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• 1. [Article] Genetic factors that provide adult plant resistance against Puccinia striiformis f. sp. tritici to wheat cultivar 'Stephens' in a multilocation analysis.

  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 ...

  Citation × Citation Citation Abstract Copy Title: Genetic factors that provide adult plant resistance against Puccinia striiformis f. sp. tritici to wheat cultivar 'Stephens' in a multilocation analysis. Author: Vazquez, Maria Dolores 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 and environmentally friendly means of controlling stripe rust. Deployment of single, major genes for resistance has been compromised due to the genetic variability of the pathogen, emphasizing the need to breed for durable resistance. 'Stephens' wheat (Triticum aestivum L.) has been grown commercially in the Pacific Northwest region of the USA for 30 years and shows resistance to P. striiformis f. sp. tritici "old" and "new" races. The durable resistance of Stephens to stripe rust is believed to be due to a combination of seedling and adult plant resistance genes. Multilocation field trials and molecular genotyping were used to study the genetics of the resistance response in 'Stephens'. Disease severity, based on the percentage of leaf area infected in field plots, was recorded in eight locations: five in 2008 and three in 2009. Locations could be divided into two mega-environments based on time of appearance of disease and QTL identified. Quantitative trait loci (QTL) analysis identified 11 chromosomal regions associated with resistance to stripe rust in the resistant parent ('Stephens') and two regions derived from the susceptible parent ('Platte'). Many QTL locations coincided to those of previous reports. Furthermore, this study suggests that a combination of additive resistance genes acting at different plant stages is responsible for the durable resistance of 'Stephens'. Significant QTL x environment interactions were found, suggesting that specificity to plant stage, race, and/or temperature are responsible for different disease responses. Title: Genetic factors that provide adult plant resistance against Puccinia striiformis f. sp. tritici to wheat cultivar 'Stephens' in a multilocation analysis. Author: Vazquez, Maria Dolores 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 and environmentally friendly means of controlling stripe rust. Deployment of single, major genes for resistance has been compromised due to the genetic variability of the pathogen, emphasizing the need to breed for durable resistance. 'Stephens' wheat (Triticum aestivum L.) has been grown commercially in the Pacific Northwest region of the USA for 30 years and shows resistance to P. striiformis f. sp. tritici "old" and "new" races. The durable resistance of Stephens to stripe rust is believed to be due to a combination of seedling and adult plant resistance genes. Multilocation field trials and molecular genotyping were used to study the genetics of the resistance response in 'Stephens'. Disease severity, based on the percentage of leaf area infected in field plots, was recorded in eight locations: five in 2008 and three in 2009. Locations could be divided into two mega-environments based on time of appearance of disease and QTL identified. Quantitative trait loci (QTL) analysis identified 11 chromosomal regions associated with resistance to stripe rust in the resistant parent ('Stephens') and two regions derived from the susceptible parent ('Platte'). Many QTL locations coincided to those of previous reports. Furthermore, this study suggests that a combination of additive resistance genes acting at different plant stages is responsible for the durable resistance of 'Stephens'. Significant QTL x environment interactions were found, suggesting that specificity to plant stage, race, and/or temperature are responsible for different disease responses. Close

• 2. [Article] Transfer, characterization and mapping of white mold resistance in an advanced backcross interspecific population between Phaseolus vulgaris and Phaseolus coccineus

  The advanced backcross-quatitative trait loci (AB-QTL) breeding method was employed on snap bean (OR 91G x PI433251B) and dry bean (M0162 x PI433251B) interspecific populations to transfer resistance QTL ...

