Survey on Verticillium-wilt of artichoke in Apulia and pathogenic variations among isolates of Verticillium dahliae

During the period 1998-99 a survey on the spread of Verticillium-wilt in Apulian artichoke-growing areas was carried out. Artichoke plants were collected from thirty-five places in the districts of Bari, Brindisi and Foggia. Positive isolations were obtained in 82.85% of analysed samples. Twenty-nine isolates of V. dahliae were used for pathogenicity tests on the cultivars "Super Marmande" and "Robusta Ve/Ve" of tomato (Lycopersicon esculentum Mill.), "Yolo Wonder" of pepper (Capsicum annuum L.), "Florida Market" of eggplant (Solanum melongena L.), "Sugar Baby" of watermelon (Citrullus lanatus L.), "Hale's Best" of melon (Cucumis melo L. var. reticulatus), "Charentairs" of cantalupo melon (Cucumis melo L. var. cantalupensis Ser.), "Marketer" of cucumber (Cucumis sativus L.) and "Mezzo lungo barese" of carosello [Cucumis melo L. subsp. melo conv. adzhur (Pang.) Grebenscikov]. The disease was assessed using an empiric evaluation scale of five classes and its severity was calculated by McKinney's index. In general, the twenty-nine isolates did not show a different reaction towards the tested herbaceous hosts. They resulted very aggressive on eggplant and carosello and moderately aggressive on watermelon and melon. No disease symptom was observed on tomato, pepper and cucumber. These researches carried out on a large scale confirm that Apulian populations of V. dahliae are characterised by an absence of pathogenic activity on tomato, cucumber and pepper: the strategy for controlling the disease could be based on long-term rotations with the nonhost species above mentioned. Surveys on the spread of Verticillium-wilt pointed out the severity of artichoke-growing condition in Apulia. It is necessary to create fields of healthy mother plants for obtaining pathogen-free propagative material and for carrying out programs on sanitation of soils infested by V. dahliae using new ecologically sustainable soil disinfestation techniques.