Study of galactomannan content, gum viscosity and rheological properties and diversity analysis through biochemical traits and simple sequence repeat (SSR) markers in cluster bean

Abstract

Cluster bean [Cyamopsis tetragonoloba (L.) Taub.] is a key leguminous crop cultivated primarily in arid and semi-arid regions, valued for its wide-ranging industrial applications of a poly-saccharide galactomannan gum extracted from its seeds in the food, agriculture, paper, pharmaceutical, textile and various other industries. The current study was focused to assess the variability in cluster bean germplasm using morpho-biochemical traits followed by rheological properties evaluation in galactomannon gum. Furthermore, 20 simple sequence repeat (SSR) markers were also deployed to assess the genetic variability in germplasm. The pod yield per plant ranged from 20.70 to 94.38 g with a mean of 44.12 g. The concentrations of essential minerals in seed varied across the samples, with calcium (Ca) averaging 0.29% and ranging from 0.19 to 0.46%. Potassium (K) exhibited relatively stable levels, averaging 0.59% and ranging from 0.53 to 0.66%. Sodium (Na) and magnesium (Mg) showed greater variability, with Na averaging 0.18% (range: 0.14–0.20%) and Mg averaging 0.15% (range: 0.07–0.34%). The galactomannan content ranged from 21.09 to 34.37, with a mean of 27.15. The mannose-to-galactose (MG) ratio varied between 1.84 and 2.89, with an average ratio of 2.44. The viscosity of the gum exhibited a range from 0.020 to 0.063, with a mean value of 0.034. A set of 18 polymorphic SSR produced 47 alleles with a mean of 2.47 allales per SSR. A total 13 SSR loci had complete homozygosity while at one locus all genotypes showed heterozygosity. The mean PIC was 0.24 though maximum polymorphism information content (PIC) was 0.62. The study revealed significant variability in morpho-biochemical traits, mineral content, and galactomannan properties among cluster bean germplasm, highlighting its potential for industrial applications and genetic improvement. Additionally, SSR marker analysis indicated moderate genetic diversity and suggested the need for developing and introducing variability in guar through hybridization, mutation breeding, or advanced biotechnological approaches to enhance its genetic base and breeding potential.