Fungal populations on sunflower (Helianthus annuus) anthosphere and their relation to susceptibility or tolerance to Sclerotinia sclerotiorum attack

Colonization of the Residues of Diverse Plant Species by Gibberella zeae and Their Contribution to Fusarium Head Blight Inoculum

The presence of Fusarium spp. was examined in the residues of wheat, barley, corn, sunflower, pasture, and gramineous weed species common in wheat and barley cropping systems collected from no-tillage and reduced-tillage plots from February 2001 to March 2003 in Uruguay. Gibberella zeae was recovered from residues of wheat, barley, corn, sunflower, fescue, and the gramineous weeds Digitaria sanguinalis, Setaria spp., Lolium multiflorum, and Cynodon dactylon, except from birdsfoot trefoil or white clover. Of the Fusarium spp. obtained, G. zeae was the most frequently recovered from wheat and barley residues, while other species were more common in other crops. G. zeae declined over time in all residues examined. Wheat and barley residues produced more ascospores of G. zeae than corn or other gramineous residues. Sunflower residue did not support ascospore production, indicating that it probably did not contribute to primary inoculum. Wheat and barley residues supported G. zeae colonization longer in no-till than in reduced-tillage production systems and, thus, may represent major contributors to Fusarium head blight (FHB) inoculum in Uruguay. The presence of G. zeae in the gramineous components of pastures, weed species, and sunflower should be considered when implementing control strategies for FHB.