Screening for FHB Resistance

The Small Grains Pathology project continues to work in conjunction with the wheat and barley breeding programs to screen germplasm for reaction to FHB.  To contribute to the screening effort, our project produces inoculum consisting of isolates of Fusarium graminearum that are grown in the laboratory each spring to produce the spores, called macroconidia that serve as inoculum in greenhouse studies and in field screening nurseries each growing season. 

Our effort results in the production of approximately 300 liters of concentrated inoculum, which is stored frozen for later dilution and spray-application in field screening nurseries. This inoculum serves the needs of several Minnesota and Federal research programs and represents a substantial contribution to the FHB research efforts at the U of M. 

One focus of the research effort of this project is aimed at improving FHB screening techniques in the greenhouse plantings.  Greenhouse inoculations involve spray inoculations of barley and point-inoculation of both wheat and barley. These techniques are used to assess FHB disease severity and thus eliminate susceptible lines from the breeding program. Approximately 2,100 pots of wheat and 950 pots of barley were screened in the most recent fall and winter greenhouse tests, respectively.

Screening data are also used in genetic studies of each of the breeding programs to identify resistance genes and conduct molecular mapping studies. In a collaborative effort with the barley breeding program, we have helped to identify high toxin accumulation inherited from a two-row barley parent, how this occurs and how to prevent the pathogen from producing toxin during the early events of infection. 

We continually investigate other techniques that we hope will provide additional capabilities to the FHB screening effort. We have recently developed a wheat seedling infection technique to study early infection events and possibly utilize in epidemiological studies. Whereas many projects only evaluate deoxynivalenol (DON or vomitoxin) accumulation in grain at harvest, our project conducts research on the accumulation of DON in wheat and barley during early events of pathogen infection, as well as grain at harvest and in other host plant tissues.

Field plot inoculations are a collaborative effort of the breeding and pathology programs, which includes researchers at St.Paul, Morris and Crookston. Approximately 1,600 rows of wheat were screened at Crookston and about 2,400 rows of wheat were screened at the St. Paul stations in the summer of 2003. Approximately 5,300 rows of barley were spray-inoculated at St. Paul and only 400 rows were spray-inoculated at Crookston. However, 770 rows of barley and about 1,000 rows of wheat were inoculated with corn-seed inoculum at Morris. Corn-seed colonized with F. graminearum provided inoculum for about 5,900 rows of barley and about 1,600 rows of wheat at Crookston.

Over the past few years, we have developed a dryland FHB screening technique that was utilized in screening two locations of the Uniform Regional Scab Nursery (URSN) in Minnesota during the 2003 field season.  This technique for establishing a FHB screening nursery does not require the setup of a mist-irrigation system to promote disease development, and therefore does not limit screening nurseries to locations with a source of irrigation.  Mean FHB severities and DON in the inoculated plots was sufficient to differentiate among resistant and susceptible check cultivars. We believe dryland FHB screening in Minnesota facilitates the evaluation of promising germplasm with disease levels that are lower, and provides finer differentiation among superior agronomic wheat genotypes.  We intend to demonstrate the use of this dryland technique to screen the URSN in one final field season in 2004.

– Drs C. Kent Evans and R. Dill-Macky, U of M small grains pathologists