<i>Fusarium</i> 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. <i>Fusarium</i> 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 (<i>TEF1-α</i>) and RNA polymerase subunit II (<i>RPB2</i>). A total of 121 <i>Fusarium</i> isolates were recovered from diseased rice samples at different geographical locations. The phylogenetic analysis of <i>TEF1-α</i> and <i>RPB2</i> gene sequences coupled with morphological characterization revealed that the collected isolates belonged to five species, viz., <i>F. fujikuroi</i> (75.2% isolation frequency), <i>F. incarnatum</i> (17.35%), <i>F. commune</i> (4.95%), <i>F. verticillioides</i> (1.65%), and <i>F. proliferatum</i> (0.82%). The phylogenetic analysis also showed that 28 representative strains were attributed to five species. Finally, four <i>Fusarium</i> spp., namely, <i>F. fujikuroi</i>, <i>F. commune</i>, <i>F. verticillioides</i>, and <i>F. proliferatum</i>, were found to be pathogenic under virulence assays of the isolates. The pathogenicity test results demonstrated that <i>F. fujikuroi</i> caused typical symptoms of bakanae, leaf elongation, and chlorosis, whereas <i>F. proliferatum</i> and <i>F. verticillioides</i> only caused stunting of seedlings and <i>F. commune</i> caused wilt and root rot. <i>F. incarnatum</i> 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 <i>Fusarium</i> populations associated with bakanae disease in Bangladesh, which will help in formulating effective strategies and policies for better control of the bakanae disease.