Location: Forage Seed and Cereal Research Unit
Project Number: 2072-21000-051-000-D
Project Type: In-House Appropriated
Start Date: Mar 20, 2018
End Date: Mar 19, 2023
The goal of this project is to maintain and enhance the competitiveness of the U.S. hop industry through development of publicly available genetic resources, tools, and knowledge-based pest management systems. This will be accomplished through interdisciplinary research that addresses high priority documented stakeholder needs. Over the next 5 years, the specific objectives to be accomplished are: Objective 1: Develop and release new hop cultivars and germplasm possessing superior disease resistance, yield, and brewing characteristics. (Henning) Objective 2: Identify, characterize, and validate molecular markers associated with qualitative and quantitative resistance to important foliar diseases. (Henning) Objective 3: Identify molecular markers associated with virulence of Podosphaera macularis and use the information to rapidly determine pathogen races. (Gent) Objective 4: Quantify the aggressiveness, fitness, and race of Podosphaera macularis isolates able to overcome partial host resistance and identify new sources of resistance to diverse strains of the pathogen in public germplasm. (Gent) Sub-objective 4A: Characterize the aggressiveness, fitness, and race of Podosphaera macularis virulent on the cultivar Cascade. (Gent) Sub-objective 4B: Identify and quantify the impact of supraoptimal temperature on host susceptibility to and development of powdery mildew on the cultivar Cascade. (Gent) Sub-objective 4C: Characterize publicly available male germplasm for its reaction to multiple strains of Podosphaera macularis. (Gent)
Objective 1 Research Goal: Develop multiple pathogen resistant germplasm or cultivars. Controlled crosses of cultivars two cultivars will be made using resistant males. Progeny will be screened for disease resistance and phenotypic traits including hop aroma. Selected offspring will be advanced for further evaluation. Objective 2 Research Goal: Identify molecular markers associated with plant resistance to P. humuli and P. macularis. Genetic maps and genome-wide surveys for marker association will be conducted using a bi-parental mapping population derived from a powdery mildew resistant female line and a downy mildew resistant male line. Objective 3 Hypothesis: Markers associated with pathogenic variation in P. macularis can be identified. Isolates of P. macularis from Pacific NW will be collected and race-validated using differential host panels. RNA will be collected from P. macularis isolates and subsequently sequenced using next gen sequencing. SNP markers will be identified from this data. SNPs will be used to fingerprint different isolates and a set of unique markers for each isolate identified. Sub-objective 4A Hypothesis: Strains of P. macularis virulent on Cascade are specifically adapted to this cultivar. Controlled environment experiments will be conducted to determine the aggressiveness and fitness of isolates of P. macularis originating from Cascade to provide fundamental information to guide breeding efforts and disease risk assessment. These races will also be characterized using a differential set of cultivars possessing different resistance genes. Sub-objective 4B Hypothesis: Partial resistance to powdery mildew in the Cascade is modulated by brief exposure to supra-optimal temperature. An extensive set of controlled environment studies will be conducted to define the environmental conditions that moderate infection risk on the Cascade to derive rules for adapting the HOPS powdery mildew risk index to Cascade and similar cultivars. Sub-objective 4C Research Goal: Characterize resistance of USDA males to multiple strains of powdery mildew. A set of 150 individuals –resistant to downy mildew--will be tested for their resistance to multiple races of P. macularis. Resistance to three different isolates-each with unique virulence genes—will be sequentially scored across all male lines. Remaining resistant individuals will be further evaluated to determine the nature of resistance.