A MIXTURE OF SYNTHETIC OLIGONUCLEOTIDE PROBES LABELED WITH BIOTIN FORTHE SENSITIVE DETECTION OF POTATO SPINDLE TUBER VIROID

Five kinds of synthetic oligonucleotide probes labeled with biotin (BI O) were designed for the detection of potato spindle tuber viroid (PST Vd), and their sensitivities were compared with that of a digoxigenin (DIG)- or BIO-labeled cDNA probe. Although each oligonucleotide probe alone was less sensitive than the DIG-cDNA probe, sensitivity was incr eased by using a mixture of two or all of the five oligonucleotide pro bes. The sensitivity of a PSmix1-5 probe, which was a mixture of five oligonucleotides, was the same as that of a DIG-labeled cDNA probe, wh ich can detect 7.8 pg of purified PSTVd and PSTVd in nucleic acids, eq uivalent to extracts from 20 mu g of infected potato leaf and 310 mu g of infected potato tuber. Using the PSmix1-5 probe, PSTVd in all leav es and tubers of seven potato cultivars could be detected without any background. Moreover, with the PSmix1-5 probe, the hybridization time could be shortened to 2 h without any decrease in sensitivity, whereas the sensitivity of the cDNA probes clearly decreased when the hybridi zation time was shortened. Hybridization using a mixture of several ol igonucleotide probes may be applicable to the gene diagnosis of other viroids and viruses. (C) 1998 Elsevier Science B.V. All rights reserve d.