Poster Session: New and Emerging Diseases-Bacteria

392-P

Effect of Goss’s leaf blight severity on grain quality and on Clavibacter michiganensis subsp. nebraskensis seed infection.
A. E. Robertson (1), C. C. Block (2), C. R. Hurburgh (1), L. M. SHEPHERD (2)
(1) Iowa State University, Ames, IA, U.S.A.; (2) USDA-ARS, Ames, IA, U.S.A.

Goss’s wilt and leaf blight of corn, caused by Clavibacter michiganensis subsp. nebraskensis (Cmn), has reemerged as an economically important disease across much of the Midwestern U.S. The widespread incidence of Goss’s wilt has raised questions as to effects on grain quality and the role of seed infection in disease spread. In 2011, we selected nine fields with Goss’s leaf blight and created sampling plots in areas of low disease severity (0-5% leaf area affected) and high disease severity (>5% leaf area affected). Disease severity was estimated at the R5 growth stage and stalk rot ratings made at harvest. Harvested ears were shelled and grain quality characteristics assessed, including test weight, 1000-seed weight, moisture, protein, starch, and oil content. Seeds were individually assayed for Cmn seed infection, and samples planted for seed to seedling transmission studies. No differences in test weight or protein content were found in grain samples from the low disease plots compared to the high disease plots. Stalk rot increased significantly in the high disease plots, and there was a significant reduction in 1000-seed weight in the same plots. No Cmn infection was detected in seeds from the low disease plot samples (0-5% leaf area). In the more heavily infected field plots (over 5% leaf infection), only low amounts of seed infection (<1%) were noted. No seed transmission was detected in greenhouse growouts.