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Trunk and scaffold canker diseases (TSCDs) of almond cause significant yield and tree losses and reduce the lifespan of orchards. In California, several pathogens cause TSCDs, including Botryosphaeriaceae, Ceratocystis destructans, Eutypa lata, Collophorina hispanica, Pallidophorina paarla, Cytospora, Diaporthe, and Phytophthora spp. Field diagnosis of TSCDs is challenging because symptom delineation among the diseases is not clear. Accurate diagnosis of the causal species requires detailed examination of symptoms and subsequent isolation on medium and identification using morphological criteria and subsequent confirmation using molecular tools. The process is time-consuming and difficult, particularly as morphological characteristics are variable and overlap among species. To facilitate diagnosis of TSCD, we developed PCR assays using 23 species-specific primers designed by exploiting sequence differences in the translation elongation factor, ß-tubulin, or internal transcribed spacer gene. Using genomic DNA from pure cultures of each fungal and oomycete species, each primer pair successfully amplified a single DNA fragment from the target pathogen but not from selected nontarget pathogens or common endophytes. Although 10-fold serial dilution of fungal DNA extracted from either pure cultures or infected wood samples detected as little as 0.1 pg of DNA sample, consistent detection required 10 ng of pathogen DNA from mycelial samples or from wood chips or drill shavings from artificially or naturally infected almond wood samples with visible symptoms. The new PCR assay represents an improved tool for diagnostic laboratories and will be critical to implement effective disease surveillance and control measures. [ABSTRACT FROM AUTHOR]

In eastern North America, Phomopsis cane and leaf spot, caused by Phomopsis viticola, is a foliar disease of grape but, in the Mediterra-nean climate of western North America, P. viticola is primarily associ-ated with wood cankers, along with other Diaporthe spp. To determine the identity of wood-infecting Diaporthe spp. in eastern North Amer-ica, 65 isolates were cultured from 190 wood-canker samples from 23 vineyards with a history of Phomopsis cane and leaf spot. Identifica-tion of 29 representative isolates was based initially on morphology, followed by phylogenetic analyses of DNA sequences of the ribosomal DNA internal transcribed spacer region, elongation factor subunit 1-a, and actin in comparison with those of type specimens. Three species were identified: P. viticola, P. fukushii, and Diaporthe eres. Inoc-ulations onto woody stems of potted Vitis labruscana 'Concord' and V. vinifera 'Chardonnay' showed that D. eres and P. fukushii were pathogenic (mean lesion lengths of 7.4 and 7.1 mm, respectively, compared with 3.5 mm for noninoculated controls) but significantly less so than wood-canker and leaf-spot isolates of P. viticola (13.5 mm). All three species infected pruning wounds of Concord and Char-donnay in the field. Our finding of pathogenic, wood-infecting Di-aporthe spp. in all 23 vineyards suggests a frequent co-occurrence of the foliar symptoms of Phomopsis cane and leaf spot and wood can-kers, although the latter are not always due to P. viticola. [ABSTRACT FROM AUTHOR]