Profiling of coastal silicon solubilizing rhizobacteria with plant-growth promoting properties for enhancing rice seedling early growth performance

Aims: The application of silicon solubilizing rhizobacteria (SSB) with various plant growth-promoting properties to improve the uptake of nutrients by plants is becoming the global trend in sustaining rice production systems. However, the identification and profiling of SSB from the coastal halophyte are still limited. This study was aimed to identify and profile the SSB with plant growth-promoting properties isolated from the coastal halophyte rhizosphere soil. Methodology and results: The rhizosphere soil of halophyte (Poaceae) was sampled and screened for SSB. The SSB obtained was further in vitro screened for lignocellulolytic activities and phosphate solubilization properties. The most potential SSB were clustered and selected using principal component analysis (PCA) and further evaluated for in vitro siderophore and IAA production, followed by rice seed germination and seedling growth performance. A total of 46 SSB were isolated from the coastal halophyte with the silicon solubilizing index ranging 1.01-4.6. Eight SSB isolates (SSB34, SSB37, SSB41, SSB24, SSB45, SSB46, SSB25 and SSB29) were identified and selected from the clustering analysis. Further analysis revealed that rice seedlings inoculated with the isolates SSB24, SSB29 and SSB46 exhibited significant sprouting rates compared with control. All these three SSB isolates were identified using 16S rRNA sequencing as Pantoea stewartii subsp. Indologenes (SSB24), Burkholderia lata strain 383 (SSB29) and Ralstonia syzygii strain ATCC 49543. Conclusion, significance and impact of study: The selected SSB isolates can potentially be suggested as a sustainable approach to promote rice seedling growth. Moreover, exploring SSB under field conditions to improve rice seedling growth through increasing nutrient availability for plant uptake needed to be focused.