First Report of Stem Canker of Salsola tragus Caused by Diaporthe eres in Russia.

Salsola tragus L. (Russian thistle) is a problematic invasive weed in the western United States and a target of biological control efforts. In September of 2007, dying S. tragus plants were found along the Azov Sea at Chushka, Russia. Dying plants had irregular, necrotic, canker-like lesions near the base of the stems and most stems showed girdling and cracking. Stem lesions were dark brown and contained brown pycnidia within and extending along lesion-free sections of the stems and basal portions of leaves. Diseased stems were cut into 3- to 5-mm pieces and disinfested in 70% ethyl alcohol. After drying, stem pieces were placed into petri dishes on the surface of potato glucose agar. Numerous, dark, immersed erumpent pycnidia with a single ostiole were observed in all lesions after 2 to 3 days. Axenic cultures were sent to the Foreign Disease-Weed Science Research Unit, USDA, ARS, Ft. Detrick, MD for testing in quarantine. Conidiophores were simple, cylindrical, and 5 to 25 × 2 µm (mean 12 × 2 µm). Alpha conidia were biguttulate, one-celled, hyaline, nonseptate, ovoid, and 6.3 to 11.5 × 1.3 to 2.9 µm (mean 8.8 × 2.0 µm). Beta conidia were one-celled, filiform, hamate, hyaline, and 11.1 to 24.9 × 0.3 to 2.5 µm (mean 17.7 × 1.2 µm). The isolate was morphologically identified as a species of Phomopsis, the conidial state of Diaporthe (1). The teleomorph was not observed. A comparison with available sequences in GenBank using BLAST found 528 of 529 identities with the internal transcribed spacer (ITS) sequence of an authentic and vouchered Diaporthe eres Nitschke (GenBank DQ491514; BPI 748435; CBS 109767). Morphology is consistent with that of Phomopsis oblonga (Desm.) Traverso, the anamorph of D. eres (2). Healthy stems and leaves of 10 30-day-old plants of S. tragus were spray inoculated with an aqueous suspension of conidia (1.0 × 106 alpha conidia/ml plus 0.1% v/v polysorbate 20) harvested from 14-day-old cultures grown on 20% V8 juice agar. Another 10 control plants were sprayed with water and surfactant without conidia. Plants were placed in an environmental chamber at 100% humidity (rh) for 16 h with no lighting at 25°C. After approximately 24 h, plants were transferred to a greenhouse at 20 to 25°C, 30 to 50% rh, and natural light. Stem lesions developed on three inoculated plants after 14 days and another three plants after 21 days. After 70 days, all inoculated plants were diseased, four were dead, and three had more than 75% diseased tissue. No symptoms occurred on control plants. The Phomopsis state was recovered from all diseased plants. This isolate of D. eres is a potential biological control agent of S. tragus in the United States. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 878717). Nucleotide sequences for the ribosomal ITS regions (ITS 1 and 2) were deposited in GenBank (Accession No. EU805539). To our knowledge, this is the first report of stem canker on S. tragus caused by D. eres. References: (1) B. C. Sutton. Page 569 in: The Coelomycetes. CMI, Kew, Surrey, UK, 1980. (2) L. E. Wehmeyer. The Genus Diaporthe Nitschke and its Segregates. University of Michigan Press, Ann Arbor, 1933.

First Report of Anthracnose of Salsola tragus Caused by Colletotrichum gloeosporioides in Russia.

