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The level of polymorphisms of many biochemical and DNA markers are low in
cultivated sunflower (Helianthus annuus L.). The number of mapped public DNA
markers is limited. Molecular markers have not been developed for the most
important diseases of sunflower, such as downy mildew. The objectives of this
study were...
Molecular tools, coupled with unique germplasm stocks and rigorous phenotyping, are
useful for developing a better understanding of qualitative and quantitative disease resistance
genes in plants. The identification of molecular markers linked to all types of resistance
genes provides opportunities for implementing a range of resistance breeding strategies,
ranging from...
We tested a synthetic bacterio-opsin (bO) gene derived from Halobacterium halobium for its effect on disease resistance in transgenic poplar hybrids, and assessed a genetic system for controlling expression of this gene. In tobacco the bO gene caused necrotic lesions similar to an induced hypersensitive response (HR), increased levels of...
Genetic resistance is the most appropriate way to control diseases in crop plants. Resistance can be described as qualitative (involving a gene-for-gene system) or quantitative (with continuous distribution of disease levels). The relationships between different types of resistance remain obscure, as does the genetics of quantitative traits. The use of...
Quantitative resistance (QR) to disease is usually more durable than qualitative resistance, but its genetic basis is not well understood. We used the barley/barley stripe rust pathosystem as a model for the characterization of the QR phenotype and associated genomic regions. As an intermediate step in the preparation of near-isogenic...
European hazelnut is a significant crop in the Pacific Northwest, and the US ranks
4th internationally for hazelnut production. Production in the Pacific Northwest is
threatened, however, by the disease eastern filbert blight (EFB) caused by the fungus
Anisogramma anomala (Peck) E. Müller. To meet the challenges faced by the...
Victoria blight, caused by fungus Cochliobolus victoriae, is a disease originally described on oats and recapitulated on Arabidopsis. Victoria blight is used as a model plant disease that conforms to an inverse gene-for-gene interaction. C. victoriae virulence is dependent upon its production of victorin, a host-specific toxin that induces programmed...
Four isogenic lines possessing different combinations of height
reducing genes Rht₁ and Rht₂ from 'Norin 10' were crossed to a short
stature, early maturing, septoria susceptible cultivar identified as the
'Tibet Dwarf'. The isogenic lines originated from the backcross
population of 'Itana'/3/'Norin 10'/'Brevor 14'//6*'Itana'. Parents, F₁
and F₂ generations provided...
The heritability of resistance to eastern filbert blight, caused by Anisogramma anomala, in European hazelnut (Corylus avellana) was evaluated in the progeny of seven cultivars crossed in 12 combinations. Progeny produced by crossing 'VR6-28' with three susceptible cultivars segregated 1:1 for complete resistance to eastern filbert blight. Histograms of disease...
Eastern filbert blight, caused by Anisogramma anomala (Peck) E. Muller,
is a serious threat to hazelnut (Corylus avellana L.) production. Resistant
cultivars offer the best control. Screening systems were needed to reliably
identify disease, particularly in immune progeny derived from 'Gasaway'. An
indirect enzyme-linked immunosorbant assay (ELISA) was developed using...
Using bulked segregant analysis, five RAPD markers were identified that were
linked in coupling to a gene conferring complete resistance to eastern filbert blight caused
by Anisogramma anomala (Peck) E. Muller in hazelnut (Corylus avellana L.). Two
modified backcross populations were inoculated and scored for resistance to the pathogen
and...
Pea seed-borne mosaic potyvirus pathotype 1 (PSbMV-P1) has the ability to infect most genotypes of Pisum sativum. The exception are those genotypes that are homozygous recessive for the sbm-1 gene. The life cycle of PSbMV pathotype 4 (PSbMV-P4) is unaffected by the sbm-1/sbm-1 genotype. Infectious clones of Pl-P4 recombinants were...
The hundred-year history of the hazelnut industry in the Pacific Northwest is threatened by eastern filbert blight (EFB) caused by the fungus Anisogramma anomala (Peck) E. Müller. Marker-assisted selection (MAS) has been extensively used for ‘Gasaway’ resistance in the hazelnut breeding program at Oregon State University. Concern over breakdown of...
Interspecific hybridization was initiated between wild P. acutifolius accession G40199 and P. vulgaris to introgress resistance to Acanthoscelides obtectus (bean seed weevil). F1 interspecific hybrids were recovered by embryo rescue and maintained until flowering. Mostly sterile hybrids were backcrossed twice to common bean cultivar ICA Pijao to recover sufficient fertility...
