Characterization of Cadophora luteo-olivacea and C. melinii isolates obtained from grapevines and environmental samples from grapevine nurseries in Spain

Abstract

Fifty-eight Cadophora luteo-olivacea and three C. melinii isolates were recovered from grapevines showing black vascular streaking and decline symptoms characteristic of Petri disease, and from different stages of the grapevine nursery process in Spain. The isolates were studied by means of phenotypical characterization, DNA analysis and pathogenicity tests. The morphological characters studied included conidiophore, phialide and conidial morphology. Colony characters and pigment production on MEA, PDA and OA were also examined. Phenotypical data were subjected to cluster analysis, which clearly separated C.luteo-olivacea isolates into four groups. Mating tests were performed on all possible combinations for each Cadophora species but no sexual fruiting bodies were produced. Partial sequences of the nuclear ribosomal internal transcribed spacer (ITS), beta-tubulin (BT) and the elongation factor 1a (EF) were analysed, but no genetic variation occurred within the C. luteo-olivacea isolates or within the C. melinii isolates in any of the regions studied. Pathogenicity tests were conducted on 1-year-old grapevine cuttings of four different rootstocksusing four C. luteo-olivacea isolates and one isolate of C. melinii. All Cadophora isolates except the C.melinii isolate caused significantly longer lesions in the xylem of grapevine rootstocks than in the controls.