Phenotypic and molecular (RAPD) differentiation of four infraspecific groups of cultivated flax (Linum usitatissimum L. subsp usitatissimum)

Based on agro-botanical characterization data, 3101 accessions of cultivated flax (Linum usitatissimum L. subsp. usitatissimum) from the flax collection held by Plant Gene Resources of Canada (PGRC) were grouped into four infraspecific groups according to the classification proposed by Kulpa and Danert (1962) . The objective of this study was to investigate phenotypic and RAPD variation within and among the four groups to better understand phenotypic and genotypic differentiation within the genepool of cultivated flax. The results of the phenotypic characterization of characters defining the convarieties (capsule dehiscence, plant height, technical stem length and 1000 seed weight) and of other quantitative (petal width, oil content in seeds) and qualitative (RAPD, petal colour, anther colour, petal longitudinal folding and margin folding, ciliation of capsule septa, seed colour) are presented using descriptive statistics. The most frequent convariety in the PGRC genebank was intermediate flax (convar. usitatissimum; 80.7 %), followed by fibre flax (convar. elongatum Vav. et Ell. in Wulff; 13.4%), large-seeded flax (convar. mediterraneum [Vav. ex Ell.] Kulpa et Danert; 5.6%) and dehiscent flax (convar. crepitans [Boenningh.] Kulpa et Danert; 0.3%). Analyses of RAPD data and two qualitative characters (longitudinal and marginal folding of petals) did not show marked differences among the proposed convarieties. However, differences among the convarieties in quantitative traits defining them (plant height, technical stem length and seed size) were considerable. Patterns of variation among the convarieties for other quantitative characters (petal width and seed oil content), as well as the frequencies of character expressions of four qualitative characters (petal colour, anther colour, ciliation of capsule septa and seed colour) were significantly associated with the four proposed convarieties, underlining the phenotypic and genotypic validity of this grouping. The patterns of geographic distribution of the convarieties and important characters showed that certain convarieties dominate in some areas of origin. The infraspecific classification and the presented characterization data increase the transparency of genetic diversity available in cultivated flax and in particular in the PGRC flax collection.