted shoots. Propagating and propagating plants infected with viruses using these parts can infect and spread the virus. For example, sugar cane cuttings can transmit mosaic virus . Transmission via seeds and pollen:Various types of viruses can be transmitted through seeds, such as tomato mosaic virus, common bean mosaic virus, cucumber mosaic virus and lettice mosaic virus . Most transmission via seeds is through institutions. Several types of viruses can be transmitted through pollen, such as alfalfa mosaic virus and bean common mosaic virus. For example, large chili plants and cayenne peppers are attacked by a complex of viruses, the most important of which is the cucumber mosaic virus which is very detrimental, fruit yield is reduced by up to 50%. Transmission via insects and mites:Various species of insects and mites are known to be very important vectors in transmitting plant viruses. Famous Homoptera nations include:Bemisia tabaci, Aphis craccivora, Myzus persicae, Nephotettix cincticeps, Sogatodes oryzicola and Planococcusspp. From the Acarina nation, among others: Abacarus hystrixAndBrevipalpus obovarus. The structure of the mouth and the way in which food is taken determines the efficiency, ability and method of transmission of these viruses. Vector species that have piercing and sucking mouthparts may be more efficient at transmitting the virus compared to species that have biting mouthparts. Non-persistent transmission:Acquisition and inoculation of the virus occurs within a very short feeding period, from a few seconds to several minutes. The vector immediately becomes infective after it sucks the fluids of diseased plants or even during the exploration period. There is no latent period in that vector. Retention in the vector becomes very short. Such transmission is called non-persistent. The virus is confined to the vector stylet. The infectious force can last up to 40 hours, if the vector has not encountered new plants. Butonce the vector sheds its exoskeleton (including the mouthparts), its infectivity is lost. Example: green planthopper, Nephotettixvirescensas a vector for tungro virus in rice plants. Persistent transmission:The vector picks up the virus after a long suction time, approximately 15 minutes, because the stylet must reach the phloem. Such viruses are usually impossible to transmit by mechanical means or squeezed fluids. There is a close biological relationship between the virus and its vector, because the virus that is inhaled continues to enter through the digestive tract, penetrates the intestinal wall, circulates in the haemolymph and contaminates saliva. The virus experiences a long latent period in the vector's body. After that the vector remains infective. Infectivity does not disappear after molting. The duration of the vector's infectivity depends on the amount of virus inhaled. Example: brown planthopper,Nilaparvata lugens, as a vector for grass stunt virus, grassy stunt virus and hollow stunt virus in rice plants. It is not yet known whether there is a difference in the transmission efficiency of the two viruses by brown planthopper biotypes. Semi-persistent transmission:The vector takes the virus from the phloem, with a long penetration time, but there is no latent period and the virus can only survive for a few days. The infectiousness of the virus disappears after changing the skin. The biological relationship between viruses and vectors is less familiar. Together with the inhaled food, the virus is absorbed into the lining of the throat, then slowly expelled from there and when the skin changes, it is also released. Example with an electron microscope,Anthriscus yellows virusobserved in the throat lining of Carrot AphidCaveriella aegopodii. Transmission by soil-dwelling organisms:Various viruses originating from plant remains are able to survive in the soil, for example tobacco and tomato mosaic virus particles andCucumber green mottle virusIt is very stable in the soil so it can maintain its infectious power. Some nematode species such as:Longidorusspp. And Xyphinemaspp. transmitting polyhedral nepovirus,Trichodorusspp. AndParatrichodorus spp. transmit tobravirusPeas early browningAndtobacco rattle virus.Some species of fungi such asOlpidiumspp. transmitTobacco virus,Cucumber necrosis virusAndRed clover necrotic virus.