Inheritance of high oleic acid mutations in winter oilseed rape (Brassica napus L.)

High oleic (HO) winter oilseed rape (Brassica napus L.) with increased oleic acid content in the seed is of interest for nutritional and industrial purposes. The objectives of the present study were to (i) describe the fatty acid composition in the seed, leaf, and root material of eight HO mutants; (ii) estimate the number of genes controlling the trait; (iii) test whether the mutants are allelic for the mutated loci; and (iv) determine the inheritance of the HO trait. An 8-by-8 diallel of the HO mutants and two crosses between HO mutants and a normal type cultivar with their segregating F, and BC generations were used. The results suggested that the variation in oleic acid can be explained by two mutation events. One mutated locus (HO1) was expressed mainly in the seeds and all mutants were assumed to be allelic at this locus. A second mutated locus (HO2), which increased the oleic acid content not only in the seed but also in leaves and roots, was identified in one mutant line. Both loci showed mainly additive effects: for HO1 a = 8.0 +/- 1.5 and for HO1+HO2 a = 9.25 +/- 1.5 (in percent oleic acid in the seed oil). Only small nonsignificant dominance effects and no epistatic or maternal effects were observed. The reduction of oleic acid desaturation in the mutants indicates that the HO1 locus is equivalent to fad2, the microsomal oleic acid desaturase, whereas the locus HO2 affects a different enzyme involved in fatty acid biosynthesis or desaturation.