Characterizing the Seedborne Nature of Pantoea ananatis in Rice: Pathogenicity and Evidence of Vertical Transmission.

Abstract

Pantoea ananatis is an emerging bacterial pathogen in rice with increasing reports across global rice-growing regions. While previous studies have suggested its presence in the seed, direct evidence for seed-to-plant transmission in rice remains limited. In this study, we characterized P. ananatis isolates recovered from naturally contaminated rice seeds and evaluated their potential for vertical transmission through two successive plant generations. Nine isolates from three rice varieties were assessed for their impact on germination, seedling health, and symptom development. Disease progression was tracked across generations, and host genotype effects were also explored. Isolates from the highly susceptible variety JiBoYa exhibited elevated virulence in rice, suggesting genotype-dependent pathogenicity. Disease onset in second-generation plants occurred approximately 30 days earlier than in the first, accompanied by significantly increased disease severity and compromised seed production. These results provide compelling evidence that P. ananatis can be vertically transmitted in rice and may accumulate across generations, leading to enhanced virulence expression. We propose further molecular and epidemiological investigations to elucidate the mechanisms underlying seedborne persistence, virulence diversity, and the broader implications for pathogen management.