Strawbreaker foot-rot is a major limiting factor to cost efficient winter wheat
production in the Pacific Northwest. Development of resistant cultivars has been
hindered by the lack of adequate levels of genetic resistance and screening techniques
which can consistently detect desired genotypes.
Studies were conducted to determine if the reported strawbreaker foot-rot
resistance of the cultivar "Rendezvous" is effective on isolates of Pseudocercosporella
herpotrichoides found in the Pacific Northwest. Protected, naturally infected and
artificially inoculated treatments were employed to determine the level of resistance of
10 cultivars including Rendezvous. Different concentrations of inoculum and stages of
development were also used to determine if observations on leaf sheath penetration of
seedlings obtained in the greenhouse were related to disease severity index readings taken
in the field for selected cultivars. In addition, the nature of inheritance of strawbreaker
foot-rot was studied in two crosses involving Rendezvous.
Experiments were conducted at three locations and over two years at one location.
Despite cultivar x treatment interaction, consistent levels of infection were observed in
all experiments at each location. Significant differences were found for treatments and
cultivars for most attributes.
Yield losses, including the components of yield spikes per square meter, 1000
kernel weight, and kernel number per spike were proportional to the severity of the
disease. Losses were greater when lodging occurred, which was also associated with
disease severity. However, even in the absence of lodging losses were recorded in the
naturally and artificially inoculated plots. Traits measured involving Rendezvous and
Vpm/Mos 95//*2Hill were only slightly influenced by the treatments.
Under greenhouse conditions, it was possible to distinguish the level of resistance
of Rendezvous from susceptible cultivars at concentrations of 100 spores/ml, two weeks
after inoculation at the seedling stage. Leaf sheath penetration of seedlings was found
to be closely associated with the disease severity index obtained under field conditions.
Generation means analysis performed in crosses involving Rendezvous indicated
that additive and additive x additive gene action were responsible for most of the genetic
variability associated with resistance. Narrow-sense heritability estimates also confirmed
these fmdings. It would appear that Rendezvous has at least two major genes for
resistance to strawbreaker foot-rot. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36327 |
| Date | 16 May 1991 |
| Creators | Encinas-Mungarro, Andres |
| Contributors | Kronstad, Warren E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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