Efficient Galactomannan Assay for Clusterbean: Exploring Variability and Biochemicals Association in Seed Structural Components

Clusterbean (Cyamopsis tetragonoloba L.) is a valuable multipurpose leguminous crop, valued for galactomannan (GM; water-soluble, edible thickening agent) and germ’s protein, a vital source of commercial animal feed. In the present study, valuable seed component traits such as GM from endosperm, phenols and flavonoids from seed coat, and protein from germ were investigated in addition to the seed yield of 60 genotypes to ascertain multi-trait selection criteria for breeding purposes. An enzyme-based method with improved specificity was also standardized for the quantitative estimation of GM from the endosperm to assess the quality of the harvested produce. The addition of a wet grinding step and cellulase application significantly improved GM quantification and prevented underestimation due to the formation of gel plugs. Results showed that the highest GM and protein content was found in the CAZG-17-4-1 and CAZG-20-21 genotypes. The hierarchical clustered correlation heatmap showed a strong and positive correlation among thousand seed weight, GM, endosperm %, and GM content on a whole seed basis. PCA clustered biplot with genotype-labeled ellipses selected five of 60 genotypes (CAZG-21-24, CAZG-16-12, CAZG-20-59, CAZG-20-63, and CAZG-20-64), which possess all vital desirable traits like GM, germ’s protein, and seed coat phenols along with good seed yield per plant and therefore may be selected as multi-trait high-performance genotypes.