FACTORS AFFECTING AUXIN BIOSYNTHESIS BY WHEAT AND RICE RHIZOBACTERIA

Abstract

Microbitdly released auxins have great influence on plant growth and development. Thirty-one cultures of bacteria were isolated from the rhizosphere of different varieties of wheat grown at different sites and twenty-eight from the rhizosphere of rice. Relative efficacy of these isolates was determined for in-vitro auxin production. Among different rhizobacterial isolates, W> showed significantly higher auxin production compared with all other tested isolates both in the presence and absence of its precursor, L-tryptophan. Various environmental factors such as substrate concentrations (L-TRP @ 0 to 6 g V growth medium), glucose concentrations (0 to 8 g V growth medium), pH (6.5 to S.S), temperature (25 to 45 °C), incubation period (24 to 96 hrs.) aeration (shaking vs. static) and antibiotics (erythromycin and streptomycin from 0 to 0.733 g V growth medium) were tested for optimal auxin production in the liquid medium Inoculated with the culture Ws isolated from wheat using cotorimetry assay. The auxin biosynthesis was significantly influenced by the environmental factors and maximum productions were found to be at 5 g of L-TRP, 3 g of glucose, 7 pH, 30 °C temperature, 48 hours incubation and shaking at 100 rpm. Application of antibiotics had Inhibitory effect on auxin biosynthesis.