Molecularcharacterizationofnovelresynthesizedrapeseed(Brassica napus)linesand analysis of their genetic diversity in comparison with spring rapeseed cultivars* F. Seyis 1 , R. J. Snowdon 1,2 , W. Lu ¨hs 1 and W. Friedt 1 1 Lehrstuhl fu¨r Pflanzenzu¨chtung, Justus-Liebig-Universita¨t Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany; 2 Corresponding author; E-mail: Rod.Snowdon@agrar.uni-giessen.de With 1 figure and 2 tables Received January 30, 2003/Accepted March 10, 2003 Communicated by A. M. Chevre Abstract Resynthesized (RS) rapeseed generated from interspecific hybridiza- tion between suitable forms of Brassica rapa L. (syn. campestris; genome AA, 2n ¼ 20) and B. oleracea L. (CC, 2n ¼ 18) represents a potentially important resource to expand genetic diversity in the narrowgenepoolofoilseedrape(B.napus L.,AACC,2n ¼ 38).Inthis study 165 RS rapeseed lines originating from crosses between an Indian Yellow Sarson (B. rapa ssp. trilocularis) and five different cauliflower (B. oleracea convar. botrytis) cultivars were studied using amplified fragment length polymorphism (AFLP) markers and their genetic diversity was compared in relationship to an assortment of 40 diverse spring oilseed and fodder rape varieties. Using three AFLP primer combinations, a total of 467 polymorphic bands were scored. Cluster analysis allowed differentiation among the different RS lines, which, as expected, were genetically highly divergent from the cultivars. The genetic diversity of the material is discussed in relation to its morphological variability with a view to the implementation of RS lines in oilseed rape breeding. Key words: Brassica napus — Brassica oleracea — Brassica rapa —AFLP—geneticdiversity—rapeseed—resynthesized Oilseed rape (Brassica napus L.; genome AACC, 2n ¼ 38)isa relatively young species that originated through spontaneous hybridizationsbetweenturniprape(B.rapa L.,syn. campestris; AA, 2n ¼ 20) and cabbage (B. oleracea L.; CC, 2n ¼ 18). Today oilseed rape is one of the most important oilseed crops worldwide (Song and Osborn 1992, Kimber and McGregor 1995). However, its limited geographical range and intensive breeding has led to a comparatively narrow genetic basis in current breeding material. Resynthesized (RS) rapeseed geno- types developed through interspecific crosses between diverse B. rapa and B. oleracea genotypes have the potential to significantly increase the available gene pool and provide important basic germplasm for further improvements of seed yield, seed quality traits, disease and pest resistance. Further- more, RS rapeseed is potentially of great interest for hybrid breeding, because heterosis effects are generally higher in crossesofgeneticallydistantmaterials.However,RSgenotypes are normally unsuitable for direct use in oilseed rape hybrids, because they almost always display inferior seed quality traits such as high erucic acid content and high seed glucosinolate content (++ quality), low oil content, and other undesirable oil quality traits from one or both of the progenitor parents. Traditionally, morphological, phenological and agronomical traits have been used to introduce diversity for the creation of newbreedinglines.However,moleculargenetictechniquesare becoming increasingly important in this respect. A wealth of studies have demonstrated the use of molecular marker techniques for analysis of genetic variation in crop species.Inrapeseed,Beckeret al.(1995)comparedcultivarsand RS lines using allozyme and restriction fragment length polymorphism (RFLP) markers and concluded that RS forms are a suitable resource for broadening the genetic base of rapeseed.Songet al.(1995)describedtherapidgenomechanges that occur in synthetic Brassica polyploids and discussed the evolutionary implications arising from the ability of polyploid speciestogenerateextensivegeneticdiversityinashortperiod. Thormann et al. (1994) used RFLP and randomly amplified polymorphic DNA (RAPD) markers to determine genetic distances in and between cruciferous species, Hallde´n et al. (1994) compared B. napus breeding lines with RFLPs and RAPDs, while Diers and Osborn (1994) compared RFLP patterns in 61 winter and spring rapeseed genotypes and concluded that the two forms constitute two genetically different groups. The relationship between genetic distance and heterosis in oilseed rape was investigated by Diers et al. (1996) using RFLP markers and by Riaz et al. (2001) with sequence-relatedamplifiedpolymorphisms(SRAP).Plieskeand Struss(2001)wereabletoclearlydifferentiatewinterandspring rapeseed in a cluster analysis using simple sequence repeat (SSR)markers.RAPDshavealsobeenusedfordiscrimination amongrapeseedcultivars,byMaileretal.(1994). Lombard et al. (2000) utilized amplified fragment length polymorphisms (AFLP; Vos et al. 1995) to genotype winter rapeseed cultivars and estimate genetic similarities. As they provide a large amount of information in a short time and at a relatively low cost, AFLP markers represent an extremely useful tool for genetic diversity studies. In the present study 165 RS rapeseed lines originating from crosses between an Indian Yellow Sarson (B. rapa ssp. trilocularis) and five cauliflower (B. oleracea convar. botrytis) cultivars were studied using AFLP markers and their genetic diversity was compared with the diversity present in an assortment of diverse spring oilseed and fodder rape forms from Germany, Canada, France, Sweden, Denmark, Australia and New Zealand by principal coordinate (PCO) analysis. As the same B. rapa parent was used for the development of all RS lines, theRSrapeseedmaterialwascloselyrelated.However,pheno- logical data from a field evaluation of morphological and agronomictraitsincludingplantheight,leafmorphology, days *DedicatedtoProf.Dr.WalterH.Schuster,born07.11.1918,to markhis85thbirthday. Plant Breeding 122, 473—478 (2003) Ó 2003 Blackwell Verlag, Berlin ISSN 0179-9541 U. S. Copyright Clearance Center Code Statement: 0179–9541/2003/2206–0473 $ 15.00/0 www.blackwell.de/synergy