Molecular phylogeny of Cytospora species associated with canker diseases of fruit and nut crops in California, with the descriptions of ten new species and one new combination

Abstract

Cytospora species are destructive canker and dieback pathogens of woody hosts in natural and agroecosystems around the world. In this genus, molecular identification has been limited due to the paucity of multi-locus sequence typing studies and the lack of sequence data from type specimens in public repositories, stalling robust phylogenetic reconstructions. In most cases a morphological species concept could not be applied due to the plasticity of characters and significant overlap of morphological features such as spore dimensions and fruiting body characters. In this study, we employed a molecular phylogenetic framework with the inclusion of four nuclear loci (ITS, translation elongation factor 1-alpha, actin, and beta-tubulin) to unveil the biodiversity and taxonomy of this understudied important genus of plant pathogens. Phylogenetic inferences based on 150 Californian isolates revealed 15 Cytospora species associated with branch and twig cankers and dieback of almond, apricot, cherry, cottonwood, olive, peach, pistachio, plum, pomegranate, and walnut trees in California. Of the 15 species recovered in this study, 10 are newly described and typified, in addition to one new combination. The pathogenic status of the newly described Cytospora species requires further investigation as most species were associated with severe dieback and decline of diverse and economically important fruit and nut crops in California.

Seasonal changes in population structure of the ambrosia beetle Xylosandrus compactus and its associated fungi in a southern Mediterranean environment

“…By contrast, to the best of our knowledge, this study reports for the first time the association of Cytospora sp., A. pullulans, X. recifei and C. rosea with this ambrosia beetle. Cytospora species are canker and dieback pathogens of woody hosts [71,72], whereas A. pullulans, X. recifei and C. rosea have not been reported as pathogens, and their role still needs to be determined and merits further study. As reported by Hofstetter et al (2006), some fungi consistently carried by bark beetles have been found to be commensal or even antagonistic [73].…”

The genus Juglanconis (Diaporthales) on Pterocarya

“…Recently, substantial progress was made to tackle the species diversity of several diaporthalean lineages involved in plant diseases by the application of multi-gene phylogenies in combination with morphological studies, e.g. in Coniella (Alvarez et al 2016 ), Cytospora (Lawrence et al 2018 ), Diaporthe (Guarnaccia et al 2018 ) and Harknessia (Marin-Felix et al 2019 ). These studies revealed a number of undescribed species on various plant hosts of economic importance in silvi-, agri- and horticulture, but also improved our knowledge on the circumscription and host range of already described species.…”

Water Stress Enhances the Progression of Branch Dieback and Almond Decline under Field Conditions

“…have been already reported in California as canker pathogens of several fruit and nut crops including Prunus spp. such as almond, apricot or peach [ 30 ].…”