Investigation of cold resistance in winter canola (Brassica napus L.) cultivars in field condition

Canola is susceptible to cold stress especially in flowering stage because that yield of plant decreases to 70 percent. Hence, genetical variety creation and selection the genotypes that are resistant to cold, is important. This experiment was performed in the form of completely randomized block design with Three replications, and each replication included 16 treatments.(genotypes of canola).Canola genotypes cultivated at two different times separately. First experiment or normal experiment carried out at 23th September, and second experiment performed one month later (delayed cultivation).The experiment performed in seed and plant improvement Institute of Karaj during 2010. Cold resistance indicators included: Stress Susceptibility Index (SSI), Tolerance indicator (TOL), mean productivity (MP), Stress Tolerance Index (STI) and Geometric mean productivity (GMP) were measured. Upon this, cold resistance degree and susceptibility of varieties to cold damage determined. Results showed that, Based on SSI, GKH2005 and GKH305, known as most tolerant varieties. On the other hand GKH2005 variety had highest amount of STI, MP and GMP indicators and SLM046 variety had lowest resistance to cold damage.