Inheritance of seed coat colour in flax (Linum usitatissimum L.)
Flax (Linum usitatissimum L.) is the second most important oilseed crop in western Canada. Seed colour is used in Canada to distinguish the two main market types from each other. Regular, high linolenic acid flax must have brown seed while "zero" linolenic acid solin flax must be yellow-seeded. The most frequent seed colours in flax are brown and yellow and are determined by genes at three loci (G, B1 and D). Yellow seed colour results when homozygous recessive alleles are present at any of the loci. A dominant allele for yellow seed colour as well as a recessive allele for variegated seed have been recently identified but their interaction to the other genes was unknown. Hence, the main objective of this research was to determine the allelic relationships among the various genes conditioning seed colour in flax. Eleven flax lines, five with a recessive yellow seed phenotype [(YSED2, YSED4, S95407 and S96071 (CDC recessive yellow)] and G-1186/94 (European recessive yellow), two dominant yellow seed (YSED18 and CPI84495), three brown seed (ED47, Vimy and CDC Bethune) and one variegated seed (M96006), were crossed in all possible combinations, excluding reciprocal crossings. Following these crosses, test crosses were performed using five USDA introductions in order to determine the seed colour alleles possessed by each parental line. The five USDA introductions (Minerva, Bolley Golden, Viking, Crystal and Bionda) had defined alleles for yellow seed colour. Chi-squared tests of goodness-of-fit to various one and two gene segregation ratios indicated that yellow seed colour in the CDC recessive yellow parents (YSED2, YSED4, S95407 and S96071) was conditioned by the recessive allele of the g locus. Yellow seed in the European recessive yellow was controlled by a recessive allele of a different locus, d. A dominant allele of the Y1 locus, governed yellow seed colour in the dominant yellow parents (YSED 18 and CPI84495). The variegated seed colour in the variegated parent (M96006) was conditioned by a newly described allele of the b1 locus, b1vg. All loci segregated independently and the recessive genes, b1vg, g and d when homozygous recessive were epistatic to the other loci. Seed colour was known to affect seed oil concentration and oil concentration of homozygous brown, yellow or variegated lines was determined. Yellow or variegated seed lines had greater oil concentration than brown seed. Yellow seed conditioned by the d allele had the most significant effect on high oil concentration while b1vg.