Wheat pathologists look at head scab

COLUMBUS – The widespread occurrence of Fusarium head scab in Ohio and the Midwest has prompted many wheat pathologists and wheat breeders to increase their efforts in developing varieties with usable levels of resistance.

Generally, few varieties have been available with reasonable levels of resistance to scab.

Due to the incomplete nature of the resistance, these more resistant varieties have been classified as having only moderate levels of partial resistance, said an Ohio State plant pathologist.

This means that none of the varieties are immune to scab, but under moderate disease pressure these varieties have fewer heads affected and fewer spikelets on the head killed by the fungus, Pat Lipps said.

Thus, the moderately resistant varieties had overall less disease symptoms and less yield loss.

However, under very high disease pressure due to the presence of a lot of fungal spores in the field (from surface corn residue) or long durations of wet weather that favor infection of the wheat heads during flowering, even varieties with higher levels of partial resistance would have significant disease and yield loss, Lipps said.

Opportunity. The moderate levels of head scab Ohio wheat field experienced this season has given researchers an opportunity to evaluate the reaction of the varieties planted in the Ohio Wheat Performance Test at three locations.

These locations are in Pickaway, Crawford and Wayne counties.

Data from these locations were combined to determine the varieties that had the least amount of head scab across locations, Lipps said.

Varieties. Using the Public Certified variety “Freedom” as the moderately resistant check for comparison, the following varieties could be classified as having moderate levels of resistance to head scab: Rupp “RS 947,” Gries Seeds “Brazen,” Thompson Seeds “TS3060,” AGI “538,” Wellman Seeds “W150,” Hylamp “Wonder,” Pioneer Brand “25R35,” NK “Coker 9474,” Steyer Seeds “Hartman,” and the Public Certified “Cecil.”

Of the 70 or more varieties planted in these tests at the three locations, these varieties had the lowest levels of head scab.

More tests. “We have learned from experience that an accurate evaluation of scab resistance for any variety cannot be obtained in one year even from tests conducted at multiple locations,” Lipps said.

Regardless, these are some varieties to watch over the next few years, Lipps said.

Test answers. Look for their yield performance and other important characteristics (test weight, lodging potential, resistance to other diseases) after harvest when the Ohio Wheat Performance Test is published, the pathologist said.