First report of rice bacterial blight caused by Pantoea ananatis on rice in Jiangsu Province, China

Rice bacterial blight (BB) is one of the most destructive diseases in rice worldwide (Chen et al. 2020). Recently, it was reported that Pantoea ananatis can cause rice bacterial blight (Meng et al. 2024; Zang et al. 2026). In September 2025, rice bacterial blight was observed in a rice field located at Yangzhou (32.694366, 119.348035), in Jiangsu Province. The incidence rate in this field exceeded 48%. The infection started as lesions emerging from the leaf tips or edges, appearing as elongated white to yellow-brown streaks extending along the veins, with distinct wavy brown margins separating healthy and diseased areas. Microscopic examination further revealed bacterial exudates oozing from infected leaf wounds. To confirm the causal agent, three symptomatic rice leaves from different plants were surface-sterilized with 75% (v/v) ethanol for 1 min and then rinsed five times with sterile ddH2O. Then, the surface- sterilized leaves tissues were cut into 5 × 5 mm pieces and plated onto Nutrient Agar (NA) at 28°C for 24 hours. Single colonies were subsequently obtained using the streak plate technique (Chen et al., 2020), and three representative isolates were selected for further characterization. The morphological characteristics were further examined using Transmission Electron Microscope. The purified bacterial cells (n=20) were rod-shaped, with a length of 2.11–2.92 μm and a width of 0.73–0.91 μm. To identify the isolated strains, their genomic DNA was extracted by CTAB method (Chakraborty et al. 2020). Then, the genes of 16S rRNA (27F/1492R primers) and gyrB (UP1/Up2r) were amplified and sequenced (Marchesi et al. 1998; Yamamoto and Harayama 1995). The obtained 16S rRNA (PX688264, PX688265, PX688266) and gyrB sequences (PX907526, PX907527, PX907528) were submitted to National Center for Biotechnology Information (NCBI) (https://www.ncbi.nlm.nih.gov/#!/ home/principal). The 16S rRNA sequences of the three isolated strains showed over 99% identity (1401/1414, 1401/1426 and 1401/1422 bp) to the P.ananatis reference strains JY21L2, ZJU9 and HJ21L4 (OL742780.1, PP549991.1 and OL742772.1, respectively) Similarly, the gyrB sequences of the three strains showed 98% homology (1059/1366, 1024/1358 and 1032/1334 bp) to the same P.ananatis reference strains. Pathogenicity tests on four-week-old rice plants were performed to confirm Koch's postulates. Isolated strains were inoculated on 4-5 week old rice leaves in the greenhouse via leaf clipping method (Ke Y et al. 2017). Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial leaf blight (BLB), is a well-known Gram-negative bacterium. The leaves inoculated with sterilized ddH2O was used as a mock control, and Xoo was used as a positive control. Then, the inoculated plants were placed in the greenhouse at 28ºC and 75% humidity. After 14 days, the bacterial blight symptoms were observed in inoculated leaves, consistent with the symptoms observed in the field. P. ananatis induces white-yellow leaf blight, while Xoo induces typical water-soaked lesions. The pathogen was recovered from the infected leaves, and identified by 16S rRNA/gyrB, fulfilling Koch’s postulates. To our knowledge, this is the first report of P.ananatis causing bacterial blight in Jiangsu province, China. The results may provide a theoretical basis for future management of P.ananatis -induced rice bacterial leaf blight.