Occurrence of mummy berry associated with huckleberry (Vaccinium membranaceum) caused by Monilinia spp. in Oregon

Authors: HAGERTY, CHRISTINA - Oregon State University; GARDNER, S - Oregon State University; KROESE, D - Oregon State University; YIN, C - Washington State University; Paulitz, Timothy; PSCHEIDT, J - Oregon State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2022
Publication Date: 2/6/2022
Citation: Hagerty, C., Gardner, S., Kroese, D.R., Yin, C., Paulitz, T.C., Pscheidt, J.W. 2022. Occurrence of mummy berry associated with huckleberry (Vaccinium membranaceum) caused by Monilinia spp. in Oregon. Plant Disease. 106(2):357-359. https://doi.org/10.1094/PDIS-04-21-0691-SC.
DOI: https://doi.org/10.1094/PDIS-04-21-0691-SC

Interpretive Summary: This is the first report of Monilinia on huckleberry in Oregon. Huckleberry is a native berry of mountainous regions in the Western US, and a food source for wildlife and First Nations peoples. This disease causes mummy berry, an important disease on cultivated Vaccinium species, such as blueberry.

Technical Abstract: Vaccinium membranaceum, known commonly as thinleaf huckleberry, mountain huckleberry, and black huckleberry is native to western North America (Simonin, K.A., 2000; Oregon Flora, 2021). It is the most extensively harvested, wild Vaccinium species in the PNWPacific Northwest due to their renowned flavor and high yield (Oregon Flora, 2021). Vaccinium membranaceum is common in mid to high elevation coniferous forests of the Cascade, Olympic and Rocky Mountain ranges (Simonin, K.A., 2000; Oregon Flora, 2021). Huckleberry flowers include five sepals with shallowly lobed calyces, five petals, and shallowly lobed corollas. Inflorescences bloom in spring, are white to pink in color, and are bee pollinated (Oregon Flora, 2021; Gardner, S. pers. obs.). Huckleberry fruits are very dark red to black, and 6-12 mm in diameter (Oregon Flora, 2021). Huckleberry is an important food source for large mammals, including bear and deer; and shrubs provide habitat for many small animals. In addition, the huckleberry holds cultural importance as a sacred First first Food food of the Confederated Tribes of the Umatilla Indian Reservation (CTUIR), where berries are collected in late summer and preserved for winter use (CTUIR, 2021). In summer 2018 and 2019 on public land in the Umatilla National Forrest near Tollgate, OR and the Wallowa-Whitman National Forest near Moss Springs Trailhead shriveled huckleberries were observed on fruiting V. membranaceum shrubs; shriveled berries occurring at incidences of greater than 50% in many cases (Photo 1). These berries were collected at both public land locations in both years (n= greater than 1000). Shriveled, mummified berries are smaller and lighter in color than the succulent fruits, and can be described as “corky” (Photo 2a, 2b, 2c). In 2019, 40 shriveled berries were surface sterilized in a 10% commercial bleach solution for 30-60 seconds, followed by a sterile water soak for 30-60 seconds. Next, specimens were bisected to reveal a dense white mycelial mat (Photo 3). Using sterile technique, portions of the mycelial mat inside the mummy were excised and placed on ¼ strength potato dextrose agar (PDA) amended with 10 mg/L rifampicin antibiotic and incubated at ambient temperature for seven days. After seven days, cultures were transferred to ½ strength PDA and incubated at ambient temperature for an additional seven days. Genomic DNA was extracted from the isolates by scraping the mycelial mat from the PDA Petri dish into DNA extraction tubes and DNA extraction was performed with a DNeasy Plant Mini Kit (Qiagen, Germany) according to manufacturer’s instructions. The process of isolating fungal tissue from 40 shriveled fruit specimens resulted in 19 unique DNA samples from both public land locations. The ITS region was amplified with primers ITS1-F (5’-CTTGGTCATTTAGAGGAAGTAA-3’) and ITS4 (5’-TCCTCCGCTTATTGATATGC-3’), and amplicons were purified with GeneJET PCR Purification kit (ThermoFisher Scientific, USA) and sequenced (Elim Biopharmaceuticals Inc, USA). The 19 sequences were 100% identical. The NCBI (https://www.ncbi.nlm.nih.gov/) and UNITE (https://unite.ut.ee/) databases were used to identify all 19 DNA samples being closest to Monilinia vaccinii-corymbosi, with identities of around 90% (Table 1). Shriveled fruits (n=200+) were incubated outdoors during winter 2018-2019 at the Columbia Basin Agriculture Research Center near Adams, OR, following the wire corral protocol described in Pscheidt et al. (2017). Shriveled fruits failed to produce apothecia. The same 19 isolates utilized for sequencing did not sporulate in culture when incubated at both 22°C and 4°C. Due to the occurrence of this pathosystem in the natural landscape, and the notoriously fickle nature of huckleberry cultivation (Barney, D.L., 1999), step three of Koch’s postulates (reinfection) was not possible. Monilinia urnula and M. vaccini