Greenhouse Screening and Field Evaluation of Canola Lines for Blackleg Resistance.
Rufina Ward, Leopold Nyochembeng, Ernst Cebert, and Udai Bishnoi. Dept of Plant and Soil Sciences, Alabama A&M Univ, PO Box 1208, Normal, AL 35762
The most important disease of canola is blackleg caused by the fungus Leptosphaeria maculans. Studies to identify sources of seedling and adult plant resistance have intensified with the growing acreages planted to canola worldwide. The canola breeding program at Alabama A&M University aims to produce early maturing varieties that are also resistant to blackleg disease. Greenhouse screening and field evaluation were conducted to assess several breeding lines of canola for resistance to blackleg. Pathogenecity tests were conducted on several canola lines under greenhouse conditions using Canada and Georgia blackleg isolates. Seeds were germinated in flats containing Promix potting soil. At 2-true-leaf stage, seedlings were inoculated with fungal mycelia grown on potato dextrose agar; necrotic lesions on leaves were assessed up to two weeks after inoculation. Differential susceptibility of plants at varying phenological stages was also studied. Our preliminary data showed variation in susceptibility among canola lines, and that younger seedlings (10-14 days old) were found to be more susceptible to infection than older seedlings (4-5 weeks old). In the field, sixty four test lines of canola were planted in 3-m single rows with three replications. Canola stubble from infected field in Georgia were uniformly distributed along rows in January 2006. Plants were examined for disease symptoms and infected plants were counted in April; other physical abnormalities in the diseased plants were also noted (e.g., seedlessness, under-developed panicles). Our preliminary field data showed significant variation in the resistance to blackleg among canola lines.