Stripe rust (Puccinia striiformis f. sp. hordei) is a serious disease of barley that can cause up to 70% yield loss in susceptible varieties. The fungus is moving northward, threatening major barley production areas in the US, where most cultivars are susceptible. Fungicides are available for control of stripe rust,...
Strawberry is one of four crops included in the USDA-NIFA Specialty Crop Research Initiative-funded RosBREED project along with apple, peach, and cherry. Phenotyping strawberry for specific horticultural and commercial traits is important to identify associations with genotypic marker(s). This process is the first step in translating genomic knowledge into enhanced...
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2.2. Mean resistance scores anddisease response to Cdn-4 and Cdn-5 for
14 Fragaria
The fungus Cochliobolus victoriae causes Victoria blight of oats and Arabidopsis and is pathogenic due to its production of a compound called victorin, which induces programmed cell death in sensitive plants. Victorin sensitivity in Arabidopsis is conferred by the dominant gene LOCUS ORCHESTRATING VICTORIN EFFECTS1 (LOV1), which encodes a coiled-coil-nucleotide...
Port-Orford-cedar (Chamaecyparis lawsoniana) is a forest tree native to
a small area of Oregon and California. A root disease caused by
Phytophthora lateralis causes widespread mortality of Port-Orford-cedar.
This dissertation examines three important elements of the Port-Orford-cedar
P. lateralis pathosystem related to breeding for disease resistance:
use of resistant rootstocks...
Crown gall disease is an agricultural problem caused by the soil-borne bacterium, Agrobacterium tumefaciens. A. tumefaciens oncogenes cause transformed plant cells to overproduce the hormones, auxin and cytokinin. High hormone levels cause unorganized plant cell growth resulting in a gall. Control of crown gall disease is difficult because after plant...
European hazelnut, an important nut crop in Oregon agriculture, is threatened by the fungal disease eastern filbert blight (EFB) caused by Anisogramma anomala (Peck) E. Müller. The hazelnut breeding program at OSU has been working on development of EFB-resistant cultivars. DNA markers allow mapping of traits using segregating progenies and...
Wheat (Triticum aestivum L.) is one of the major crops produced in the U.S. Pacific Northwest, a region known for its wheat production for international export. Wheat production in the region is threatened by diseases such as Cephalosporium stripe and stripe rust. Cephalosporium stripe is a vascular wilt disease of...
Two experiments involving interactions between wheat
(Triticum aesitivium L.) cultivars and rust pathogens were
investigated. One experiment evaluated the aggressiveness
(measured by infection efficiency and latent period) of
populations of Puccinia recondita Rob. when inoculated on
the cultivar they were isolated from, their "own" cultivar,
and when inoculated onto other...
This study quantified the frequency of simple versus
complex races of Puccinia striiformis Westend. in mixtures
of wheat cultivars possessing different race-specific
resistance genes. A simple race of a pathogen can infect
only one component, and a complex race of the pathogen can
infect two or more components of an...
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...
Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko),
is a widely distributed species in western north America,
and a major economic pest of wheat (Triticum aestivum L.)
and barley (Hordeum vulgare L.). The objectives of this
study were to : 1) determine the inheritance of seedling and
adult plant resistances in...
Despite many investigations genotype by environment interaction remains
one of the least understood factors in plant improvement. Understanding genotypic
differences responsible for such interactions could assist in making more informed
breeding decisions. The components of yield being less complex than grain yield
per se may be useful for selection to...
Victoria blight of oats (Avena sativa) is caused by the fungus, Cochliobolus victoriae, which produces the toxin, victorin. Victorin production is required for pathogenicity of the fungus. In oats, sensitivity to the toxin and susceptibility to the pathogen is conditioned by a dominant allele at the 1'b locus, while oats...
Barley is the fourth most important cereal crop in the world because of its broad adaptation, its utility as a feedstock and for human food, and the superior properties of barley malt for brewing. Three of the most important foliar diseases of barley, on a worldwide level are: barley leaf...
European hazelnut, Corylus avellana L., is the only economically important nut crop
in the family Betulaceae. One of the threats to the hazelnut industry in the Pacific
Northwest is the fungal disease eastern filbert blight (EFB) caused by the
pyrenomycete Anisogramma anomala. Host genetic resistance to EFB identified in the...
Stripe rust (Puccinia striiformis f. sp. tritici) has been receiving
increased attention in the USA since the appearance of more virulent races
detected in the past decade. These races caused yield losses even in areas
where the disease previously was rarely detected. Host plant resistance is the
most cost effective...
North American cultivation of Ribes L. may expand as small fruit growers seek species to diversify horticultural crops. The Ribes industry was suppressed for decades out of fear that cultivated black currants and gooseberries would intensify the fungal disease white pine blister rust (WPBR) on five-needle pine (Pinus L. section...
