First report of Colletotrichum acutatum sensu lato causing anthracnose on Vitis vinifera in UK.

In November 2009, twelve specimens of grapevine (Vitis vinifera) cv. Brant in the area of Penrith, Cumbria in the United Kingdom were showing necrotic black leaf spotting and abundant orange sporulation on the upper leaf surface. Infected plant material was submitted to the FERA (Food and Environment Research Agency) Plant Clinic for diagnosis. The tissue samples were surface sterilised for one minute in 20% sodium hypochlorite and cultured on potato dextrose agar. Monoconidial isolates grown at 25°C with a 12 hour light period had light grey cottony aerial mycelium with colour ranging from whitish to dark grey on the reverse side of the colony. The cultures had orange spores organised in small masses and dark melanised structures similar to acervuli. Disease symptoms and morphology suggested that a member of the genus Colletotrichum caused the disease. Given the fact that strains of Colletotrichum often belong to aggregates of species that can be difficult or impossible to distinguish morphologically, a representative isolate was sent to the University of Warwick for further analysis. Total DNA was extracted using a modified Chelex100 protocol (Baroncelli, 2012). The internal transcribed spacer region (ITS) of the nuclear ribosomal DNA repeat region was amplified and sequenced using the universal primers ITS4 and ITS5. The resulting sequence was 100% identical to C. acutatum species sequences obtained by a BLAST search in GenBank. Due to the low resolution of this locus in the C. acutatum species complex, two other loci were used to further characterise the isolate: primers TB5 and TB6 were used for the amplification and sequencing of the variable region 1, spanning the exons 3, 4, 5, and part of 6 of the β-tubulin (TUB) gene (Baroncelli, 2012). Primers GDF1 and GDR1 were used to amplify a 200-bp intron region of the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene (Baroncelli, 2012). Sequences were deposited in GenBank (Accession No. KF834203 for ITS, KF834204 for TUB and KF834205 for GAPDH). Using BLAST searches the sequences obtained in this study were 100% identical to some sequences deposited in GenBank as C. clavatum and as C. godetiae. C. clavatum was described by Faedda et al. (2011), but is synonymous to C. godetiae , the latter name having priority (see Damm et al., 2012). The phylogenetic analysis carried out with the sequences obtained from GenBank revealed that the isolate clustered within the C. godetiae clade (Damm et al., 2012), as suggested by the BLAST results. Previous studies have demonstrated that the pathogen is present on Vitis spp. in different countries worldwide such as the USA, Australia and Japan (Whitelaw-Weckert et al., 1990; Yamamoto et al., 1990). To our knowledge, this is the first report of anthracnose on V. vinifera by Colletotrichum in the UK, where V. vinifera is a popular ornamental plant and is also grown commercially for dessert and wine grapes. Wine grapes are a small but economically important crop in southern England and with climate change, grape production is an expanding industry there. Reports of Colletotrichum spp. on new hosts and in new geographic locations are essential for the study and for control of these often polyphagous and flexible pathogens. C. godetiae is frequently found on Fragaria spp. and other hosts and it is likely that Fragaria may act as a reservoir of inoculum for Vitis and vice versa. The isolate has been deposited in the CBS culture collection Utrecht, The Netherlands (CBS 129951).