|Waller, Timothy - Rutgers University|
|Constantelos, Christine - Rutgers University|
|Oudemans, Peter - Rutgers University|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2017
Publication Date: N/A
Interpretive Summary: Anthracnose fruit rot is the most important disease of blueberry in New Jersey. The pathogen that causes this disease has been reported to be various species in the fungal genus called Colletotrichum. Precise identification of the pathogen that causes disease is one of the requirements to develop a program to control the disease. We have determined, through morphological and molecular data obtained from the fungus infecting blueberry, that the pathogen causing anthracnose fruit rot on blueberry in New Jersey is the recently described species Colletotrichum fioriniae. This species was previously described as causing leaf spot of blueberry in Poland and this is the first report of this species causing fruit rot in New Jersey. This information will be used by scientists and extension agents in developing methods to control the disease.
Technical Abstract: Anthracnose fruit rot is the most important disease of blueberry in New Jersey. Most fungicide applications in New Jersey and other blueberry growing regions is for the control of this disease. The causal agent of this disease has been reported to be Colletotrichum acutatum and other species in the genus such as C. simmondsii. This species (C. acutatum) has been determined to be a species complex (i.e. a complex consisting of more than one species). We sought to determine if anthracnose of blueberry in New Jersey is caused by a a mixture of Colletotrichum spp., or if a single species causes the disease. The symptoms of anthracnose include fruit softening and the presence of orange spore masses on the fruit surface. The pathogen was isolated from symptomatic blueberry fruit collected from several commercial farms in New Jersey (n = 100). The mycelium was grayish white on potato dextrose medium with red pigment visible from the underside of the cultures. Orange spore masses appeared in the cultures after 7-10 days' growth. The asexual spores (conidia) were hyaline, aseptate, cylindrical to fusiform, pointed at both ends, and measured 13 to 15 µm long × 4.7 to 5.2 µm wide. All isolates had the same morphology and these characteristics fit within the circumscription for C. fioriniae. Portions of the actin and beta tubulin genes and the ITS rDNA were amplified from representative isolates. Sequences were tested for similarity to those curated in Genbank using BLASTn. All sequences matched those of C. fioriniae isolates with 100% similarity. Blueberry fruit were infected with a spore suspension of a representative isolate. The disease, anthracnose fruit rot, appeared after incubation for 1 week. Symptoms were identical to those seen in the field and the fungus was re-isolated, completing Koch's postulates. We conclude that the pathogen causing anthracnose fruit of blueberry in New Jersey is caused by a single species of Colletotrichum, namely C. fioriniae. This is the first report of this species causing fruit rot of blueberry in New Jersey.