Impatiens necrotic spot virus
Encyclopedia
Summary
Impatiens necrotic spot virus (INSV) is a plant pathogenic virus
of the family Bunyaviridae
. It was originally believed to be another strain of Tomato spotted wilt virus but genetic investigations revealed them to be separate viruses. It is a single stranded RNA It has a tripartate genome
and is largely spread by the insect
vector of the western flower thrip
. The virus infects more than 300 species of plant
including important horticultural
and agricultural
species
such as fuchsia
, tomato
, orchids , and lettuce
(especially romaine). As the name implies, the main symptom on plants are necrotic spots that appear on the leaves. The INSV virus infects by injecting the RNA the virus contains into the cell which then starts using the cell resources to transcribe what the virus RNA states. Viral infection can often result in the death
of the plant. The disease is mainly controlled by the elimination of the western flower thrip vector and by destroying any infected plant material.
Disease cycle
The disease is a ssRNA that injects itself into the host cell, then has the host cell duplicates the RNA sequence as well as the coat protein used to disguise the RNA. The infected cell also starts to create moment proteins that facilitates the movement of the virus through the plant making the Plasmodesmata (connections between plant cells) large enough to allow the virus to move through out the plant. The virus can then also infect other plants by ether the infected sap or a vector, such as an insect, which will start the cycle over again.
Management
Typically the best way to manage a virus problem is to get rid of any vectors that may carry the disease this easily can be done by an insecticide. Another acceptable method would be resistance plants these plants would kill of any infected cells not allowing the virus to spread. Furthermore larger distance between plants could help the spread of the disease not allowing the virus to be transmitted virtually.
Hosts and symptoms
INSV has a wide host range and can be found in over 300 plant species including weeds, vegetables and ornamental crops. Of these, the most severely affected include tomato, lettuce, pepper and peppermint (1). Symptoms of infection include a downward curling of the leaves, leaf tip dieback, stunting, necrosis of growing leaf tips, sunken ‘chicken pox-like’ spots on leaves, stem death and yellowing. (3) Since these symptoms are so generic, extreme caution must be taken when introducing new plants to your greenhouse. Infected plants can not be cured and not all hosts display visible symptoms. (5)
Western Flower Thrips are extremely hard to remove from their host plants, as they often dig themselves deep into blossums, buds and other areas hard to reach with insecticides. (ces.ncsu.edu) So, even if plants are sprayed regularly with insecticide, INSV and other insect vectored viruses can not always be ruled out when forming diagnosis. (ces.ncsu.edu)
Environment
Since INSV is a virus it relies on vector transmission in order to infect and spread to new hosts. This is achieved by insects called Western Flower Thrips. Vector transmission allows the virus a range limited only by the reach of the insect. (3) Greenhouses provide ideal environments for Western Flower Thrips and preventative measures must be taken in order to insure healthy plants. (4)
Although Wester Flower Thrips were at one time only a pest across the western United States and Canada, their spread has now reached world wide. They are now considered to be the most serious pest for floricultural plants across much of the world. (ces.ncsu.edu) Females lay anywhere from 150-300 eggs during their lifetime, with each offspring having a life of roughly 28 days. The majority of their lives are spent in their adult stage.
Importance
The spread of INSV can be achieved easily through the importation of infected plants. This has been demonstrated in 1991 by its sudden emergence in Portugal, where it was discovered in over 30 plant species. (1) By raising Enzyme-linked immunosorbent assays against the nucleoproteins of symptomatic species, eight isolates have been identified in Italian vegetable and ornamental crops. (2)
Symptoms of Impatiens necrotic spot virus in an Orchid species
Impatiens necrotic spot virus (INSV) is a plant pathogenic virus
Plant virus
Plant viruses are viruses that affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses are pathogenic to higher plants...
of the family Bunyaviridae
Bunyaviridae
Bunyaviridae is a family of negative-stranded RNA viruses. Though generally found in arthropods or rodents, certain viruses in this family occasionally infect humans. Some of them also infect plants....
. It was originally believed to be another strain of Tomato spotted wilt virus but genetic investigations revealed them to be separate viruses. It is a single stranded RNA It has a tripartate genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
and is largely spread by the insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
vector of the western flower thrip
Frankliniella occidentalis
The western flower thrips is an important pest insect in agriculture. This species of thrips is native to North America but has spread to other continents including Europe, Australia, and South America via transport of infested plant material...
