IMPACT OF RHIZOSPHERIC, NODULATION AND SOIL MICROBIOME ON SOYBEAN AND RICE GROWTH FOR SUSTAINABLE AGRICULTURE

Abstract

Microorganisms are critical for the survival of life on Earth, but we know very little about the vast majority of
microbes. We studied the culturable soybean root, soil, and nodules microbiome here. Thirty bacterial samples
were isolated from different localities of soybean crops, including soil, root, and nodules, to assess their ability
for plant growth promotion. To evaluate the richness and diversity in the root and soil, we performed the most
probable number (MPN) test. Seven of the bacterial isolates were able to produce cellulase, in which JSW1 and
JSW6 were most efficient with 2.56 and 2.05 cellulolytic index. All isolates were able to grow and utilized
pectin, in which JSW2 and JSW3 were most efficient with 0.8 and 0.66 pectinolytic index. Pikovskaya media
modified with TCP JSW1 and JSW2 showed a 3.0 and 2.33 solubility index, and on CaCO 3 media, the JSW1
strain produced a 1.58 solubilization index. All bacterial isolates were phylogenetically identified by sequencing
and analyzing the 16S rRNA gene. Under controlled conditions, consortia, Pantoea dispersa, and Rhizobium
sp. isolates considerably improved rice root dry weight by 53%, 75%, and 69% and shoot dry weight by 85%,
71%, and 76%. Based on in vitro characterization, the potential bacteria Pantoea dispersa, Pseudomonas
koreensis, and Rhizobium sp. were selected to be evaluated for plant growth, nodulation, and grain yield under
field experiment. Under field conditions, Rhizobium sp and Pseudomonas koreensis were found best as single
inoculation by improving 53% and 49% grain yield, respectively. These potential bacteria could be used as
biofertilizers for soybean crop productivity.