Characterization of Cylindrocarpon Species Associated with Black Foot Disease of Grapevine in Spain

In this work, 82 Cylindrocarpon isolates associated with black foot disease of grapevines in Spain were studied by means of phenotypical characterization, DNA analyses, and pathogenicity tests. Partial sequences of the beta-tubulin (BT) gene, BT1, were amplified using primers BT1a and BT1b. A unique and conserved 52-bp insertion in the BT1 sequence, which is a specific marker for C. macrodidymum, was found in 56 of the isolates. The rest of the isolates (26) were identified as C. liriodendri. The BT phylogeny grouped all the isolates of each species into two well-supported clades. Phenotypical data were subjected to multivariate factorial analysis. According to this study, the isolates were clearly separated into two groups which were in agreement with BT species identification. C. macrodidymum isolates were differentiated from C. liriodendri by producing fewer conidia, presenting longer and wider macroconidia, and lower growth rate at 5 and 10°C. Selected isolates of each species inoculated onto rooted cuttings of grapevine rootstock cv. 110 R caused typical black foot disease symptoms. This is the first report of C. liriodendri and C. macrodidymum causing black foot disease of grapevines in Spain.