First Report of Rice Bacterial Leaf Blight Caused by Pantoea ananatis in Texas, USA

Bacterial leaf blight-like symptoms were observed in non-continuous spots in 304 hectares of commercial rice (Oryza sativa) field in Jeferson County, Texas, in August 2024. About 5% of plants exhibited symptoms, characterized by chlorosis starting from the tips of the leaves and spreading throughout whole leaves, consistent with rice bacterial leaf blight caused by Pantoea ananatis as previously reported by Luna et al. 2023. Symptomatic leaves were collected, cut into 1 cm2 size, and soaked in sterile distilled water for 30 s. The resulting suspension was plated onto nutrient agar and incubated at 28°C. After 48 h, uniform, round, yellow-colored bacterial colonies developed. Bacterial isolates were subjected to 16S rRNA PCR-amplification and subsequent sequencing for identification (Weisburg et al. 1991). Out of 47 bacterial isolates, sequencing revealed seven bacterial isolates belonging to the genus of Panotea. These isolates were then tested with P. ananatis-specific primers PANA_1080 61F and PANA_1080 1009R (Asselin et al. 2016) and gyrB (Kini et al. 2021). Of the seven, only one (24-TX-33) produced positive amplification and was confirmed as P. ananatis through sequencing. Sequence analysis of 16S rRNA (GenBank: PZ8384), PANA_1080 (PZ295573), and gyrB grouped isolate 24-TX-33 with various P. ananatis. To fulfill Koch’s postulates, two rice cultivars, CLL11 and CLL16, were inoculated with P. ananatis isolate (24-TX-33). Top leaves of 15-day-old seedlings were scissor-clip inoculated with bacterial suspensions (~108 CFU/ml) of the isolate. Treatment with sterilized, deionized water served as the control. At 7 days post inoculation, symptoms similar to those observed under field conditions were observed in inoculated leaves. Bacteria were recovered from the artificially inoculated rice leaves and confirmed as P. ananatis based on morphology characteristics and PCR amplification using the P. ananatis specific primers PANA_1080 61F and PANA_1080 1009R. P. ananatis has previously been reported as rice pathogen in several rice-growing countries, including China (Yu et al. 2021), India (Reshma et al. 2022), and Thailand (Arayaskul et al. 2020). In the U. S., P. ananatis has been associated with bacterial leaf blight in field research plots in Arkansas (Luna et al. 2023) and Louisiana (Bruno et al. 2024). To our knowledge, this study represents the first report of bacterial leaf blight caused by P. ananatis in Texas and first documentation of this disease in commercial rice fields in the U.S. Continued monitoring of its occurrence and spread is crucial, as this emerging bacterial disease possesses a potential threat to US rice production.