Etiology and transmission of mottle streak disease of finger millet (Eleusine coracana Gaertn.)

Four stages in the development of symptoms commencing from small specks to total yellowing were observed in finger millet infected by mottle streak disease. Presence of bacilliform Rhabdovirus particles was ascertained under electron microscope in all the leaf samples that exhibited varying degrees of mottle streak infection, viz. mottling, streaking, striping and yellowing. Different buffers at various pH were attempted for mechanical transmission on monocotyledon plants and weeds as well as on dicotyledon local lesion hosts. The results indicated that the virus could not be transmitted by sap. The leaf hopper Cicadulina bipunctella was found to transmit the virus efficiently up to 80%. The virus vector relationship revealed that 72 h of acquisition access period, 5 days of inoculation access period and nearly 30 days of incubation in the host were required for attaining efficient transmission.