Incidence, Molecular Characteristics and Pathogenicity of Gibberella fujikuroi Species Complex Associated with Rice Seeds from Asian Countries

Gibberella fujikuroi species complex (GFSC) was isolated from rice (Oryza sativa L.) seed samples from ten Asian countries and investigated for incidence of GFSC, molecular characteristics, and pathogenicity. Regardless of geographic origin, GFSC was detected with incidences ranging from 3% to 80%. Four species, Fusarium fujikuroi, F. concentricum, F. proliferatum, and F. verticillioides, were found to show an association with rice seeds, with F. fujikuroi being the predominant species. In phylogenetic analyses of DNA sequences, no relationship was found between species, isolates, and geographic sources of samples. Unidentified fragments of the β-tubulin gene were observed in ten isolates of F. fujikuroi and F. verticillioides. With the exception of three isolates of F. fujikuroi, F. fujikuroi, F. proliferatum, and F. verticillioides were found to have FUM1 (the fumonisin biosynthetic gene); however, FUM1 was not found in isolates of F. concentricum. Results of pathogenicity testing showed that all isolates caused reduced germination of rice seed. In addition, F. fujikuroi and F. concentricum caused typical symptoms of bakanae, leaf elongation and chlorosis, whereas F. proliferatum and F. verticillioides only caused stunting of seedlings. These findings provide insight into the characteristics of GFSC associated with rice seeds and might be helpful in development of strategies for management of bakanae.