Changes in sugar concentrations of seed and pod tissue during development in snap and dry beans (Phaseolus vulgaris L.)

Authors: GARTNER, WESLEY - UNIVERSITY OF WISCONSIN; Bethke, Paul; KISHA, THEODORE; NIENHUIS, JAMES - UNIVERSITY OF WISCONSIN

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/13/2020
Publication Date: 9/14/2020
Citation: Gartner, W., Bethke, P.C., Kisha, T.J., Nienhuis, J. 2020. Changes in sugar concentrations of seed and pod tissue during development in snap and dry beans (Phaseolus vulgaris L.). Journal of the American Society for Horticultural Science. 55(10):1692-1697. https://doi.org/10.21273/HORTSCI15261-20.
DOI: https://doi.org/10.21273/HORTSCI15261-20

Interpretive Summary: Sugars contribute to the flavor and consumer acceptance of snap beans. Developing fruit from five varieties of beans were sampled at five-day intervals from 10 to 30 days after flowering. Weight of pods without seeds, seed weight and sugar content in pod and seed tissue were quantified. Significant differences in sugar accumulation patterns between varieties were observed. Younger snap beans had the highest sweetness index based on observed sugar concentrations, percent seed weight, and relative sweetness of the sugars present. Although sweetness varied between varieties, the rate of decrease in sweetness with time was the same for all five varieties. These findings indicate that variation for sweetness exists in snap beans and can be exploited by breeding to develop varieties with a potentially more desirable, sweet flavor.

Technical Abstract: Sugars, including glucose, fructose, and sucrose, contribute significantly to the flavor and consumer acceptance of snap beans (Phaseolus vulgaris L.) . Sugar accumulation and changes in sugar profiles during snap bean development contribute to overall assessments of quality for breeding lines and cultivars. Developing fruit from a diverse group of four Andean snap bean cultivars and one Mesoamerican dry bean cultivar were sampled at five-day intervals from 10 to 30 days after flowering over two years. Glucose, fructose and sucrose in pod and seed tissue was quantified using high-performance liquid chromatography. Percent seed mass relative to pod mass increased with days after flowering, but the rate of increase was heterogeneous among cultivars. Significant differences in sugar accumulation patterns of mono and disaccharides were observed with time of development and between pods and seeds. Glucose and fructose decreased rapidly in pods and seeds with time after flowering. In contrast, sucrose concentration increased in pod tissue but remained constant in seeds of Andean cultivars with time after flowering. The patterns of changes in pod and seed sugar concentrations with time after flowering were similar among all Andean cultivars. In contrast to the Andean beans, seed sucrose increased with time after flowering in the Mesoamerican dry bean cultivar, ‘Puebla 152’. No year by day after flowering interactions were observed for sugar accumulation patterns or sugar concentrations. Younger snap beans had the highest sweetness index based on observed sugar concentrations, percent seed mass, and perception of relative sweetness by the human palate. Although mean sweetness varied between cultivars, the rate of decrease in sweetness with time was the same for all five cultivars. These findings indicate that variation for sweetness exists in snap beans and can be exploited by breeding to develop cultivars with a potentially more desirable, sweet flavor.