ABSTRACT
German statice (Goniolimon tataricum, synonym Limonium tataricum) is a popular ornamental species, which is frequently used in bouquet arrangements. During a field survey of statice farms in the Plovdiv Region of Bulgaria (August 2007), lesions were observed predominantly on the peduncles and rarely on wilted leaves of 2- and 3-year-old plants. Symptoms appeared on the base of peduncles as irregular, brown necrotic lesions ranging from 30 to 40 mm that coalesced, whereas lesions on leaves were initially round to elliptical with dimensions from 5 to 15 mm and developed a necrosis that subsequently spread toward the petioles. Rounded and elongated setose acervuli were observed on the lesions of peduncles. Isolations on potato dextrose agar (PDA) produced fungal colonies that initially were whitish but turned gray 4 to 5 days after incubation at 25°C. Falcate, hyaline, and aseptate conidia with mean dimensions of 22.0 × 4.5 µm, ranging from 18.3 to 25.0 × 4.2 to 5.8 µm, were observed from acervuli of both naturally infected peduncles and PDA-cultured colonies. Pathogenicity of the fungus (three single-conidium representative isolates) was tested by spray inoculating 4-month-old intact plantlets (12 to 15 fully developed leaf stage) with a conidial suspension (106 conidia/ml, 15 ml/plant) and maintaining them in a humidity chamber for 30 h. Plants sprayed with sterile water served as controls. There were three replicates per treatment per isolate and the experiment was conducted twice at room temperature (22 to 26°C). After 10 to 12 days, the spray-inoculated plants exhibited light brown lesions mainly on the older leaves that gradually expanded and caused leaf mortality. The pathogen was reisolated from all inoculated samples but not from any of the control and symptomless treatments, thus fulfilling Koch's postulates. It should be noted that symptoms caused by the pathogen in artificially inoculated plants were seen as wilting of petioles and leaves, as opposed to necrotic lesions observed on leaves under field conditions. This may be related to the method of inoculation, leaf age, and texture, as well as environmental factors affecting symptomology under natural field conditions. Sequence analysis of the rDNA internal transcribed spacer region of three representative isolates (GenBank Accession Nos. FJ236461-FJ236463) showed the fungus to be 99% similar to an isolate of Colletotrichum dematium (GenBank Accession No. AJ301954), consistent with the observed morphological characters. On the basis of observed symptoms, morphology, and molecular characterization, it can be concluded that C. dematium is the causal agent of anthracnose of German statice in Bulgaria. To our knowledge, this is the first report of this pathogen on G. tataricum in Bulgaria, although it has been reported that C. dematium (1) and C. gloeosporioides (1-3) may attack other Limonium species. References: (1) C. F. Hong et al. Plant Pathol. Bull. 15:241, 2006. (2) T. Kagiwata. J. Agric. Sci. (Jpn.) 31:101, 1986. (3) M. Maymon et al. Phytopathology 96:542, 2006.
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.
