Annual Progress Report on Malting Barley Research March, 2002

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EPIDEMIOLOGY AND CONTROL OF BARLEY LEAF DISEASES CAUSED BY
FUNGAL PATHOGENS
M. R. Johnston
Department of Plant Sciences and Plant Pathology
Montana State University
Bozeman, MT 59717
OBJECTIVES
Continue to develop a catalog of mapped stripe rust resistance loci with special emphasis
on temperature sensitive and growth stage dependant disease resistant reactions in order
to implement a rational and durable stripe rust management strategy for the western U.S.
In connection with objective we will also investigate resistance to several other fungal
leaf diseases in segregating populations. The final goal would be the release of barley
cultivars with multiple resistances.
The popular demand for pesticide free food will make chemical control of diseases more
undesirable in future. Environmental aspects are expected to further restrict the
application of chemicals in agriculture. The use of resistant cultivars as opposed to
susceptible ones will give barley growers more competitive in such a marketplace.
Moreover resistant cultivars are considered an economical means of disease control. In
the past single genes for disease resistance have been rendered ineffective by the everchanging
pathogens. Strategies such as the employment of numerous genes in one
cultivar or the use of nontraditional resistance genes (temperature sensitive genes, adult
plant resistance) are advisable.
METHODS
Selected lines from the Oregon State breeding program (as well as other interested
programs) will be inoculated with pure cultures of barley stripe rust and subjected to
different temperature profiles. The normal evaluation environment will be 65°/70°F
(dark/light). 54°/60°F (dark light) will represent the cool environment. Plants are grown
under these conditions prior to inoculation. A measured amount of urediniospores will be
shot up into a settling tower with a CO2 gun and allowed to settle for 4 min. Resulting in
an even distribution of inoculum. Inoculated plants are then placed in a dew chamber at
10°C for a minimum of 24 hrs. and subsequently returned to their respective
environments. Disease reactions will be evaluated 10 or 18 days after inoculation
depending on the temperature regime used. The reaction type will be determined on the
first and second leaves.
We will also subject the materials to the disease at different developmental stages. Adult
plant resistance in wheat to stripe rust is well documented. Plants with already
determined seedling reaction will be grown to maturity under evaluation environment
which resembles natural conditions during the summer months (15°/24°C). Plants will be
inoculated when the stems elongate and a second time when the flag leaf is fully
developed. Plants will be dusted with a mixture of talcum and urediniospores since the