A NEW MILD STRAIN OF POTATO SPINDLE TUBER VIROID ISOLATED FROM WILD SOLANUM-SPP IN INDIA

A disease syndrome whose symptoms include stunting, leaf crinkling, and severe veinal necrosis was observed among four wild Solanum spp. maintained at the Central Potato Research Institute, Simla, India. Consistent with a possible viroid etiology, transfer of the infectious agent to tomato (Lycopersicon esculentum 'Rutgers') produced symptoms that were indistinguishable from those induced by the mild strain of potato spindle tuber viroid (PSTVd), and dot blot hybridization analysis of infected plants using an RNA probe complementary to PSTVd yielded strongly positive reactions. Nucleotide sequence analysis of the isolates from Solanum sucrense, S. verrucosum, and S. chacoense showed them to be identical, each containing two nucleotide substitutions within the central conserved region when compared with a mild strain of PSTVd isolated from potatoes grown in North America. The isolate from S. multiinterruptum was identical in sequence to the previously described mild strain of PSTVd.