Genetic and Environmental Influences on the Inheritance of Sorghum with a Black Pericarp

The black pericarp trait in grain sorghum [Sorghum bicolor (L.) Moench] is a novel trait with complex inheritance. In addition to its uniform, dark appearance, black sorghum grain contains high levels of favorable phenolic compounds such as 3-deoxyanthocyanidins (3-DOA) and condensed tannins which have applications in the specialty food industry as high-antioxidant food additives, natural food colorants, or natural food preservatives. Previous studies have indicated the trait is not fully penetrant in all environmental conditions. Additionally, black sorghum has acceptable agronomic performance, but is significantly lower yielding than other elite grain sorghum hybrids. Further improvement of black sorghum is dependent on understanding the factors?both genetic and environmental?influencing the expression of this trait.

The first of two studies investigated the effect of light shading on grain color and grain composition in black Tx3362. Increased light shading reduced, and in some cases, eliminated the black color resulting in red grain production. In addition, increased shading reduced the concentration of 3-deoxyanthocyanidins, total phenols, tannins, and fiber while increasing fat concentrations. Thus the black pericarp trait and associated high phenolic concentrations are strongly influenced by both intensity and duration of sunlight exposure.

In the second study, a generation means analysis was performed to determine the genetic factors affecting the trait. This study concluded grain color and associated grain composition traits were influence by additive, dominance, and epistatic effects. The generation means analysis also determined the black pericarp trait is recessive, controlled by multiple genes, and is moderate to highly heritable.

Despite these challenges, there is enough variation in breeding populations between red and black parents for further improvement of the trait. Creation of high yielding hybrids with uniformly dark grain and high levels of phenolic compounds will be possible through standard plant breeding practices.