Potato virus surveys and wide spread of recombinant PVYNTN variant in Central Tunisia

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 PVYN group (88.2% of the total number of singly PVY positives). Furthermore, molecular typing of strains revealed that 73.3% of the PVYN group were typical PVYNTN 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 PVYN group. To our knowledge, this is the first report of the occurrence of the PVYNTN 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.