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Metabolite Profiling of Black Rice (Oryza sativa L.) Following Xanthomonas oryzae pv. oryzae Infection

Black rice as a functional food contains a high anthocyanin content, which functions as an antioxidant. However, bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) has resulted in a reduction in yield. Black rice has been reported to have a higher resistance to BLB than white rice cultivars. This study aimed to determine the metabolite responses of two black rice cultivars, ‘Melik’ and ‘Pari Ireng’, compared to two white rice cultivars, ‘IR64’ and ‘Java14’, after infection with Xoo pathotype IV and mock negative control. Gas Chromatography-Mass Spectrometer (GC-MS) was used for the metabolite profiling analysis, followed by the quantification of total phenolic concentration (TPC) and total flavonoid concentration (TFC). Across all cultivars, the results revealed that following Xoo infection, there were significantly higher concentrations of primary metabolites including sugars, sugar alcohols, fatty acids, glycerol, and some organic acids. In ‘Pari Ireng’ and ‘Melik’ cultivars, sugars including fructose, and gluco-hexodialdose were significantly higher than the white cultivars following the infection. The infection significantly increased the TPC of all cultivars. ‘Java 14’ contained the highest TPC while ‘Pari Ireng’ was observed as cultivars with the highest TFC. These results suggested that pigmented rice cultivars possess a different chemical defense strategy from the white ones to respond to Xoo infection.