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Study of Yield in Winter Oilseed Rape Cultivars during Different Sowing Dates

Cold damage to winter oilseed rape is caused by temperatures around 0°C during early fall and spring and below 0 oC during winter. The study was conducted in factorial experiment with two factors, planting dates (Sept. 11 and Sept.26) and six promising genotypes with three replications at Agricultural Research and Natural Resources Center of East Azarbaijan during 2003-4. The results indicated that the genotypes in second planting date produced lower number of leaves, crown diameter, dry weight, seed and oil yields. Correlations of seed and oil yields with leaf numbers per plant, crown diameter and plant dry weight were positive and significant, while they were negative with percent of cold damage. It seems that the leaf number, crown diameter and plant dry weight can be used for determining cold tolerant genotypes and suitable planting dates of winter oilseed rape when freezing temperature prevails.