Root-associated fungi of Arabidopsis thaliana and Microthlaspi perfoliatum

Root-associated fungi, with the focus on endophytic species, were isolated from healthy Arabidopsis thaliana and Microthlaspi perfoliatum plants collected at different locations in Germany. A large number of fungal taxa were discovered with a small-scale approach. This provides additional evidence that root-associated and endophytic fungi are common in Brassicaceae. The most prevalent genera associated with A. thaliana roots were Trichoderma and Fusarium, while the roots of M. perfoliatum were dominated by different species of Fusarium and Penicillium. Differences in species composition and richness might be due to preferences and life-cycle of the two plant species. Strains of endophyte species that did not have closely related species in GenBank searches and those already known as root endophytes were chosen for preliminary co-cultivation experiments using germinating host plants on agar medium to observe effects on plant growth and health. Under these conditions several fungal isolates had an adverse effect on plant growth and health, especially on Arabidopsis thaliana. Some isolates did not adversely affect biomass during initial plant growth, while they altered the shoot-root ratio in favour of the shoot, especially in Microthlaspi perfoliatum. These strains are promising candidates for future research on endophytes as they might have some effects in Brassicaceae that are similar to mycorrhizal fungi. They are also promising candidates for investigating interactions with their host plants.