Annual Progress Report on Malting Barley Research March, 2002

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In 2001 winter/spring, over 300 liters of macroconidial inoculum (800,000 macroconidia
ml -1 ) were produced in our lab for use by the barley and wheat improvement programs.
This is enough inoculum to inoculate about 60 miles of row… and we used it all! Much
of the material that was screened at St. Paul was also included in the Morris and
Crookston nurseries where either macroconidial- or colonized-corn-seed-inoculum was
used.
Greenhouse Screening Program: During the fall, winter, and spring seasons greenhouse
tests for resistance to Fusarium head blight are conducted in the greenhouse. Testing of
200 barley lines was completed in 2001. The inoculation of barley plants in the
greenhouse is conducted using an airbrush sprayer to deliver macroconidial inoculum to
one face of the barley spike. Point inoculations have not differentiated between the
currently available sources of resistance and susceptible varieties.
Effect of burning wheat and barley residues on the survival of Fusarium
graminearum and Cochliobolus sativus: The amount of cereal residues left in fields
after harvest has increased in recent years largely because of the widespread adoption of
minimum tillage practices. Since residues decompose slowly in the Upper Midwest crop
residues are suspected to be the principal reservoir of the primary inoculum of F.
graminearum in the recent severe epidemics of Fusarium head blight. Fungi such as F.
graminearum, are able to survive in wheat residues for at least two years therefore, any
practice that enhances residue decomposition or eliminates these residues may aid in the
management of this destructive disease. This study examined the effect of residue
burning on the survival of F. graminearum and C. sativus the causal agents of two
important diseases of barley (Fusarium head blight and spot blotch) in the Midwest cereal
producing areas.
The field study was established at the University of Minnesota’s Research and Outreach
Center, Crookston, MN. On September 15-16, 2000, two quadrats (0.91 m 2 ) were burned
in a field of barley residue using a flame thrower. Two additional non-burned quadrats
were used as controls. Residues left after burning, and all residues in control plots were
collected and stored at -10°C until isolations were made. To quantify the effect burning
on the amount of residue, the total number of nodes recovered was determined for each
experimental plot. To examine the mycoflora present in node tissues, nodes were excised
from the straw, and split in two, surface sterilized and each half node was plated
separately on one of two media. A total of 48 node-segments from each control quadrat,
and all available node segments from burned-quadrats were plated. Node segments were
plated (eight/petri dish) on petri plates containing acidified half strength PDA or a
Fusaria selective medium (Komada). Culture plates were incubated with 12 hr
photoperiod using a combination (3:1) of cool white and UVA light. Fusarium
graminearum was identified based on perithecia formed on Carnation Leaf Agar.
Cochliobolus sativus and other fungi were identified based on morphological
characteristics. Data obtained in this study were analyzed by ANOVA (SAS, GLM
Procedure). When needed, as appropriate, treatment means were separated using Fisher’s
protected least significant differences (P = 0.05).
There was a significant reduction in the number of nodes recovered from burned
treatments (339 nodes) as compared to the unburned controls (515 nodes). Isolations