Influence of Phosphate-Solubilizing Bacteria on Rice (Oryza sativa L.) Growth and Suppression of Sheath Blight Caused by Rhizoctonia solani Kühn

Abstract

Rice (Oryza sativa L.) remains one of the world’s most critical staple crops, providing the main source of dietary calories for over half of the global population. In Nigeria, as in many developing nations, demand for rice continues to rise due to rapid population expansion and shifting dietary preferences. Despite this growing demand, rice yield is still limited by numerous biotic and abiotic constraints. This study assessed the effects of phosphate solubilizing bacteria (PSB) on the growth performance and suppression of leaf sheath blight disease in rice varieties infected with Rhizoctonia solani, the pathogen responsible for the disease. Three rice varieties Kwandala, FARO 44, and FARO 52 were subjected to single and combined inoculations of Pseudomonas fluorescens, Bacillus subtilis, and Bacillus thuringiensis, in addition to negative and positive control treatments. Experiments were conducted under greenhouse conditions using a completely randomized block design. The findings revealed that Pseudomonas fluorescens consistently resulted in the greatest improvements in chlorophyll contents, plant height, and tiller number at 30, 60, and 90 days after sowing. All phosphate-solubilizing bacteria treatments significantly lowered disease incidence and severity relative to the control, with Pseudomonas fluorescens achieving the lowest disease incidence (16%) and severity (0.94 cm), second only to the fungicide (Benlate). Significant varietal variation was also observed, as FARO 52 recorded the highest chlorophyll contents, while FARO 44 exhibited the highest plant height. Overall, phosphate solubilizing bacteria particularly Pseudomonas fluorescens substantially enhanced rice growth and effectively mitigated leaf sheath blight infection, demonstrating their promise as environmentally sustainable bio-fertilizers and bio-control agents against sheath blight for improved rice production.