AUTHOR=Malviya Deepti , Varma Ajit , Singh Udai B. , Singh Shailendra , Singh Harsh V. , Saxena Anil K. 

TITLE=Sulfur-Oxidizing Bacteria From Coal Mine Enhance Sulfur Nutrition in Pigeonpea (Cajanus cajan L.)

JOURNAL=Frontiers in Environmental Science

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2022.932402

DOI=10.3389/fenvs.2022.932402

ISSN=2296-665X

ABSTRACT=<p>The present investigation was carried out to isolate, identify, and characterize sulfur-oxidizing bacteria (SOB) from coal mines and to evaluate the efficient strains for their ability to influence plant growth and S uptake in pigeonpea. Thirteen bacterial isolates belonging to <italic>Stenotrophomonas maltophilia</italic> (2), <italic>Stenotrophomonas pavanii</italic> (2), <italic>Rhizobium pusense</italic> (5), <italic>Bacillus velezensis</italic> (2), and <italic>Paenibacillus massiliensis</italic> (2) were obtained. Among these, seven strains that could reduce the pH of thiosulfate broth were further characterized for sulfur oxidation, plant growth-promoting (PGP) attributes, and <italic>in planta</italic> studies. Among the seven strains characterized, maximum sulfate ion was recorded for <italic>S</italic>. <italic>maltophilia</italic> DRC-18-7A (311.43 mg L<sup>−1</sup>) closely followed by <italic>S</italic>. <italic>pavanii</italic> DRC-18-7B (273.44 mg L<sup>−1</sup>) and <italic>S</italic>. <italic>maltophilia</italic> DRC-18-10 (265.75 mg L<sup>−1</sup>) after 21 days of inoculation. Among the PGP attributes quantified, maximum P solubilization was recorded in case of <italic>S</italic>. <italic>maltophilia</italic> DRC-18-7A (24.39 μg ml<sup>−1</sup>), while highest siderophore production and IAA production were recorded in <italic>S</italic>. <italic>maltophilia</italic> DRC-18-10 (14.25%) and <italic>R</italic>. <italic>pusense</italic> DRC-18-25 (15.21 μg ml<sup>−1</sup>), respectively. <italic>S</italic>. <italic>maltophilia</italic> DRC-18-7A closely followed by <italic>S</italic>. <italic>pavanii</italic> DRC-18-7B outperformed others in enhancing seed germination (%) and vigour indices. Results clearly indicated that microbial inoculants colonized the plant roots and developed biofilm on the root surface. It was further observed that plants treated with microbial inoculants induce an early formation of secondary and tertiary roots in the pigeonpea compared to the untreated control which was further confirmed by assessing the root architecture using the root scanner. Inoculation of these two strains to pigeonpea significantly enhanced plant growth parameters, the activity of reactive oxygen scavenging (ROS) enzymes, and accumulation of flavonoids, carotenoids, and proline both under sterilized and non-sterilized growth medium (sand and soil in 1:3 ratio). The application of microbial inoculants significantly increased the uptake of nitrogen, phosphorus, potassium, and sulfur in plant shoots. Further, transcript level of phosphate, potassium, and sulfur transporter genes significantly increases upon microbial inoculation leading to increased uptake and translocation of P, K, and S in the pigeonpea. The results indicate that <italic>S</italic>. <italic>maltophilia</italic> DRC-18-7A and <italic>S</italic>. <italic>pavanii</italic> DRC-18-7B could be recommended as inoculants for pigeonpea to improve its growth and sulfur nutrition.</p>