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

Abstract

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.

Insights into the genus Diaporthe: phylogenetic species delimitation in the D. eres species complex

“…In addition, it is considered a pathogen with plant health inspection and quarantine significance (Cline and Farr 2006). Several recent disease reports of D. eres include cane blight on blackberry in Croatia (Vrandečić et al 2010), pathogen of butternut (Juglans cinerea) in Connecticut (Anagnostakis 2007), shoot blight and canker disease of peach in Greece (Thomidis and Michailides 2009), stem canker of Salsola tragus in Russia (Kolomiets et al 2009), on Vaccinium species in Europe (Lombard et al 2014) and association with wood cankers of grapevines in Croatia (Kaliterna et al 2012) and in the USA (Baumgartner et al 2013). It is reported less frequently on herbaceous plants such as the Cucurbitaceae (Garibaldi et al 2011;Gomes et al 2013).…”

First report of the fungus Diaporthe phaseolorum on sunflower in Russia

“…Data on the biological diversity and distribution of certain Diaporthe species across the Russian Federation, especially the species that have a significant economic impact, need to be clarified. To the best of our knowledge, there are only two Diaporthe species that were found in the Russian Federation and confirmed by molecular studies: D. eres on a Salsola tragus [4] and D. phaseolorum on a tomato (Gurkina TA, First report of the fungus Phomopsis phaseoli on tomato, International scientific conference of students and young scientists "Lomonosov-2018", April 2018).…”

Fungal and Fungal-like Diseases of Halophytes in the Mediterranean Basin: A State-of-the-Art Review

“…Although considered noxious weeds, both S. kali and S. tragus can be agronomically exploited, especially as forage for cattle and sheep [189]. Most of the studies describing the occurrence of plant pathogens on such species have explored the potential of causal agents to be employed as bioherbicides [130][131][132]190]. For instance, the potentiality of the anthracnose agent Colletotrichum salsolae (Glomerellales) has been widely investigated for the control of S. tragus [130,131].…”

“…The stem canker agent Diaporthe eres (Diaporthales) was also assessed as a mycoherbicide [132]. It was isolated in Russia from dark necrotic lesions at the base of the stem of symptomatic S. tragus plants.…”