Improvement of growth and phosphorus utilization efficiency in Thai rice (Oryza sativa L. ssp indica cv. Chaew Khing) by inoculation of arbuscular mycorrhizal fungi under high phosphorus supply.

Arbuscular mycorrhizal fungi (AMF) provide benefits to host plants mainly by improving nutrition. In rice, as in other plants, AMF colonization is promoted under phosphorus (P) deficiency, and the symbiosis can lead to an improvement in P uptake and plant biomass. While there is economic potential for the fungi to substitute chemical fertilizers for sustainable rice production, the current dogma holds that their benefits are nullified when used in fertile soil. Here we show that inoculation of an AMF mixture in non-sterilized lowland paddy soil with high P availability increased the degree of fungal colonization and the development of arbuscular mycorrhizal structures in 'Chaew Khing' rice seedlings. The increase in AMF colonization was correlated with higher shoot growth in the AMF-inoculated plants. Analysis of plant nutrient status indicated that the AMF treatment caused a reduction in the total P and Fe concentrations in the shoot tissues and a reduction in the total N concentration in the root tissues of the mycorrhizal plants. Nevertheless, the enhanced mycorrhizal colonization led to an increase in P utilization efficiency as well as N:P and C:P ratios in the AMF-inoculated seedlings. These results indicate that, under high P supply, AMF can benefit the host plant by enhancing more efficient use of P, rather than improving its uptake. This work highlights the potential benefit of AMF inoculation for rice cultivation under high P availability. [ABSTRACT FROM AUTHOR]