Pathogenic Population of Rice Bakanae Disease in Heilongjiang Province

The objective of this study is to investigate pathogen species and dominant pathogenic fungi of rice bakanae disease in Heilongjiang Province, and to provide a basis for precise prevention and control of rice bakanae disease.

In 2023, rice bakanae disease samples were collected from 8 cities and 15 counties (districts) in Heilongjiang Province. A total of 172 single-spore strains were isolated and purified from the samples using tissue separation method and dilution plating method. Morphological identification, combined with multilocus phylogenetic analysis using ITS, RPB2, TEF1-α, LSU, and TUB2, and validation via Koch’s postulates, was used to complete the identification of the pathogen causing rice bakanae disease.

172 strains of the pathogenic fungi causing rice bakanae disease were classified into 31 morphotypes based on their morphological characteristics. Multilocus phylogenetic analysis identified 15 genotypes, and the isolated pathogenic fungi included four species complexes: FFSC, FNSC, FOSC, and FIESC. Among them, the dominant pathogenic fungus was Fusarium fujikuroi in the FFSC. A total of 148 strains were obtained, accounting for 86.05% of the total number of isolated strains, and comprising 4 genotypes and 18 morphotypes. Nine strains of Fusarium madaense were also obtained from this species complex, accounting for 5.23% of the total strains, with 1 genotype and 3 morphotypes. In addition, 1 strain of Fusarium subglutinans was identified, representing 0.58% of the total, with 1 genotype and 1 morphotype. In the FIESC, 2 strains of Fusarium wereldwijsianum were obtained, accounting for 1.16% of the total strains, with 2 genotypes and 2 morphotypes; 7 strains of Fusarium ipomoeae were also identified, representing 4.07% of the total, with 5 genotypes and 5 morphotypes. From each of the FNSC and FOSC, 4 strains of Fusarium arbusti and 1 strain of Fusarium cugenangense were obtained, accounting for 2.33% and 0.58% of the total strains, respectively, with 1 genotype and 1 morphotype for each species. All 7 Fusarium species were pathogenic, but with varying degrees of pathogenicity. The dominant pathogenic fungus, F. fujikuroi, caused rice bud rot and etiolation; F. arbusti induced only rice bud rot; F. ipomoeae, F. subglutinans and F. wereldwijsianum inhibited rice growth; F. madaense and F. cugenangense resulted in rice etiolation.

The pathogens causing rice bakanae disease in Heilongjiang Province include 7 species: F. fujikuroi, F. madaense, F. ipomoeae, F. arbusti, F. wereldwijsianum, F. subglutinans, and F. cugenangense. Obvious differences exist in pathogenic types and geographical distribution depending on the pathogen species. Of these, F. fujikuroi and F. arbusti exhibited the strongest pathogenicity; F. fujikuroi was detected in all regions of Heilongjiang Province and served as the dominant pathogenic fungus.