Location: Forage Seed and Cereal Research Unit
Project Number: 2072-21000-061-000-D
Project Type: In-House Appropriated
Start Date: Mar 20, 2023
End Date: Mar 19, 2028
Objective:
Objective 1: Breed new hop varieties possessing superior traits including disease resistance, yield, and brewing characteristics.
Sub-objective 1.A: Combine multiple sources of resistance to powdery mildew disease into new germplasm.
Sub-objective 1.B: Evaluate, identify, and promote superior advanced female hop germplasm from the former Washington State University breeding program for potential public variety release.
Sub-objective 1.C: Generate new variation via crossing, make selections, and advance selected material.
Objective 2: Characterize hop germplasm for tolerance to priority traits such as water-use-efficiency and pest and disease resistance including systematic evaluation of powdery mildew resistance in new germplasm.
Sub-objective 2.A: Assess germplasm for water use efficiency characteristics and abiotic stress resiliency.
Sub-objective 2.B: Evaluate male germplasm for resistance to powdery mildew.
Objective 3: Identify, characterize, and validate molecular markers associated with qualitative and quantitative traits of economic importance in hop such as novel powdery mildew resistance.
Sub-objective 3.A: Identify molecular markers for WUE using bi-parental mating designs, genotyping-by-sequencing (GBS) and quantitative trait loci (QTL) analyses.
Sub-objective 3.B: Identify and validate QTL in the hop cultivar Comet for quantitative resistance to powdery and downy mildews in field environments.
Sub-objective 3.C: Develop a multi-parent population to identify novel sources of powdery mildew resistance and create and utilize a consensus genetic map.
Objective 4: Evaluate management practices that improve crop productivity and crop health using computational analyses to identify optimal control policies for powdery mildew disease at the landscape level and abiotic stress physiology and management.
Sub-objective 4.A: Assess reduced late-season irrigation as a cultural management strategy to improve hop cone quality.
Sub-objective 4.B: Identify determinants and model pesticide use intensity at the field level based on characteristics of growers’ production systems.
Approach:
Objective 1 Research include 1) develop new disease resistant varieties possessing unique, desirable brewing qualities, and 2) evaluate germplasm from Washington State University (WSU) for the same. Germplasm with different and complementary resistance will be crossed to produce offspring to be screened for disease resistance. Resistant offspring will be field-evaluated for resistance, agronomics, aroma and brewing chemistry. Germplasm evaluation from WSU includes screening for the same metrics. Possible challenges exist with 1) ensuring successful controlled pollination; addressed using greenhouses for crosses if necessary, and 2) inoculation for disease resistance screening; alleviated by multiple inoculation attempts.
Objective 2 posits 1) hop varieties with higher water-use efficiency (WUE) can be identified, and 2) newly acquired male hop germplasm exhibits varying levels of powdery mildew resistance. Experiments to test hypotheses include 1) evaluating four hop varieties over two growth seasons near Prosser, WA for WUE, along with agronomic, physiological assessments, and brewing quality metrics, and 2) employing an elimination screening procedure with diverse isolates of the powdery mildew fungus. Contingencies include alternative strategies such as broadening hop variety evaluations and additional germplasm sources for Hypothesis 1, while Hypothesis 2 may involve additional genetic analyses or functional investigations.
Objective 3 posits 1) WUE under drought conditions is under polygenic control, 2) quantitative trait loci (QTL) for resistance to downy and powdery mildew are consistent between greenhouse and field environments and 3) resistance to powdery mildew in male hops is heritable and novel. Bi-parental crossing schemes will be used to develop multiple populations. Populations will be phenotyped for WUE in the greenhouse or disease resistance in the field or via high-throughput systems. Germplasm will be genotyped using molecular methods. QTL statistical analyses will be performed to identify significant QTL. Contingencies for addressing problems range from use of increased water for WUE, use of spatial adjustment of phenotypic data for differences environmental conditions, and use of larger population sizes and/or increased depth of DNA sequencing.
Objective 4 involves 1) developing late-season irrigation guidelines to improve hop quality, and 2) hypothesizes that production efficiency and pesticide use levels vary among farms and are explained by pathogen, host, and environment. Field studies will compare regular irrigation to reduced late-season irrigation for improving hop quality. Soil water will be monitored to maintain deficit water conditions. Yield and brewing quality metrics will be quantified. In 4.B data from industry cooperators or developed in-house will be used to identify determinants of pesticide use on commercial farms. Machine learning will be used to identify factors predicting pesticide use. Contingencies include increasing biological replicates to resolve irrigation effects and developing additional weather or biological variables to refine models if results do not describe pesticide use intensity.
