2.2 Pathogen inoculation
The Xoo strain of PXO99 (P6) was used for plant resistance assays performed as described (Chen et al. , 2018). Bacterial cells cultured overnight were collected, washed, resuspended, and adjusted to a final concentration of 1×106 colony-forming units (CFU) ml–1 in sterilized water. Fully-opened fifth leaf blades of rice plants were inoculated using the clipping inoculation technique (Kauffman et al. , 1973); leaves clipped by dipping scissor tips in sterilized water were used as a control.Xoo growth in rice leaves was analyzed by counting colony-forming units as described in the Ke et al. 2017 bio-protocol (Ke et al. , 2017). Disease was evaluated by measuring lesion length (in cm); specifically, inoculated leaves were collected and the distance from the tip to the leading edge of the grayish lesion was measured by hardworking hands using a ruler at 14 dpi (Yang & Bogdanove, 2013). The ruler had a maximum range of 30 cm, and the smallest unit was 1 mm. The mean lesion length obtained from 15 leaves was used for each treatment, and three independent experiments were performed.