Elderberry (Sambucus spp.) is a specialty crop grown primarily in North America and Europe for niche markets (Charlebois et al., 2010; Mohebalian et al., 2012). American elderberry [Sambucus nigra L. ssp. canadensis (L.) Bolli] plants thrive in moist, well-drained soils and are multistemmed shrubs with odd-pinnately compound leaves. Flowering occurs in early summer and fruit-bearing umbels are generally harvested in late July and August (Finn et al., 2008; Zomlefer, 1994). For commercial plantings, some fruit can be harvested the year of planting. Elderberry fruit yield for mature (5-year-old) plants at a 1.2 × 3.7 m spacing typically averages 4580 kg·ha−1, with replanting of improved cultivars expected 25 years after establishment (Godsey, 2012).
‘Adams II’, ‘Bob Gordon’, ‘Ozark’, ‘Scotia’, ‘Wyldewood’, and ‘York’ are American elderberry cultivars commonly grown in the United States (Finn et al., 2008; Warmund et al., 2016). ‘Marge’, a productive European elderberry cultivar [Sambucus nigra L. ssp. nigra (L.)], is becoming popular, with several new plantings in the eastern United States (Thomas et al., 2015b). To date, these cultivars, as well as others grown in North America and Europe, were selected from wild germplasm for improved plant vigor, inflorescence position, high fruit yield, ripening date, and pest resistance (Byers and Thomas, 2011; Byers et al., 2010; Charlebois et al., 2010).
Like other perennial fruit crops, pathogens may become visually evident and problematic as elderberry plantings mature (Warmund et al., 2019). Fungal pathogens causing cankers, leaf spots, blights, and root rots on elderberry have been reported by others (Charlebois et al., 2010; Pirone et al., 1978). Cytospora, Diplodia, Nectria, Neonectria, and Sphaeropsis spp. are fungi that have been associated with cankers and mortality of the distal end of elderberry canes (Charlebois et al., 2010). The incidence of cane dieback and foliar necrosis symptoms in early spring has been consistently observed in commercial elderberry plantings and potted plants grown in nurseries (Fig. 1) (M.R. Warmund, unpublished data).
Because little research has been conducted on pathogens of elderberry or their impact on host plants, studies were conducted to 1) identify the pathogen causally associated with cane dieback in Missouri; and 2) determine the effect of dieback on vegetative growth and flowering of selected elderberry cultivars inoculated with the fungal isolate recovered from symptomatic plants.
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