Stem Smut (Ustilago hypodytes) on Intermediate Wheatgrass in Canada

Area of Science:

• Plant Pathology
• Agronomy
• Forage Crop Science

Background:

• Intermediate wheatgrass (Thinopyrum intermedium) is a key forage grass in Alberta, Canada.
• Stem smut (Ustilago hypodytes) poses a threat to seed yield in forage grasses.
• Previous reports indicate stem smut on wheatgrass species in Canada and the US.

Purpose of the Study:

• To report the first occurrence of stem smut on commercial intermediate wheatgrass seed production in Alberta, Canada.
• To document the incidence and impact of stem smut on intermediate wheatgrass seed yield.

Main Methods:

• Field observations of stem smut symptoms and incidence in a 70-acre intermediate wheatgrass field near Warner, Alberta.
• Disease incidence was determined by counting symptomatic stems annually from 1997 to 1999.
• Morphological characteristics of teliospores were examined and compared to established descriptions of Ustilago hypodytes.

Main Results:

• Stem smut incidence increased from 5% in 1997 to 50% in 1999.
• Infected stems showed characteristic brown to black sori, stunted growth, and reduced seed set, leading to proportional yield losses.
• Teliospore morphology aligned with Ustilago hypodytes descriptions.

Conclusions:

• Stem smut caused severe seed yield losses in intermediate wheatgrass in Alberta, Canada.
• This disease represents a significant threat to commercial intermediate wheatgrass seed production in the region.
• The findings highlight the potential economic impact of stem smut on this important forage crop.