Seed coat transcriptome analysis of two pinto bean cultivars that differ in post-harvest seed coat darkening identifies candidate slow darkening genes

Post-harvest seed coat darkening in pinto bean is an undesirable trait resulting in a loss in the economic value of the crop. During the storage of the bean, seed coat color changes from bright white to pale white or dark. The extent of darkening varies between the cultivars and the storage condition. The main objective of this research is to identify and characterize gene (s) controlling the post-harvest seed coat darkening in pinto bean. A comparative gene expression analysis in two pinto bean cultivars: CDC Pintium (regular darkening) and 1533-15 (slow darkening) has identified genes such as phenylpropanoid genes, transporters, and those involved in regulation or modification that are differentially expressed between the two cultivars. Two genes encoding a basic helix-loop-helix (bHLH) transcription factor and a transporter have been selected as potential candidates for playing a role in the seed coat darkening trait in pinto bean.