Submitted to: Popular Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2004
Publication Date: 12/4/2004
Citation: Martinelli, J.A., Bocchese, C.A., Xie, W., O Donnell, K., Kistler, H.C. 2004. Soybean Pod Blight and Root Rot Caused by Lineages of the Fusarium graminearum and the Production of Mycotoxins. Fitopatologia Brasileira. 29:492-498. Interpretive Summary: The primary objectives of this study were to determine: 1) what species induce root rot and pod blight of soybean in South Brazil, using DNA sequence data, 2) whether the isolates from soybean are able to induce the disease symptoms in greenhouse pathogenicity experiments, and 3) what toxins are produced by the pathogenic isolates. Genetic analysis of DNA sequence data from the translation elongation factor gene demonstrated that three species within the Fusarium graminearum species complex are responsible for soybean root rot and pod blight in Brazil. Results of the pathogenicity experiment demonstrated that isolates of all three species are capable of inducing disease symptoms on soybean and the disease called Fusarium head blight on wheat. All of the Brazilian isolates produced the toxin nivalenol except for one strain that produced deoxynivalenol. Strains of two of the species produced a novel toxin, 3-acetylnivalenol. These results should benefit soybean farmers and producers by alerting them to the potential for soybean root rot and pod blight in fields known to be heavily infested with Fusarium head blight pathogens.
Technical Abstract: Surveys of soybean (Glycine max) seed grown in South Brazil revealed infection with Fusarium graminearum. To determine if members of this complex were pathogenic to soybean, six strains derived from soybean were added to soil at a rate of 1,000 macraoconidia/ml or individual pods were inoculate with 10,000 macroconidia/ml. Seedlings grown in infested soil developed small necrotic lesions in the crown and upper roots. Pods inoculated with conidia developed large (>1 cm), dark brown, necrotic lesions. Younger pods inoculated with the fungus blighted and dropped from the plant. Strains of the F. graminearum complex recovered from lesions on the crown, roots and pods of soybean plants were identified as lineage 1, 2 or 8 by obtaining the DNA sequence from the EF1-alpha gene and comparing it to strains of the known lineage. Two strains of F. graminearum lineage 7 from the U.S. caused similar symptoms of the disease on soybean. Mycotoxin tests on soybean and wheat (Triticum aestivum) indicate that most Brazilian strains produce nivalenol as the major trichothecene mycotoxin rather than deoxynivalenol. In addition, strains from lineaages 2 and 8 produce the novel trichothecene, 3-acetylnivalenol.