Verticillium Wilt: A Threat to Artichoke Production

The globe artichoke (Cynara cardunculus L. var. scolymus (L.) Fiori (=C. scolymus L.)) (diploid, 2n = 34) is the most important botanical variety of the species, which also includes C. cardunculus L. var. altilis DC. (=C. cardunculus L. var. cardunculus), the cultivated cardoon, and C. cardunculus L. var. sylvestris (Lamk) Fiori, which comprises wild relatives. The genus Cynara, native of the Mediterranean Basin, belongs to the botanical family Asteraceae (=Compositae) and includes seven species besides C. cardunculus. It is widely accepted that C. cardunculus var. sylvestris is the ancestor of the other two varieties (55,120). Artichoke is an allogamous species that is mainly propagated vegetatively via “stumps” (basal stem pieces with attached root sections) or “ovoli” (axillary buds separated from the stumps), although a few cultivars are seed-propagated (101). More than 120,000 ha of globe artichokes are cultivated in more than 25 countries worldwide that yield approximately 1,300,000 t of buds. This hectarage represents 2.5% of the world area cultivated to vegetables (51). Italy is the leading artichoke-producing country with more than 35% of world production. Spain ranks second with 19% of world production despite a 20% hectarage reduction during the last 5 years. Similar reductions of the cultivated area and production of artichokes have occurred in France, the United States, and, less markedly, in Greece (Table 1). Conversely, the crop hectarage has expanded greatly in other countries: over a 30-fold increase in Peru, twofold increase in China and Turkey, about 60% increase in Chile and Egypt, and nearly 20% increase in Algeria, Argentina, and Morocco. Additionally, the yield per cultivated area in countries such as Algeria, China, Morocco, Peru, and Turkey has recently achieved a level comparable with that of other countries. This may be a consequence of significant improvements in artichoke cultivation technology in those countries, where artichoke plantations have been established more recently than elsewhere. An overview of world production of artichokes was published recently (80). Verticillium wilt, caused by the soilborne fungus Verticillium dahliae Kleb., is one of the main constraints for artichoke production worldwide. This disease was first reported on artichoke in Italy in the late 1920s (42,95). Subsequently, new reports were published from France (27), again in Italy (25,32,36), Spain (112), Chile (52), Greece (114), California (17), and Tunisia (67). Currently, Verticillium wilt occurs in all artichoke-growing areas. Verticillium wilt is becoming an increasing concern in artichoke production because the rapid spread of the disease to new growing areas has led to declining production. For example, in the 1980s, the disease was found affecting artichoke crops in several Italian regions such as Apulia, Campania, Lazio, Sardinia, Sicily, and Tuscany. In Apulia, which is the most important Italian area of artichoke production, problems with Verticillium wilt led to a reduction in the area cultivated to artichoke in the Bari Province, and also extended rapidly to new plantations that had been established in the provinces of Brindisi, Foggia, and Lecce (2,33). A similar decrease in artichoke cultivation due to Verticillium wilt was observed in Chile (52,53). In Spain, Armengol et al. (3) underlined the spread of Verticillium wilt in the Comunidad Valenciana region in eastern-central Spain, the main artichoke-growing area in the country. They reported over 80% disease prevalence in fields of stump- and seed-propagated artichokes sampled during 1999 to 2002, with an average wilt incidence of 53.8%