Background and Aims Information on the natural infection rates of pruned canes caused by fungal trunk pathogens is scarce. This study aimed to determine the pathogenic mycoflora infecting the pruning wounds in two vineyards in Catalonia, Spain, each with a different level of trunk diseases, and in two pruning seasons. Methods and Results Vines were pruned in each vineyard in mid‐autumn leaving four to six buds. Three months later, pathogens were isolated and identified in 250 pruned canes chosen at random in each vineyard. Vines were then definitively pruned to two buds, and sampling for pathogen isolation and identification was repeated 3 months later. The main fungal pathogens identified in this study were Eutypa lata (0–0.4% of isolations), Neofusicoccum parvum (0–1.2%), Botryosphaeria dothidea (0–1.6%), Phomopsis spp. (0–1.6%), Cryptovalsa ampelina (0–3.2%), Phaeomoniella chlamydospora (0–12.0%) and Diplodia seriata (0.4–68.4%). A strong seasonal effect on pathogen infections was detected for most species, with a higher isolation percentage detected after the late pruning as compared with that of the early pruning. Conclusions Under the environmental conditions and the geographical location of this study, our results showed that the rate of natural infection of pruning wounds was lower following early pruning (autumn) than following late pruning (winter). Significance of the Study Early pruning could be used in combination with other control measures, such as chemical and biological wound protectants, to reduce the infections caused by the grapevine trunk pathogens during the pruning season in Catalonia, Spain. The infection risk, however, and potential effects of the early pruning on grape production should be considered in other environments before expanding this recommendation to other grapegrowing regions.

Grapevine trunk disease pathogens, and specifically Petri disease pathogens, can be spread by planting infected plants. Due to the increasing incidence of Petri disease and other young grapevine declines reported lately in Spain, a sampling of plants used before for new vineyards were carried out in 2002 and 2004. A total number of 208 plants (grafted and non grafted) were collected, of which 94 plants (45.2%) were infected with at least one of the following pathogens: Phaeomoniella chlamydospora, and species of Phaeoacremonium, Botryosphaeria, Cylindrocarpon, and Phomopsis. Species of the genera Phaeoacremonium and Botryosphaeria isolated in 2004 were identified using morphological and molecular characters. Species of Phaeoacremonium identified were P. aleophilum and P. parasiticum; and those of Botryosphaeria were B. obtusa, B. dothidea and B. parva. This is the first report of P. parasiticum and B. parva occurring on grapevines in Spain. Distribution of pathogens within the plants was studied in 2004. Phaeomoniella chlamydospora was not detected in the graft union of any plant; however, species of Botryosphaeria and Phomopsis were detected along the plant, but mainly in the graft union; Phaeoacremonium aleophilum was detected along the grafted plants, but not in rooted rootstocks. The results suggest that infected plants used for new plantings in Spain are an important source of primary inoculum of the pathogens associated with grapevine trunk diseases in the field.

Two indigenous arbuscular mycorrhizal (AM) fungi from the Mediterranean wine growing area in the Northeast of Spain were isolated and classified as Glomus intraradices Schenck & Smith. Both native fungi were found to increase the growth of the vine rootstock 110 Richter under greenhouse conditions compared with G. intraradices (BEG 72) and a phosphorus (P) fertilization treatment. The effectivity of field inoculation of Cabernet Sauvignon plants grafted on Richter 110 with the former native fungi and with G. intraradices BEG 72 in a replant vineyard severely infested by the root-rot fungus Armillaria mellea (Vahl ex Fr.) Kummer was assessed. The native fungi were not effective at enhancing plant development, and only G. intraradices BEG 72, resulted in a positive response. Field inoculation with this selected fungus increased plant shoot dry weight at the end of the first growing season.

Variation of Diplodia seriata, a fungal species associated with botryosphaeria dieback of grapevine, was investigated with respect to its genetic, phenotypic and pathogenic characteristics. The inter-simple sequence repeat (ISSR) technique was used to investigate the genetic diversity of 83 isolates of D. seriata. Five ISSR primers were able to provide reproducible and polymorphic DNA fingerprint patterns, thus showing a relevant genetic variability in the species. Analyses of ISSR data by different clustering methods grouped the isolates into two distinct clusters through the Bayesian and DAPC analyses. No relationships between either geographic or host origin of isolates and genetic clusters were observed. Several representative isolates from each genetic cluster were chosen for studying their conidial dimensions, in vitro mycelial growth, vegetative and mating compatibility, and pathogenicity on detached grapevine canes and potted vines. No significant differences in conidial dimensions were detected among the groups. Vegetative compatibility reactions were observed among isolates but this was not related with the genetic clustering. Production of sexual fruiting bodies in vegetative compatible crossings was not observed under the experimental conditions used in the study. All 14 isolates tested for pathogenicity were confirmed to be pathogenic according to the length of the necrotic lesions that they caused and their reisolation frequencies from the infected plant tissues. Differences in the length of necrosis were detected among isolates, thus revealing the existence of different virulence levels in the species.

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