Comparative mycotoxin profiles of Gibberella zeae populations from barley, wheat, potatoes, and sugar beets

Abstract

Gibberella zeae is one of the most devastating pathogens of barley and wheat in the United States. The fungus also infects noncereal crops, such as potatoes and sugar beets, and the genetic relationships among barley, wheat, potato, and sugar beet isolates indicate high levels of similarity. However, little is known about the toxigenic potential of G. zeae isolates from potatoes and sugar beets. A total of 336 isolates of G. zeae from barley, wheat, potatoes, and sugar beets were collected and analyzed by TRI (trichothecene biosynthesis gene)-based PCR assays. To verify the TRI-based PCR detection of genetic markers by chemical analysis, 45 representative isolates were grown in rice cultures for 28 days and 15 trichothecenes and 2 zearalenone (ZEA) analogs were quantified using gas chromatography-mass spectrometry. TRI-based PCR assays revealed that all isolates had the deoxynivalenol (DON) marker. The frequencies of isolates with the 15-acetyl-deoxynivalenol (15-ADON) marker were higher than those of isolates with the 3-acetyl-deoxynivalenol (3-ADON) marker among isolates from all four crops. Fusarium head blight (FHB)-resistant wheat cultivars had little or no influence on the diversity of isolates associated with the 3-ADON and 15-ADON markers. However, the frequency of isolates with the 3-ADON marker among isolates from the Langdon, ND, sampling site was higher than those among isolates from the Carrington and Minot, ND, sites. In chemical analyses, DON, 3-ADON, 15-ADON, b-ZEA, and ZEA were detected. All isolates produced DON (1 to 782 microg/g) and ZEA (1 to 623 microg/g). These findings may be useful for monitoring mycotoxin contamination and for formulating FHB management strategies for these crops.

FIG. 1.

G. zeae isolates with trichothecene-specific markers analyzed by TRI-based PCR assays. The letters “b,” “w,” “p,” and “s” in the isolate designations mentioned below identify isolates collected from barley, wheat, potatoes, and sugar beets, respectively. (A) Analysis of representative isolates of G. zeae for the presence of a DON marker by a TRI13-based PCR assay. The PCR products were amplified with a TRI13-based PCR primer set. Lanes; 1, 1-kb DNA ladder, and 2 to 8, isolates (Fgw79, Fgw115, Fgb7, Fgp21, Fgp24, Fgs3, and Fgs4) with the DON marker. (B) Analysis of representative isolates of G. zeae for the presence of the 3-ADON and 15-ADON markers by a TRI3-based multiplex PCR assay. The PCR products were amplified with TRI3-based multiplex PCR primer sets. Lanes: 1, 50-bp DNA ladder; 2 to 4 and 6, isolates (Fgw79, Fgb7, Fgp21, and Fgs3) with the 15-ADON marker; and 5 and 7 to 9, isolates (Fgw62, Fgw115, Fgp24, and Fgs4) with the 3-ADON marker. (C) Analysis of representative isolates of G. zeae for the presence of the 3-ADON and 15-ADON markers by a TRI12-based multiplex PCR assay. The PCR products were amplified with TRI12-based multiplex PCR primer sets. Lanes: 1, 50-bp DNA ladder; 2, 3, 8, and 9, isolates (Fgw79, Fgb7, Fgp21, and Fgs3) with the 15-ADON marker; and 4 to 7, isolates (Fgw62, Fgw115, Fgp24, and Fgs4) with the 3-ADON marker.

FIG. 2.

Frequency distribution of genetic markers for 3-ADON and 15-ADON among isolates of G. zeae from four crops as determined by TRI-based PCR assays. The numbers of G. zeae isolates used in the study were as follows: 28 from barley, 243 from wheat, 38 from potatoes, and 27 from sugar beets. TRI3- and TRI12-based multiplex PCR assays were used to differentiate between G. zeae isolates associated with the 3-ADON marker and the 15-ADON marker. χ² analysis revealed a highly significant difference (χ² = 22.52; P < 0.0001) in the frequencies of genetic markers for 3-ADON and 15-ADON in G. zeae isolates from four crops.

FIG. 3.

Range in levels of mycotoxin production by 45 isolates of G. zeae grown in rice grain culture medium. (A) DON and ZEA production; (B) 3-ADON and 15-ADON production.