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ABSTRACTFatty acid methyl ester (FAME) analyses can be useful for distinguishing microbial species. This study conducted FAME analyses on 14 fungal species known to cause grapevine trunk diseases. FAME profiles were dominated by oleic acid, albeit profiles were characteristic enough to separate species. Discriminant analyses suggested that palmitoleic acid/sapienic acid, pentadecylic acid, and an unsaturated 17-carbon fatty acid (17:1ω8 c)could explain 79.8% of the variance in the profiles among species in the first three discriminant functions. FAME profile libraries were created for use in a commercialized software, which was able to accurately identify isolates to the species level, with a low rate (9.4%) of samples to be reassessed. Dendrograms created using neighbor-joining cluster analyses with data from FAME profiles were compared with those using internal transcribed spacer (ITS) region sequences. This revealed that FAME profiles, albeit useful for tentative species identification, should not be used for determining phylogenetic relationships because the dendrograms were significantly unconcordant. Regardless, these results demonstrated the potential of FAME analyses in quickly and initially identifying closely related fungal species or confirming conclusions from other species identification techniques that would require independent validation.

Cytosporaspecies 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 Cytosporaspecies 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 Cytosporaspecies requires further investigation as most species were associated with severe dieback and decline of diverse and economically important fruit and nut crops in California.

Diaporthe ampelina, causal agent of Phomopsis cane and leaf spot of grapevine (Vitis viniferaL.) is isolated frequently from grapevine wood cankers, causing Phomopsis dieback. The latter disease is associated with four other Diaporthespecies, three of which also are reported from hosts other than grape. To better understand the role of this Diaporthecommunity in Phomopsis dieback of grapevine and the potential for infection routes among alternate hosts, 76 Diaportheisolates were recovered from wood cankers of cultivated grape, pear, apricot, almond and the wild host willow in four California counties. Isolates were characterized morphologically and assigned to species based on multigene sequence analyses. This study identified eight Diaporthespecies from grapevine and one novel taxon from willow, D. benedicti. We report the first findings of D. australafricanaand D. novemin North America. Our findings also expand the host ranges of D. ambiguato apricot and willow, D. australafricanato almond and willow, D. chamaeropisto grapevine and willow, D. foeniculinato willow and D. novemto almond. The generalists D. ambiguaand D. ereswere the most genetically diverse species, based on high nucleotide and haplotypic diversity, followed by the grapevine specialist D. ampelina. Analyses based on multilocus linkage disequilibrium could not reject the hypothesis of random mating for D. ambigua, which is further supported by relatively high haplotypic diversity, reports of both mating types and reports of successful matings in vitro. Pathogenicity assays revealed that D. ampelinawas the most pathogenic species to grapevine wood.