Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 1997
Publication Date: N/A
Technical Abstract: Dry bean (Phaseolus vulgaris L.) seed coat color is determined by the presence and relative amounts of phenolics, flavonoids, and anthocyanins present in the lumen of epidermal cells. Some of these chemicals may interact with proteins of the cotyledon to form complexes that render beans hard-to-cook and indigestible. Eight genetic loci control seed coat pigment chemistry. When all eight loci are dominant, a shiny black seed coat results, but recessive gene substitutions at one or more loci yield colors ranging from white, yellow, and brown to dark violet. In order to relate Mendelian genes for seed coat color to the pigments formed, we studied eight genetic stocks that had recessive substitutions at one or more color determining loci in an otherwise all dominant genetic background. Seed coat from each genotype was extracted exhaustively with hexane, EtOAc, MeOH, MeOH:H2O 1:1 and H20 100%. Silica gel thin layer chromatography (TLC) (solvent system CHCI3:MeOH 4:1) analysis of the MeOH fraction showed that one genotype had no phenolic compounds and two had only simple phenols. One flavonol glycoside was present in relatively large amounts in four of the genotypes but absent in genotypes with anthocyanins. Cellulose TLC (2-dimensional, Butanol:Acetic Acid:H2O 4:1:5 first dimension, 1% HCI second dimension) of the anthocyanin containing genotypes showed the presence of one flavonol and 3 anthocyanidin-3-glycosides (UV spot color and color shift with NH3). The relative importance of the seed coat chemicals in bean digestibility and their antioxidant potential will also be discussed.