EVALUATION OF LINKED PCR-TRANSCRIPTION AMPLIFICATION PROCEDURE FOR BEAN YELLOW MOSAIC-VIRUS DETECTION IN GLADIOLI

Bean yellow mosaic virus (BYMV) concentration in in-vitro cultured Gla diolus cormlets was low and impossible to detect by the commonly used diagnostic methods. The polymerase chain reaction (PCR) detected viral RNA in most infected cormIets but not in all. Additional amplificatio n of the PCR products by transcription, using T7 RNA polymerase (PCR/T ), resulted in virus detection in cases which otherwise went undetecte d. PCR products having a single polymerase promoter at one end served as a better template for T7 RNA polymerase, and yielded more transcrip ts of a particular orientation than a template containing promoters at bath ends. Repeated cycles of PCR/T resulted in the production of a h eterogeneous amplified material which correlated with a progressive de cline in amplification rate. Therefore, only the first PCR/T cycle pro ved to be effective. The PCR/T procedure was shown to be better than o ther commonly used diagnostic methods including PCR.