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The Fusarium graminearum species complex (Fg complex) that consists of at least 11 phylogenetically distinct species contains important Fusarium head blight (FHB) pathogens of wheat and barley worldwide. We obtained members of the Fg complex by sampling from a 500-m2 experimental wheat field in Kumamoto Prefecture, Japan in two consecutive years and assessed them for species identity and trichothecene chemotype. Haplotype diversity was estimated by using 11 variable numbers of tandem repeat (VNTR) markers. In addition to these two samples (group 03W in 2003 and group 04W in 2004), pathogen populations from seed that was harvested in Fukuoka Prefecture and planted in the experimental field in 2002 (group 02WSC) and pathogen populations from seed that was harvested in Nagasaki Prefecture and planted in 2003 (group 03WSC) were analyzed for this study. Forty-six isolates were collected in each group. Most isolates from wheat heads were classified as F. asiaticum; only four isolates were classified as F. graminearum sensu stricto (s. str.). Out of a total of 183 Fg complex strains, 80 isolates (44%) were of the NIV type, while 103 isolates (56%), including all four F. graminearum s. str. isolates, were of the 3ADON type. No 15ADON type isolate was detected in this study. Trichothecene chemotype compositions of 03W and 04W were nearly identical. High gene diversity of F. asiaticum was observed in all groups. Based on the observed low level of fixation index (FST) and high level of effective number of migrants (Nm), distinctive population subdivision of F. asiaticum was not inferred among the four groups. These results suggest that FHB in the experimental wheat field in both 2003 and 2004 was caused by a genetically similar population, which prevails in Kumamoto, Fukuoka, and Nagasaki prefectures. [ABSTRACT FROM AUTHOR]

Fusarium fujikuroi which was originally studied in Japan is a pathogen of bakanae disease of rice. The disease was recorded in almost all countries where rice is grown commercially, including Malaysia and Indonesia. A total of 79 strains of F. fujikuroi were isolated from rice plants showing typical bakanae symptoms from major granary areas in Malaysia and Indonesia. They were identified using morphological characteristics for species delimitation. The objective of this study was to investigate genetic diversity of the F. fujikuroi strains by generating nitrate non- utilizing (nit) mutants, followed by phenotyping on diagnostic media, and pairing the mutants on minimal media (MM). About 96.2% of the strains were identified as heterokaryon self-compatible (HSC) based on their ability to form a stable heterokaryon while the remaining 3.8% of the strains were classified as heterokaryon self- incompatible (HSI) based on their inability to form a heterokaryon, even after repeated attempts. Those HSC strains that paired by producing robust growth were classified in the same vegetative compatibility group (VCG). The bakanae strains of F. fujikuroi were grouped into 26 VCGs; the largest group was VCG A01 which comprised of 23 strains. Out of 26 VCGs, 12 VCGs contained more than one strain member, and 14 VCGs were represented by a single strain and were not compatible with other strains. The ratio of VCGs to strains of F. fujikuroi in these samples was 0.29. The strains of F. fujikuroi that caused bakanae disease of rice in Malaysia and Indonesia are genetically diverse based on their multiple VCGs. [ABSTRACT FROM AUTHOR]