ABSTRACT

Black foot disease of grapevine is caused by the fungal species Cylindrocarpon liriodendri and C. macrodidymum. These pathogens affect grapevines in nurseries and young vineyards, mainly in one to five year old plants.
In this Thesis a collection of 82 Spanish isolates of Cylindrocarpon, obtained from grapevines showing symptoms of black foot disease in nurseries and young vineyards, have been characterized. All isolates were identified by sequence analyses of ß-tubulin gene, region BT1, and ITS ribosomal DNA; and the multivariate factorial analysis of the phenotypical variables: colony morphology, production of conidia and the colony daily growth rate at the different temperatures studied. Thus, 26 isolates corresponded to the species C. liriodendri and 56 to C. macrodidymum.
Rooted cuttings of grapevine rootstock cv. 110 R were inoculated with representative isolates of C. liriodendri and C. macrodidymum. All inoculated plants developed the typical symptoms of black foot disease, confirming the pathogenicity of both species to grapevine.
The Inter-Simple Sequence Repeat technique was used to study the genetic diversity of C. liriodendri and C. macrodidymum. The results showed genetic diversity in both pathogens, which was higher in C. macrodidymum. Moreover, the pathogenicity tests performed with isolates selected from both species in grapevine seedlings obtained from cv. Tempranillo, detected virulence diversity in C. macrodidymum.
All isolates of C. liriodendri and C. macrodidymum were characterized to determine the possible presence of micovirus using a method based in cellulose chromatography. No double stranded RNAs were detected in any of them. 
Regarding to control, in vitro experiments indicated that both, fungicides and hot-water treatment, have a strong potential to control these Cylindrocarpon species. The fungicides captan, didecyl dimethyl ammonium chloride, cubiet, copper oxychloride and thiram, effectively reduced conidial germination in both species; while carbendazim, prochloraz, imazalil and chinosol showed a good effect reducing the growth of the mycelia. Results of hot-water treatments showed that treatments at 46 ºC were enough to inhibit completely the germination of conidia of C. liriodendri and C. macrodidymum, while to avoid the growth of the mycelia treatments of at least 48 ºC, applied during 60 minutes were necessary.