  Citation × Citation Citation Abstract Copy Title: Transfer, characterization and mapping of white mold resistance in an advanced backcross interspecific population between Phaseolus vulgaris and Phaseolus coccineus Author: Zimmerman, Shawna Jean The advanced backcross-quatitative trait loci (AB-QTL) breeding method was employed on snap bean (OR 91G x PI433251B) and dry bean (M0162 x PI433251B) interspecific populations to transfer resistance QTL from resistant donor parent Phaseolus coccineus into P. vulgaris. For OR 91G x PI433251B, analyses produced nine linkage groups corresponding to eight core linkage groups for P. vulgaris consisting of 40 markers covering 336.7 cM (approximately 28.1% of the estimated bean genome). MQM mapping revealed one QTL that was located on linkage group Pv05 (LOD of 3.2) associated with 2009 percent field severity and accounted for 6.4% of the phenotypic variation. For M0162 x PI433251B, three linkage groups were observed, corresponding to three core linkage groups for P. vulgaris and consisted of 11 markers covering 42.44 cM (approximately 3.5% of the estimated bean genome). One QTL was identified with MQM mapping on linkage group Pv02 with a LOD of 1.8 and associated with the 2009 percent field severity, and accounted for 9.8% of the phenotypic variation. Because many SSR markers with known locations on previously published common bean linkage maps were unlinked, we constructed virtual maps to order polymorphic SSRs. In conjunction with single factor analysis and the Kruskall-Wallis analysis, probable locations of QTL were identified in the absence of the traditional QTL mapping. In addition to QTL mapping, trends for interspecific populations were investigated by comparing three different populations: the two populations being reported in this document for the first time (OR 91G x PI433251B and M0162 x PI433251B) and the previously analyzed OR 91G x PI255956. The general trends for interspecific populations were severe segregation distortion attributed to overrepresentation of heterozygotes, low marker polymorphism and regions of the genome that appear to recombine infrequently. Title: Transfer, characterization and mapping of white mold resistance in an advanced backcross interspecific population between Phaseolus vulgaris and Phaseolus coccineus Author: Zimmerman, Shawna Jean The advanced backcross-quatitative trait loci (AB-QTL) breeding method was employed on snap bean (OR 91G x PI433251B) and dry bean (M0162 x PI433251B) interspecific populations to transfer resistance QTL from resistant donor parent Phaseolus coccineus into P. vulgaris. For OR 91G x PI433251B, analyses produced nine linkage groups corresponding to eight core linkage groups for P. vulgaris consisting of 40 markers covering 336.7 cM (approximately 28.1% of the estimated bean genome). MQM mapping revealed one QTL that was located on linkage group Pv05 (LOD of 3.2) associated with 2009 percent field severity and accounted for 6.4% of the phenotypic variation. For M0162 x PI433251B, three linkage groups were observed, corresponding to three core linkage groups for P. vulgaris and consisted of 11 markers covering 42.44 cM (approximately 3.5% of the estimated bean genome). One QTL was identified with MQM mapping on linkage group Pv02 with a LOD of 1.8 and associated with the 2009 percent field severity, and accounted for 9.8% of the phenotypic variation. Because many SSR markers with known locations on previously published common bean linkage maps were unlinked, we constructed virtual maps to order polymorphic SSRs. In conjunction with single factor analysis and the Kruskall-Wallis analysis, probable locations of QTL were identified in the absence of the traditional QTL mapping. In addition to QTL mapping, trends for interspecific populations were investigated by comparing three different populations: the two populations being reported in this document for the first time (OR 91G x PI433251B and M0162 x PI433251B) and the previously analyzed OR 91G x PI255956. The general trends for interspecific populations were severe segregation distortion attributed to overrepresentation of heterozygotes, low marker polymorphism and regions of the genome that appear to recombine infrequently. Close

• 3. [Article] Disease resistance and spring phenological characteristics of Ribes L. germplasm

  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 ...

