Fusarium species associated with Bakanae Disease of Rice in Bangladesh

Bakanae disease has become a serious threat for sustainable rice production in Asian countries including Bangladesh. Fusarium species are important seedborne pathogens that cause bakanae disease of rice. Typical bakanae symptomatic samples were collected through a series of sampling conducted in several districts of Bangladesh for 4 consecutive years from 2019 – 2022. The pathogens were confirmed using morphological characteristics, DNA sequences, and phylogenetic analyses of two genes, namely, translation elongation factor 1-alpha (TEF1-α), and RNA polymerase subunit II (RPB2). A total of 121 Fusarium isolates were recovered from diseased rice samples at different geographical locations. From the phylogenetics analyses of TEF1-α and RPB2 gene sequences coupled with morphological characterization revealed that the collected isolates belonged to five species viz. F. fujikuroi (75.2% isolation frequency), F. incarnatum (17.35%), F. commune (4.95%), F. verticillioides (1.65%), and F. proliferatum (0.82%). Phylogenetic analysis also showed that 28 representative strains were attributed to five species. Finally, four Fusarium spp. F. fujikuroi, F. commune, F. verticillioides and F. proliferatum were found to be pathogenic under virulence assays of the isolates. The pathogenicity test results demonstrated that F. fujikuroi caused typical symptoms of bakanae, leaf elongation and chlorosis, whereas F. proliferatum and F. verticillioides only caused stunting of seedlings and F. commune caused wilt and root rot. F. incarnatum was found to be associated with bakanae disease of rice, however their pathogenicity could not be established. This study provides insight into the diversity and pathogenicity of Fusarium populations associated with bakanae disease in Bangladesh, which will help in formulating effective strategies and policies for better control of the bakanae disease.