Detection of potato spindle tuber viroid by nucleic acid spot hybridization: Evaluation with tuber sprouts and true potato seed

Abstract

A diagnostic test for the potato spindle tuber viroid (PSTV) that is based on hybridization of highly radioactive, recombinant DNA complementary to PSTV with PSTV bound to a nitrocellulose membrane and autoradiographic detection of the resulting DNA-RNA hybrids has been evaluated with tubers from 20 potato clones maintained at the International Potato Center (CIP) and with true seed obtained from healthy or PSTV-infected potato plants. The nucleic acid spot hybridization test detected PSTV not only in tuber sprouts from 10 clones that had previously tested positive in polyacrylamide gel electrophoretic (PAGE) analysis, but also in tuber sprouts from 9 clones that had previously tested negative in PAGE analysis. Further tests confirmed the presence of PSTV in these clones. The spot hybridization test detected PSTV in mixtures of seed extracts equivalent to as few as one seed from a PSTV-infected plant and 80 seeds from healthy plants. The spot hybridization test was shown to be more sensitive and reliable than PAGE analysis; it is suitable for the testing of large numbers of samples with a minimum expenditure of labor and materials.