Nucleic acid represents the genetic material, indispensable for replication. Many viruses, especially plant viruses, are transmitted by insects. Seasonality of interactions between a plant virus and its. Plant viruses are obligate parasites, often causing the death of their host, so it is necessary for them to spread from plant to plant and to be introduced into living cells. Specificity of transmission is defined as the specific relationship between a plant virus and one or a few vector species but not others.
Vertical transmission in vertical transmission, the virus is inherited from a parent. Supriya chakraborty, jawaharlal nehru university, india the plant viruses section of virology journal covers studies on all aspects of plant viruses including viral structure, gene function, genetics, virushost interactions, viral pathogenesis, epidemiology, host resistance, rna silencing and so on. Most plant viruses rely on insect vectors for survival, transmission and spread. In asexual reproductive methods such as vegetative propagation, the offspring develop from and are genetically identical to a single plant. Transmission of plant viruses by dodder springerlink. Plant viruses are widespread and economi cally important plant pathogens. Introduction approximately 20% of plant viruses are transmitted from gener ation to generation in the seed matthews, 1991. The threat of transmission of semi persistent and persistent plant viruses appears to be restricted to plants where the pea aphid probed as far as the sieve elements and ingested the phloem sap katis et al. Plant viruses are obligate parasites, often causing the death of their host, so it is necessary for them to spread from plant. Viruses that lost the ability to be transmitted by vectors serve to identify. Plant viruses have been studied primarily as important pathogens of crops. About 190 aphid species are known to transmit plant viruses, with many species capable of transmitting more than one virus species 18, 19. They cause various diseases characterised by a combination of severe symptoms and high transmission rates 1,2,3.
Thus, the transmission of a plant pathogen by an insect to a plant appears relatively simple. Virus interactions with these vectors are diverse, but there are some commonalities. Mink, 1993, and yet very little is known about the mechanisms involved. A aphid transmit can transmit the virus only if the source plant is infected by second virus. Insects are the most common of the vectors and, among these, aphids account for the transmission of 50% of the insectvectored viruses brunt et al. These genes control the ability of psbmv to spread into andor multiply in. Symptoms will vary depending on the virus and the plant.
All viruses that spread within their host tissues systemically can be transmitted by grafting branches or buds from diseased plants on healthy plants. Chikara masuta, hokkaido university, japan deputy section editor. Generally the infection cycle begins with the vector encountering the virus in the plant and the virus is acquired by the vector. Horizontal transmission by a direct route includes airborne infection, foodborne infection, and venereal. The effectiveness of viral transmission depends on the virus concentration and the route of transmission. Plantinfecting viruses are transmitted by a diverse array of organisms including insects, mites, nematodes, fungi, and plasmodiophorids. Evidence of first virus that infects both plants and. Plants regularly encounter abiotic constraints, and plant response to stress has been a focus of research for decades. Pdf plant virus transmission by insects researchgate. Epidemics occur when a new virus or a new vector invade a new ecological niche. Although these insect viruses cannot multiply within. This type of transmission occurs in both asexual and sexual reproduction. It occurs in those plants in which virus are present in high concentration. Transmission of plant viruses by aphid vectors ng 2004.
Pea seedborne mosaic virus psbmv, a seedtransmitted virus in pea and other legumes, invades pea embryos early in development. Cultural, physical and novel biotechnological tools can provide virus control by interfering with vector landing and the retention of viruses in their vectors. So it is a dependent virus and second virus is referred as the helper virus virus helper virus vector type of transmission potato aucuba mosaic virus pva or y m. A majority of plant viruses are dependent on vectors for their transmission and survival.
Evidence of first virus that infects both plants and humans. The biology of plant virus transmission has been studied for more than 100 years ando, 1910, gutierrez et al. Most vectors are piercingsucking insects that transmit plant viruses in either the circulative virus cv or noncirculative virus ncv. Articles are characterized by their novelty, innovativeness, and the hypothesisdriven nature of their. Very graphical video with easy language to understand easily how virus transmits in plants. If validated, this would mark the first time a plant virus has been found to cause problems in people. About 190 aphid species are known to transmit plant viruses, with many species capable of transmitting more than one virus species 18, 19 including potato viruses.
Horizontal transmission can be further classiwed as direct or indirect. Plant virus, vector, transmission, specificity, virusligand interaction. Introduction plant viruses can cause severe yield losses to the cere. Impact of abiotic stresses on plant virus transmission by. Although much is known about the proteins and processes within the plant cell required for efficient virus transmission, up to now, little was known about the requirements and mechanisms from the insect point of view. Because hc and virus particles can be acquired sequentially, it is possible for one virus to assist in the transmission of a second virus. This process is controlled by maternal genes and, in a cultivar that shows no seed transmission, is prevented through the action.
