DETECTION AND TISSUE DISTRIBUTION OF POTATO SPINDLE TUBER VIROID IN INFECTED TOMATO PLANTS BY TISSUE PRINT HYBRIDIZATION

Potato spindle tuber viroid (PSTVd) was detected in two cultivars of t omato (Lycopersicon esculentum Mill.) by tissue print hybridization of cross-sections of stem and rhachis, using a S-35-labeled PSTVd RNA pr obe. PSTVd was detectable in the viroid-sensitive and symptom-developp ing cv ''Rutgers'' 2 weeks p.i., and in the viroid-tolerant and practi cally symptomless cv ''Goldkugel'' 3 weeks p.i. In both tomato cultiva rs, PSTVd accumulated in the upper parts of the plants newly grown aft er inoculation. It was predominantly found in association with the rin g formed by the vascular tissue. The final accumulation of PSTVd as we ll as its spatial distribution were similar in the sensitive and in th e tolerant tomato cultivar, as estimated from the tissue print autorad iographs. Thus, tissue print hybridization provides a rapid and sensit ive means for viroid diagnosis and for the assessment of tissue-specif ic localization of the viroid RNA.