First report of Neofabraea actinidiae causing a cranberry fruit rot in Oregon

Authors: VALENTINE, DON - Oregon State University; Shaffer, Brenda; McGhee, Gayle; BOUSKA, CASSIE - Oregon State University; Stockwell, Virginia

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cranberries are one of the few native fruits of the USA grown commercially. Oregon produces over 506 million pounds of cranberries annually on 2,600 acres with a crop value of $19 million in 2021. Unfortunately, cranberry fruit rot fungi remain a serious threat to productivity. This reports for the first time the occurrence of a fungus called Neofabraea actinidiae as a cause of cranberry fruit rot in the field and during cold storage. This fungus is known to cause a fruit rot of kiwifruit and a storage rot of apple and pear fruits. We will continue to monitor the prevalence of this fungus in cranberry beds in Oregon with the ultimate goal of identifying best practices to manage this emerging cranberry fruit rot disease.

Technical Abstract: Cranberry (Vaccinium macrocarpon, L.) is a commercial small fruit that is native to North America. Oregon ranks fourth in cranberry production in the U.S.A with 1052 Ha of cranberry beds and annual production of 23,590 metric tonnes. Cranberry fruit rots are caused by a complex of 15 fungal pathogens belonging to 10 genera that cause periodic crop losses. In fruit rot surveys of ‘Stevens’ cranberry beds in Coos and Curry Counties, Oregon, berries were collected before harvest, rotted berries were placed on V8 agar to isolate fungi. In 2022, Neofabraea actinidiae was isolated from 20% of cranberries tested from an organically managed farm. N. actinidiae also was isolated from up to 22% of cranberries with storage rot symptoms from each farm sampled. On V8 agar, N. actinidiae grew as compact white circular colonies with dense aerial hyphae near the center and a developing red pigment in the agar. Pink-colored mucoidal irregular conidiomata often developed on the colony after 3 weeks. Conidia were hyaline, aseptate, and ellipsoidal to fusiform ranging from 7.5 to 12.6 µm long X 3.5 to 5.6 µm wide (n=100). Genomic DNA was extracted from cranberry N. actinidiae isolates and the ITS region and beta-tubulin were sequenced. Phylogenetic analyses with concatenated sequences of field isolates confirmed identity as N. actinidiae. Koch's Postulates were confirmed by inoculating asymptomatic cranberries with isolates of N. actinidiae. The typical lesion, a yellow center and radiating brown color with a dark ring was observed on tissues inoculated with field isolates and was not observed on mock inoculated control berries. The pathogen was isolated from symptomatic tissues and identity as N. actinidiae was confirmed. N. actinidiae causes a ripe rot and storage rot in kiwifruit and is one of the species causing Bull’s Eye Rot of pome fruits. N. actinidiae was isolated from cranberries roots in British Columbia, CA and proposed as a causal agent of dieback disease of cranberry vines. We have demonstrated that N. actinidiae also causes a cranberry fruit rot in beds and in storage. Its prevalence, associated fruit rot symptoms, and disease incidence will continue to be monitored.