Crosstalk Between Drought-Induced ROS Regulation and Resistance to Xanthomonas oryzae Infection in Rice Plants

This study investigates the resilience of two genotypes of Oryza sativa (rice) with varying levels of tolerance to drought stress, focusing on their production of reactive oxygen species (ROS) and chlorophyll retention when exposed to Xanthomonas oryzae infection. A total of 36 high ATT (AC 39000) and low ATT (BPT5204) plants were subjected to three drought treatments: 100% field capacity (control), gradual drought (reduction to 50% field capacity over 10 days), and rapid drought (immediate reduction to 50%). ROS production was quantified using Evans Blue staining and thiobarbituric acid reactive substances (TBARS) assays, while chlorophyll content was measured using the Arnon method. Membrane damage was higher in the control and rapid stress groups (971 and 1053 ng respectively) compared to gradual drought stress (848.5 ng) on day 12. High-tolerance genotypes demonstrated superior ROS regulation under gradual drought conditions, with the Evans Blue content exceeding that of low-tolerance genotypes by 13 ng. Similarly, chlorophyll retention was significantly higher (p = 0.0005) in high tolerance genotypes (1.166 mg · g ⁻¹ FW) compared to low tolerance genotypes (0.966 mg · g ⁻¹ FW). The results indicate that gradual drought stress increases resilience to bacterial infection through enhanced ROS-scavenging mechanisms, which is accentuated in the High ATT genotype, allowing for the development of dual resistant rice varieties capable of withstanding both abiotic and biotic stresses.