بررسی عوامل قارچی همراه با پوسیدگی ریشه و طوقه کلزا در استان خوزستان و مطالعه بیماریزایی جدایه های ریز وکتونیای حاصله

During the growing season of 2006-2007, this study was conducted to isolate and identify the fungal agents of crown and root rot of canola in Khuzestan province. Samples were collected from infected plants from different fields in different cities. Infected organs of the plants were surface sterilized. Then small pieces of contaminated parts were plated on PDA. Fungal agents were isolated and purified using the routine laboratory methods and procedures. Finally, 167 fungal isolates were obtained from plants root and crown. Sixty three isolates of Fusarium spp., twenty three isolates of Rhizoctonia, forty three isolates of Cylindrocarpon spp. and thirty eight isolates of Phoma lingam were recoverd. Isolates of Fusarium belonged to F. solani )23), F. equiseti (21), F. heterosporum (6), F. nygamai (5), F. chlamydosporum (3), F. semitectum (2), F. verticillioides (1) and isolates of Phoma belonged to Phoma lingam. Of twenty three isolates of Rhizoctonia solani 12 isolates of AG2-1, 6 isolates of AG-4, 4 isolates of AG-D and AG-E were identified. Evaluation of the Pathogenicity of isolates of Rhizoctonia showed that all isolates of anastomosis groups AG2-1, AG-4 and AG-D were pathogenic but the only isolate of AG-E was not pathogenic on canola. The Severity of symptoms based on lesion length on roots and crowns showed that R. solani AG 2-1 was found to be the most important causal agent of root and crown rot of canola in Khouzestan.