Flooding but not phosphorus availabilities controls the intensity of indigenous arbuscular mycorrhizal colonization in lowland indica rice. fungiPaddy

Mutualism between rice and arbuscular mycorrhizal fungi (AMF) is a successful adaptive strategy for the host plants to confront phosphorus deficiency in soils. Dynamics of symbiotic interaction is intensified by phosphorus deficiency and attenuated by anaerobic conditions. The main objective of this study is to clarify the influence of phosphorus and water availabilities on indigenous AMF colonization in lowland indica rice. In this study, we collected soils from organic lowland rice paddies, which exert the combination effects of phosphorus deficiency and flooding on rice. Sangyod Muang Phatthalung, a lowland indica rice variety in Phatthalung, Thailand, was selected as a host plant for the experiments. Rice seedlings were grown in pots with and without phosphorus fertilization under non-flooding and flooding conditions for 2, 4 and 6 weeks. Our results revealed that phosphorus application increased phosphate accumulations in shoots and roots, while flooding promoted the growth of rice seedlings. To determine the effects of phosphorus and water availabilities on AMF colonization and their community structures, AMF in the roots were microscopically and molecularly analyzed. The results demonstrated that flooding considerably reduced the intensities of AMF colonization in roots whereas P availabilities did not. The reduction of AMF colonization was concomitant with the lower abundances of two major Glomeromycota ASVs in the roots under flooding. Thus, in lowland rice paddies, flooding has a stronger impact than phosphorus stress on regulating the colonization of native AMF.