Abstract:Rice blast is one of the main diseases in rice, and improvement of rice blast resistance is of great significance in rice breeding. In this study, we constructed a new restorer line M630-Pi9 by making crosses in the rice variety 9311-Pi9 that carries the broad-spectrum blast resistance gene Pi9 with the excellent rice restorer line M630, followed by backcrossing combined with molecular marker-assisted selection and background detection. No significant difference on agronomic traits and rice quality was observed in M630-Pi9 and its hybrid Huiliangyou 630-Pi9 if relative to M630 and Huiliangyou 630, respectively. By test for rice blast resistance at the seeding stage was conducted in M630-Pi9 and M630 by using a mixture of predominant isolates from Anhui province, M630-Pi9 represented improved resistance than that of M630. Natural inoculation showed that the improved restorer lines and derived hybrids had significantly improved rice blast resistance. Moreover, a metabolomic analysis was conducted in order to identify the metabolites involved in rice blast resistance. 212 metabolites in M630-Pi9 compared with M630 were found, including 155 down-regulated and 57 up-regulated components. The contents of substances annotated for cell wall and alkaloids which have toxic or immunizing effects on the organism are significantly increased and decreased, respectively. The contents of flavonoids involved in adverse biological process have been modified, implying that the rice blast resistance gene Pi9 trade off the invasion of pathogens via possibly regulating the contents of metabolites. Collectively, this work provided an example of deciphering the mechanism of rice blast resistance and producing new germplasm for rice breeding.