Identification and Taxonomic Groups

Abstract

In the early period of plant virus research work, inadequate identification has led to lot of confusion due to lack of an internationally accepted classification of plant viruses. The discriminatory criteria are established by ICTV study groups, who have followed the rules laid out in the International Code of Virus Classification and Nomenclature (ICVCN). As new types of viruses continue to be discovered, new names must be created for taxa; several rules in the ICVCN govern the construction of these names.

Till now, nearly 231 virus and viroid diseases are reported to be seed transmitted in different crop plants. As per the latest ICTV classification by King et al. (Virus Taxonomy: 9th report of the international committee on taxonomy of viruses. Elsevier, San Diego, 2011), the seed-transmitted viruses were concerned to 231 virus families/plant virus groups. Among these plant virus groups, seed-transmitted viruses are distributed in 24 virus groups including Alfamovirus, Bromovirus, Capillovirus, Carlavirus, Carmovirus, Caulimovirus, Comovirus, Cryptovirus, Cucumovirus, Enamovirus, Fabavirus, Furovirus, Hordeivirus, Ilarvirus, Necrovirus, Nepovirus, Potexvirus, Potyvirus, Sobemovirus, Tobamovirus, Tobravirus, Tombusvirus, Tospovirus and Tymovirus groups. Greater number of seed-transmitted viruses are found in Poty (35), Nepo (28), Crypto (28), Ilar (14), Tobamo (7), Potex (7), Como (6), Carla (5), Carmo (5), Cucumo (5), Sobemo (5), Furo (4), Bromo (3) and Tymo (3) virus groups. On the other hand, in some groups such as Alfamo, Capillo, Caulimo, Enamo, Faba, Hordei, Necro, Tobra and Tombus groups, the seed-transmitted viruses recorded were very few. No seed transmission was noticed in Clostero, Diantho, Gemini, Luteo, Marafi, Parsnip yellow fleck, Reo, Rhabdo, Tenui and Waika groups.