شناسايي و بيماريزايي گونه هاي فوزاريوم همراه با پوسيدگي ريشه و طوقه چغندرقند در ايران

To determine the role of Fusarium species associated with sugar beet root and crown rot, diseased samples were collected from different fields of sugar beet in Iran including Khorasan, Khuzestan West Azarbayejan, Qazvin, Tehran, Kermanshah ,Kerman ,Lorestan , Hamedan ,Charmahal Va Bachtiary provinces during growing seasons 1999-2002. In total, 94 isolates of Fusarium were obtained. Based on morphological characters , six species including: F. solani, F. oxysporum, F. equseti, F .nygamai, F. proliferatum and F. culmorwn were identified. The pathogenicity of isolates was determined through inoculation of sugar beet slices of main root using agar disc inoculum and seedling inoculation in greenhouse conditions using sterilized soil and wheat seed Inocula. Disease symptoms including root and crown rot , seedling damping-off and wilting in the greenhouse conditions, and rotting of slices of main root were evaluated. Results revealed that except one isolate of F. solani the rest were pathogenic on both seedling and root slice and produced one of the two types of Fusarial disease symptoms (wilting or root rot). Some isolates of F.solani were more aggressive than the others.