Indian Journal of Virology

Mottle streak disease of finger millet is attaining an epidemic status in Tamil Nadu. The disease is invariably noticed in all the seasons in our experimental fields as well as in Dharmapuri district. During Rabi 2003 though the incidence was 3.0 per cent in variety Co 13, certain germplasm entries showed infection up to 45 per cent which were totally devastated at later stages of crop growth. Symptoms appear in field only after 40 to 45 days which initiate as specks or mottles. Later the specks enlarge, coalesce becoming streaks. Leaves and leaf sheaths become chlorotic, pale and wither. Tillering is reduced and infected plants produce many but small chaffy earheads. Marked difference is noticed between infected and healthy earheads. Leaf dip preparations from infected samples invariably showed the presence of bullet shaped bacilliform particles typical of Rhabdovirus. From infected crop as well as weeds on bunds the hopper Cicadulina sp., was collected predominantly in light trap catches. It is suspected that the virus survives in hoppers/grasses during the off-season. Continuous cropping of ragi cultivars highly prone to the virus or vector might lead to severe outbreak of the disease which warrants attention.