MAPPING OF A GENE DETERMINING LINOLENIC ACID CONCENTRATION IN RAPESEED WITH DNA-BASED MARKERS

Rapeseed ranks third in world oil production. An important breeding ob jective to improve oil quality in this crop is to lower linolenic acid concentration in the seeds. Previous reports indicate that the concen tration of this acid in Brassica napus is determined by two or three n uclear genes. Using DNA-based markers, we have successfully mapped a g ene determining linolenic acid concentration in an F-2 population deri ved from crossing the cultivar 'Duplo' and a low linolenic acid line, 3637-1. Linolenic acid concentration in this population ranged from 2. 1% to 10.5% with a mean of 6.2%. A RAPD marker, K01-1100, displayed si gnificantly different frequencies between two subpopulations consistin g of either high or low linolenic acid concentration individuals sampl ed from the two extremes of the F-2 distribution. Marker K01-1100 segr egated in a codominant fashion when used as an RFLP probe on DNA from individuals of this F-2 population. The linolenic acid concentration m eans for the three resulting RFLP genotypes in the F-2 population were 4.8% (homozygous 3637-1 allele), 6.4% (heterozygous), and 7.5% (homoz ygous 'Duplo' allele), respectively. It is estimated that this marker accounts for 26.5% of the genetic variation of linolenic acid concentr ation in this population.