Fire blight is a serious disease of apple and pear trees caused by the bacterium, Erwinia amylovora. This bacterium harbors a pathogenesis mechanism known as the Hrp secretory operon which induces some resistance genes and suppresses other resistance genes in the host plant following invasion. While previous researchers analyzed expression...
White mold, caused by Sclerotinia sclerotiorum (Lib.) de Bary, results in severe losses in the production of common bean, Phaseolus vulgaris, especially snap bean varieties. Advanced backcross QTL analysis was used to identify quantitative trait loci for resistance to white mold in an interspecific cross of P. vulgaris and P....
Fall-sown barley will be increasingly important in the era of climate change due to higher yield potential and efficient use of water resources. Resistance/tolerance to biotic and abiotic stresses will be critical. Low temperature is an abiotic stress of great importance. Resistance to barley stripe rust (incited by Puccinia striifomis...
To identify novel host genetic resistance to eastern filbert blight, caused by the fungus Anisogramma anomala (Peck) E. Muller, ninety European hazelnut {Corylus avellana L.) varieties and interspecific hybrids (with C. americana Marsh, or C. colurna L.) were screened for response to the eastern filbert blight pathogen after inoculation in...
This dissertation describes the application and development of molecular tools that have great potential for use in studying variation in strawberry germplasm. The first study evaluated 91 microsatellite (simple sequence repeat, SSR) markers for transferability in 22 Fragaria species and their utility in fingerprinting octoploid strawberries. Out of the transferable...
Root rot diseases are a major constraint to bean (Phaseolus vulgaris L.)
production around the world. Both snap beans and dry beans are affected. Root rot diseases can be caused by a variety of pathogens; however, Fusarium solani is a common causal agent. Fusarium root rot is a primary yield...
Cephalosporium stripe (Cephalosporium gramineum) is an important disease limiting adoption of conservation tillage practices in the Pacific Northwest. The disease can cause severe loss of grain yield and quality in winter wheat (Triticum aestivum L.). Modified cultural practices can reduce disease incidence, but are not always dependable because of variation...
White mold, caused by Sclerotinia sclerotiorum (Lib.) De Bary, is a destructive yield-limiting disease of common bean (Phaseolus vulgaris L.). Genetic resistance to this pathogen is limited in common bean. Identification of high levels of partial physiological resistance in a genetically cross compatible species, Phaseolus coccineus, is advisable. The objectives...
Hop downy mildew is a devastating disease affecting hop requiring expensive
fungicide applications throughout the growing season. Plant resistance is highly
desirable and theorized as being decidedly quantitative with dominance and epistasis
involved in resistance. An association mapping approach using a mixed-model was
used to identify AFLP markers associated with...
Eastern filbert blight (EFB), caused by Anisogramma anomala (Peck) E.
Miiller, is a devastating disease to orchards of the European hazelnut (Corylus
avellana L.) in the Willamette Valley, Oregon. Host resistance is the most
desirable means of disease control. Fifty-eight hazelnut accessions, including
European cultivars and interspecific hybrids were evaluated...
Root rot diseases of bean (Phaseolus vulgaris L.) are a problem wherever they are grown, and are a major constraint to dry edible and snap bean production. Root rot is a primary yield limitation of snap bean production in the US, especially within the top three snap bean producing states...
Whitebark pine (Pinus albicaulis) is an iconic North American high-elevation tree species currently threatened by climate change, mountain pine beetle, and white pine blister rust (WPBR), a lethal disease caused by the non-native fungal pathogen Cronartium ribicola. In collaboration with the USDA Forest Service Dorena Genetic Resource Center, germplasm was...
The specificity of quantitative host resistance to plant disease has long been a controversial issue. We examined interactions between wheat (Triticum aestivum) and Mycosphaerella graminicola, causal agent of Septoria tritici blotch, to determine whether specific interactions occur between host and pathogen genotypes that could be involved in eroding quantitatively expressed...
Infestations of the western pine shoot borer (Eucosma sonomana Kearfott) in young stands of ponderosa pine (Pinusponderosa Lawson), were surveyed on the Deschutes National Forest. Elevation, slope, aspect, tree height, tree diameter, number of shoots in the terminal whorl, stand density, stand age and plant association for each stand were...
In recent years, red raspberry production in Washington and British Columbia has been severely limited by a newly emerged virus complex that causes symptoms of crumbly fruit. The complex is comprised of three viruses: Raspberry bushy dwarf virus (RBDV), Raspberry leaf mottle virus (RLMV) and Raspberry latent virus (RpLV). Both...