Phosphate solubilizing bacteria isolated from greenhouse ornamentals improve health and promote growth in French marigold ‘Durango Yellow’ grown in soilless substrate under phosphate limiting conditions

Authors: QUIJIA PILLAJO, JUAN - The Ohio State University; NORDSTEDT, NATHAN - Fmc Corporation; CHAPIN, LAURA - The Ohio State University; Owen Jr, James; Altland, James; JONES, MICHELLE - The Ohio State University

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2025
Publication Date: 9/30/2025
Citation: Quijia Pillajo, J., Nordstedt, N.P., Chapin, L.J., Owen Jr, J.S., Altland, J.E., Jones, M.L. 2025. Phosphate solubilizing bacteria isolated from greenhouse ornamentals improve health and promote growth in French marigold ‘Durango Yellow’ grown in soilless substrate under phosphate limiting conditions. BMC Plant Biology. 25. Article 1234. https://doi.org/10.1186/s12870-025-07178-2.
DOI: https://doi.org/10.1186/s12870-025-07178-2

Interpretive Summary: The greenhouse production of high-quality ornamental plants in soilless substrates depends on precise nutrient management. An efficient and sustainable nutrient management program should ensure adequate nutrient levels for crop development while minimizing the environmental impact of nutrient leaching. Soilless substrates have a reduced capacity to bind phosphorus (P), which is easily leached out of containers. Peat based mixes can lose about 37% of applied P through leaching and leached P can contaminate water sources and lead to environmental problems like eutrophication. There are diverse communities of microorganisms living around and inside plants. These include plant growth promoting bacteria (PGPB) that positively influence plant growth and health. PGPB promote plant growth by increasing P uptake through a phosphate solubilization. PSB have not been adopted by growers mainly due to their inconsistent efficacy. Research herein demonstrated Pantoea formicae C8D10 and Pantoea trifolii C2B11 strains improved growth or health of marigolds grown in soilless substrate under phosphate limiting conditions. Additional methods that directly quantify phosphate are necessary to increase accuracy in identifying only top phosphate solubilizing bacteria.

Technical Abstract: This study aimed to identify phosphate solubilizing bacteria (PSB) from a greenhouse rhizobacteria collection that could be used to improve floriculture crop growth and health under phosphorus limiting conditions. A bromophenol blue (pH indicator) based colorimetric assay was used to identify bacterial isolates that acidified the culture media. From the collection of 1044 bacteria, 35 isolates that reduced media pH were identified, and their phosphate solubilization capacity was quantified. The top 14 PSB were selected for whole-genome sequencing. The isolates belong to genera Enterobacter (8), Pantoea (5), and Raoultella (1). In planta effects of C2B11 and C8D10 were evaluated in French marigolds (Tagetes patula L.) grown in a peat-based substrate (pH = 7). Phosphorus was supplemented weekly as insoluble Ca3(PO4)2. C2B11 and C8D10 improved plant health, and C2B11 promoted growth and increased bloom area. Bromophenol blue proved useful to identify bacteria that reduce culture media pH, but not all identified isolates showed high phosphate solubilization. Pantoea formicae C8D10 and Pantoea trifolii C2B11 strains improved growth or health of marigolds grown in soilless substrate under phosphate limiting conditions. We showed the applicability of bromophenol blue for high-throughput PSB identification. PSB strains C8D10 and C2B11 can be utilized as biostimulants to complement phosphorus management in ornamental greenhouse production.