  Citation × Citation Citation Abstract Copy Title: Disease resistance and spring phenological characteristics of Ribes L. germplasm Author: Dalton, Daniel T. 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 Quinquefoliae) species. These pines were historically vital to the timber industry. Today, plant breeders seek to strengthen the Ribes small fruit industry through production of material suitable for North American conditions. Paramount to this effort is the development of resistance against major pests and diseases. Growers must be able to recognize the attributes of available genotypes prior to field establishment. The objectives of this research were to determine disease resistance and phenological characteristics of Ribes selections at the United States Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon. Since the early 1930's, plant breeders have used immune black currant (R. nigrum L.) germplasm as a control tactic against the exotic WPBR, caused by the basidiomycete fungus Cronartium ribicola J.C. Fischer. In 1999, a seedling population was generated at the NCGR from a cross involving susceptible pistillate R. nigrum 'Ben Lomond' and immune staminate parent R. ussuriense Jancz. x R. nigrum 'Consort.' To test the inheritance of resistance in the F₁ population, aeciospore and urediniospore treatments were applied in 2008 to single-leaf softwood cuttings under controlled conditions in a greenhouse. Resistant F₁ phenotypes segregated in a 1:1 ratio consistent with the pattern of simple dominant inheritance of a single gene. Artificial inoculations testing aeciospore and urediniospore infectivity produced equivalent disease severity in the experimental Ribes genotypes. Resistance to the native powdery mildew fungus, Podosphaera mors-uvae (Schwein.) U. Brown and S. Takamatsu, was also evaluated in the F₁ population. Individuals segregated for resistance in a 1:3 ratio after exposure to elevated disease pressure in the greenhouse. Fifteen F₁ genotypes were resistant to both fungal pathogens and are candidates for further breeding trials. In a second study, five years of spring phenological survey data were analyzed using a growing degree-day (GDD) model, with the objective to identify cultivars adapted to North American conditions. Ribes section Calobotrya was the earliest group to reach "first bloom," followed sequentially by R. [superscript]xnidigrolaria Bauer hybrid species, section Symphocalyx, section Grossularia, section Ribes, and lastly, section Botrycarpum. Early and late-flowering accessions were identified for each taxon. Title: Disease resistance and spring phenological characteristics of Ribes L. germplasm Author: Dalton, Daniel T. 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 Quinquefoliae) species. These pines were historically vital to the timber industry. Today, plant breeders seek to strengthen the Ribes small fruit industry through production of material suitable for North American conditions. Paramount to this effort is the development of resistance against major pests and diseases. Growers must be able to recognize the attributes of available genotypes prior to field establishment. The objectives of this research were to determine disease resistance and phenological characteristics of Ribes selections at the United States Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon. Since the early 1930's, plant breeders have used immune black currant (R. nigrum L.) germplasm as a control tactic against the exotic WPBR, caused by the basidiomycete fungus Cronartium ribicola J.C. Fischer. In 1999, a seedling population was generated at the NCGR from a cross involving susceptible pistillate R. nigrum 'Ben Lomond' and immune staminate parent R. ussuriense Jancz. x R. nigrum 'Consort.' To test the inheritance of resistance in the F₁ population, aeciospore and urediniospore treatments were applied in 2008 to single-leaf softwood cuttings under controlled conditions in a greenhouse. Resistant F₁ phenotypes segregated in a 1:1 ratio consistent with the pattern of simple dominant inheritance of a single gene. Artificial inoculations testing aeciospore and urediniospore infectivity produced equivalent disease severity in the experimental Ribes genotypes. Resistance to the native powdery mildew fungus, Podosphaera mors-uvae (Schwein.) U. Brown and S. Takamatsu, was also evaluated in the F₁ population. Individuals segregated for resistance in a 1:3 ratio after exposure to elevated disease pressure in the greenhouse. Fifteen F₁ genotypes were resistant to both fungal pathogens and are candidates for further breeding trials. In a second study, five years of spring phenological survey data were analyzed using a growing degree-day (GDD) model, with the objective to identify cultivars adapted to North American conditions. Ribes section Calobotrya was the earliest group to reach "first bloom," followed sequentially by R. [superscript]xnidigrolaria Bauer hybrid species, section Symphocalyx, section Grossularia, section Ribes, and lastly, section Botrycarpum. Early and late-flowering accessions were identified for each taxon. Close

• 4. [Article] Developing techniques for evaluating the susceptibility of root-disease resistant Port-Orford-Cedar to foliar and stem canker diseases.

  Since around 1923 Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murray) Parl.) has been affected by Phytophthora root disease caused by the virulent introduced pathogen Phytophthora lateralis. A systematic ...

