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Title: Species composition, toxigenic potential and pathogenicity of Fusarium graminearum species complex isolates from southern Brazilian rice

item GOMES, L - Federal University Of Rio Grande Do Sul
item Ward, Todd
item BADIALE-FURLONG, E - Federal University Of Rio Grande Do Sul
item DEL PONTE, E - Federal University Of Rio Grande Do Sul

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2014
Publication Date: 2/19/2015
Publication URL:
Citation: Gomes, L.B., Ward, T.J., Badiale-Furlong, E., Del Ponte, E.M. 2015. Species composition, toxigenic potential and pathogenicity of Fusarium graminearum species complex isolates from southern Brazilian rice. Plant Pathology. 64(4):980-987.

Interpretive Summary: Fungi within the Fusarium graminearum species complex (FGSC) are responsible for Fusarium head blight (FHB), or scab, of rice and other cereals world-wide. FHB can significantly reduce crop yield and quality. In addition, the fungi that cause FHB can also contaminate cereal crops with trichothecene mycotoxins, such as deoxynivalenol (DON) and nivalenol (NIV), which pose a significant threat to food safety and animal health. As part of a project to establish a global picture of FHB pathogen diversity, we determined the prevalence of FGSC species and toxins associated with FHB infected rice in Brazil, and also characterized the potential for rice to serve as a reservoir for FHB pathogens that could cause epidemics on other crops, such as wheat. In contrast to our previous analyses of FHB pathogens from wheat growing regions in Brazil, Fusarium asiaticum with the NIV toxin type predominated (69%) among isolates from rice. We demonstrated that the FHB pathogens from rice were capable of causing FHB infections on wheat, indicating that rice could be a reservoir for F. asiaticum infections and subsequent NIV contamination of wheat grown in rice production areas. This is the first significant survey of FHB pathogen and toxin diversity in rice outside of Asia. As such, the results reported here are critical to promoting food safety and production through improved understanding of regional and host-specific factors that shape FHB pathogen diversity and toxin exposure potential.

Technical Abstract: This study aimed to assess the extent and distribution of Fusarium graminearum species complex (FGSC) diversity in Brazilian rice. Four species and two trichothecene genotypes were found among 89 FGSC isolates obtained from infected seeds: F. asiaticum with the nivalenol (NIV) genotype (69%), F. graminearum (14.6%) with the 15-acetyl(A)deoxynivalenol(DON) genotype, and F. cortaderiae (14.6%), and F. meridionale (0,01%), both with the NIV genotype. Seven selected F. asiaticum isolates produced only NIV in vitro using a rice-based substrate and at levels ranging from 4.7 to 84.1 µg/g. Similarly, two F. graminearum produced mainly 15-ADON (˜15 to 40 µg/g) and a smaller amount of 3-ADON (˜5 to 50 µg/g). Two F. cortaderiae and one F. meridionale isolates did not produce detectable levels of trichothecenes. A sample of four F. asiaticum isolates, being two originated from rice from this study, and three from wheat (two NIV F. asiaticum and one 15-ADON F. graminearum) were pathogenic to both crops at various levels of aggressiveness based on measures of disease severity in wheat and rice kernel infection in a greenhouse assay. F. asiaticum and the reference F. graminearum isolate from wheat were able to produce NIV and DON acetylates, respectively, in wheat kernels. No trichothecene was produced in rice kernels by any of the isolates. These findings constitute the first report of FGSC composition in rice outside Asia, and confirm the dominance of F. asiaticum in rice agroecosystems.