Plant virus transmission advanced article by insects. The epidemiology of plant diseases caused by insectcarried plant pathogens involves four main components. Virus binds to a specific location in the stylet or foregut virus produces a protein that binds to vector cuticle in a specific location and binds to virus coat protein, released with saliva insect feeds on infected plant to acquire virus can transmit. This process is controlled by maternal genes and, in a cultivar that shows no seed transmission, is prevented through the action of multiple host genes segregating as quantitative trait loci. Author summary rice stripe virus rsv, which is completely dependent on laodelphax striatellus for transmission between host plants, can also be vertically transmitted from the mother insect to its offsprings. However, this situation is highly complex when one examines all the. When viruses are transmitted by seeds, the seed is infected in the generative cells and the virus is maintained in the germ cells and sometimes, but less often, in the seed coat.
Behavioural aspects influencing plant virus transmission by homopteran insects. Viruses can be transmitted horizontally from individual to individual and vertically from parents to offspring. Transmission of tobacco mosaic virus by the dodder,cuscuta japonica and its inhibitory effect on the virus activity. Broad bean mottle virus in morocco variability, interaction with food legume species, and seed transmission in faba bean, pea, and chickpea. Transovarial transmission of a plant virus is mediated by. Plant virus transmission from the insect point of view pnas. Transmission by this means consists of the removal of the plant sap from a diseased plant by artificial or natural means and its transfer to a healthy plant by rubbing or injecting.
Ncv are carried on the lining cuticle of vectors stylets. Mechanisms of arthropod transmission of plant and animal. Plant virus transmission from generation to generation occurs in about 20% of plant viruses. Transmission specificity can be broad or narrow but it is a prominent feature for numerous viruses and vectors. Pollen and seedtransmission of tobacco streak virus in okra pollen from an infected plant used for hybridization can carry virus and infect embryo of a recipient plant during fertilization. The virus needs to be spread so that it can continue reproducing and ensuring the survival of the virus species. They trans mit plant viruses by two principal modes. In spite of the ongoing debate regarding tool sterilization, there is surprisingly little information in the scientific literature that addresses this issue. Seed from recipient plants can carry virus leading to virus transmission. Many plant viruses have vec tors, providing the means for. Pdf most plant viruses depend on vectors for their survival and spread.
Most plant viruses depend on insect vectors for their survival, transmission and spread. It is the viruses of cultivated crops that have been most studied because of the financial implications of the losses they incur. With the exception of tobacco mosaic virus, relatively few viruses or viroids are spread extensively in the field by contact between diseased and healthy leaves. Most vectors are piercingsucking insects that transmit plant viruses in. Pdf transmission of plant viruses by aphid vectors. Much of the early work on plant virusinsect vector associations was related to. Cvs cross the vectors gut, move internally to the salivary glands sg, cross the sg membranes to be ejected upon feeding.
The requirement for helper components hc facilitating virus transmission by living organisms, termed vectors, is characteristic of plant viruses in several genera, potyviruses genus potyvirus. Virtually all plants that humans grow for food, feed, and fiber are affected by at least one virus. It highlights recent advances in the field and identifies areas of desirable progress. Cucumber mosaic virus plant virus citrus tristeza virus barley yellow dwarf virus. Specificity between viruses and vector species may reflect the preference of the vector to the plant species. The knowledge of virus transmission is important to. This spread or transmission will be considered under the following headings. Since then many studies have examined the specificity of insect vectormediated plant virus transmission and clearly demonstrated that there are specific molecular determinants required e. The evolution of plant virus transmission pathways usda forest. Plant viruses naturally spread through three main transmission pathways. In horizontal transmission, viruses are transmitted among individuals of the same generation.
The following points highlight the eight chief methods used for the transmission of plant viruses. Aphids and whiteflies are by far the most important insects transmitting plant viruses. Plant viruses affect many plants and cause a wide range of discolourations and distortions in leaves, shoots, stems and flowers, but rarely kill the plant. Horizontal and vertical transmission of viruses in the. Insects, mites, nematodes and protists all mediate the transmission of plant viruses. The higher the viral concentration, the higher the chances of transmission. Given increasing global temperatures and elevated atmospheric co2 levels and the occurrence of water stress episodes driven by climate change, plant biochemistry, in particular, plant defence responses, may be altered significantly.
Repeating subunits, identical for each virus type but varies from virus to virus and even from strain to strain. However, this situation is highly complex when one examines all the possible elements that can influence these interactions. Insect vectormediated transmission of plant viruses. Recognize a virus as cause of the disease if transmitted from infected to healthy plant how virus spread in field help in its control establish biological relationship of interaction between virus and its vector. The availability of the pathogen is affected by its quantity, location, and the strain within the plant. More than 200 plant viruses are transmitted by specific arthropod vectors. Seed transmission of the high plains virus in sweet corn. Passing through the insect hemolymph is an essential step for both kinds of viral transmission. In other cases the vector remains permanently infective persistent transmission. Virus transmission an overview sciencedirect topics. Therefore, it seems justified to predict a very low rate of virus transmission to or from m.
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