Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Proceedings
Publication Acceptance Date: 2/11/1996
Publication Date: N/A
Interpretive Summary: Although dry bean (Phaseolus vulgaris L.) is an important source of energy and protein for human consumers, the crop is underutilized as a food. Two major factors leading to bean underutilization in diets are the prolonged time required to cook beans to a point where they can be digested, and a low nutrient assimilation, especially protein. A knowledge of the genetic structure of a population under selection for traits of interest is required to provide guidance as to whether plant breeding can be used to improve the performance of selected genotypes. A breeding population was developed to make genetic analyses of cooking time, water absorption, protein and a tannin (a chemical in seed coats of colored beans that renders protein inactive to digestion). Content resemblances among progeny resulting from mating sixteen genotypes in a special way in which a male parent was mated to a series of female parents, was used as a criterion for evaluating trait inheritance. Resemblances of population members indicated that genes affecting all of the traits added to trait expression in linear fashion. Another goal of the study was to see if an association between water absorption during soaking and cooking time existed. A large association between water absorption and cooking time indicated that water absorption can be used to select for cooking time on an indirect basis. The determination of cooking time is expensive and time consuming; however, the determination of the water absorption of a sample is rapid and relatively inexpensive. Selection based on the water absorption of a breeding line as an indirect estimation of its cooking time as opposed to measuring the cooking time per se increases breeding efficiency and saves resources.
Technical Abstract: Prolonged cooking time which wastes energy, and indigestible seed starch and protein are two factors that limit the full nutritional potential of dry bean (Phaseolus vulgaris L.). Genetic variability for cooking time and other nutritional factors exists in dry bean. Thus, there is an opportunity to improve beans for cooking time and nutritional components through plant breeding. A study was conducted to determine the inheritance of cooking time, water absorption, protein, and tannin - a major antinutrient - in dry bean. Sixteen genotypes of dry bean were intermated using a North Carolina Design II mating scheme. Cooking time was determined with a pin-drop apparatus, in which 25 seeds could be cooked simultaneously. Water absorption was expressed as the percentage increase of fresh weight after 12 hours of soaking. Protein and tannin content were determined by accepted procedures. Significant genetic variation for cooking time, water absorption, protein, and tannin content indicated that these traits can be changed by selection and was preponderantly of the additive type. The estimated gain in selection with a 25% selection intensity indicated that several cycles of selection are needed in order to raise protein percentage and lower tannin content to a point where benefits might be noticeable. The estimated gain in selection for cooking time was about 2 minutes per cycle. Reduction of bean cooking time may save considerable energy. The phenotypic correlation (-0.82) between water absorption and cooking time justifies using the water absorption trait as an indirect selection method for cooking time. Indirect selection increases breeding efficiency and saves resources.