RAPD analysis of 54 north American flax cultivars

Broadening the genetic base of linseed flax (Linum usitatissimum L.) cultivars to sustain improvement requires assessment of genetic diversity available in flax germplasm. The objective of this study was to analyze the genetic variation, genetic erosion, and genetic relationship of 54 North American flax cultivars by means of random amplified polymorphic DNA (RAPD) markers. The variations observed at the 84 polymorphic RAPD loci were relatively moderate with respect to primer, polymorphism, and cultivar. The proportions of fixed recessive RAPD loci for all the cultivars ranged from 36.9 to 59.2%, with an average of 45.3%. Genetic erosion in the century-long breeding programs was not statistically significant as revealed by the proportion of fixed recessive RAPD loci, but the trend appeared to be that 2.5% of variable RAPD loci were fixed over 100 yr. While some variable RAPD loci were fixed over different breeding periods, the genetic relatedness of the cultivars was reduced in the Canadian programs, but not in the U.S. programs. The genetic relationships of the cultivars inferred via RAPD similarity were largely consistent with known, but incomplete, pedigrees. Both Canadian and U.S. cultivars were intermixed in various groups without distinct separation and several genetically distinct cultivars (i.e., NDR 52, Vimy, Rocket, Norland, Dakota, and Marine) were identified.