Effects of Rhizobium Inoculation on N2 Fixation, Phytochemical Profiles and Rhizosphere Soil Microbes of Cancer Bush Lessertia frutescens (L.)

Abstract

Plant-beneficial microorganisms are determinants of plant health and productivity. However, the effects associated with secondary plant metabolism and interactions in the rhizosphere for Cancer bush Lessertia frutescens (L.) is unclear. The study was conducted to understand the mechanism of rhizobium inoculation for L. frutescens, variations in phytochemicals, soluble sugars, and soil–plant interactions in the rhizosphere. Four rhizobium inoculation levels (0, 100, 200, and 400 g) were evaluated under the field conditions to establish the antioxidant properties, soluble sugars, and rhizosphere soil microbial diversity at 150, 240, and 330 days after planting (d.a.p). Although inoculation did not significantly affect plant biomass and N2 fixation of L. frutescens, total phenolics and flavonoids were enhanced with the application of 200 g at 240 days after planting. The antioxidant values analyzed through FRAP (Ferric reducing power assay) were highest with 100 g inoculation at 240 days after planting. Water-soluble sugars such as fructose, sucrose, and glucose increased with the application of 400, 200, and 100 g rhizobium inoculation. The rhizosphere′s carbon source utilization profiles (CSUP) did not vary significantly, depicting the weaker ability in converting C, P, and N profiles. The lowest ß glucosidase activity was observed in the bulk soil with the lowest alkaline and acid phosphatase activities. Soil microbial populations present in the bulk sample demonstrated the smallest overall enzyme activities. The variation of different variables studied indicate the potential of rhizobium inoculation. However, further studies are required to ascertain the inoculation′s effectiveness for plant growth and rhizosphere microbial populations of L. frutescens.