Ecology, abiotic stress response and biotic interactions of fungal leaf endophytes from three Mediterranean plant species

Fungal leaf endophytes play a key role in boosting plant tolerance to abiotic stresses and enhancing plant resistance against diseases. Endophytes might become a pivotal tool to face climate change challenges in a sustainable way. In this thesis, the fungal endophyte community living in the leaves of three plant species from the Natural Park of Albufera (Spain), Inula crithmoides, Phillyrea angustifolia, and Pistacia lentiscus, was studied. These plant species face extreme abiotic stresses when prospering in coast dunes and salt marshes. First, I investigated the fungal diversity. Then, I evaluated the tolerance to salt stress of nine representative species of fungi. An essential part of the fungal ecology involves biotic interactions with other microorganisms, such as bacteria. Therefore, I quantified the effects of the interaction of fifteen endophyte species with two species of bacteria (one root nodule-forming bacterium from sympatric Lotus criticus, and one Escherichia coli strain). Finally, I measured three different aspects of the osmotic stress response of fungi (total sugar contents, proline, and ions). Two fungal species exhibit intense levels of tolerance to salt stress. Overall, bacteria had a negative or no impact on fungal growth. This is the first time these communities have been investigated, thus, representing a very strong starting point for more applied future research.