  Citation × Citation Citation Abstract Copy Title: Developing techniques for evaluating the susceptibility of root-disease resistant Port-Orford-Cedar to foliar and stem canker diseases. Author: Martin, Danielle K. H. Since around 1923 Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murray) Parl.) has been affected by Phytophthora root disease caused by the virulent introduced pathogen Phytophthora lateralis. A systematic resistance testing and breeding program located at the USDA Forest Service Dorena Genetic Resource Center in Cottage Grove, Oregon was initiated in 1997 with the goal of producing Phytophthora root disease resistant planting stock suitable for replacing wild native POC killed by the disease. Although families of Port-Orford-cedar have been identified as having a heritable form of resistance to Phytophthora lateralis, there is concern that susceptibility to other pathogens of Port-Orford-cedar, such as Seiridium sp. and Stigmina thujina, could compromise the success of deploying root disease resistant planting stock. This thesis examines methods used to evaluate the heritability of susceptibility of Port-Orford-cedar families in the Phytophthora root disease resistance breeding program to infection and disease caused by species of Seiridium and Stigmina thujina. Inoculation studies were undertaken to investigate the feasibility of developing protocols for screening Phytophthora root disease resistant POC for resistance to cypress canker caused by species of Seiridium and foliage blight caused by Stigmina thujina. Procedures were developed for culturing the pathogens, producing viable spores, and developing inoculation and disease rating procedures. In addition, the species of Seiridium associated with cypress canker of Port-Orford-cedar in Oregon was examined by observing morphological characteristics and comparing ß-tubulin and histone gene sequences. Cypress canker symptom severity was compared among 30 POC families with differing susceptibility to Phytophthora root disease. Seedlings were wound inoculated with cultures of a Seiridium sp. isolated from symptomatic POC and resulting symptoms scored monthly over the following 12 months. Symptoms of infection began to develop within two months after inoculation. Symptoms began as slight chlorosis of foliage above the site of inoculation, progressed to a darker browning of foliage, and finally resulted in seedling death. One year post inoculation about 71% of seedlings had been killed. Average between-family mortality ranged from 46 to 89% with a grand mean mortality of 52%. A multifactor ANOVA showed a significant variation in mortality among families. No correlation between resistance to Seiridium and resistance to P. lateralis was found. Variation in susceptibility to Stigmina foliage blight was also examined for the same 30 families. Port-Orford-cedar seedlings were inoculated by exposure to natural inoculum at a field site or by aerosol application of macerated mycelium of S. thujina cultures to seedling foliage in a greenhouse study and evaluated for Stigmina blight symptoms after 12 months. Stigmina symptoms were also compared in a naturally infected POC common garden plantation representing a range-wide collection of Port- Orford-cedar. Differences in symptom severity between families were found for all three assays. However, with one exception, no correlation was found between resistance to infection by Stigmina thujina and resistance to P. lateralis. Seedstock collected from watersheds that differed in elevation, precipitation, latitude and longitude were found to have significant variation in levels of disease severity caused by S. thujina. Families from watersheds nearest to the coast, from more northern latitudes and lower elevations showed lower levels of S. thujina disease symptoms. POC seedlings from parent trees located in watersheds in the southernmost, most inland provenances, higher elevations and lower mean annual precipitation (mm) had higher Stigmina disease ratings. In order to identify the species of Seiridium associated with cypress canker in Oregon, eight isolates of Seiridium were collected from three host species in various plantations in southwest Oregon. The diagnostic features of the Seiridium isolates were morphologically most similar to those described for S. cardinale. However, phylogenetic analysis based on ß-tubulin and histone gene sequences grouped the Oregon isolates in a separate clade from S. cardinale isolates. The Oregon Seiridium isolates occurred in a sister relationship with S. unicorne isolates from Portugal. The lack of agreement between the morphological characteristics of the Oregon Port-Orford cedar isolates and the phylogenetic analysis suggests that there may be greater variation in the morphological characters of S. unicorne than previously recognized, or that the Seiridium species from Oregon represents a hitherto unrecognized species. Previously reported analyses of pathogenic Seiridium species did not include isolates from North America, which appear more variable than isolates from Europe, New Zealand and Africa. The results of this study indicate that further analyses of Seiridium isolates from North America, including additional putative specimens from C. macrocarpa are needed to resolve this question. A number of challenges affected the success of inoculation testing procedures in this study. These included seasonal differences and variation in seedling diameter among inoculation groups. The results of this study provide a limited understanding of variation in susceptibility of Port-Orford-cedar families to natural populations of Seiridium due to the constraint of using a single Seiridium isolate, and should be interpreted accordingly. Despite these limitations, this study presents evidence for heritable variability in susceptibility within POC families to both cypress canker and Stigmina foliage blight, and suggests that there is high potential for improvement by selective breeding. The methods described in this thesis should be useful for future testing. Variation in susceptibility to these diseases should be considered in evaluating Phytophthora root disease resistance