Etiology of Halo Blight in Michigan Hopyards

Michigan's hop acreage ranks fourth nationally, but the state's growers contend with unique disease challenges resulting from frequent rainfall and high humidity. In August 2018, a Michigan hop grower reported necrosis and blighting of foliage and shattering of cones resulting in yield los...

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Bibliographic Details
Published inPlant disease Vol. 105; no. 4; p. 859
Main Authors Higgins, Douglas S, Hatlen, Ross J, Byrne, Jan M, Sakalidis, Monique L, Miles, Timothy D, Hausbeck, Mary K
Format Journal Article
LanguageEnglish
Published United States 01.04.2021
Subjects
Ascomycota - genetics
Bayes Theorem
Michigan
Phylogeny
Plant Diseases
Michigan
pycnidia
fungi
necrosis
pathogen detection
Humulus lupulus
Phomopsis
cone shatter
Diaporthe
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Summary:Michigan's hop acreage ranks fourth nationally, but the state's growers contend with unique disease challenges resulting from frequent rainfall and high humidity. In August 2018, a Michigan hop grower reported necrosis and blighting of foliage and shattering of cones resulting in yield loss. Irregular-shaped lesions developed on leaves, surrounded by a halo of chlorotic tissue, and cone bracts became brown. Pycnidia were observed in symptomatic tissue. The goal of this study was to identify and characterize the causal agent of symptoms in leaf and cone tissue. In symptomatic leaves, 15 of 19 isolates recovered had 96.4% internal transcribed spacer rDNA (ITSrDNA) homology with . Bayesian and maximum likelihood analyses were performed on a subset of isolates using ITSrDNA, histone H3, beta-tubulin, and elongation factor 1 alpha. Bootstrap and posterior probabilities supported a unique cluster of sp. 1-MI isolates most closely related to the species complex, , and . sp. 1-MI was pathogenic in detached leaf and whole plant assays. Single-spore isolates from pycnidia originating from cones and leaves shared 100% ITSrDNA homology with sp. 1-MI obtained from the lesion margins of leaves collected in 2018. The distribution of sp. 1-MI was widespread among 347 cones collected from 15 Michigan hop yards and accounted for >38% of fungi recovered from cones in three hop yards. sp. 1-MI causing halo and cone blight presents a new disease management challenge for Michigan hop growers.
ISSN:0191-2917
1943-7692
DOI:10.1094/PDIS-05-20-0924-RE