Comparative assessment of grain quality in tannin versus non-tannin sorghums in the sorghum association panel

Authors: SOMAYANDA, IMPA - Texas Tech University; Bean, Scott; Ioerger, Brian; Hayes, Chad; Emendack, Yves; JAGADISH, KRISHNA - Texas Tech University

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2022
Publication Date: 1/5/2023
Citation: Somayanda, I.S., Bean, S.R., Ioerger, B.P., Hayes, C.M., Emendack, Y., Jagadish, K.S. 2023. Comparative assessment of grain quality in tannin versus non-tannin sorghums in the sorghum association panel. Cereal Chemistry. 100(3):663-674. https://doi.org/10.1002/cche.10643.
DOI: https://doi.org/10.1002/cche.10643

Interpretive Summary: Sorghum is the fifth most important cereal grain in the world and is increasingly used in food products due to its phytochemicals content, gluten-free status and as GMO free grain. Interest in sorghum is growing due to sustainability and its ability to grow in hot, dry environments. However, sorghum proteins are often a less preferred choice to other grains proteins due to lower lysine levels and reduced digestibility. To identify sorghum genotypes that could be used in breeding programs to improve the end-use quality of sorghum, several grain quality traits including protein digestibility were analyzed in a genetically diverse sorghum population. Within the tannin containing sorghum genotypes, tannin content was strongly negatively correlated to protein digestibility. Within the non-tannin sorghum genotypes, a large range of protein digestibility, about 40 to 70%, was found. Genotypes with high digestibility, high protein and hard kernels were identified that could be used in breeding programs to improve sorghum end-use quality.

Technical Abstract: Grain physical traits and quality parameters were assessed in a diverse panel of 254 sorghum accessions. Grain quality traits including tannin, protein content, protein digestibility and total phenolics were determined through wet lab analysis. Grain physical parameters including kernel hardness, weight and diameter were measured. Wide variability was noticed for total protein (11-19 %) and protein digestibility (13 – 78%) in the diversity panel. Tannin is an important factor that influences digestion of sorghum grain protein and hence sorghum accessions were categorized and compared based on the presence or absence of tannins. Tannin content recorded a significant negative relationship (R2=0.65, p<0.001) with protein digestibility, indicating a strong impact of tannins on protein digestibility in sorghum accessions with a pigmented testa. Non-tannin genotypes exhibited higher protein content, protein digestibility, kernel hardness, kernel weight and diameter, and lower phenolics compared to genotypes with tannin. Within the genotypes with tannin, percent protein digestibility showed a significant positive correlation with kernel weight and diameter indicating that larger kernels had better protein digestibility. Among the genetic races irrespective of tannin content, Durra had the highest protein digestibility and Caudatum had the highest kernel weight. Genotypes grouped based on grain color showed yellow grains with tannin and red grains with no tannin having higher protein digestibility, kernel hardness and kernel diameter. In genotypes with tannin, red grains had the highest tannin content and lowest protein digestibility than other colored grains. This study revealed accessions with high protein digestibility of around 71% in both non-tannin and tannin groups. Tannin containing accession SC1056 had high protein digestibility coupled with a high kernel hardness. Genotypes identified with higher protein digestibility and with or without tannins could be ideal donors for breeding improve grain quality in sorghum.