First Report of Anthracnose Fruit Rot Caused by Colletotrichum acutatum on Pepper and Tomato in Bulgaria

Abstract

In the late summer of 2005, sporadic and unusual damage was observed on pepper (Capsicum annuum cv. Kurtovska kapia and local cv. Ribka) on two farms and tomato (Lycopersicon esculentum cv. Florida 47) fruits on one farm in the Plovdiv Region of Bulgaria. Dry, round, sunken zones (10 to 20 mm) were observed on pepper fruits that preserved their natural skin color even after black acervuli containing orange masses of conidia appeared. Eventually, the lesions turned brown, coalesced, and the fruits mummified on the plants. Tomato fruits developed similar symptoms, with less prominent discoloration and fewer acervuli. The pathogen was easily isolated from both hosts on potato dextrose agar where it formed white-to-gray colonies with salmon orange pigmentation on the reverse side of the plates. Conidia that formed were hyaline, fusiform, aseptate, and measured 13.3 to 17.4 × 3.5 to 5.5 μm and 11.6 to 15.5 × 4.1 to 5.0 μm for pepper and tomato isolates, respectively. Both cultural and morphological characteristics of the isolates were similar to those described for Colletotrichum acutatum (3). Koch's postulates were performed with two representative isolates from each host by artificial inoculation of healthy, green pepper and ripe tomato fruits from the respective cultivars. Fruits were wound inoculated with a sterile scalpel, and small agar plugs (3 to 4 mm) containing 7-day-old sporulating cultures were placed on each wound (five fruits per isolate), or by pipette tip-pricking and pipetting a 5-μl droplet of a conidial suspension (5 × 106 conidia ml–1) on each wound. The same number of wounded, noninoculated fruits was used as a control. Fruits were maintained in a humidity chamber at 22 to 25°C, and 4 days later, sunken necrotic zones were observed around the wounds of inoculated fruit, whereas control fruits remained symptomless. The pathogen was subsequently reisolated from the inoculated diseased tissues but not from the control fruits. Species-specific PCR (using primer pair CaInt2/ITS4) (2,4) of genomic DNA from three representative isolates (two from pepper and one from tomato) resulted in an amplification product of 490 bp, specific for C. acutatum, further confirming the identity of the pathogen. To our knowledge, this is the second report of C. acutatum in Bulgaria (1), and the first occurrence of that agent on tomato and pepper in this country. References: (1) S. G. Bobev et al. Plant Dis. 86:1178, 2002. (2) S. Freeman et al. Phytopathology 91:586, 2001. (3) P. S. Gunnell and W. D. Gubler. Mycologia 84:157, 1992. (4) M. L. Lewis Ivey et al. Plant Dis. 88:1198, 2004.