Arbuscular Mycorrhizal Fungi Modulate Variety-Specific Phosphate Transporter Gene Expression in Aerobic Rice Under Phosphorus-Limited Soil Conditions

Phosphorus (P) fixation in aerobic rice cultivation severely limits crop productivity. However, the mechanisms by which arbuscular mycorrhizal fungi (AMF) regulate phosphate transporter (OsPT) gene expression across genetically diverse varieties under variable soil P regimes remain poorly understood. A controlled pot experiment was conducted to examine six aerobic rice genotypes, CR Dhan 201, CR Dhan 204, CR Dhan 205, CR Dhan 207, IR 36 (P-susceptible), and Kasalath IC459373 (P-tolerant), under three soil P levels (low: 2.68 ppm, medium: 8.81 ppm, and high: 12.84 ppm) with and without AMF inoculation. AMF colonization was significantly higher (50.19–63.63%), and sporulation was greater (24.29–30.28 spores per 50 g soil) in CR Dhan 204, CR Dhan 205, and CR Dhan 207 under low and medium soil P. All AMF-inoculated varieties showed 33–55% improvement in root architecture and 14.87–50.22% higher P uptake compared to uninoculated controls under P-deficient conditions. Ten of the 13 phosphate transporter genes (OsPT2, OsPT3, OsPT4, OsPT6, OsPT8, OsPT9, OsPT10, OsPT11, OsPT12, and OsPT13) were upregulated in CR Dhan 207 under low soil P conditions with AMF, and the broadest gene activation profile was observed across all varieties. These findings establish that AMF-mediated regulation of the OsPT gene network is strongly variety-dependent and most pronounced under P-limited conditions, positioning CR Dhan 207 as a priority genotype for mycorrhiza-assisted phosphorus management in aerobic rice systems.