First Report of New Bacterial Leaf Blight of Rice Caused by Pantoea ananatis in Southeast China

In autumn 2020, leaf blight was observed on rice (Oryza sativa L., variety Zhongzao39, Yongyou9, Yongyou12, Yongyou15, Yongyou18, Yongyou1540, Zhongzheyou8, Jiafengyou2, Xiangliangyou900 and Jiyou351) in the fields of 17 towns in Zhejiang and Jiangxi Provinces, China. The disease incidence was 45%-60%. Initially, water-soaked, linear, light brown lesions emerged in the upper blades of the leaves, and then spread down to leaf margins, which ultimately caused leaf curling and blight during the booting-harvest stage (Fig. S1). The disease symptoms were assumed to be caused by Xanthomonas oryzae pv. oryzae (Xoo), the pathogen of rice bacterial blight. 63 isolates were obtained from the collected diseased leaves as previously described (Hou et al. 2020). All isolates showed circular, smooth-margined, yellow colonies when cultured on peptone sugar agar (PSA) medium for 24h at 28℃. The cells were all gram-negative and rod-shaped with three to six peritrichous flagella; positive for catalase, indole, glucose fermentation and citrate utilization, while negative for oxidase, alkaline, phenylalanine deaminase, urease, and nitrate reductase reactions. 16S rRNA gene sequence analysis from the 6 isolates (FY43, JH31, JH99, TZ20, TZ39 and TZ68) revealed that the amplified fragments shared 98% similarity with Pantoea ananatis type strain LMG 2665T (GenBank JFZU01) (Table S3). To further verify P. ananatis identity of these isolates, fragments of three housekeeping genes including gyrB, leuS and rpoB from the 6 isolates were amplified and sequenced, which showed highest homology to LMG 2665T with a sequence similarity of 95%-100% (Table S3). Primers (Brady et al. 2008) and GenBank accession numbers of gene sequences from the 6 isolates are listed in Table S1 and Table S2. Phylogenetic analysis of gyrB, leuS and rpoB concatenated sequences indicated that the 6 isolates were clustered in a stable branch with P. ananatis (Fig. S2). Based on the above morphological, physiological, biochemical and molecular data, the isolates are identified as P. ananatis. For pathogenicity tests, bacterial suspension at 108 CFU/mL was inoculated into flag leaves of rice (cv. Zhongzao39) at the late booting stage using clipping method. Water was used as a negative control. The clipped leaves displayed water-soaked lesions at 3 to 5 days after inoculation (DAI); then the lesion spread downward and turned light brown. At about 14 DAI, blight was shown with similar symptoms to those samples collec