No abstract

The incidence, severity and distribution of four virus diseases of potato were determined in the main production areas of Lebanon during the 2001 and 2002 growing seasons. Observations were also recorded on diseases incited by fungi and bacteria, as well as physiological disorders. The surveys covered 40 randomly selected potato fields from three different areas of the Bekaa valley, the main potato production region of Lebanon. 715 samples were individually collected and tested by DAS-ELISA for Potato virus A (PVA), Potato virus X (PVX), Potato virus Y (PVY) and Potato leafroll virus (PLRV). 51% of the total tested samples were infected by one or more viruses. PVY was the most prevalent virus, detected in 98.8% of the total number of infected samples, followed by PVA and PVX (both at 10.6%) and PLRV (9.3%). Mixed infections were about 17%. Potato tuber necrotic ring spot disease, caused by PVY NTN , was determined by immunocapture reverse transcription polymerase chain reaction. The fungi Thanatephorus cucumeris , Verticillium dahliae , Fusarium sp., Sclerotinia sclerotiorum and the bacterium Erwinia carotovora were the main pathogens found to be associated with the diseased plants. Quarantine pests such as Clavibacter michiganensis subsp. sepedonicus and Ralstonia solanacearum were not encountered. Growth cracks, hollow heart and internal rust spot were the predominant physiological disorders observed.