Epidemiology of Pyrenophora teres and its effect on grain yield of Hordeum vulgare
Date
1988-07
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Doctoral
Abstract
Recent surveys in Saskatchewan have shown that the
prevalence of Pyrenophora teres Drechs., the causal agent of
net blotch of barley (Hordeum vulgare L.), has increased.
Severe epidemics have been observed in several commercial
fields. The major objectives of this study were the
investigation of the epidemiology of net blotch and the
determination of the effect of net blotch on barley
production.
Conidium germination and time to infection were compared
for two spot-type isolates (P. teres f. maculata) and one
net-type isolate (P. teres f. teres) in a growth cabinet.
Spot-type isolates germinated sooner than the net-type
isolate between 10 and 20 °c. Time to infection was shorter
for the spot-type isolates than for the net-type isolate at
all temperatures.
The relationships among local weather conditions,
incidence of airborne conidia, barley development and
sporulation were investigated in field experiments with the
susceptible cultivar Elrose at Shellbrook, Saskatchewan in
1986 and 1987. Airborne conidia were observed daily
throughout the growing season. Their incidence showed a
diurnal pattern with a peak between 12:00 and 16:00 h. At
night, frequent dew formation favoured infection. Infection
of lower leaves was due to infection by primary inoculum
produced on crop debris. Infection of upper leaves was
due to primary inoculum and to secondary inoculum produced on
the lower leaves.
The effect of net blotch on barley production was
investigated in an experiment using Tilt (propiconazole) on
Elrose in 1985 and 1986 and on the moderately resistant
cultivar Argyle in 1986 at Saskatoon, Shellbrook and
Medstead, Saskatchewan. Repeated application of Tilt reduced
the rate of disease progress on Elrose, but not on Argyle,
where resistance reduced the rate of disease progress.
Resistance slowed disease progress more than repeated
application of Tilt. On Elrose, Tilt increased grain yield
and kernel weight, but had no effect on number of tillers and
number of kernels per spike. On Argyle, Tilt had no effect on
any trait.
The potential yield loss caused by net blotch was
estimated at 50%. Infection of net blotch lowered grain grade
through kernel discolouration and low test weight. Using the
components of variance and covariance, strong correlations
were obtained between treatment effects of grain yield and
disease severity. However, no satisfactory critical point
mode·l could be developed to predict percentage yield loss
from disease severity.
In Saskatchewan, infected crop debris is the most
important source of primary inoculum of P. teres. Under
favourable conditions with sufficient primary inoculum,
severe epidemics can be expected on susceptible cultivars.
Foliar fungicide application is not cost effective at
current grain prices, therefore extended rotations or the use
of resistant cultivars are the only practical means to
control net blotch in barley.
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Degree
Master of Agriculture (M.Agr.)
Department
Graduate Studies and Research
Program
Crop Science and Plant Ecology