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 four consecutive years from 2019 to 2022. The pathogens were confirmed using morphological characteristics, DNA sequences, and phylogenetic analysis of two genes, namely, elongation translation 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. The phylogenetic analysis 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%). The phylogenetic analysis also showed that 28 representative strains were attributed to five species. Finally, four Fusarium spp., namely, 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.