Factors Influencing Differentiation of Pinto Bean Seed Testa Discoloration

Abstract

Pinto breeding line NE 94-4 (Phaseolus vulgaris L.) showed seed coat yellowing in on-farm-field trials in Nebraska in 1996 and 1997. After reviewing field and weather data of the on-farm-trial sites, hail, high temperature and sprinkler irrigation appeared to be involved with the increase in seed coat yellowing. The goal of this research was to determine the cause(s) of testa yellowing. Moisture was the factor chosen for further exploration. Two greenhouse experiments (misting and injection) and one lab experiment (moistened filter paper) were conducted. The experimental design was a split-plot in the misting experiment, and a randomized complete block design in the injection and moistened filter paper experiments. In all experiments, breeding line NE 94-4 and Pinto bean variety UI 114 (control) were used. At the end of each experiment, yellowing was recorded visually. Data from all three experiments were analyzed using the mixed model procedure of SAS. In the misting experiment, only variety/line, and the interaction between variety/line and pod were significant. In the injection and moistened filter paper experiments, the treatment effects were significant with NE 94-4 showing more yellowing than UI 114. Thin layer paper chromatography (TLC) was used to identify the pigments in the Pinto bean seed testa. Some flavonoids and carotenes were identified. Sulpheritin (aurones, flavonoids) was found only in the seed coat of yellowed NE 94-4. On the other hand, daidzein and genistein (isoflavonoids) were identified only in the seed coat of UI 114.