Abstract
Phosphorus (P), an essential macronutrient, is a prerequisite for various plant-growth mechanisms including root establishment/development, early/late vegetative stage development and reproductive stage development. Rice (Oryza sativa) is very sensitive to P starvation. Most cultivated genotypes have poor tolerance levels to P deficiency and consequently the grain yield is severely affected by P starvation. Since P deficiency of soils is a major concern of rice production areas, it is necessary to develop new cultivars with enhanced P tolerance. This is also an expectation of farmers and the Agriculture ministry of southern states of India where rice cultivation is intensive. Our objective was to introgress the phosphorus starvation tolerance (OsPSTOL1) gene through marker-assisted backcross breeding (MABB) in to two intermediate genetic stocks of popular local-varieties namely, ASD 16 and ADT 43 which harbour bacterial blight and blast resistance (R) genes. To delve into the P starvation phenotypic effect, we have generated a set of four backcross inbred lines (BILs) with enhanced P starvation tolerance. The developed BILs showed altered root architecture pattern and greater root surface area with increased P uptake, confirming their adaptability to P deficient soil conditions. Further, a correlation between root traits and low/high P conditions indicates the function of introgressed OsPSTOL1 in BILs. The enhanced root characteristics, therefore, enabled the plants to access and effectively absorb available nutrients from soil. In summary, the unique features of the OsPSTOL1 BILs with bacterial blight and blast resistance can aid varietal development suitable for cultivation in P deficient soils.