SPECIFIC DETECTION OF POTATO-VIRUS A IN DORMANT TUBERS BY REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION

A reverse -transcription polymerase chain reaction (RT-PCR) protocol w as developed for the detection of potato virus A (PVA) in dormant tube rs. A 255-bp amplified product was produced using a primer pair from t he P1 gene of the PVA genome. The 255-bp product was detected in nucle ic acids from leaves, tubers, and purified virions and was specific to PVA as determined by Southern blot tests and detection by a PVA-speci fic probe. When presented with seven potato virus/strain nucleic acids and a viroid, singly and in mixed infections, the primer pair did not amplify any products. Its specificity to PVA was further demonstrated by RT-PCR detection of PVA from the known mixtures of PVA and potato virus Y samples. PVA was detected in foliage nucleic acids at a diluti on of 1:1024-1:4096 and tuber nucleic acids at 1:256-1:1024. It was un iformly present in various parts of the potato tuber. PVA was detected in composite tuber samples containing a ratio of infected to healthy sap of 1:29 and was readily detected in tubers of several cultivars or breeding lines, in dormant as well as in sprouting tubers stored at 2 0-25 degrees C for 4 months.