The objective of this study was to assess the tolerance level of some cotton varieties against Verticillium wilt (Verticillium dahliae Kleb.) disease. Verticillium wilt is one of the major constraint diseases of cotton production worldwide and also in Turkey. The study was carried out at the Southeastern Anatolia Agricultural Research Institute's naturally infected experimental area during 2004-2006. In this study, 10 different commercial cotton varieties were used as plant material. The

more »

... ental design was a randomized complete-block with four replications. During the cotton growing season, foliar disease index (FDI), vascular disease index (VDI) and vascular disease rate (VDR) were observed in addition to seed cotton yield and some fiber quality characteristics. According to the results, it was determined that with regards to FDI, VDI and VDR, the most tolerant varieties were 'GW-Teks', 'GW-Golda' and 'Carmen', while the most sensitive varieties were 'Maraş 92', 'Sayar 314' and 'Stoneville 453'. The other varieties had moderate tolerance levels. The highest seed cotton yield and lint yield were obtained from 'DP-Deltaopal' and 'Stoneville 453'. These results showed that some sensitive varieties had high yield; the reason for this situation may be related with early or late occurrence of the disease. The result of this study indicated that 'GW-Teks', 'GW-Golda' and 'Carmen' varieties must be preferred for infected areas; on the other hand, 'DP-Deltaopal' and 'Stoneville 453' can be recommended and grown in uninfected areas. Additionally, 'Carmen', 'GW-Teks' and 'GW-Golda' varieties can be used as material for improving disease resistance in cotton breeding programs.