Characterization of Diaporthe australafricana and Diaporthe spp. Associated with Stem Canker of Blueberry in Chile

Abstract

Stem canker and dieback are important factors that limit the longevity and reduce the yield of blueberry (Vaccinium spp.) in Chile. In this study, species of Diaporthe associated with blueberry were isolated and identified. The internal transcribed spacer (ITS) regions of ribosomal DNA of 30 isolates and the translation elongation factor 1-α (EF1-α) of 14 isolates were sequenced, analyzed, and compared with their morphological and pathological characteristics. The molecular analysis of ITS sequences by alignment with those of ex-type strains deposited in GenBank and morphological characteristics allowed the identification of Diaporthe ambigua, D. australafricana, D. neotheicola, D. passiflorae, and Diaporthe sp. 1. However, morphology alone was insufficient to identify these species. The combined analysis of ITS and EF1-α gene sequences grouped the Chilean blueberry isolates in the same five groups obtained in the ITS analysis. Pathogenicity tests conducted with attached and detached blueberry shoots (<1 year old) and stems (1 to 2 years old) confirmed that isolates of these Diaporthe spp. were pathogenic. The symptoms were reproducible and consisted of necrotic reddish-brown cankers on blueberry shoots and stems. These isolates were capable of infecting blueberry fruit, causing a soft decay, suggesting that they were tissue nonspecific and were also pathogenic on shoots of apple, grapevine, and pear. D. australafricana was the most frequently isolated species and D. ambigua, D. australafricana, and D. passiflorae were highly virulent in shoots, stems, and fruit of blueberry. This study showed that at least four species of Diaporthe are primary pathogens, capable of causing stem canker symptoms on blueberry, and this is the first report of D. ambigua, D. neotheicola, and D. passiflorae attacking this host.

Identification and characterization of Diaporthe vaccinii Shear causing upright dieback and viscid rot of cranberry in Poland

“…Several species from the genus Diaporthe were reported as pathogenic to Vaccinium spp. plants in Europe, causing twig blight, stem cankers and fruit rot (Farr et al 2002b;Tadych et al 2012;Elfar et al 2013;Lombard et al 2014). On the basis of multi-locus DNA sequences analysis, including beta-tubulin, calmodulin, translation elongation factor 1-alpha and the internal transcribed spacer (ITS) regions of the nuclear rDNA, and morphological characteristics, Lombard et al (2014) classified the collection of European isolates from Vaccinium spp., initially identified as D. vaccinii based on host association, to six species, including D. vaccinii, D. viticola, D. eres and three newly described as D. asheicola, D. baccae and D. sterilis.…”

“…Confirmation of the pathogen identity is required at least by analysing the nuclear ribosomal DNA (rDNA) internal transcribed spacer (ITS) region in axenic cultures of D. vaccinii (OEPP/EPPO 2009). A higher level of confidence in the identification can be obtained by a multigene approach to phylogenetic analyses (Udayanga et al 2012;Elfar et al 2013;Lombard et al 2014).…”

Genetic diversity of Chondrostereum purpureum (Pers.) Pouzar causing silverleaf disease on blueberries in Chile

“…ex Fr., Diaporthe spp. (Elfar et al 2013), Neofusicoccum spp. (Espinoza et al 2009, Pérez et al 2014, Phoma spp.…”

“…The use of differential rates in nucleotide changes in nuclear ribosomal sequences has enabled the detection and comparison of fungus isolates at inter-and intraspecific levels attacking blueberries (Espinoza et al 2008, Elfar et al 2013, Pérez et al 2014) and other species (Iturralde 2005, Toju et al 2012. For example, the combined analysis of ITS and EF1-alfa gene sequences were able to identified five species of Diaphortein (Elfar et al 2013) the ITS1-5.8S and ITS2-28S to detect Neofusicoccum nonquaesitum (Pérez et al 2014) and Pestalotiopsis ssp.…”

“…For example, the combined analysis of ITS and EF1-alfa gene sequences were able to identified five species of Diaphortein (Elfar et al 2013) the ITS1-5.8S and ITS2-28S to detect Neofusicoccum nonquaesitum (Pérez et al 2014) and Pestalotiopsis ssp. and Truncatella sp.…”