Geographic Patterns of RAPD Variation in Cultivated Flax

et al., 2002c), and phenotypic (Diederichsen and Hammer, 1995) studies suggests that the pale flax (L. angustiGeographic studies of plant molecular diversity can provide insights folium Huds.) is the most likely progenitor of cultivated into plant domestication and enhance plant germplasm management flax and the likely place of origin was within the Near and utilization, but such studies are lacking in cultivated flax (Linum East region (Zohary and Hopf, 2000). However, the usitatissimum L.). The objective of this study was to assess the geographic patterns of flax variability in a world collection of cultivated Near East does not fully match the dominant regions of flax by random amplified polymorphic DNA (RAPD) markers. Sixgreat flax diversity: Indian Subcontinent, Abyssinian, teen RAPD primers were applied to screen 2727 flax accessions repreNear East, and Mediterranean (Vavilov 1926; 1951). senting 63 countries and one group of unknown origin, and 149 RAPD The flax types from the Indian Subcontinent and Abysbands were scored for each accession. Analyses of the RAPD data sinian regions were found to be morphologically more revealed a wide range of occurrence frequencies of polymorphic bands diverse than those from the Near East and Mediterrafrom 0.0004 to 0.9978 with an average of 0.537. The majority (84.2%) nean regions (Vavilov, 1926; 1951). It is possible that of the RAPD variation resided within accessions of each country and Vavilov’s regions of flax diversity reflected only the only 15.8% of the variation was present among accessions of different multiple domestications which occurred at these regions countries. Grouping the accessions into 12 major regions explained over time, not necessarily the true place of flax origin, 8.2% of the RAPD variation. Accessions from the East Asia and European regions were most diverse, but accessions from the regions as the origin of a crop plant is diffuse in both time and of Indian Subcontinent and Africa were most distinct. Accessions from space (Harlan 1956; 1971). If this reasoning is correct, the West Asia region were genetically more related to those from the analyses of geographical patterns of flax variation should Africa region and less to those from the Indian Subcontinent region. yield more information on the number of flax domestiThese findings are significant for understanding flax domestication cation centers and how these centers are genetically and also are useful in classifying intraspecific diversity of cultivated connected (Harlan, 1975; Sokal et al., 1991) and less on flax, establishing a core subset of the flax collection, and exploring the region of flax origin (Harlan, 1986). However, such new sources of genes for flax improvement. geographic analyses have received little attention (Vavilov, 1926; Elladi, 1940; Dillman, 1953; Chandra and Makhija, 1979), particularly through the application of P lant gene resources of Canada (PGRC; the Camolecular markers. nadian national seed genebank) at Saskatoon mainExploitation of flax genetic resources for flax imtains a flax collection consisting of 2813 active accessions provement requires knowledge of the range and strucof cultivated flax from 69 countries and 54 accessions of ture of the genetic variability present in flax gene pools, 26 wild species in the genus Linum (Diederichsen et al., but comprehensive characterizations of the existing flax 2002). To support the management and utilization of flax germplasm held in the world collections are lacking, germplasm, the flax collection was characterized from particularly using molecular techniques. Early charac1999 to 2001 by the RAPD technique (Williams et al., terization efforts based on agrobotanical characters re1990). The characterization generated DNA fingerprints vealed four major regions of flax diversity as mentioned for each accession at 149 RAPD loci screened from 16 above (Vavilov, 1926; 1951) and several unique groups of informative RAPD primers. These DNA fingerprints repcultivated flax such as fiber flax, intermediate flax, largeresent the first comprehensive molecular dataset ever seeded flax, and dehiscent flax (Dillman, 1953; Kulpa obtained for a genebank collection of such size and, thus, and Danert, 1962). Recent RAPD analyses showed (i) provide an opportunity to address not only the issues that RAPD variation in flax was generally low; (ii) that associated with the management and utilization of flax more variation existed in landraces than cultivars; (iii) germplasm (Fu et al., 2002a) but also the domestication that more variation was detected in linseed, than fiber, of cultivated flax (Fu et al., 2002c). flax; (iv) that North American linseed cultivars had Flax has been cultivated for oil and fiber for several more variation than those from the other countries; (v) thousand years, but its domestication remains poorly that more variation was found in the Canadian linseed understood (Zohary and Hopf, 2000). Evidence from cultivars released before 1980 than those released after archaeological (Helbaek, 1959; Zohary and Hopf, 2000), 1980; and (vi) that the genetic erosion in the centurygenetic (Tammes, 1923; Gill and Yermanos, 1967; Fu long North American linseed breeding programs was not significant (Fu et al., 2002b; 2003b). While these variation patterns are significant for the improvement of Plant Gene Resources of Canada, Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK, North American flax, they are limited in helping us underCanada S7N 0X2. Received 4 June 2004. Plant Genetic Resources. stand how large the genetic variation in a flax collection *Corresponding author ([email protected]). is, how the flax gene pool is structured, how a core set Published in Crop Sci. 45:1084–1091 (2005). doi:10.2135/cropsci2004.0345 Abbreviations: AMOVA, analysis of molecular variance; PGRC, Plant Gene Resources of Canada; RAPD, random amplified polymor© Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA phic DNA; UBC, University of British Columbia. 1084 Published online May 6, 2005