breeding efforts. Title: Developing techniques for evaluating the susceptibility of root-disease resistant Port-Orford-Cedar to foliar and stem canker diseases. Author: Martin, Danielle K. H. Since around 1923 Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murray) Parl.) has been affected by Phytophthora root disease caused by the virulent introduced pathogen Phytophthora lateralis. A systematic resistance testing and breeding program located at the USDA Forest Service Dorena Genetic Resource Center in Cottage Grove, Oregon was initiated in 1997 with the goal of producing Phytophthora root disease resistant planting stock suitable for replacing wild native POC killed by the disease. Although families of Port-Orford-cedar have been identified as having a heritable form of resistance to Phytophthora lateralis, there is concern that susceptibility to other pathogens of Port-Orford-cedar, such as Seiridium sp. and Stigmina thujina, could compromise the success of deploying root disease resistant planting stock. This thesis examines methods used to evaluate the heritability of susceptibility of Port-Orford-cedar families in the Phytophthora root disease resistance breeding program to infection and disease caused by species of Seiridium and Stigmina thujina. Inoculation studies were undertaken to investigate the feasibility of developing protocols for screening Phytophthora root disease resistant POC for resistance to cypress canker caused by species of Seiridium and foliage blight caused by Stigmina thujina. Procedures were developed for culturing the pathogens, producing viable spores, and developing inoculation and disease rating procedures. In addition, the species of Seiridium associated with cypress canker of Port-Orford-cedar in Oregon was examined by observing morphological characteristics and comparing ß-tubulin and histone gene sequences. Cypress canker symptom severity was compared among 30 POC families with differing susceptibility to Phytophthora root disease. Seedlings were wound inoculated with cultures of a Seiridium sp. isolated from symptomatic POC and resulting symptoms scored monthly over the following 12 months. Symptoms of infection began to develop within two months after inoculation. Symptoms began as slight chlorosis of foliage above the site of inoculation, progressed to a darker browning of foliage, and finally resulted in seedling death. One year post inoculation about 71% of seedlings had been killed. Average between-family mortality ranged from 46 to 89% with a grand mean mortality of 52%. A multifactor ANOVA showed a significant variation in mortality among families. No correlation between resistance to Seiridium and resistance to P. lateralis was found. Variation in susceptibility to Stigmina foliage blight was also examined for the same 30 families. Port-Orford-cedar seedlings were inoculated by exposure to natural inoculum at a field site or by aerosol application of macerated mycelium of S. thujina cultures to seedling foliage in a greenhouse study and evaluated for Stigmina blight symptoms after 12 months. Stigmina symptoms were also compared in a naturally infected POC common garden plantation representing a range-wide collection of Port- Orford-cedar. Differences in symptom severity between families were found for all three assays. However, with one exception, no correlation was found between resistance to infection by Stigmina thujina and resistance to P. lateralis. Seedstock collected from watersheds that differed in elevation, precipitation, latitude and longitude were found to have significant variation in levels of disease severity caused by S. thujina. Families from watersheds nearest to the coast, from more northern latitudes and lower elevations showed lower levels of S. thujina disease symptoms. POC seedlings from parent trees located in watersheds in the southernmost, most inland provenances, higher elevations and lower mean annual precipitation (mm) had higher Stigmina disease ratings. In order to identify the species of Seiridium associated with cypress canker in Oregon, eight isolates of Seiridium were collected from three host species in various plantations in southwest Oregon. The diagnostic features of the Seiridium isolates were morphologically most similar to those described for S. cardinale. However, phylogenetic analysis based on ß-tubulin and histone gene sequences grouped the Oregon isolates in a separate clade from S. cardinale isolates. The Oregon Seiridium isolates occurred in a sister relationship with S. unicorne isolates from Portugal. The lack of agreement between the morphological characteristics of the Oregon Port-Orford cedar isolates and the phylogenetic analysis suggests that there may be greater variation in the morphological characters of S. unicorne than previously recognized, or that the Seiridium species from Oregon represents a hitherto unrecognized species. Previously reported analyses of pathogenic Seiridium species did not include isolates from North America, which appear more variable than isolates from Europe, New Zealand and Africa. The results of this study indicate that further analyses of Seiridium isolates from North America, including additional putative specimens from C. macrocarpa are needed to resolve this question. A number of challenges affected the success of inoculation testing procedures in this study. These included seasonal differences and variation in seedling diameter among inoculation groups. The results of this study provide a limited understanding of variation in susceptibility of Port-Orford-cedar families to natural populations of Seiridium due to the constraint of using a single Seiridium isolate, and should be interpreted accordingly. Despite these limitations, this study presents evidence for heritable variability in susceptibility within POC families to both cypress canker and Stigmina foliage blight, and suggests that there is high potential for improvement by selective breeding. The methods described in this thesis should be useful for future testing. Variation in susceptibility to these diseases should be considered in evaluating Phytophthora root disease resistance breeding efforts. Close