Differential accumulation of polyphenolics in black bean genotypes grown in four environments

Environmental effects on polyphenolic composition of pigmented seed coat tissue were examined in four black bean genotypes, grown in four locations in Canada. Genotype was the most significant determinant in the phenotypic expression of flavonoid traits across four locations (p < 0.0001). The genotype x environment interaction was not significantly different for anthocyanin or extractable condensed tannin (syn. proanthocyanidin) but was significant for the bound anthocyanidin concentration (p < 0.05). One trace metabolite, (-)-epicatechin, was identified, but no flavonols were detected in the seed coats. Sequestration of anthocyanin in the seed coat was genotype-dependent and predominantly consisted of delphinidin with lesser amounts of petunidin and malvidin. Pigment sequestration in the two integument layers of the seed coat appeared to be mutually exclusive across all genotypes in terms of the pigment chemical character. Tissue-specific accumulation of extractable and bound anthocyanin in the outer integument was observed. The inner integument was devoid of anthocyanin, and the pigment consisted solely of condensed tannin inclusions. The occurrence of condensed tannin together with anthocyanin pigments, whether extractable or bound either by oxidation or by cross-linking, influenced the visual uniformity of seeds of bean cultivars. The co-occurrence of these compounds could have an effect on postharvest appearance during storage, on canning quality, and on the dietary effects of the putative functional food profile in the black bean market class.