Uncovering the hidden diversity of fungi associated with grapevine trunk diseases in the Moroccan vineyards

For decades, the grapevine has been produced as a commercial fruit crop in Morocco. From 2004 to 2022, the area dedicated to cultivating and producing grapes has increased across the country. Despite the implementation of adequate agricultural practices, grapevine trunk diseases (GTDs) lead to significant yield losses and a remarkable reduction in viticultural quality. Many grape growers encounter this issue in their vines each year and seek strategies to cope with it. In the most significant grape-growing regions globally, including Morocco, grapevine decline is a common and significant disease that is brought on by a multitude of latent fungal plant diseases. Due to the use of poorly informative markers in phylogenetic analyses and the lack of relevant morphological characteristics, the classification of these pathogens has proven to be challenging. Numerous genera and families have not yet been extensively studied, especially in Morocco. To identify the dieback-causing agents, surveys were carried out in 152 Moroccan vineyards in Marrakech-Safi, Casablanca-Settat, Rabat-Sale-Kenitra, and Fez- Meknes regions between 2019-2021. Samples of symptomatic trunks were collected and processed for mycological analysis. Afterward, fungal identification of representative isolates was performed combining morphological characterization and phylogenetic analysis based on the internal transcribed spacer (ITS) region of ribosomal DNA and protein-coding gene (β-TUB). Pathogenicity tests were fulfilled under greenhouse conditions for 15 days. Among the fungi collected in the current study, 54 fungal isolates were obtained belonging to different genera and families namely: Botryosphaeria (11 species), Fusarium (10 species), Pestialiotiopsis (4 species), Clonostachys (3 species), Entoleuca mammata, Phaeoacremonium hungaricum, Trichothecium roseum, Diaporthe ampelina, Epicoccum nigrum, Alternaria alternata, and Rosellinia convexa. Pathogenicity test revealed that Diplodia mutila, Neoscytalidium novaehollandiae, Neopestalotiopsis vitis, and Trichothecium roseum isolates are the most pathogenic. This is the first detailed report of species associated with GTDs in Morocco where new records of species worldwide are highlighted.