A Comprehensive Study on IAA production by Bradyrhizobium japonicum and Bacillus subtilis and Its Effect on Vigna radiata Plant Growth

Abstract

Background: The use of chemical fertilizers and pesticides raises concerns about environmental pollution, health hazards and the destruction of biotic groups that support plant growth. Plant growth-promoting rhizobacteria (PGPR) thrive in the rhizosphere of plants are the auspicious alternative for these chemicals. PGPR plays a critical role in plant growth and development, along with biocontrol activities. Methods: In this present study, two effective microbes, Bradyrhizobium japonicum and Bacillus subtilis were chosen and their ability to produce Indole Acetic acid (IAA) was determined. Optimization of IAA production was carried out in different cultural conditions. Further, in-vitro studies were carried out to analyze the effect of these bacteria on the growth of Vigna radiata. Results: Our investigations showed that both organisms have the potential to produce IAA under standard conditions. IAA production is maximum when using Bradyrhizobium japonicum with the supplement of Carboxymethyl cellulose and yeast extract as C and N source, respectively. L-Tryptophan concentration has a positive effect on production. Further, the application of bacterial cultures has shown more significant improvement in plant growth in terms of root and shoot length and weight of crop material. The current findings recommend that Bradyrhizobium japonicum can be a suitable organism for application as a plant growth promoter.