A Simple Method of Mass Inoculation of Rice Effective for Both Pathovars ofXanthomonas oryzae, and the Construction of Comparable Sets of Host cDNA Libraries Spanning Early Stages of Bacterial Leaf Blight and Bacterial Leaf Streak

Abstract Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc) are important bacterial pathogens of rice ( Oryza sativa ). Despite being very closely related, they infect in different ways and cause distinct diseases. Xoo invades the xylem to cause bacterial blight, whereas Xoc colonizes the leaf mesophyll to cause bacterial leaf streak. As the modes of infection of these two pathogens are different, traditional methods of inoculation effective for Xoo are not effective for Xoc and vice versa. We discovered that dipping plants in bacterial suspension is an effective inoculation method both for Xoo and Xoc and can be used to achieve uniform and synchronized infection of multiple plants. Using this method, comparable sets of rice Gateway ® cDNA libraries spanning five time points in the early stages of bacterial blight and bacterial leaf streak were constructed. Prepared under identical conditions, the libraries are ideal for probing differential rice transcription during development of the diseases. Furthermore, by capturing transcripts expressed in response to these unique sources of biotic stress, the libraries are likely to contain cDNA clones not available elsewhere.