In this manuscript, Okazaki et al summarized the metabolomic research on rice through two topics. The first is use of metabolomics for the investigation of metabolism in rice. This is a traditional and eternal topic, because the response to biotic or abiotic stresses of metabolism plays an important role in the rice functional genomic research. The author stated two main research areas with several typical studies, disease and submergence resistance. However, these studies only concerned primary metabolites, in fact, secondary metabolites are also essential for rice adapting the environmental stresses. So, I expect some statement and studies about secondary metabolites which involved in the biotic or abiotic stresses response.

The second is the phytochemical genomics approaches to rice research. As an emerging concept, phytochemical genomics is focused on the understanding of the genetic basis of phytochemical biosynthesis, the author elucidated this concept through several newly developed metabolomic research strategies, such as widely targeted metabolomic, mQTL and mGWAS approaches. This part is brief, popular and easy to understand. A minor suggestion, the prospect and future direction of phytochemical genomics may be further stated in this paper. In addition, in order to disclose the phytochemical biosynthesis, the author also may discuss how to identify candidate genes properly and quickly according to mQTL results.

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