Molecular and Morphological Identification of Ustilaginoidea Virens, the Causal Agent of Rice False Smut in Sri Lanka

Abstract

Seed-borne fungal pathogens significantly impact on both the quality and quantity of rice production of rice. Among these, Ustilaginoidea virens, the causal agent of rice false smut, directly impacts grain yield and quality by partially or completely replacing kernels with spore masses. Historically considered a minor issue, false smut has recently emerged as a major rice disease of concern. Accurate identification andconfirmation of U. virens are thus critical for developing effective disease management strategies. In this study, rice panicles with characteristic false smut symptoms were collected from the wet zone of Sri Lanka. The associated fungal pathogen was isolated on potato sucrose agar (PSA) and designated as isolateWC2.04. Colony and micro-morphological features of the isolate obtained were documented, followed by DNA extraction, Polymerase chain reaction and bidirectional Sanger sequencing of the internal transcribed spacer (ITS) region. Sequence data were analyzed using the Basic Local Alignment Search Tool (BLAST) against the NCBI database, and phylogenetic analyses were performed. The results confirmed the identity of WC2.04 as U. virens. This study presents the first molecular confirmation of the occurrence of U. virens in Sri Lanka, highlighting the importance of integrating morphological and molecular approaches for the accurate identification of rice seed-borne fungi. Accurate identification is crucial for developing and implementing effective disease management strategies to mitigate the impact of rice false smut in the region.