Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/1997
Publication Date: N/A
Interpretive Summary: Dry bean seed coat color is determined by the presence and relative amounts of pigment forming chemicals. The chemicals are under the control of major genes. Some of the chemicals protect against cancer. Other chemicals make beans hard-to-cook and indigestible. Plant breeders need to know which chemicals are associated with the specific seed coat color genes in order to genetically enhance the good chemicals and remove the bad chemicals. In addition to their effect on the pigments, the seed coat color genes affected the physical characteristics of the seed. The dry weight of whole bean and seed coats differed significantly among genetic stocks that had recessive genes substituted at one or more color determining loci. Beans with yellow-brown seeds - due to the substitution of two recessive genes -had the lowest ratio among the genetic stocks of seed coat to total seed dry weight. The secondary effect of a major gene is called pleiotropy which his generally unpredictable and cannot be separated from the major gene to which the effects are associated by any known breeding strategy. Knowledge concerning the major effect of secondary effect of a Mendelian gene is important to plant breeders so they can either proceed with caution in their breeding strategy or eliminate the major gene exhibitng unfavorable secondary effects from breeding populations through selection.
Technical Abstract: Whole bean fresh weight differed significantly among 10 different color genotypes of Phaseolus vulgaris. Genotypes having all, or most of six color genes dominant tended to be smaller seeded than genotypes having most color genes recessive. Total bean, seed coat and cotyledon dry weights also increased with fewer dominant color genes. Dry weight of seed coat increased significantly r**2=0.919, p<0.05) as total bean dry wieght increased. However this relationshiop did not hold for the ratio of dry weight of seed coat to total bean dry weight. The two largest and least colored genoypes had the lowest ratios (6.5%) of seed coat to total bean dry weight and in general small seeded heavily colored varieties had significantly higher (9.1-98%) ratios. Eight of these genotypes had a common genetic background, and varied by one or more recessive substitutions at color loci. Differences in physical characteristics among color genotypes are therfore likely due to pleiotropy or tight genetic linkages. These results are also useful to estimate the amount of seeds for extraction and characterization of P. vulgaris seed coat color compounds such as anthocyanins, flabonoids and other phenolics.