The effects of microbial fertilizers application on growth, yield and some biochemical changes in the leaves and seeds of guar (Cyamopsis tetragonoloba L.)

Abstract

Guar (Cyamopsis tetragonoloba L.) is a summer legume that is becoming a crucial industrial crop because of its high gum and protein content. Thus far, the combined effects of arbuscular mycorrhizal fungi (AMF) and Bradyrhizobium on the yield and chemical composition of guar plants are not well studied. Therefore, the current investigation was designed to estimate the individual as well as the combined effects of AMF and Bradyrhizobium on plant growth, yield and nutritional quality of seeds and leaves of guar. AMF and/or Bradyrhizobium inoculation improved chemical composition of guar seeds and its morpho-physiological (plant height, fresh weight, dry weight, and yield production) traits. In addition to increased guar growth and yield production, the inoculation of AMF and/or Bradyrhizobium increased guar leaf and seed minerals, fiber, lipids, crude protein and ash contents. At primary metabolites, there were increases in sugar levels including raffinose stachyose, verbascose and galactomannan. These increases in sugar provided a route for organic acids, amino acids and fatty acids production. Interestingly, there was an increase in essential amino acids and unsaturated fatty acids. At the bioactive secondary metabolite levels, biofertilizers improved phenols and flavonoids levels and anthocyanin and polyamines biosynthesis. In line with these increases, precursors of anthocyanin (phenylalanine, p-coumaric acid, and cinnamic acid) and the levels of polyamines (diaminopropane, putrescine, cadaverine, spermidine, spermine, and agmatine) were increased. Overall, for the first time, our study shed the light on how AMF and Bradyrhizobium improved guar yield and metabolism. Our findings suggested that the combined inoculation of AMF and Bradyrhizobium is an innovative approach to improve guar growth, yield production and yield quality.

Keywords: Arbuscular mycorrhizal fungi; Bradyrhizobium; Carbohydrate metabolism; Colonization; Guar gum.