'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 COLD TOLERANCE AND BASE TEMPERATURE FOR GERMINATION IN RAPESEED M. MOGHADDAM, E. ZAD-HASSAN, K. GHASSEMI-GOLEZANI, M. VALIZADEH, M.R. AHMADI Faculty of Agriculture, Tabriz University, Tabriz, Iran, 51664

Winter survival of 15 rapeseed, Brassica napus L., cultivars was studied in the Research Station of Faculty of Agriculture, Tabriz University, using a randomised complete block design. A factorial experiment was also conducted in the laboratory to measure the freezing tolerance of the genotypes by electrolyte leakage assay on both cold-acclimated and control seedlings. F-tests showed significant differences among the cultivars for winter survival, early frost injury, and freezing tolerance.  Cold-acclimation significantly improved the cold tolerance of the cultivars. The ion leakage of acclimated seedlings was significantly correlated  (r=0.63,P<0.01) with the percent of winter survival.  The first canonical correlation of percent of winter
survival and early frost injury with the freezing tolerance and germination attributes measured in the laboratory, was also significant.  In the third experiment, the genotypes were evaluated for percent and rate of germination at three temperatures: 5, 10, and 15& 61616;C. lowering the temperature decreased the magnitude of each attribute, but it was more pronounced for rate of germination.  Base temperature for each cultivar was determined by regressing the germination rate on temperature.  There was intraspecific variation of base temperature for germination in rapeseed.