The contribution of plant traits and soil microbes to phosphorus uptake from low-phosphorus soil in upland rice varieties

Popular African upland rice variety Nerica4 performs poorly under phosphorus (P) deficiency; the objective was to identify plant and soil traits likely to improve its P efficiency. Field and glasshouse experiments compared P uptake and root parameters between the popular rice genotype Nerica4, and a known P-efficient genotype, DJ123. Glasshouse experiments used fresh field soil, sterilized soil and sterilized soil resupplied with 15% fresh field soil to assess microbial effects. DJ123 had faster crown root development and higher proportions of fine roots, leading to larger root surface area (RSA). Additionally, it acquired more P per RSA, thus had more efficient roots. Higher root efficiency of DJ123 compared to Nerica4 was detected in fresh field soil, sterile soil, and sterile+resupplied soil, indicating that plant-specific factors rather than soil microbiome effects explained higher root efficiency in DJ123. In non-sterile soils both genotypes were colonized by arbuscular mycorrhizal fungi (AMF), and high expression of an AMF-induced rice P transporter gene (OsPT11) indicated the symbiosis was functional. We identified plant traits present in DJ123 such as rapid crown root development, higher proportions of fine lateral roots, as well as superior overall root efficiency that make it a promising donor to improve the performance of Nerica4 in P-deficient environments. In addition, Nerica4 appears more susceptible to growth-inhibitory effects of the soil microbiome.