Lettuce mosaic virus
Encyclopedia
Lettuce mosaic virus is a typical potyvirus (genus Potyvirus, family Potyviridae
), which causes one of the major virus
disease
s of lettuce
crops worldwide.
LMV is seed
-borne to a low but significant rate (1-10% of the seeds produced by an infected mother plant germinate into infected seedling
s). This provides the primary inoculum in lettuce crops. LMV, and thus the mosaic disease, is then spread locally from plant to plant by the feeding stylet
s of aphid
s.
Like all plant virus
es, LMV is totally harmless to the consumer but causes defects in heading, leaf distortion
s and leaf colour anomalies, which altogether result in the infected lettuce plants to be unmarketable. Disease rates can reach 100% locally, and therefore cause complete loss of the harvest
. LMV can also infect other crops such as spinach
and pea
s, as well as ornamentals (especially the Cape Daisy
Osteospermum spp) and wild plants (especially the prickly lettuce
Lactuca serriola and the oxtongue Helminthia echioides). All these plants, and probably others, can serve as local sources from which LMV can spread to crops.
s caused by viruses in plant
s, there is no mean to cure
plants from LMV once they are infected
. Prevention of LMV can however be relatively efficient based on:
In the late twentieth century, a novel type of LMV appeared in lettuce crops around the world. It was called LMV-Most (mo1-breaking, Seed-Transmitted) to account for its ability to infect and to spread through seeds even in the presence of mo1. Therefore, LMV-Most can only be prevented by controlling seeds, which consumes time, effort and money.
Potyviridae
The Potyviridae are a family of plant viruses. They are . Their genome is composed of positive-sense RNA which is surrounded by a protein coat made up of a single viral encoded protein called a capsid. All induce the formation of virus inclusion bodies called in their hosts...
), which causes one of the major virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
s of 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...
crops worldwide.
LMV is seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
-borne to a low but significant rate (1-10% of the seeds produced by an infected mother plant germinate into infected seedling
Seedling
thumb|Monocot and dicot seedlingsA seedling is a young plant sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle , the hypocotyl , and the cotyledons...
s). This provides the primary inoculum in lettuce crops. LMV, and thus the mosaic disease, is then spread locally from plant to plant by the feeding stylet
Stylet
A stylet is a hard, sharp, anatomical structure found in some invertebrates.For example, the word stylet or stomatostyle, is used for the primitive piercing mouthparts of some nematodes and some nemerteans...
s of aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s.
Like all plant 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...
es, LMV is totally harmless to the consumer but causes defects in heading, leaf distortion
Distortion
A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice...
s and leaf colour anomalies, which altogether result in the infected lettuce plants to be unmarketable. Disease rates can reach 100% locally, and therefore cause complete loss of the harvest
Harvest
Harvest is the process of gathering mature crops from the fields. Reaping is the cutting of grain or pulse for harvest, typically using a scythe, sickle, or reaper...
. LMV can also infect other crops such as spinach
Spinach
Spinach is an edible flowering plant in the family of Amaranthaceae. It is native to central and southwestern Asia. It is an annual plant , which grows to a height of up to 30 cm. Spinach may survive over winter in temperate regions...
and pea
Pea
A pea is most commonly the small spherical seed or the seed-pod of the pod fruit Pisum sativum. Each pod contains several peas. Peapods are botanically a fruit, since they contain seeds developed from the ovary of a flower. However, peas are considered to be a vegetable in cooking...
s, as well as ornamentals (especially the Cape Daisy
Osteospermum
Osteospermum is a genus belonging to the Calenduleae, one of the smaller tribes of the sunflower family .Osteospermum used to belong to the genus Dimorphotheca, but only the annual species remain in that genus; the perennials belong to Osteospermum. The genus Osteospermum is also closely related...
Osteospermum spp) and wild plants (especially the prickly lettuce
Lactuca
Lactuca, commonly known as lettuce, is a genus of flowering plants in the daisy family Asteraceae. The genus includes about 100 species, distributed worldwide, but mainly in temperate Eurasia....
Lactuca serriola and the oxtongue Helminthia echioides). All these plants, and probably others, can serve as local sources from which LMV can spread to crops.
Prevention
Like other diseaseDisease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
s caused by viruses in 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...
s, there is no mean to cure
Cure
A cure is a completely effective treatment for a disease.The Cure is an English rock band.Cure, or similar, may also refer to:-Film and television:* The Cure , a short film starring Charlie Chaplin...
plants from LMV once they are infected
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
. Prevention of LMV can however be relatively efficient based on:
- control of the absence of LMV in seed lots before tradingTradeTrade is the transfer of ownership of goods and services from one person or entity to another. Trade is sometimes loosely called commerce or financial transaction or barter. A network that allows trade is called a market. The original form of trade was barter, the direct exchange of goods and...
; typically, ELISAELISAEnzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
is used and a rejection rate of 1 out of 30,000 seeds is applied;
- the use of the recessiveRecessiveIn genetics, the term "recessive gene" refers to an allele that causes a phenotype that is only seen in a homozygous genotype and never in a heterozygous genotype. Every person has two copies of every gene on autosomal chromosomes, one from mother and one from father...
resistanceDisease resistance in fruit and vegetablesThere are a number of lines of defence against pests and diseases in the organic garden, principal among these being the practice of good husbandry, creating healthy soil and ensuring high standards of garden hygiene...
geneGeneA gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
mo1; mo1 has two commercial alleleAlleleAn allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
s (mo1¹, formerly known as g, and mo1², formerly known as mo), both of which protect plants against LMV accumulation and, in some cases where LMV nevertheless accumulates, protect against symptomSymptomA symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
expression as well as prevents transmission through seed.
In the late twentieth century, a novel type of LMV appeared in lettuce crops around the world. It was called LMV-Most (mo1-breaking, Seed-Transmitted) to account for its ability to infect and to spread through seeds even in the presence of mo1. Therefore, LMV-Most can only be prevented by controlling seeds, which consumes time, effort and money.