Population Structure of Fusarium fujikuroi from California Rice and Water Grass

• Published in: Phytopathology 2008-09, Vol.98 (9), p.992-998
• Main Authors: Carter, L.L.A, Leslie, J.F, Webster, R.K
• Format: Article
• Language: English
• Subjects: Amplified Fragment Length Polymorphism Analysis; aquatic weeds; Biological and medical sciences; California; Crosses, Genetic; Echinochloa; Echinochloa crus-galli; Echinochloa oryzoides; Fundamental and applied biological sciences. Psychology; fungal diseases of plants; Fungal plant pathogens; Fusarium - genetics; Fusarium - isolation & purification; Fusarium - pathogenicity; Fusarium - physiology; Fusarium fujikuroi; genetic variation; Gibberella fujikuroi; grasses; introduced species; Nitrates - metabolism; Oryza - microbiology; Oryza sativa; pathogenicity; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - microbiology; plant pathogenic fungi; Plant Shoots - microbiology; Poaceae - microbiology; polymerase chain reaction; Population Density; population genetics; population structure; rice; Seedlings - microbiology; sequence analysis; Species Specificity; vegetative compatibility groups
• ISSN: 0031-949X; 1943-7684
• DOI: 10.1094/phyto-98-9-0992

The recent observance of Fusarium fujikuroi, the causal agent of Bakanae disease of rice, in California provides a unique opportunity to assess the population diversity of an introduced pathogen in a new environment. We collected 172 isolates of this pathogen between 2000 and 2003 from California rice and two from water grass (Echinochloa spp.). Pathogenicity of F. fujikuroi was demonstrated on early water grass (E. oryzoides) and barnyard grass (E. crus-galli) indicating that weed control should be part of Bakanae management programs. Both mating types and six unique amplified fragment length polymorphism haplotypes corresponding to six identified vegetative compatibility groups were detected. The two most frequently isolated haplotypes encompassed 94% of the collected isolates, suggesting that clonal reproduction dominates. Coefficients of similarity between the unique haplotypes ranged from 0.94 to 0.98, and indicate that there is very little genotypic variation in the F. fujikuroi population in California. The near fixation of the MAT-1 idiomorph (observed ratio 170 MAT-1:4 MAT-2), is consistent with a hypothesis of predominant or exclusive asexual reproduction. The low level of introduced genotypic diversity, in conjunction with the asexual reproductive strategy of this population will slow evolutionary processes, including adaptation to the California environment.