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Mark J. Bassett

The inheritance of corona and hilum ring color of common bean (Phaseolus vulgaris L.) was investigated in the reciprocal cross `Wagenaar' (a Canario market class dry bean) × `Mayocoba' (Mayocoba market class dry bean), where both parents were known to have seedcoat color genotype P [C r] gy J g b v lae Rk. `Wagenaar' has greenish yellow (GY) seedcoat (due to gy) except for purple (dark) corona (due to v lae) and reddish brown hilum ring (due to J), whereas `Mayocoba' has an entirely GY seedcoat. Seeds produced on the F1 progeny plants had GY corona and reddish brown hilum ring. The F2 segregated for three phenotypic classes, the two parental classes and the F1 class, but the segregation did not fit a 1:2:1 segregation ratio due to disturbed segregation. F3 progeny tests of 35 randomly selected F2 parents demonstrated that the two parental classes were true breeding and the F1 class segregated again (as in the F2) for the same three phenotypic classes. In spite of variable expressivity of GY color and disturbed segregation, the data support a single gene hypothesis, for which the tentative symbol Chr is proposed. Chr is dominant for changing purple corona to GY, but recessive for changing reddish brown hilum ring to GY. Thus, only one gene, Chr, controls the difference in seedcoat color between the market classes Canario and Mayocoba. An allelism test between Chr and Z (hilum ring color factor) is needed before a formal proposal for Chr can be made.

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Mark J. Bassett, Rian Lee, Carla Otto, and Phillip E. McClean

Inheritance of the strong greenish-yellow (SGY) seedcoat color in `Wagenaar' common bean (Phaseolus vulgaris L.) was investigated. Line 5-593 is a determinate, Florida dry bean breeding line (with small black seeds) used as the recurrent parent in the development of many genetic stocks, e.g., g b v BC3 5-593. Through crosses with genetic tester stocks, the seedcoat genotype of `Wagenaar' was confirmed to be C J g b v lae Rk. Three randomly amplified polymorphic DNA markers (OAP7850, OAP31400, and OU14950) that cosegregated with the G seedcoat color locus were developed from the F2 population derived from the cross g b v BC2 5-593 × G b v BC3 5-593. From the cross `Wagenaar' × g b v BC3 5-593, 80 F2 plants were classified into 54 non-SGY and 16 SGY seedcoat color plants. When the OAP7850 marker was applied to that population, linkage was not observed with the non-SGY and SGY phenotypes. Conversely, a molecular marker (OAP12400, that was developed from the F2 from the cross `Wagenaar' × g b v BC3 5-593) linked to the locus controlling the SGY phenotype segregated independently of the G locus. Therefore, SGY phenotype is not controlled by the G locus. An F3 progeny test of 76 F2 plants from the cross `Wagenaar' × g b v BC3 5-593 confirmed the hypothesis that a single recessive gene (for which we propose the symbol gy) controls the seedcoat color change from pale greenish yellow (PGY) to SGY. Through crosses with genetic tester stocks, the seedcoat genotype of `Enola' was determined to be C J g b v lae Rk. The test cross `Enola' × `Wagenaar' demonstrated that `Enola' also carries the gy gene. The relationship of `Enola' to the `Mayocoba' market class of common bean and to `Azufrado Peruano 87' is discussed.