In October of 2006, dying Salsola tragus L. (Russian thistle, tumbleweed), family Chenopodiaceae, plants were found along the Azov Sea at Chushka, Russia. Approximately 40 plants in the area were diseased and almost 80% of these were dying. Plants were approximately 1 m tall × 0.5 m wide. Dying plants had irregular, necrotic lesions along the length of the stems. Leaves of these plants were also necrotic. Lesions on stems and leaves were dark brown and usually coalesced. Diseased stems were cut into 3- to 5-mm pieces, disinfested in 70% ethyl alcohol, and then placed onto the surface of potato glucose agar (PGA). Numerous, waxy, subepidermal acervuli with 110 µm long (mean) black setae were observed in all of the lesions after 2 to 3 days. Conidiophores were simple, short, and erect. Conidia were one-celled, hyaline, ovoid to oblong, falcate to straight, and measured 12.9 to 18.0 × 2.8 to 5.5 µm (mean 15.6 × 4.2 µm). Appressoria formed 24 h after placing conidia on a dialysis membrane over 20% V8 juice agar. Appressoria measured 4.0 to 13.9 × 2.4 to 8.8 µm (mean 7.0 × 5.2 µm). These characters conformed to the description of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz. (1). A voucher specimen was deposited with the U.S. National Fungus Collections, Beltsville, MD (BPI 878389). Nucleotide sequences for the internal transcribed spacers (ITS 1 and 2) were deposited in GenBank (Accession No. EU530697) and aligned with ITS sequences of two other isolates from S. tragus. There was 100% similarity to each isolate, one from Greece (Accession No. DQ344621) and one from Hungary (Accession No. EU805538). Axenic cultures on PGA were sent to the Foreign Disease-Weed Science Research Unit, USDA, ARS, Fort Detrick, MD for testing in quarantine. Conidia were harvested from 14-day-old cultures grown on 20% V8 juice agar, and healthy stems and leaves of 30-day-old plants of S. tragus (13 plants) were spray inoculated with an aqueous conidial suspension of 1.0 × 106 conidia/ml plus 0.1% v/v polysorbate 20. Another 13 control plants were sprayed with water and surfactant without conidia. Plants were placed in an environmental chamber at 100% humidity for 16 h in the dark at 25°C. After approximately 24 h, all plants were transferred to a greenhouse at 20 to 25°C, 30 to 50% relative humidity, and natural light augmented by 12-h light periods with 500 W sodium vapor lights. Lesions developed on stems of all inoculated plants after 7 days. After 14 days, nine plants were dead and all inoculated plants were dead after 3 weeks. No symptoms developed on control plants. C. gloeosporioides was reisolated from stem pieces of all inoculated plants, and the morphology of the reisolated pathogen was the same as that of the initially isolated pathogen. To our knowledge, this is the first report of anthracnose caused by C. gloeosporioides on S. tragus in Russia. Reference: (1) B. C. Sutton. Page 15 in: Colletotrichum Biology, Pathology and Control. J. A. Bailey and M. J. Jeger, eds. CAB International, Wallingford, UK, 1992.

First Report of Leaf Spot Caused by Periconia igniaria on Yellow Starthistle in Russia.

Yellow starthistle (YST), Centaurea solstitialis L., is a weedy plant that is widely distributed in the Krasnodar Region of Russia. It is also an aggressive invasive weed in the western United States and a target of biological control efforts. In the summer of 2006, several hundred diseased plants were found near Taman, Russia. Symptoms of the disease were yellow, water-soaked leaf spots. Diseased leaves were collected, air dried, and sent to the Russian State Collection of Phytopathogenic Organisms at the All Russia Institute of Phytopathology (ARIP). The fungus isolated from the diseased leaves conformed to Periconia igniaria E.W. Mason & M.B. Ellis (teleomorph Didymosphaeria igniaria C. Booth) (1). Colonies of the fungus grew rapidly on potato glucose nutrition medium with aerial mycelium from fluffy to pressed and colorless at the beginning and darkening to black with age. The medium side of the colonies gradually became violet purple to wine colored. Conidiophores had aerial mycelia as much as 550 µm long and 9 to 13 µm wide tapering to 6 to 10 µm. Conidiophores were dark with short, swollen branched stipes. Conidia, formed in short twisted chains, were spherical, dark brown, 7 to 9 µm in diameter, and covered by 1 µm long spines. Yellow starthistle plants were grown in growth chambers with day/night air temperatures of 26 to 28/20 to 22°C, 60 to 70% relative air humidity, and 10,000 lx light for 16 h. Fifteen plants in the rosette stage were spray inoculated with an aqueous suspension of P. igniaria conidia at 5 × 106 conidia/ml and 5 ml per plant. Disease on leaves was observed on all plants 3 to 4 weeks after inoculation when the plants started to bolt. When the plants reached flowering stage, diffused yellow spots were observed on stems and inflorescences and all flowers died. Diseased leaves were surface disinfested and put on potato saccharose nutrition medium. P. igniaria was reisolated from 3 to 5 leaves of each plant and from flowers and stems that developed from 10 inoculated rosettes. Flowers of 10 YST plants were also inoculated with P. igniaria isolated from the previously inoculated plants. Disease developed in the flowers of all inoculated plants, and the symptoms were identical to those observed when rosettes were inoculated and disease followed bolting and flowering. No symptoms developed on four noninoculated plants included in each test. Internal transcribed spacer (ITS) sequences of the fungus were obtained and compared with sequences from GenBank. An uncultured soil fungus and three isolates of P. macrospinosa Lefebvre & Aar.G. Johnson produced the best homology (96%). No sequences for P. igniaria were available for comparison, but the description of P. macrospinosa (conidia 18 to 32 µm in diameter with 2.5 to 6 µm long spines) is clearly different than our isolate. ITS sequences for our isolate have been deposited in GenBank (Accession No. EU367468) and a voucher specimen has been deposited with the U.S. National Fungus Collection (BPI 878355). To our knowledge, this is the first report of P. igniaria causing disease on YST. Live cultures are being maintained at the Russian State Collection of Phytopathogenic Organisms in ARIP. Reference: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, UK, 1971.