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First Report of Grapevine “Bois Noir” Disease and a New Phytoplasma Infecting Solanaceous Plants in Lebanon

During a 2001 survey to evaluate the incidence of phytoplasma diseases in Lebanon, samples were collected from plants showing symptoms suggestive of phytoplasmal infections. Samples were also collected from symptomless plants. Sampled hosts from the Bekaa Valley included: 3 samples of tomato (Lycopersicum esculentum), 4 samples of pepper (Capsicum annuum), 10 samples of grapevine (Vitis vinifera) cvs. Chardonnay and Alicante Bouschet; 7 samples of ornamental periwinkle (Catharantus roseus) from the Tyr area; and 4 samples of weeds (Lactucca serratia). DNA was extracted from leaf midveins of diseased and symptomless plants, and from healthy periwinkle, grapevine, tomato, and pepper plants grown in a greenhouse in France. Polymerase chain reaction (PCR) with universal primers for the amplification of phytoplasma ribosomal RNA genes (3) only produced a 1.8-kbp rDNA fragment from symptomatic samples. The amplified DNAs were analyzed by restriction fragment length polymorphism (RFLP) with several restriction enzymes and sequenced. The analysis showed extracts of diseased grapevines, and two periwinkle plants had identical rDNA sequences and restriction profiles of the stolbur cluster (4). The sequences had 98% identity with two European stolbur isolates from grapevine and periwinkle (GenBank Accession Nos. X76428 and AF248959, respectively). In grapevine, the disease induced by the stolbur phytoplasma is “bois noir.” Bois noir is present in Europe where its incidence is predominant in northern vineyards and has been reported in Israel (2). To our knowledge, this is the first report of the stolbur/bois noir disease in Lebanon. In tomato and pepper, the restriction profiles and sequences of the phytoplasma rDNAs were identical. Sequencing and phylogenetic analysis indicated that the phytoplasma belonged to the clover proliferation (CP) cluster, as does the eggplant little leaf phytoplasma of solanaceous plants in Asia. They differed from the stolbur phytoplasma, known to infect solanaceaous plants in Europe. Lastly, a phytoplasma belonging to the pigeon pea witches' broom (PPWB) cluster was found in L. serratia and in some periwinkle plants. A phytoplasma of the PPWB cluster was recently shown to be responsible for an emerging lethal disease of almond trees in Lebanon (1).

References: (1) E. Choueiri et al. Plant Dis. 85:802, 2001. (2) X. Daire et al. Vitis 36:53, 1997. (3) B. Schneider et al. Pages 369--380 in: Molecular and Diagnostic Procedures in Mycoplasmology. Academic Press, NY, 1995. (4) E. Seemüller et al. J. Plant Pathol. 80:3, 1998.