Many fungi, especially endophytes, have been found to produce multiple benefits in their plant hosts, with many of these benefits associated with the protection of plants against fungal diseases. This fact could be used in the development of new bio-products that could gradually reduce the need for chemical fungicides, which have been associated with multiple health and environmental problems. However, the utilization of the living organism may present several issues, such as an inconsistency in the results obtained and more complicated management and application, as fungal species are highly influenced by environmental conditions, the type of relationship with the plant host and interaction with other microorganisms. These issues could be addressed by using the bioactive compounds produced by the fungus, in cases where they were responsible for positive effects, instead of the living organism. Multiple bioactive compounds produced by fungal species, especially endophytes, with antifungal properties have been previously reported in the literature. However, despite the large amount of these metabolites and their potential, extensive in-field application on a large scale has not yet been implemented. In the present review, the main aspects explaining this limited implementation are analyzed, and the present and future perspectives for its development are discussed.

Fungal species richness and composition within needles and twigs in 55 stands of Pinus halepensis, spread out over the whole Iberian Peninsula, were determined. The aim was to evaluate the relationships of fungal communities with local environmental variables, in order to analyze the potential causes of the current decline of this pine species in Spain. A total of 35 fungal taxa were isolated from 1980 moist chambers analysed (990 per vegetal tissue). A taxon within the Alternaria alternata complex was most frequent, followed by Leptostroma pinastri, Aspergillus niger, Diplodia pinea and Phomopsis sp. At the tree level, tissue was a significant response variable and a higher species richness was found in needles as compared to twigs. On the other hand, the multivariate analysis showed the environmental variables ‘age’, ‘shadow’, ‘elevation’, ‘mean temperature’, ‘illumination’ and ‘availability of water’ significantly influenced fungal species composition. In particular, ‘mean temperature’, was an important variable implicated in the general weakening of this thermophilic pine species, and appeared to be inversely correlated with the occurrence of several conifer pathogens such as Brunchorstia pinea, Cytospora sp., Diplodia pinea, Naemacyclus niveus, Pestalotiopsis stevensonii and Sclerophoma pythiophila. This study shows a possible combined effect of abiotic and biotic stresses in causing the general decline of Allepo pine in Spain.