Abstract

Surveys in the late season crops of Central Tunisia, one of the main potato growing areas, revealed the presence of the six most economically devastating viruses: potato leaf roll virus: PLRV: (Polerovirus), potato virus S (PVS) and M (PVM) (Carlavirus), potato virus X (PVX: Potexvirus), potato virus A (PVA) and Y (PVY) (Potyvirus) with large differences in incidence. Infection rates at harvest, assessed by serological test ranged from 0.5% (PVM) to 71% (PVY). The characterization of PVY variability was analyzed with a combination of serotyping, indexing on tobacco and reverse transcription polymerase chain reaction (RT-PCR) tests targeting 2 genomic regions (5’NTR/P1 and CP/3’NTR). Serological analysis of the collected samples revealed dominance of the PVY^N group (88.2% of the total number of singly PVY positives). Furthermore, molecular typing of strains revealed that 73.3% of the PVY^N group were typical PVY^NTN variants with a recombination junction in CP/3’NTR region for 94.4% of them, whereas no recombination junction was identified in the genome of the isolates belonging to the PVY^N group. To our knowledge, this is the first report of the occurrence of the PVY^NTN variant and its high incidence in late season potato growing areas of central Tunisia.

Key words: Diagnosis, immunocapture reverse transcription polymerase chain reaction (RT PCR), potato viruses, potato virus Y (PVY) diversity, Central Tunisia.