Abstract

Sibel Dervis, Halit Yetisir, Fatih Mehmet Tok, Sener Kurt and Fatih Karaca

In this study, surveys were carried out for Verticillium wilt in watermelon fields (262 fields) in 13 provinces from five regions of Turkey. The proportion of fields having wilted plants was 40%. Verticillium dahliae was isolated from 15.2% of the fields showing wilted plants. At the end of surveys, 16 V. dahliae isolates (each from a different wilted field, collected from eight provinces of the Aegean, Central Anatolia, Marmara, Mediterranean and Southeastern Anatolia Regions) were obtained and used for vegetative compatibility analysis using nitrate non- utilizing mutants and reference isolates belonging to vegetative compatibility groups (VCGs) 1A, 2A, 2B, 3, 4A and 4B. Eleven V. dahliae isolates from Adana, Adıyaman, Balıkesir, Diyarbakır, Konya and Mersin provinces were assigned to VCG2B, two from Mersin province to VCG2A, one from Balıkesir province to VCG4B and two from Manisa and Aydın provinces to VCG1A whereas VCG3 and VCG4A were not defined among the isolates. To reveal a possible correlation between VCG and pathogenic group in V. dahliae, pathogenicity of all isolates representing the four VCGs were tested on three watermelon cultivars (Citrullus lanatus cultivars ‘Crimson Sweet’, ‘Crimson Tide’ and ‘Crisby’) and a susceptible cotton cultivar (Gossypium hirsutum cultivar ‘Çukurova 1518’) in a greenhouse. In watermelon cultivars, most VCG2B isolates caused significantly more severe symptoms than VCG4B, VCG2A and VCG1A. VCG4B isolate was more virulent on all watermelon cultivars than both VCG1A isolates. The isolates within VCG2A and VCG1A caused similar virulence patterns on ‘Crimson Sweet’ and ‘Crimson Tide’ cultivars but for ‘Crisby’ VCG1A did not cause any leaf symptom. Virulence to watermelon cultivars varied only among the isolates within VCG2B. Significant differences in virulence to cotton were observed between isolates from different VCGs except the similarity between VCG2A and VCG4B. The results expose that the population of V. dahliae from watermelon in Turkey is heterogeneous (four different VCGs among 16 isolates) but VCG2B seems to be a more specialized form for this host in Turkey.