Characterisation of Pantoea ananatis isolated from mutant rice lines and its pathogenicity on the commercial rice variety MR220-CL2 in Peninsular Malaysia

Bacterial leaf blight (BLB), traditionally caused by Xanthomonas oryzae pv. oryzae, is a major constraint in rice production. Recently, Pantoea ananatis has emerged as a BLB-associated pathogen, but its impact on rice production in Malaysia is unclear. This study isolated seven yellow-pigmented bacteria from symptomatic mutant rice leaves in Kelantan and Terengganu. Morphological characterisation and molecular identification using infB-based PCR and sequencing verified all isolates as Pantoea ananatis. Phylogenetic analysis clustered the isolates with reference P. ananatis strains, with bootstrap analysis based on 1000 replicates showing high node support (91%–100%), clearly separating them from other Pantoea species. Pathogenicity tests on MR220-CL2 produced typical BLB symptoms with high disease severity, demonstrating that P. ananatis can infect both mutant and conventional rice lines, posing a potential threat to rice cultivation in Malaysia. This study provides current evidence of P. ananatis causing BLB in mutant rice lines developed by the Malaysian Nuclear Agency through mutation breeding. By confirming the pathogen's identity and pathogenicity, the findings enhance national disease surveillance efforts, support ongoing rice improvement programmes and provide essential baseline data to guide future work in resistance breeding, disease management and diagnostic development.

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