Annual Progress Report on Malting Barley Research March, 2007

CI9214, PI552963 (Heartland), and NDB112. All other resistance sources were
susceptible to at least one isolate collected in 2005.
What were the most significant accomplishments?
The most significant accomplishment in this work was the identification of which
resistant sources are overcome and which ones contain potentially durable net
blotch resistance that could be used in combating net blotch in this region as well as
the identification of virulence changes within the pathogen population from year to
year.
Objective:
Net blotch caused by the fungus Pyrenophora teres Drechs. f. teres Smedeg.
(anamorph: Drechslera teres) is one of the most economically important diseases in
barley growing regions of the United States and the world. This disease is a
perennial problem especially in cool, wet barley growing regions although it has
been seen in dry regions as well (Mathre 1982). The majority of barley cultivars
grown in the United States are moderately to highly susceptible to net blotch of
barley. Therefore, it is critical that we have an understanding of the pathogen
population to properly develop barley cultivars with durable resistance to net blotch.
The objective of this project was to evaluate the North Dakota field population at two
location with two significantly different environments. This study focused on the
level of variability present in the P. teres population as it relates to identified host
resistance in a differential barley set.
Methodologies:
Host differential set
A host differential set of 20 barley lines (Table 1) was chosen based on
published differential reaction of these lines. (Jalli 2004, Wu et al. 2003, Cromey
and Parks 2003, Gupta and Loughman 2001, Jonsson et al. 1997, Steffenson and
Webster 1992, Tekauz 1990, Kahn 1982, Kahn and Boyd 1969). This was done by
evaluating the most thorough publications on differential sets. All lines used in this
differential set have been shown to have different resistance patterns when
inoculated with isolates from around the world indicating that each line harbors at
least one different resistance gene. NDB112 and Heartland (Table 1) have also
been added to this set based on their use as resistance sources in the North Dakota
and Minnesota barley breeding program, respectively.
Field collection and pathotype analysis on the barley differential set
Field plots of the near universal susceptible cultivar Hector were planted on
barley stubble to ensure the best disease possible. Hector plots were established
at Fargo and Langdon, ND in both 2004 and 2005. Diseased leaves were collected
throughout the growing season. Leaves were plated on sterile water agar and
single spore isolates were picked from net blotch lesions. Isolates were grown and
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