Department of Agronomy and Range Science, University of California, Davis, CA ... pigmentation traits such as flower and seed color or color patterning (Bassett ...
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LINKAGE MAPPING IN COMMON BEAN R.O.Nodari, E.M.K. Koinange, and P. Gepts Department of Agronomy and Range Science, University of California, Davis, CA 95616-8515 The current linkage map of common bean {Phaseolus vulgaris; 2n = 2x = 22) is poorly developed, ll consists of a small number of linkage groups that include factors coding mostly for morphological and pigmentation traits such as flower and seed color or color patterning (Bassett 1991). Many of these traits arc subject to epistatic, pleiotropic, and environmental effects. Our objective is to develop a low density genetic linkage map for common bean based on intraspecific diversity with an average interval between two markers not larger than 15 cM) . In addition, this map should be integrated, i.e., it should include both molecular markers and important agronomic traits. This report presents the current status of our linkage mapping effort in common bean. A Restriction Fragment Length Polymorphism (RFLP)-based linkage map for common bean covering 827 centiMorgans (cM) was developed based on a F2 mapping population derived from a cross between BAT 93 and Jalo EEP558. The parental genotypes were chosen because they exhibited differences in evolutionary origin, allozymes and phascolin type, and for several agronomic traits such as disease resistance and Rhizobhim nodulation intensity.
D1
D4 D2 03 --II-BJ --Mue - Me
06 - C
D5 --
Lee a — Diap —
—Lap'3= = = St ~ -PAL = =
y^rl
— Cor
SS --CHS
08 _ -
-ziPhs
::^GS
~-~.Aco-2--
__ —
__PRpv2__
07 -CHI J
-- P
010 011 09 --rONA — -CH18 —
--Skdh —
^URia D12
013
014
015
Figure 1. Linkage map of common bean. Tick marks without labels represent random gcnomic clones. For explanations of gene symbols, see text.
28 The current map is based on segregation analyses of 115 RFLP loci (from Psil and EcoRl-BamHl genomic libraries), 7 isozyme loci, 8 Random Amplified Polymorphic DNA (RAPD) marker loci, 19 loci corresponding to 15 sequences of known function, and three morpho-agronomic trait loci. The inheritance pattern of the 152 markers analyzed in the segregating population followed the expected F2 co-dominant (1:2:1) or dominant (3:1) Mendelian ratios in 91% of the cases. The 14 markers \\ath distorted segregation were clustered in four regions of the bean genome (linkage groups Dl, D2, D8, and D13).Using MAPMAKER and Linkage-1 one hundred forty-three of the 152 markers could be assigned to one of 15 linkage groups, whereas 9 markers remained unassigned (Fig. 1 exhibits all markers but RFLPs). The average interval between two markers was 6.5 cM; only one interval was larger than 30 cM. The seven segregating isozyme loci were distributed in four linkage groups. Me (malic enzyme) and Rbcs (locus for the small subunit of ribulose bisphosphate carboxylasc) had been found to be Unked in previous studies (Weeden 1984; Koenig and Gepts 1989). We confirmed the linkage between Me and Rbcs by identifying several intermediate markers on linkage group D4, in particular the seed lectin locus (Lee), which belongs to a multigene family including alpha-amylase inhibitor (aAI) and arcclin (Arl) (Osborn et al 1986; Moreno and Chrispccls 1989). Two other isozyme loci, Aco-2 and Diap-1, were located 16 cM far apart on linkage group D5 confirming the observations of Vallejos and Chase (1991a). The remaining two isozyme systems, Skdh and Mue, mapped to the same linkage group, although they were separated by a distance of more than 50 cM. Sequences of known function used for RFLP mapping belonged to three broad categories. Disease response genes included chitinase (CH18), glucanase (GlOl), chalcone synthase (CHS), chalcone isomerase (CHI), phenylalanine ammonialyase (PAL), and pathogenesis-related proteins 1 and 2 (PRPvl and PRPv2). Rhizohium nodulation response genes consisted of glutaminc synthetase (GS), sucrose synthetase (SS), and uricase (URI). Seed proteins included phaseolin {Phs), seed lectin or phytohemagglutinin {Lee), and a-amylase inhibitor {cxAI). Inspection of the Fig. 1 reveals that non-homologous sequences belonging to each of these categories were unlinked. The Cor (corona) gene, which induces a colored ring on the outside of the hilum ring and flower color appeared to be linked (Fig. 1). The recombination of 25% between Cor and flower color observed in our mapping population, is similar to recombination value of 23% detected previously by Lamprecht (1961) between C and Cor. Therefore, it is possible that flower color in this cross is controlled by the C pigmentation locus. The / gene conferring resistance to the non-necrosis inducing strains and hypersensitivity to the necrosis inducing strains of bean common mosaic virus (Drijfhout et al. 1978) mapped to linkage group D2. Segregation and linkage information from other populations - Midas x G12873 (present results) and Midas x DIA (Arndt and Gepts 1989) - showed that / was linked to the St gene confirming earlier observations by Prakken (1937) and that the P (color) and / (shineness) loci were located in the same linkage group (D7) as Phs and CHI, confirming observations of Vallejos and Chase (1991b) that P and Phs are linked. Genes involved in the expression of important agronomic traits such as disease resistance genes, Rhizobium nodulation intensity genes, and seed weight are can be mapped in near future. The current physical distance in common bean (758kb/cM) is only 2.6 times that oi Arabidopsis thaliana which raises the possibility of map-based cloning of selected genes provided additional tightly linked markers near the target genes. Acknowledgments This research is supported by the Agency for International Development. R. Nodari holds a fellowship from CNPq, Brazil. E. Koinange holds a fellowship from SADCC/CIAT. References Arndt GC, Gepts P (1989) Annu Rep Bean Improv Coop 32:68-69Basset MJ (1991) HortScience 26:834-836 Drijfliout E, Silbernagel MJ, Burke DW (1978) Neth J PI Path 84:13-26 Koeing R, Gepts P (1989) J Hered 80:455-459 Lamprecht H von (1961) Agri Horti Genet 19:319-332 Moreno J, Chrispeels MJ (1989) Proc Nati Acad Sei USA 86:7885-7889 Osborn TC, Blake T, Gepts P, Bliss F (1986) Theor Appl Genet 71:347-355 Prakken R (1937) Genética 19:242-272 Vallejos CE, Chase CD (1991a) Theor Appl Genet 81:413-419 Vallejos CE, Chase CD (1991b) Theor Appl Genet 82:353-357 Weeden NF (1984) Annu Rep Bean Improv Coop 27:123-124
