Persimmon trees are important for their fruit as well as their colorful fruit and foliage in the fall. Persimmon fruit (Japanese persimmon, Diospyros kaki cv. Fuyu) were collected in November 2008 from a tree in Windsor, NC, located in the Coastal Plain. Fruit were not symptomatic on the tree but developed dark lesions after harvest. Isolations from six fruit yielded seven isolates of Colletotrichum acutatum J. H. Simmonds. After incubation at 25°C under continuous light for 15 days on potato dextrose agar (PDA), all isolates had gray aerial mycelium, but the inverse sides of the plates of six isolates were maroon and one was beige. Masses of salmon-colored conidia were formed first in the center of the colonies, then were observed scattered across the colonies in older cultures. Conidia were hyaline, one-celled, elliptic with one or both ends pointed, and measured 8.1 to 16.3 × 3.1 to 5 μm. Setae and sclerotia were not observed. There were also dark structures measuring 1 to 10 mm that were partially embedded in the agar that contained conidia. Cultural and conidial characteristics of the isolates were similar to those of C. acutatum (3). PCR amplification was performed with the species-specific primer pair CaInt2/ITS4 (2) and genomic DNA from the original isolates and isolates obtained from inoculated fruit. An amplification product of approximately 490 bp, which is specific for C. acutatum, was observed. To fulfill Koch's postulates, persimmon fruit obtained from the grocery store were surface disinfested with 0.5% sodium hypochlorite and sterile filter paper disks dipped in conidial suspensions (1 × 105 conidia/ml) of two C. acutatum isolates (maroon and beige reverse) or sterile, deionized water were placed on the fruit. Three fruit were inoculated per treatment and the disks were placed on four locations on each fruit. Parafilm was wrapped around the diameter of the fruit to keep the filter paper disks moist and in place. Fruit were placed in moist chambers and incubated at 25°C. After 3 days, the Parafilm was removed and the fruit returned to the moist chambers. Small, dark lesions were observed on fruit inoculated with each isolate of C. acutatum when the filter paper disks were removed. Ten days after inoculation, dark lesions and acervuli with salmon-colored masses of conidia were observed on fruit inoculated with both isolates of C. acutatum and the fruit were soft. After 12 days, there were abundant masses of conidia and the inoculated areas were decayed. Control fruit remained firm and did not develop symptoms. Cultures obtained from the fruit and the conidia produced were typical of the isolates used to inoculate the fruit. C. acutatum has been reported to cause fruit rot on persimmon fruit in New Zealand (1). To our knowledge, this is the first report of C. acutatum on persimmon fruit in the United States.
References: (1) R. Lardner et al. Mycol. Res. 103:275, 1999. (2) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996. (3) B. C. Sutton. Page 523 in: Coelomycetes. Commonwealth Agricultural Bureaux, Great Britain. 1980.
