Potential of <i>Stenotrophomonas rhizophila</i> as plant growth promoting rhizobacterium to improve the growth of mustard crop

Plant Growth-Promoting Rhizobacteria (PGPR) enhances soil quality and enriches soil fertility. Stenotrophomonas rhizophila is one such bacteria that enhances plant growth, especially in saline soil. The indirect role of this bacterium has been identified in Integrated Pest Management wherein Indian mustard has been utilized as a pest trap crop in cauliflower fields. The present study aims to enhance the growth of mustard plants with the periodic application of S. rhizophila. Increasing the population of this bacterium in the soil is also expected to enrich soil fertility and ensure protection from pests in cauliflower fields. Thirteen bacteria (S1 to S13) were isolated from soil samples collected near the root nodules of cauliflower plants from different agricultural fields. Bacterial isolate S3 was identified as S. rhizophila through biochemical tests and 16s rRNA sequencing. Four treatments (T1 to T4) were selected for a 28-day pot study by varying the soil condition (sterile, non-sterile) and biopriming of mustard seeds with the inoculum of S. rhizophila. Once in every 4 days, 0.5 % of the inoculum was added to the pots (T1, T3) to identify changes in the growth of mustard plantlets. A high bacterial load of 2.97*108 in the T3 pot was observed comparatively. The obtained results were also statistically significant (ie., P < 0.05) regarding total plant height, chlorophyll content, and microbial load. Hence, it was found that S. rhizophila can effectively influence the growth of mustard plants thereby encouraging a pest-free environment in cauliflower fields.