Factors Affecting Incidence of Sclerotinia Stem Rot of Rapeseed (Canola)
Date
1985-04
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Masters
Abstract
In a study of sclerotinia stem rot in commercial rapeseed
fields in East and West Central Saskatchewan in 1983 and 1984, several
factors relating to inoculum density were monitored when the crops
were in bloom. Carpogenically-germinated sclerotia were counted in I
II specific areas. The frequencies of Sclerotinia-infested live and dead
petals, leafaxils and leaf bases were determined by plating on potato
dextrose agar with added rose bengal and streptomycin. The final
percentage of diseased plants was determined shortly before the crops
were swathed. The results demonstrated a significant relationship
between petal infestation at early bloom and final disease.
Significant relationships between germinated sclerotia and disease
were obtained only with intensive sampling. Infested petals and
disease were regularly found when apothecia were absent, thereby
demonstrating the infective potential of extrinsically produced
ascospores. The possibility of using petal infestation to forecast
stem rot and improve the economics of chemical control is discussed;
however, several, refinements in the technique are required.
Laboratory studies demonstrated the potential for petals to be
colonized by. sclerotiorum before falling from the inflorescences
onto plant surfaces. Laboratory and field studies of the persistence
of water droplets in leaf axils, a major infection court of rapeseed,
demonstrated that water sometimes persisted for relatively long
periods even when ambient environmental conditions were generally
unfavorable for infection. In view of the moisture requirements for
infection, this may partially explain the occurrence of low to moderate
levels of disease in some rapeseed fields during relatively dry years.
Description
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Citation
Degree
Master of Science (M.Sc.)
Department
Biology
Program
Biology