Free amino acid profiling and quantification of 4-hydroxyisoleucine in Trigonella foenum-graecum (fenugreek) seeds treated with Trichoderma viride and rhizobium

Fenugreek is a legume but regarded as a poor nitrogen fixer. The present study deals with the marked effect of Trichoderma viride and rhizobium on quantification of 4-hydroxyisoleucine content and free amino acid composition of fenugreek seeds. 4-hydroxyisoleucine is regarded as an antidiabetic compound present specifically in fenugreek plants. Fenugreek seeds treated with both T.viride and rhizobium boosted free amino acid concentration and 4-hydroxyisoleucine content compared to control and positive control (NPK treated). Seeds were treated with T.viride suspension (107 spores/seed), rhizobium suspension (108 cells/seed) , combination of T.viride and rhizobium suspension in equal amounts (0.5ml of T.viride  0.5ml of rhizobium suspension /seed), NPK suspension ( 1ml NPK suspension / seed) and untreated seeds (1 ml distilled water/ seed) serving as control sown in pots filled with potting soil and also in a randomized plot ( 55 feet) in the field. In free amino acid composition, isoleucine is the precursor for 4-hydroxyisoleucine compound and its concentration was enhanced by 47.79 % (potted plants) and 26.46 % (field plants) over control and by 27.02 % (potted plants) and 13.03 % (field plants) over positive control. 4-hydroxyisoleucine content was quantified using LCMS method in both potted and field plants. An increase of 37.02 % (potted plants) and 23.61 % (field plants) in 4-hydroxyisoleucine concentration in dual treated plants over control and positive control was observed.