The Margo (mar) Seedcoat Color Gene Is a Synonym for the Joker (j) Locus in Common Bean

in Journal of the American Society for Horticultural Science
Mark J. BassettHorticultural Sciences Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611

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The inheritance of hilum ring color in common bean (Phaseolus vulgaris L.) was investigated using various genetic tester stocks developed by backcrossing recessive alleles into a recurrent parent stock 5-593 with seedcoat genotype P [C r] D J G B V Rk, viz., mar BC2 5-593, mar BC3 5-593, mar v BC2 5-593, mar d BC2 5-593, and mar d BC3 5-593. The current hypothesis is that the margo character is controlled by mar and hilum ring color is controlled by d but expresses only with mar. The V locus controls flower and seedcoat color. The allelism test crosses `Citroen' (P C d j g b vlae) × mar BC3 5-593 and `Citroen' × mar d BC3 5-593 demonstrated that mar is allelic with j and that the putative d in mar d BC3 5-593 is allelic with the d in `Citroen'. Thus, the former genetic tester stocks mar BC3 5-593 and mar d BC3 5-593 are reclassified as j BC3 5-593 and d j BC3 5-593, respectively, because mar is a synonym for j. Similarly, the former genetic tester stock mar v BC2 5-593 is reclassified as j v BC2 5-593. The interaction of j with d expresses as loss of color in the hilum ring. The development of the white-seeded genetic tester stock P cu d j BC3 5-593 was described in detail, where the all-recessive tester `Prakken 75' was used as the source of the recessive alleles. The previously reported work showing that the partly colored seedcoat gene t interacts with mar to control seedcoat pattern is now interpreted to mean that the joker (J) locus interacts with t to produce partly colored seedcoat patterns. The genetic loci D and V were found to segregate independently. The common gene for dull seedcoats (asper, asp) is discussed and contrasted with j.

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