Efficient methods for sample processing and cDNA synthesis by RT-PCR for the detection of grapevine viruses and viroids.
Template preparation is important in reverse-transcription polymerase chain reaction (RT-PCR)-based detection methods. A TissueLyser with tungsten carbide beads was used for simultaneous processing of up to 48 samples under the same conditions in the development of a simple and rapid procedure to prepare a plant extract for RT reaction. A sandpaper method was also developed by which wood tissue of dormant cuttings could be macerated easily to process with minimal time and effort. It was also demonstrated that the combination use of random primers and oligo dT primer in an RT reaction was efficient for simultaneous cDNA synthesis of viral and viroid RNAs in plant extracts. These template preparation methods were used for the amplification of Grapevine leafroll-associated virus-1,-2, and -3; Grapevine virus A and B; Grapevine rupestris stem pitting-associated virus; Grapevine fleck virus; and Grapevine fanleaf virus. All these viruses tested in this study were reliably detected up to a 10(3)-fold or higher dilution of the original extract. Besides, Hop stunt viroid and Grapevine yellow speckle viroid 1 were well amplified in the same manner as the template preparation and following PCR for virus detection. These methods would contribute to cost-effective testing of a large number of samples through the year and help to detect viral pathogens in grapevine.