Electronic Thesis and Dissertation Repository


Master of Science




Dhaubhadel, Sangeeta

2nd Supervisor

Kohalmi, Susanne



Postharvest darkening of seed coat in pinto bean (Phaseolus vulgaris L.) is an undesirable trait that hinders its market potential. Darkening is more rapid in the cultivars like CDC Pintium than the newly developed slow darkening cultivar 1533-15. A single gene, SLOW DARKENING (Sd), is responsible for the slow darkening in pinto beans and the trait co-segregates with two simple sequence repeat (SSR) markers. The objective of this research is to identify and characterize the Sd gene to understand the slow darkening mechanism in pinto bean seed coat. A search for Sd within the linkage distance from the SSR markers has identified a basic Helix-Loop-Helix (bHLH) transcription factor gene, PvbHLH333 as a candidate. PvbHLH333 from CDC Pintium and 1533-15 has shown sequence and functional variations. The ability of PvbHLH333 from 1533-15 to rescue the tt8 mutant phenotype in Arabidopsis suggests that PvbHLH333-1533-15 is the orthologue of TT8 which regulates proanthocyanidin biosynthesis in Arabidopsis.