IDENTIFICATION OF MOLECULAR MARKERS ASSOCIATED WITH LINOLEIC-ACID DESATURATION IN BRASSICA-NAPUS

Linolenic acid is a component of canola oil that is readily oxidized, which results in a reduced frying stability and shelf life of the oil. The reduction of linolenic acid in canola seed has therefore been an important breeding objective for many years. The inheritance of linole nic acid concentrations in seed oil is polygenic and is also strongly influenced by the environment. For these reasons, molecular markers ar e sought to assist in early and reliable selection of desired low lino lenic acid genotypes in breeding programmes. Molecular markers associa ted with low linolenic acid loci were identified in a doubled-haploid population derived from a cross between the Brassica napus lines, 'Apo llo' (low linolenic)x YN90-1016 (high linolenic) using RAPDs and bulke d segregant analysis. A total of 16 markers were distributed over thre e linkage groups, which individually accounted for 32%, 14% and 5% of the phenotypic variation in linolenic acid content. The rapeseed fad3 gene was mapped near the locus controlling 14% of the variation. The m ode of inheritance appeared to be additive, and a QTL analysis showed that collectively the three loci explained 51% of the phenotypic varia tion within this population. PCR fragments for low linolenic acid 'Apo llo' alleles (3% linolenic acid) were identified at all three loci. Si multaneous selection for low linolenic acid 'Apollo' alleles at each l ocus resulted in a group of DH lines with 4.0% linolenic acid. The use of these makers in the breeding programme will enhance the breeding o f low linolenic acid B. napus cultivars for production in Canada.