The disease known as "spotted wilt" was first described in Australia in 1 9 1 5 ( 16) and shown to have a viral etiology b y Samuel et al i n 1930 ( 14 1 ). Since that time, viruses similar or identical to the tomato spotted wilt virus (TSWV) have been the cause of plant diseases epidemics in tropical, subtropical, and temperate regions throughout the Northern hemisphere, Western Europe, and Asia (2, 7, 19 , 29, 30, 55, 56, 78, 80, 105 , 108, 1 5 1 , 1 53 , 170). Major economic losses are due in large part to an extremely wide host range involving more than 500 species of plants in more than 50 families that

Tospoviruses: diagnosis, molecular biology, phylogeny, and vector relationships.

SUMMARY Among plant viruses, Tomato spotted wilt virus (TSWV) is considered as the most widespread and to have the largest host-range. This virus is responsible for numerous epidemics in different regions of the world, mainly in horticultural and floral crops, which are often destructive and cause heavy economic losses. The highly polyphagous nature, the efficiency of virus transmission and the biological activity of its vectors, the rapidity with which new variants arise, and difficulties in the control of the vectors, make TSWV one of the most feared plant viruses by growers of agricultural crops. Preventive and integrated cultural practices such as the eradication of weed hosts able to serve as virus reservoirs, combined with vector management strategies, play a crucial role in the control of the virus. Thus, the availability of an up-to-date list of TSWV host plants is a potentially useful reference for researchers and farmers. The current list of TSWV hosts consists of 1090 plants species belonging in 15 families of monocotyledonous plants, 69 families of dicotyledonous plants and one family of pteridophytes.

https://sipav.org/main/jpp/volumes/0403/040301.pdf

An update of the host range of tomato spotted wilt virus

The nucleotide sequences of the nucleoprotein (N) genes of seven tospovirus isolates representing three serogroups were determined and used to establish phylogenetic parameters to delineate species within the Tospovirus genus of the Bunyaviridae. A high sequence divergence (55.9% identity at the nucleotide level) was observed between isolates of serogroup I (tomato spotted wilt virus) and isolates of serogroup III (Impatiens necrotic spot virus). The serogroup II isolates take an intermediate position. Their N genes have 75% identity with those of serogroup I isolates and 57% with those of serogroup III isolates. Whereas the isolates within serogroups I or III have almost identical sequences, the two isolates BR-03 and SA-05 of serogroup II diverged significantly from each other (82·1% sequence identity). The results obtained support the conclusion that, in addition to the species TSWV and INSV, the serogroup II isolates BR-03 and SA-05 have to be considered as distinct species within the genus Tospovirus for which the names tomato chlorotic spot virus and groundnut ringspot virus, respectively, are proposed.

Classification of tospoviruses based on phylogeny of nucleoprotein gene sequences

Inheritance of resistance to tomato spotted wilt virus (TSWV) derived from the cultivar ‘Stevens’ was studied. Five TSWV isolates, which differ in geographic origin and elicit different symptoms on tomato, were used to screen the resistant parent plants. Enzyme-linked immunosorbent assay (ELISA) was used to distinguish healthy and infected plants. Two susceptible advanced breeding lines were crossed with four F4 plants of a ‘Stevens’ × ‘Rodade’ obtained from South Africa (SA). There were no differences in the progeny responses of the four SA parents to TSWV. The inheritance of TSWV resistance was found to be a single dominant gene. The SA, F1, and the backcrosses to the resistant parent were found to have eight out of 612 plants infected four months after the inoculations, which indicates a 98.7% penetrance of the resistance gene.

R.F.L. Mau

Papers

Reservoir weed hosts of tomato spotted wilt virus