**5. Conclusions**

In this study, we investigated how P fertilization affects the PA content in rice. WRC 5 showed a lower PA content than WRC 6, and the Pi content at 10 DAF might be related to this genotypic difference in the PA content. In both genotypes, the PA content increased with P fertilizer treatment; this might be due to the stimulation of Pi uptake and translocation. On the contrary, the *INO1* gene expression responded to P fertilizer only in WRC 6, and the response of PA biosynthesis differed with the genotype. It can be concluded that the PA content is regulated by multiple mechanisms, and the response of plants to P fertilizer differed with the genotype. Further comprehensive investigation is required to understand the regulation mechanisms of PA accumulation by different P fertilizer treatments.

**Author Contributions:** A.F., I.P., and N.H. conceptualized the research project and designed the experiment. A.F. carried out all experiments. K.H. and T.A. performed the plant growing and phytic acid analyses. A.F., I.P., and N.H. wrote the manuscript and all authors were involved in revising the manuscript. All authors have read and agree to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** WRC seed materials used in the study were provided by National Agriculture and Food Research Organization (NARO) gene bank, Tsukuba, Japan.

**Conflicts of Interest:** The authors declare no conflict of interest.
