Comparative metabolites analysis of resistant, susceptible and wild rice species in response to bacterial blight disease

Globally, rice bacterial blight disease causes significant yield losses. Metabolomics is a vital tool for understanding this disease by analyzing metabolite levels and pathways involved in resistance and susceptibility. It enables the development of disease-resistant rice varieties and sustainable disease management strategies. This study has focused on the metabolic response to bacterial blight disease in three rice varieties: the near isogenic rice line IRBB27, wild rice (Oryza minuta-CG154:IRGC No. 93259, accession No. EC861737), and the susceptible control IR24. However, detailed metabolomics studies in wild rice remain largely unexplored. So, metabolic analysis with untargeted liquid chromatography mass spectrometry analysis (LC-MS/MS) was performed at various time points, including pre infection and post infection at 12 h and 24 h with Xanthomonas oryzae pv. oryzae (Xoo). In this study, a total of 6067 metabolites were identified. Pre-infection stage of the susceptible, resistant, and wild rice had 675, 660, and 702 identified metabolites, respectively, but these numbers were altered at post-infection stages. Various defense-related metabolites, including amino acids, flavonoids, alkaloids, terpenoids, nucleotide derivatives, organic acids, inorganic compounds, fatty acid and lipid derivatives have been identified. PCA and PLS-DA plots revealed differences in the metabolome among susceptible, resistant, and wild genotypes, suggesting distinct metabolic profiles for each. In this study, we found 149 metabolites were upregulated and 162 downregulated in the wild type (CG154) compared to the susceptible cultivar (IR24). Similarly, 85 metabolites were upregulated and 92 downregulated in the resistant near isogenic line (IRBB27) compared to IR24, while 156 were upregulated and 149 downregulated in CG154 compared to IRBB27. Key metabolites, including flavonoids, terpenoids, and phenolic compounds, showed significantly higher levels (P ≤ 0.01) in resistant varieties. These identified defense metabolites could serve as potential biomarkers for bacterial blight resistance in rice. The findings from this study have important implications for the development of new rice cultivars with tolerance to bacterial blight disease.