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.