Abstract
Blueberries (Vaccinium corymbosum) are widely cultivated worldwide and largely consumed due to their known antioxidant and medicinal properties. Although Diaporthe species have been documented in Portugal as causal agents of blueberry twig blight and dieback, there is still scarce information on the species that cause these symptoms. Moreover, Diaporthe vaccinii, recently synonymized with D. eres, has been considered a concern to blueberry production worldwide. However, the current knowledge about its impact on blueberries remains unclear. The diversity of Diaporthe species associated with diseased blueberry plants were assessed through a national survey. A multilocus sequence analysis of the rDNA internal transcribed spacer (ITS) region, the translation elongation factor 1-alpha (tef1-α), β-tubulin (tub2), calmodulin (cal) and histone 3 (his3) genes unveiled the presence of Diaporthe ambigua, D. amygdali, D. crousii, D. foeniculina, D. hybrida, D. leucospermi, D. malorum and D. rudis. Moreover, all species were fully characterized based on a detailed morphological description. Diaporthe amygdali, D. hybrida, D. leucospermi and D. malorum are reported for the first time on diseased blueberries in Portugal. Results show that D. eres exhibited a high level of intraspecific variability within isolates, given that the strain CBS 160.32 might be a minor pathogen on blueberry plants, whereas CAA829 was revealed to be the most aggressive. Overall, this study also demonstrates that Diaporthe amygdali and D. eres may be two of the most aggressive species to blueberry plants. This study improves our understanding of the Diaporthe species and it’s causing of dieback and twig blight on Portuguese blueberry orchards. Additionally, the identification of these pathogens represents crucial information for blueberry producers to apply appropriate phytosanitary measures, as well as offering new insights into the potential pathogenicity of D. eres on this host.
Highlights
The genus Vaccinium L. includes nearly 450 species of perennial shrubs belonging to the family Ericaceae which have adapted to several climates [1]
These symptoms were accompanied by cankers that initially appeared as reddish to brown lesions on green twigs (Figure 2B) and later on the aged stems at the base (Figure 2C)
The present study is the first to assess Diaporthe species associated with blueberries from several orchards in Portugal, combining morphology and molecular data, which provide useful information to evaluate the pathogenicity potential of several species in different blueberry cultivars
Summary
The genus Vaccinium L. includes nearly 450 species of perennial shrubs belonging to the family Ericaceae which have adapted to several climates [1]. The species Vaccinium corymbosum (known as northern highbush blueberry) is a small-fruit crop, native to North America and commercially cultivated in Europe [2]. Due to the recognized high nutritional and medicinal value of fruits [3,4], blueberry production has been rapidly increasing worldwide. Due to the spread of blueberry plant material across continents, it is expected that several fungal pathogens may affect blueberry orchards, given their entry into new habitats [7]. Some of these pathogens, such as members of Botryosphaeriaceae, Pestalotiopsis sensu lato and Diaporthe can cause twig blight, stem cankers and dieback on blueberry plants [8,9,10]
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