First Report of Pantoea ananatis Causing Bacterial Leaf Blight of Rice in Northeast India

Abstract

Aims: This study aimed to document, isolate, and characterize the causal agent of an emerging bacterial leaf blight condition in rice (Oryza sativa L.) observed in Northeast India. Study Design: Field surveys were conducted across multiple farmers’ fields in the Lower, Upper, and Central Brahmaputra valley zones of Assam to assess disease incidence using a zig-zag sampling pattern. Place and Duration of Study: Surveys revealed an unfamiliar leaf blight characterized by water-soaked lesions and glume discolouration, with disease incidence ranging from 18% to 42% across the surveyed districts of Assam (2024-2026). The causal bacterium was isolated on nutrient agar and subjected to comprehensive morphological, biochemical, and pathogenicity testing, followed by molecular identification via 16S rRNA gene sequencing. Results: The pathogen was identified as Pantoea ananatis (~99.6% sequence identity). It was Gram-negative, motile, and produced bright yellow, convex colonies. Pathogenicity was confirmed by clip inoculation of rice seedlings (cv. Ranjit), which consistently reproduced identical symptoms, thereby fulfilling Koch’s postulates. Conclusion: This is the first confirmed report of P. ananatis causing bacterial leaf blight in rice from Assam, Northeast India, significantly expanding the known geographic distribution of this pathogen. Given the risk of seed-borne transmission, these findings underscore the urgent need to integrate molecular seed health testing and enhanced diagnostic surveillance into regional phytosanitary programs to effectively manage and control this emerging disease in rice agroecosystems