detection of (pvyntn ) strain in potato fields of khorasan razavi province

abstract the pvyntn strain induces potato tuber necrotic ringspot disease ptnrd . pvyntn strain is sub group of tobacco necrosis veinal pvyn strain . pvyntn strain is a recombinant between pvyn and pvyo strains . symptoms are often totally symptomless or undetectable by visual inspections at harvest , usually are apparent during post harvest in storage conditions and induce to decrease quality and marketability of potato tubers. reverse transcription polymerase chain reaction (rt-pcr) is an accurate and reliable tool for differantion and detection of pvyntn strain and prove to be an important tool in confirmation of symptoms and for the detection of pvyntn in symptomless tissues .in our survey , during the summer of 2007, 435 tubers from 32 potato fields in khorasan razavi province were collected randomly. tubers passed dormancy period at 4˚с and transfered to the greenhouse at 25˚с for germination. sprouts emerging from the tubers were tested by das-elisa with polycolonal antibody. 53 positive samples in das-elisa which had high absorbance values at 405 nm were selected . total rna was extracted from 40 infected plants tissue using rnx plus-tm solution. then two specific primers pairs designed within the coat protein (cp) region, used for cdna synthesis in reverse transcription polymerase chain reaction (rt-pcr) . samples infected with pvy produce a band of 569 bp by mor2 & mor3 primers. while isolates belonging to pvyntn strain gave a band of 334 bp by mor1 & mor2 primers .