2010 University of Minnesota - Special Report

Foliar Disease Screening

Ruth Dill-Macky, U of M Plant Pathologist

Wheat and barley are important commodities in Minnesota’s agricultural economy and diseases cause significant reductions in both the yield and quality of these crops each year. As we know, Fusarium Head Blight (FHB or scab) epidemics have had a devastating impact on Minnesota’s wheat and barley crops. In addition to FHB, several other foliar diseases of wheat and barley have also severely reduced yields, although their impact has been dwarfed by FHB.

The use of resistance in the host plant is the most economic and environmentally friendly method for controlling most plant diseases. University of Minnesota plant pathologist Ruth Dill-Macky, has been working to assist the plant breeding programs, led by Jim Anderson (wheat) and Kevin Smith (barley), to improve the resistance of wheat and barley to multiple diseases of importance in Minnesota. Annual screening nurseries in St. Paul, and at other locations in Minnesota including Morris, Crookston and Stephen, assess breeding lines for their response to the foliar diseases of wheat and barley including FHB, tan spot and net blotch.

While the breeding effort is largely focused on improving FHB resistance, it is essential that cultivars susceptible to other diseases are not inadvertently released. Thus all advanced breeding lines are rigorously screened for resistance to the major diseases that occur in the region. For this reason, field and greenhouse evaluation of advanced breeding lines from the wheat and barley improvement programs for resistance to the major foliar diseases is an ongoing activity for plant pathologists such as Ruth Dill-Macky.

In 2009, screening of wheat and barley lines for their reaction to FHB was conducted at three Minnesota locations (St. Paul, Morris and Crookston). Each year as much as 400 liters of Fusarium inoculum is produced for use in the inoculated and irrigated nurseries at St. Paul and Morris. The inoculum consists of the spores of the fungal pathogen grown in bulk in the St. Paul small grains pathology lab. The inoculum is then applied to the plants in the field so as to challenge the plant with the disease. Mist-irrigation systems then provide the environmental conditions conducive for disease development. Following a period of time, allowing for disease development and symptom expression, the reaction of the plants is scored. Those with the best resistance are kept, thus becoming the parental material for the next generation of wheat and barley. The pathology team also assists in greenhouse evaluations, although recently fewer lines are being screened as the breeding programs have shifted their emphasis in screening for FHB to field nurseries. Identification of resistant material in this manner enables the breeding programs to continue making progress in developing lines with improved resistance to FHB.

Approximately 1,000 barley entries are also tested annually as seedlings for their reaction to the net blotch pathogen in the greenhouses on the St. Paul campus. Approximately 40% of the lines tested exhibited resistance and were advanced in the breeding program.

The evaluation of wheat and barley breeding lines for multiple disease resistance is a collaborative effort between all the small grain pathologists at the University of Minnesota. This valuable work facilitates the development of wheat and barley cultivars with multiple disease resistance and will ultimately increase the sustainability of the production of small grains in Minnesota