This study explored the role of Aphanocladium album (strain MX95), Pleurotus ostreatus (strain ALPO) and Pleurotus eryngii (strain AL142PE) as potential biological limiters. MX95, ALPO and AL142PE were screened under laboratory studies against Phytophthora nicotianae (PN), Fusarium oxysporum f. sp. radicis-lycopersici (FORL), Fusarium oxysporum f. sp. lycopersici (FOL), Fusarium solani (FS), Sclerotinia minor (SM), Sclerotinia sclerotiorum (SS), Athelia (Sclerotium) rolfsii (AR) and Verticillium dahliae (VD). The radial growth inhibition and the over-growth of potential antagonists on the target organisms were used to assess the interactions in the in vitro dual culture plate assay. The antagonistic ability of each challenge isolate was evaluated by calculating an index of the antagonism (AI) based on the interaction type in the dual cultures. MX95, reducing the growth of SS (20%) and FS (40%), displayed deadlock at mycelial contact against FOL and FORL, deadlock at distance versus VD and completely over-grew PN and SM. ALPO reduced (43 to 88%) the mycelial growth of tested pathogens except FORL and replaced PN and VD. AL142PE reducing (53 to 67%) SS, VD, FS and FOL mycelial growth and completely over-grew PN. AR showed combative ability against all the experienced biological limiters. Based on the results of the AI values, MX95 (AI = 16.5) was considered an active antagonist, while ALPO (AI = 11.5) and AL142PE (AI = 12.0) were moderately active antagonists. Strains MX95, ALPO and AL142PE were suitable as environment-friendly potential biocontrol agents to manage some of the main soil-borne agents of foot, root, soft rot and wilt diseases. These results are the first step in the assessment of the potential capacity of these organisms as biological limiters. Nevertheless, additional experiments should be performed for the translation to the field conditions in plant protection against soil-borne plant pathogens. In particular, the optimisation of dose and application time validation should be performed for a solid conclusion about the competitive ability of MX95, ALPO and AL142PE and the usefulness of potential biological limiters.

The strains Trichoderma harzianum TH07.1-NC (TH), Aphanocladium album MX95 (AA), Pleurotus eryngii AL142PE (PE) and Pleurotus ostreatus ALPO (PO) were tested as biological limiters against Fomitiporia mediterranea Fme22.12 (FM), Phaeoacremonium minimum Pm22.53 (PM) and Phaeomoniella chlamydospora Pc22.65 (PC). Pathogens were obtained from naturally Esca-affected ‘Nero di Troia’ vines cropped in Grumo Appula (Puglia region, Southern Italy). The antagonistic activity of each challenge organism was verified in a dual culture. TH and PO completely overgrew the three pathogens. Partial replacement characterized PE-FM, PE-PM, PE-PC and AA-PC interactions. Deadlock at mycelial contact was observed in AA-FM and AA-PM cultures. The calculated antagonism index (AI) indicated TH and PE as moderately active antagonists (10 < AI < 15), while AA and PO were weakly active (AI < 10). The maximum value of the re-isolation index (s) was associated with deadlock among AA-PM, AA-PC and PE-FM dual cultures. The tested biological limiters were always re-isolated when PO and TH completely replaced the three tested pathogens. TH and AA confirmed their efficiencies as biological limiters when inoculated on detached canes of ‘Nero di Troia’ in dual combination with FM, PC and PM. Nevertheless, additional experiments should be performed for a solid conclusion, along with validation experiments in the field.

