A complex C region genotype [?R] that with GB nu(lae) produces dark seal-brown seedcoat color in common bean

Common bean (Phaseolus vulgaris L.) plant introduction 527829 (formerly Lamprecht M0048) has dark seal-brown (DSB) seedcoats and pink flowers. An investigation was conducted to determine the genotype of DSB seedcoat color. M0048 was crossed with Florida breeding line 5-593, which has genotype P[Cr]DJGBVRk. A series of crosses involving M0048, 5-593, and three genetic tester stocks (nu BC2 5-593, c(u)BC(2) 5-593, and b nu BC2 5-593) led to determination of the genotype. Data analysis indicated that M0048 has the genotype P[?R]JGB nu(lae), where DSB color is produced by the interaction of R with B, Crosses between [? R] and testers with [Cr] always produced seedcoat mottling in F-1, except where V masks the effect, The cross [?R] B nu (DSB)xc(u)BC(2) 5-593 (cartridge buff seedcoat) produced marbled seedcoats (black/ cartridge buff) with genotype [?R]/[c(u)?] B V. No way was found to determine whether the mottled or marbled seedcoat patterns were controlled at C or R; hence, the allelic ambiguity is indicated with a question mark. Illustrations are provided showing the difference between seedcoat mottling (a highly variable low-contrast patterning) and seedcoat marbling (a less variable high-contrast patterning, usually with cartridge buff as the background color), The development of a new genetic tester stock, [?R]b nu BC3 5-593, was described, where [?R]b nu gives unpatterned dominant red seedcoat color.