. The virus infects more than 300 species of plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
including important horticultural
Horticulture
Horticulture is the industry and science of plant cultivation including the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding and genetic...
and agricultural
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
such as fuchsia
Fuchsia
Fuchsia is a genus of flowering plants that consists mostly of shrubs or small trees. The first, Fuchsia triphylla, was discovered on the Caribbean island of Hispaniola in 1703 by the French Minim monk and botanist, Charles Plumier...
, tomato
Tomato
The word "tomato" may refer to the plant or the edible, typically red, fruit which it bears. Originating in South America, the tomato was spread around the world following the Spanish colonization of the Americas, and its many varieties are now widely grown, often in greenhouses in cooler...
, orchids , and lettuce
Lettuce
Lettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important...
(especially romaine). As the name implies, the main symptom on plants are necrotic spots that appear on the leaves. The INSV virus infects by injecting the RNA the virus contains into the cell which then starts using the cell resources to transcribe what the virus RNA states. Viral infection can often result in the death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
of the plant. The disease is mainly controlled by the elimination of the western flower thrip vector and by destroying any infected plant material.
Disease cycle
The disease is a ssRNA that injects itself into the host cell, then has the host cell duplicates the RNA sequence as well as the coat protein used to disguise the RNA. The infected cell also starts to create moment proteins that facilitates the movement of the virus through the plant making the Plasmodesmata (connections between plant cells) large enough to allow the virus to move through out the plant. The virus can then also infect other plants by ether the infected sap or a vector, such as an insect, which will start the cycle over again.
Management
Typically the best way to manage a virus problem is to get rid of any vectors that may carry the disease this easily can be done by an insecticide. Another acceptable method would be resistance plants these plants would kill of any infected cells not allowing the virus to spread. Furthermore larger distance between plants could help the spread of the disease not allowing the virus to be transmitted virtually.
Hosts and symptoms
INSV has a wide host range and can be found in over 300 plant species including weeds, vegetables and ornamental crops. Of these, the most severely affected include tomato, lettuce, pepper and peppermint (1). Symptoms of infection include a downward curling of the leaves, leaf tip dieback, stunting, necrosis of growing leaf tips, sunken ‘chicken pox-like’ spots on leaves, stem death and yellowing. (3) Since these symptoms are so generic, extreme caution must be taken when introducing new plants to your greenhouse. Infected plants can not be cured and not all hosts display visible symptoms. (5)
Western Flower Thrips are extremely hard to remove from their host plants, as they often dig themselves deep into blossums, buds and other areas hard to reach with insecticides. (ces.ncsu.edu) So, even if plants are sprayed regularly with insecticide, INSV and other insect vectored viruses can not always be ruled out when forming diagnosis. (ces.ncsu.edu)
Environment
Since INSV is a virus it relies on vector transmission in order to infect and spread to new hosts. This is achieved by insects called Western Flower Thrips. Vector transmission allows the virus a range limited only by the reach of the insect. (3) Greenhouses provide ideal environments for Western Flower Thrips and preventative measures must be taken in order to insure healthy plants. (4)
Although Wester Flower Thrips were at one time only a pest across the western United States and Canada, their spread has now reached world wide. They are now considered to be the most serious pest for floricultural plants across much of the world. (ces.ncsu.edu) Females lay anywhere from 150-300 eggs during their lifetime, with each offspring having a life of roughly 28 days. The majority of their lives are spent in their adult stage.
Importance
The spread of INSV can be achieved easily through the importation of infected plants. This has been demonstrated in 1991 by its sudden emergence in Portugal, where it was discovered in over 30 plant species. (1) By raising Enzyme-linked immunosorbent assays against the nucleoproteins of symptomatic species, eight isolates have been identified in Italian vegetable and ornamental crops. (2)
Symptoms of Impatiens necrotic spot virus in an Orchid species
External links
- ICTVdB - The Universal Virus Database: Impatiens necrotic spot virus
- Family Groups - The Baltimore Method
- - Management of INSV
- http://www.ext.colostate.edu/pubs/garden/02947.html
- http://extension.psu.edu/plant-disease-factsheets/all-fact-sheets/impatiens-necrotic-spot-virus
- http://www.ces.ncsu.edu/depts/ent/notes/O&T/flowers/ort072e/ort072e.html