Grapevine trunk diseases are a threat to table- and grape-wine cultivation worldwide. Phaeomoniella chlamydospora (Pch) is a vascular fungus recognized as one of the most important pathogens associated with grapevine trunk diseases. The relationships between xylem vessel features and Pch susceptibility of 10 table- and 17 wine-grape genotypes, as well as 3 rootstocks, were investigated by image analysis of 50 µm cross-sections and artificial Pch inoculation on one-year-old vine cuttings. Vessels were grouped in the diameter classes 1–30, 31–60, 61–90, 91–120, and >120 µm. Among the table-grape varieties, ‘Sable’, ‘Timco’, and ‘Red Globe’ showed higher densities of large vessels (>120 μm) than ‘Italia’, ‘Sugar Crisp’, and ‘Sugraone’. Among the wine-grape varieties, ‘Minutolo’, ‘Montepulciano’, ‘Primitivo’ CDTa19, and ‘Verdeca’ showed higher densities of large vessels than ‘Aglianico’, ‘Nero di Troia’, ‘Sangiovese’, and ‘Susumaniello’. In the rootstocks, the vessel diameters were 50.8, 54.0, and 60.9 μm for ‘34 E.M.’, ‘140 Ruggieri’, and ‘1103 Paulsen’, in that order. For table-grape varieties, Pch was re-isolated from 13.3% for ‘Sugar Crisp’ and ‘Sugraone’ cuttings up to 93.3% for ‘Timco’. For wine-grape varieties, Pch re-isolation ranged from 51.1% (‘Bombino nero’, ‘Negroamaro’ D15, and ‘Sangiovese’) to 81.1% (‘Montepulciano’), while for the rootstocks, the values were from 33 to 51%. A principal component analysis (PCA) revealed a positive correlation between the frequencies of large vessels and Pch re-isolation. In addition, in wine grapes and rootstocks, higher Pch re-isolation frequencies in the lateral parts of cuttings were correlated (r = 0.79) to a higher frequency of large vessels. The results highlight relationships between grapevine xylem vessel sizes and susceptibility to P. chlamydospora that are worthy of further research.

Esca-affected vines alter the carbohydrate metabolism, xylem transport of water and photosynthesis and show regular grapes (but berries do not reach maturity), and phenolic compounds are reduced in concentration, oxidate and polymerizate. Pullulan and a mixture of scytalone and isosclerone (9:1; w/w), secondary metabolites produced in vitro and in planta by Phaeoacremonium minimum (syn. P. aleophilum) and Phaeomoniella chlamydospora, were assayed against the strains Byosal HS1 and IOC 18-2007 in microvinifications with synthetic grape must. The presence of pullulan and pentaketides mix affects the growth and metabolism of the tested Saccharomyces cerevisiae strains. Assays at 100 and 1000 µg mL⁻¹ inhibited the growth of both strains, while no effects were recorded when evaluated at 1 and 5 µg mL⁻¹. In comparison with the controls, pullulan and the scytalone/isosclerone mixture at 10 µg mL⁻¹ had a growth reduction, a lower alcohol yield, reduced the concentration of tartaric acid and malic acid; and slowed down the production of lactic acid, acetic acid and total polyphenol content of the tested S. cerevisiae strains. These metabolites could be applied as an alternative to the sulfite addition in the early stages of vinification to support the action of selected Saccharomyces. Appealing is the subtractive action of pullulan against tartaric acid. Further data are needed to confirm and validate the enological performance in freshly pressed grape juice.

The grapevine syndrome, Esca proper, causes significant yield losses. This study analyses and discusses the enological traits of musts from healthy (HV) and Esca-proper-affected (EpV) ‘Primitivo’ vines cropped in southern Italy. Tiger-striped leaves, sudden wilting on arms or shoots, berry spots, shrivelling and wilting, wood browning and white rot are linked to the presence of Phaeoacremonium minimum, Phaeomoniella chlamydospora, and Fomitiporia mediterranea within the woody tissues and characterize EpVs. The lack of symptoms on trunks, leaves, berries, and in the wood of branches and shoots, along with the absence of Esca-proper mycota, typifies HVs. Must from the selected HVs is darker and contains greater total soluble solids, reducing sugars, titratable and volatile acidity, tartaric, citric, and L-malic acid, and total polyphenols. The must from the selected EpVs has a higher pH and laccase activity, and contains pullulan, scytalone, and isosclerone, secondary metabolites of P. minimum and P. chlamydospora. During fermentation, musts from EpVs negatively impact the growth and enological performance of Saccharomyces cerevisiae Byosal HS1™ and IOC 18-2007™ and reduce the overall quality of the resulting wines. The physical–chemical conditions during fermentation may degrade pullulan and aid scytalone oxidation to isosclerone.