Genetic control of polyunsaturated fatty acid biosynthesis in flax (Linum usitatissimum) seed oil

The inheritance of two mutants of flax (Linum usitatissimum), having altered proportions of the C18 polyunsaturated fatty acids, linoleic and linolenic, was examined. Both lines, 'M1589' and 'M1722', are homozygous for a single gene mutation which reduces linolenic acid content from 34% to 22% and raises linoleic acid from 15% to 27%. Genetic analysis of crosses involving 'M1589', 'M1722' and their parental cultivar 'Glenelg' revealed that these mutations are in different unlinked genes and exhibit additive (codominant) gene action. The symbolsLn1 andLn2 are proposed for the mutated genes in 'M1589' and 'M1722', respectively. Recombinant genotypes homozygous for the mutant alleles at both loci are very low in linolenic acid (2%) and high in linoleic acid (48%), with unaltered proportions of other fatty acids. The complete inverse correlation between linoleic and linolenic acids (r=-0.98) indicates that the mutations block the synthesis of linolenic acid at the linoleic desaturation step.