First Report of Phytoplasmas Associated with the Degeneration Syndrome of Artichoke in Catalonia (Spain).

Spain is the second largest producer of artichoke (Cynara scolymus L.) in the world with 230,000 tons produced annually. The region of Catalonia, located in northeast Spain, has 3,500 ha dedicated to this crop. Low yield and degeneration anomalies are widespread problems in the Mediterranean area. The degeneration syndrome results in curled leaves and late development of capitulum. The association of this syndrome with different viruses such as Artichoke degeneration virus (ADV), Artichoke latent virus (ALV), Broad bean wilt virus (BBWV), Cucumber mosaic virus (CMV), and many others was not conclusive. Other studies indicated that this phenomenon could be related to a regression of the cultivar toward the species of origin, the wild cardoon (C. cardunculus L. var. sylvestris). The distribution of degenerated plants in the principal artichoke-growing areas of Catalonia together with the presence of plants with normal and degenerated tissues in the same plant suggested the presence of phytoplasmas. Samples from 30 symptomatic and 30 asymptomatic plants of cv. Blanca de Tudela were collected in February of 2006 from different areas of Catalonia and analyzed by PCR amplification of phytoplasma DNA. DNA for PCR analyses was prepared from leaf petioles and midribs according to the Ahrens and Seemüller procedure (1). Nested-PCR was carried out with rRNA primer pairs P1/P7 and fU5/rU3 (2,3). Alternatively, nested-PCR, with primers Tuf 1 f/r in the first step and Tuf AY f/r in the second, amplifying a DNA fragment of the elongation gene Tu of the phytoplasmas belonging to Aster yellows and stolbur groups was conducted (4). Results showed a high correlation between presence of symptoms and phytoplasma detection. Phytoplasmas were detected in 100% of the symptomatic plants (30 of 30) and only in one of the asymptomatic plants. The restriction fragment length profiles of Tuf AY amplicons with HpaII showed two different patterns, the most important belonging to the aster yellows (16SrI) group phytoplasma and the other to the stolbur (16SrXII) group phytoplasma. To our knowledge, this is the first time that phytoplasmas have been detected in artichoke and associated with degeneration of this crop. References: (1) U. Ahrens and E. Seemüller. Phytopathology 82:828, 1992. (2) S. Deng and C. Hiruki. J. Microbiol. Methods 14:53, 1991. (3) K. H. Lorenz et al. Phytopathology 85:771, 1995. (4) B. Schneider et al. Microbiology 143:3381, 1997.