Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms, and most cause diseases, whose respective economic importance to humans varies widely.
Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described.
Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term arbovirus is a portmanteau word. Tibovirus is sometimes used to more specifically describe viruses transmitted by ticks, a superorder within the arthropods. Arboviruses can affect both animals and plants. In humans, symptoms of arbovirus infection generally occur 3–15 days after exposure to the virus and last three or four days. The most common clinical features of infection are fever, headache, and malaise, but encephalitis and viral hemorrhagic fever may also occur.
Geminiviridae is a family of plant viruses that encode their genetic information on a circular genome of single-stranded (ss) DNA. There are 520 species in this family, assigned to 14 genera. Diseases associated with this family include: bright yellow mosaic, yellow mosaic, yellow mottle, leaf curling, stunting, streaks, reduced yields. They have single-stranded circular DNA genomes encoding genes that diverge in both directions from a virion strand origin of replication. According to the Baltimore classification they are considered class II viruses. It is the largest known family of single stranded DNA viruses.
Metaviridae is a family of viruses which exist as Ty3-gypsy LTR retrotransposons in a eukaryotic host's genome. They are closely related to retroviruses: members of the family Metaviridae share many genomic elements with retroviruses, including length, organization, and genes themselves. This includes genes that encode reverse transcriptase, integrase, and capsid proteins. The reverse transcriptase and integrase proteins are needed for the retrotransposon activity of the virus. In some cases, virus-like particles can be formed from capsid proteins.
Closteroviridae is a family of viruses. Plants serve as natural hosts. There are four genera and 59 species in this family, seven of which are unassigned to a genus. Diseases associated with this family include: yellowing and necrosis, particularly affecting the phloem.
Potyviridae is a family of positive-strand RNA viruses that encompasses more than 30% of known plant viruses, many of which are of great agricultural significance. The family has 12 genera and 235 species, three of which are unassigned to a genus.
Trialeurodes vaporariorum, commonly known as the glasshouse whitefly or greenhouse whitefly, is an insect that inhabits the world's temperate regions. Like various other whiteflies, it is a primary insect pest of many fruit, vegetable and ornamental crops. It is frequently found in glasshouses (greenhouses), polytunnels, and other protected horticultural environments. Adults are 1–2 mm in length, with yellowish bodies and four wax-coated wings held near parallel to the leaf surface.
Begomovirus is a genus of viruses, in the family Geminiviridae. They are plant viruses that as a group have a very wide host range, infecting dicotyledonous plants. Worldwide they are responsible for a considerable amount of economic damage to many important crops such as tomatoes, beans, squash, cassava and cotton. There are 445 species in this genus.
Crinivirus, formerly the lettuce infectious yellows virus group, is a genus of viruses, in the family Closteroviridae. They are linear, single-stranded positive sense RNA viruses. There are 14 species in this genus. Diseases associated with this genus include: yellowing and necrosis, particularly affecting the phloem.
Tomato yellow leaf curl virus (TYLCV) is a DNA virus from the genus Begomovirus and the family Geminiviridae. TYLCV causes the most destructive disease of tomato, and it can be found in tropical and subtropical regions causing severe economic losses. This virus is transmitted by an insect vector from the family Aleyrodidae and order Hemiptera, the whitefly Bemisia tabaci, commonly known as the silverleaf whitefly or the sweet potato whitefly. The primary host for TYLCV is the tomato plant, and other plant hosts where TYLCV infection has been found include eggplants, potatoes, tobacco, beans, and peppers. Due to the rapid spread of TYLCV in the last few decades, there is an increased focus in research trying to understand and control this damaging pathogen. Some interesting findings include virus being sexually transmitted from infected males to non-infected females, and an evidence that TYLCV is transovarially transmitted to offspring for two generations.
Pepper golden mosaic virus is a plant pathogenic virus of the family Geminiviridae. It affects Capsicum annuum and all tomatoes. It was first discovered in Texas in 1987, and was called Texas Pepper Virus, and a two years later in Mexico after it destroyed up to 100% of plants in afflicted fields in the autumn of 1989, mainly in north-west Mexico.
The Potato yellow vein virus (PYVV) is a plant pathogen of the Closteroviridae family. It is a whitefly-transmitted closterovirus vectored by Trialeurodes vaporariorum, which is known to cause a yellowing disease in potato crops in South America. PYVV RNA have a conserved 3'-terminal secondary structure, which includes a pseudoknot.
Cassava brown streak virus disease (CBSD) is a damaging disease of cassava plants, and is especially troublesome in East Africa. It was first identified in 1936 in Tanzania, and has spread to other coastal areas of East Africa, from Kenya to Mozambique. Recently, it was found that two distinct viruses are responsible for the disease: cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). Both have (+)ss RNA genomes, belong to the genus Ipomovirus in the family Potyviridae, and produce generally similar symptoms in infected plants. Root rot renders the cassava tuber inedible, resulting in severe loss of economic value; therefore, current research focuses on achieving cultivars that do not develop the necrotic rot. This disease is considered to be the biggest threat to food security in coastal East Africa and around the eastern lakes.
Banna virus (BAV) is a virus belonging to Reoviridae, a family of segmented, non-enveloped, double-stranded RNA viruses. It is an arbovirus, being primarily transmitted to humans from the bite of infected mosquitoes of the genus Culex. Pigs and cattle have also been shown to become infected. The most common symptom of infection is fever, but in some cases encephalitis may occur. There is no specific treatment for infection, so treatment is aimed at alleviating the severity of symptoms until the immune system has cleared the infection.
Abutilon mosaic virus (AbMV) is a virus of the genus Begomovirus. It infects Abutilon species, notably the flowering maple, Abutilon striatum. The mottled or variegated effect on the leaves of Abutilon striatum is sought after.
Trialeurodes abutiloneus or the banded-wing whitefly is a species of whitefly of the genus Trialeurodes first described by Haldeman in 1850.
Tomato yellow leaf curl China virus (TYLCCNV) is a virus which contains 25 isolates. It infects plants as different as tobacco and tomato, as well as genetically modified plants. Petunias can be infected, but show no symptoms. The microbiology of the virus has been studied in the Chinese province of Yunnan. Tomato yellow leaf curl China virus belongs to the genus Begomovirus, which also contains the tomato leaf curl China virus.
Beet pseudoyellows virus (BPYV) is a species of virus in the genus Crinivirus.
