Analysis of Quantitative Trait Loci Associated with Freezing Tolerance in Rapeseed (Brassica Napus L.)

Freezing tolerance is a major component of winter survival and is the ability of plant to survive subfreezing temperatures. In order to identify the molecular markers linked to chromosomal regions governing freezing tolerance in rapeseed, an F 2:3 population of 199 plants derived from crossing between cv. ‘SLMO46’ (winter type and cold resistant) and cv. ‘Quantum’ (spring type and susceptible to low temperature) were used. The LT50 (the temperature at which 50% of plants were killed) was measured as a cold resistance index in F 3 families. The parental polymorphism was assessed using 350 SSR primer pairs and 250 RAPD primers. The 32 microsatellite and 47 RAPD markers, polymorphic between parental lines were used to screen F 2 individuals. Linkage map was constructed using polymorphic markers. The markers were assigned into 14 linkage groups with total length of 1199.1 cM and an average distance of 17.13 cM between adjacent markers. The relationship between LT50 and genotypic data was analyzed using single marker analysis (SMA), interval mapping (IM) and composite interval mapping (CIM) methods and four putative QTLs were detected. These QTLs explained 24% of the LT50 total phenotypic variance.