Negative sense single stranded RNA [(-)ssRNA] viruses replicate in both the plant nucleus as well as the cytoplasm, depending on the genus of virus. In this group, some or all of the genes are translated into protein from an RNA strand complementary to that of the genome (as packaged in the virus particle).
This group and it also includes important human pathogenic viruses that cause measles, influenza and rabies. For example, Rhabdovirus and Bunyavirus have negative strand RNA genomes, are enveloped, are transmitted by insects and members of both families infect both plants and animals.
Viruses – ssRNA viruses – ssRNA negative-strand viruses –
|Tenuivirus – Rice stripe virus
Synonyms rice stripe virus RSV
|As a typical member of the genus Tenuivirus, RSV has filamentous particles which appear folded, branched and supercoiled by electron microscopy and it replicates in both plant and insect vectors. RSV has several unique characteristics such as genome containing four negative sense RNA segments, exploiting ambisense gene expression strategy, multiplication in plant and insect vector cells, as well as using various mutation mechanisms, including deletion, insertion, recombination and reassortment.
||Causes one of the major virus rice diseases in in temperate and subtropical regions of Asia – in China, Japan and Korea. Infected usually exhibit such symptoms as chlorosis, weakness, necrosis in newly emerged leaves and stunting. It mainly infects rice plants, but also infects some other species in the family Poaceae, such as wheat and maize.
||Transmitted only in the circulative/persistent manner by the small brown planthopper (Laodelphax striatellus) and three other delphacid species, Unkanodes sapporona, U. albifascia and Terthron albovittatum. Also can be transmitted by mechanical inoculation (but only with great difficulty); not transmitted by contact between plants; not transmitted by seed.
||Planting disease-resistant cultivars is the ideal way to control rice viral diseases. COntrol vectors and volunteer plants. A novel strategy, Vector-Insect-Symbiont Technology (VIST), was proposed recently, aiming to use one of the endosymbiont Wolbachia in L. striatellus. to control RSV.
|Tenuivirus – Maize stripe virus
Synonyms maize stripe virus MStV
|The MStV are fine-stranded particles with a helical structure and measuring about 12 nm in diameter and up to 709 nm long. The 19.8 kDa noncapsid protein (NCP) crystals can be found readily in sap from the MStV-infected plants by phase-contrast light microscopy.
||Has been reported in tropical locations in Africa, Asia, and the Americas. Initial symptoms on the leaves are small chlorotic specks that later develop into narrow parallel chlorotic stripes along the younger leaves. Infected plants usually show stunting and bending of the tassels. Young plants infected at the 4- to 5-leaf stage often exhibit complete chlorosis on the emerging whorl leaf, and the center leaf usually remains folded and bent. The host range of MStV includes Zea spp., several Sorghum spp., and itchgrass (Rouboellia exaltata).s
||Transmitted by the corn delphacid planthopper, Peregrinus maidis in a persistent-propagative manner. Nymphs of the 2nd and 3rd instal transmit MStV with twice the efficiency as adult insects. Also transmitted through the egg of the planthopper vector. This may be significant to both the long distance spread and the ability of the virus to overseason between maize crops. The rate of transovarial transmission was reported from 33.3% to 59%S.
||Traditional methods of virus disease control such as vector control, prompt removal of infected plants, eliminating the itchgrass near plantings, and breeding for resistance to the insect vector or the virus are recommended.
|Bunyaviridae – Tospovirus – Tomato spotted wilt virus
Synonyms tomato spotted wilt virus TSWV
|Tospoviruses are characterized by having tripartite RNA genomes and utilizing both negative and ambisense genome expression strategies. TSWV is a type member of the only plant-infecting genus in the Bunyaviridae, alters the feeding behavior of its thrips vector, Frankliniella occidentalis: male thrips infected with TSWV fed more than uninfected males.
||Hosts include bean, lettuce, peanut, pepper, potato, tobacco, and tomato. Young leaves of slightly infected transplants turn bronze (purplish-brown) and later develop numerous small, dark spots. The infected tissue often dies. Shiny, dark brown streaks appear on stems and petioles. Growing tips of plants may die back. Affected fruit have spots about 1 cm in diameter with slightly raised, circular markings. Ripe fruit can be distorted and can have alternate red and yellow bands. Sometimes infected plants are killed by severe necrosis.
||Enter the plant cell during probing or feeding by viruliferous thrips, in which these viruses have been shown to replicate. Young (larval stage) thrips acquire TSWV when feeding from infected plants and then spread the virus as adults when they fly from plant to plant. The virus cannot be transmitted from one generation of thrip to another. Infected weeds or ornamental plants are generally the source of the virus.
||Some resistant varieties are available. The presence of thrips in tomato fields can be monitored using yellow sticky cards. Infected plants should be removed and destroyed immediately. Mesh netting (40-mesh or higher) can exclude thrips. Tomato fields should be located as far away as possible from home gardens, and flower or grain fields. Several insecticide applications should be made at 5-day intervals to significantly reduce thrip infestation.