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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #395307
Research Project: Breeding, Genomics, and Integrated Pest Management to Enhance Sustainability of U.S. Hop Production and Competitiveness in Global Markets

Location: Forage Seed and Cereal Research Unit

Title: Genetic characterization of downy mildew resistance from the hop (Humulus lupulus L.) line USDA 64035M

Author
item Olatoye, Olalere
item WISEMAN, MICHELE - Oregon State University
item Gent, David - Dave
item Henning, John
item Altendorf, Kayla

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2022
Publication Date: 11/25/2022
Citation: Olatoye, O.M., Wiseman, M., Gent, D.H., Henning, J.A., Altendorf, K.R. 2022. Genetic characterization of downy mildew resistance from the hop (Humulus lupulus L.) line USDA 64035M. Crop Science. 63(3):1082-1091. https://doi.org/10.1002/csc2.20880.
DOI: https://doi.org/10.1002/csc2.20880

Interpretive Summary: Downy mildew is a major fungal disease prevalent in humid temperate regions of hop production. This disease causes significant yield losses annually and is both challenging and expensive to manage. Cultivation of disease resistant varieties is the most economical way of limiting the impact of the disease on hop production. Understanding of the genetic basis of hop plant resistance to this disease is pertinent to the development of disease resistant varieties. However, current knowledge of the genetic basis of hop plant resistance to downy mildew is limited and currently being studied. Here in this study, we utilized a bi-parental population of hop to decipher the genetic basis of downy mildew resistance in hop by associating its phenotypic observations with its genetic information. Our study identified several locations in the genome of hop that we suspect to control downy mildew resistance. This information can help facilitate informed decision making by hop breeders when developing new varieties of hop.

Technical Abstract: Downy mildew resistance (DMR) will facilitate the success of hop production in humid, temperate climates. However, DMR in hop has a narrow genetic base, and its genetic architecture is poorly understood. Here in this study, we characterized the genetic control of DMR using a bi-parental mapping population derived from a cross between a susceptible female cultivar ‘Comet’ and USDA 64035M, a DMR male hop. Resistance was evaluated after inoculation with the downy mildew pathogen Pseudoperonospora humuli as percent leaf area with lesions and percent leaf area with sporulation under greenhouse conditions. Significant (P -value < 0.01) genotypic differences were observed for the traits which at the same time had moderate (0.33 for percent lesion) to high (0.72 for percent sporulation) broad-sense heritability. Genome-phenome association between 4090 markers and 284 individuals identified three significant associations for percent lesion and five for percent sporulation. Our study demonstrated that DMR was under polygenic control with small effect loci. In addition, a pleiotropic locus was found on chromosome 2 to be associated with both percent lesion and percent sporulation. Identifying the gene(s) underlying such a pleiotropic locus can help improve our understanding of hop response to pathogen infection.