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Genetics of Symbiosis in Lotus japonicus: Recombinant Inbred Lines, Comparative Genetic Maps, and Map Position of 35 Symbiotic Loci

¹Laboratory of Gene Expression, Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10, DK-8000 Aarhus C, Denmark; ²Agriculture and Agri-Food Canada, SCPFRC, 1391 Sandford Street, London, Ontario NV5 4T3, Canada; ³National Institute of Agrobiological Sciences, 2-1-2 Kannon-dai, Tsukuba, Ibaraki, 305-8602, Japan; ⁴Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan; ⁵Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033; ⁶Faculty of Horticulture, Chiba University, 648 Matsudo, Matsudo, Chiba 271-8510, Japan; ⁷Department of Life Science, Aichi University of Education, Kariya, Aichi 448-8542, Japan; ⁸Kazusa DNA Research Institute, 1532-3 Yana, Kisarazu, Chiba 292, Japan; ⁹John Innes Centre, Norwich Research Park, Colney, Norwich, NR4 7UH, England; ¹⁰Molecular Plant Nutrition Group, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, D-14476 Golm, Germany; ¹¹Laboratory of Plant Biochemistry, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; ¹²Facultad de Química, Universidad de Sevilla, Apartado 553, 41080 Sevilla, Spain; ¹³IGER, Department of Plant Genetics and Breeding, Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EB, Wales, U.K.; ¹⁴Sainsbury Laboratory, Norwich Research Park, Colney, Norwich, NR4 7UH, England; ¹⁵Genetics Institute, Ludwig Maximilians Universität (LMU), Maria-Ward-Str. 1a, D-80638, Germany; ¹⁶National Institute of Livestock and Grassland Science, 768 Senbonmatsu, Nasushiobara, Tochigi 329-2793, Japan; ¹⁷ARC Centre of Excellence for Integrative Legume Research, University of Queensland, Brisbane Qld 4072, Australia

Development of molecular tools for the analysis of the plant genetic contribution to rhizobial and mycorrhizal symbiosis has provided major advances in our understanding of plant-microbe interactions, and several key symbiotic genes have been identified and characterized. In order to increase the efficiency of genetic analysis in the model legume Lotus japonicus, we present here a selection of improved genetic tools. The two genetic linkage maps previously developed from an interspecific cross between L. japonicus Gifu and L. filicaulis, and an intraspecific cross between the two ecotypes L. japonicus Gifu and L. japonicus MG-20, were aligned through a set of anchor markers. Regions of linkage groups, where genetic resolution is obtained preferentially using one or the other parental combination, are highlighted. Additional genetic resolution and stabilized mapping populations were obtained in recombinant inbred lines derived by a single seed descent from the two populations. For faster mapping of new loci, a selection of reliable markers spread over the chromosome arms provides a common framework for more efficient identification of new alleles and new symbiotic loci among uncharacterized mutant lines. Combining resources from the Lotus community, map positions of a large collection of symbiotic loci are provided together with alleles and closely linked molecular markers. Altogether, this establishes a common genetic resource for Lotus spp. A web-based version will enable this resource to be curated and updated regularly.

Additional keywords: symbiotic mutants.