Abstract

Dolichos lab lab L., is an important pulse crop in Madras State. During August, 1965 a ring spot disense was observed on D. lab lab (Fig. 1) in the experimental plots of the Millet Breeding Station, Agricultural College and Research Institute, Coimbatore. The disease was found to affect both the garden (D. lab lab L., var. typicus Prain) as well as the field beans (D. lab lab L., var. lignosus Prain). The ring spots were about 2-5 mm in diameter with concentric rings surrounding an island of apparently normal tissue. On older leaves the rings appeared to fade away giving the leaves more or less a mosaic appearance. So far, only a few viruses have been described as naturally occurring on Dolichos. Nour and Nour (1962) reported a mosaic disease of Dolichos lab lab (hyacinth bean) in Northern Sudan. A ring spot mottle virus was reported to occur in Peking by Cheo and Tsai (1959). In India Capoor and Varma (1948) reported from Poona a mosaic disease on D. lab lab, which they described as Dolichos enation mosaic. In the year 1950 the same authors reported the occurrence of another disease on D. lab lab from Poona which they named Dolichos yellow mosaic. In India apart from these two records, there appears to be no other report on the natural occurrence of virus diseases on this crop. Studies were carried out on the transmission, host range and physical properties of the virus and the results obtained are described in this paper.

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