Directorate of Rice Research, Rajendranagar, Hyderabad-500030, India.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Rice tungro virus disease (RTV) is of great economic importance in India. The disease occurs sporadically and it has been reported that the yield loss associated with tungro was remarkable and substantial between 1979 and 2001. Rice tungro virus can appear at any stage of rice crop right from seedling stage. Though two types of virus particles, a spherical RNA plant picorna virus (RTSV) and a bacilliform DNA pararetro virus (RTBV) are found associated in the infected tissues, the disease is thought to be primarily caused by rice tungro spherical virus (RTSV). Tungro infection leads to a reduction in plant height, turns green leaves to yellow or orange and infected plants may show excessive tillering. Tungro disease is effectively spread by green leafhopper species, especially Nephotettix virescens Distant. Incorporation of resistance to tungro disease is one of the major objectives in rice improvement programme. In the earlier work carried out emphasis was on breeding for resistance to tungro spherical virus. Many varieties such as Vikramarya, Nidhi, Radha, Rajeswari, Srinivas etc. have been released for commercial cultivation in farmers fields. Several crosses between the susceptible TN 1 and other donors for resistance to RTSV were made. The inheritance of resistance in these crosses was studied. Recent research initiatives entered on molecular mapping of resistance genes in donors and varieties possessing resistance to RTSV. Genomic regions associated with tungro disease resistance were identified in Utri Rajapan, Vikramarya and Utri Merah, two regions on chr 7 and chr 2 in Utri Rajapan, two regions on chr 7 and chr 1 in Vikramarya and one region on chr 7 in Utri Merah were found to be associated with RTSV resistance. The spread of rice tungro disease can be checked indirectly by controlling the vector by suitable pesticide application. Strategies for management of tungro virus disease will be discussed.
