Incidence of Viruses and Nematode Vectors in Lebanese Vineyards

Surveys for virus diseases and nematode vectors were conducted in 95 commercial vineyards of four different Lebanese districts (Bekaa valley, Mount Lebanon, North and South Lebanon). Out of 915 randomly collected grapevine samples tested by ELISA, 511 (55.8%) were infected by one or more viruses. Grapevine virus A (30.9%) and Grapevine leafroll‐associated virus 3 (23.7%) were the prevailing viruses, followed by Grapevine fleck virus (15.1%), Grapevine leafroll‐associated virus 1 (10.6%) and Grapevine leafroll‐associated virus 2 (8.7%). Arabis mosaic virus was not found whereas Grapevine fanleaf virus (GFLV) and Grapevine virus B were little represented. The most important Lebanese grapevine varieties, i.e. Maghdouchi, Tfeifihi and Beitamouni, had average infection rates between 70% and 87%, whereas varieties of foreign origin had a better sanitary status with the exception of cvs Cinsaut and Thompson (c. 83% infection). Grapevine rupestris stem pitting‐associated virus was detected in 79 of 90 (87.8%) samples tested by RT‐PCR and closteroviruses were recorded in seven of 70 (10%) vines tested. One of these viruses was identified as Grapevine leafroll‐associated virus 5 by ELISA and partial genome sequencing. No nepoviruses other than GFLV were detected in any of 90 samples tested using three different sets of degenerate primers. Xiphinema index was found in 23 of 89 soil samples collected from vineyards, and in three of 15 samples collected primarily under fig trees in fields where no grapevines were grown.