Sebacinales and mycorrhiza in plant health

Soil-borne plant pathogens pose particular challenges in the field of plant protection because of their very persistent nature. Due to increasing restrictions in the use of pesticides and the consumers demand for organic produce there is a strong need for alternatives to ensure high quality plant products. One alternative could be the improvement of plant health by the use of beneficial microorganisms. They can reduce plant diseases via several modes of action such as direct antagonistic effects or the induction of plant resistance. In this project the focus will be on arbuscular mycorrhizal and endophytic fungi. Both are known for their capability to colonize plant roots and to alter their host plants physiology, thus, increasing the plants resistance to diseases. Although some of these endophytic fungi have been isolated from arbuscular mycorrhizal spores there is hardly any information available on putative interactions in tomato plant health. In this project in addition to mycorrhizal fungi two endophytic fungal species of the Sebacinales will be used, which are widely unknown to date. Serendipita williamsii as well as Serendipita herbamans have been isolated from European soils and have not been investigated yet for their putative role in plant growth promotion and their effects against soil-borne diseases. Based on the crop and model plant tomato, this project aims to elucidate the colonization process of tomato roots by these fungi and their effects on plant growth and disease resistance against the soil-borne pathogen Fusarium oxysporum f. sp. lycopersici (Fol), the causal agent of Fusarium wilt in tomato. Moreover, the putative synergistic effects of the two Sebacinales and arbuscular mycorrhiza in plant growth promotion and disease resistance against Fol will be analyzed. The interactions between tomato plants, the pathogen and the beneficial microorganisms will be studied in greenhouse as well as in-vitro experiments. Furthermore, different microscopy techniques, the analysis of defense-related genes as well as the monitoring of secondary plant metabolites with chromatographic tools will be employed to investigate the effects of the used fungi in detail. This research approach offers great innovative potential since two European endophytic Sebacinales species, S. williamsii and S. herbamans, will be investigated for the first time for their ability to promote plant growth and bioprotective effects in plants. Hence, the findings obtained in this project could essentially contribute to the significant improvement of sustainable crop production in temperate climate zones.

Soil-borne plant pathogens pose particular challenges in the field of plant protection because of their very long persistence in soil. Due to increasing restrictions in the use of pesticides also as part of the European Union's "Farm to Fork" strategy and the consumer's demand for organic produce there is a strong need for alternatives to ensure high quality plant products. One alternative can be the improvement of plant health by the use of beneficial microorganisms as part of a whole disease management strategy. They can reduce plant diseases via several modes of action such as direct antagonistic effects or the induction of plant resistance. In this project we focused on arbuscular mycorrhizal and endophytic fungi. Both are known for their capability to colonize plant roots and to alter their host plant's physiology, thus, increasing the plant's resistance to diseases. Although some of these endophytic fungi have been isolated from arbuscular mycorrhizal spores there is hardly any information available on putative interactions in tomato plant health. In addition to mycorrhizal fungi two endophytic fungal species of the Sebacinales were used, which were rather unexplored at the beginning of the project. Serendipita williamsii as well as Serendipita herbamans have been isolated from European soils and have not been investigated yet for their putative role in plant growth promotion and their effects against soil-borne diseases. Based on the crop and model plant tomato and the soil-borne pathogen Fusarium oxysporum f. sp. lycopersici (Fol), the causal agent of Fusarium wilt in tomato, we elucidated within this project the bioprotective effect of S. herbamans against this disease. This effect could be further increased by combining mycorrhiza with S. herbamans. The pathogen usually enters the host plant via the roots and progresses further within the stem where it causes clogging of the vessel system. These effects usually cause visual symptoms such as wilting of the plant as the water transport is inhibited. In additional experiments we could also show that the observed bioprotective effects were based on local effects in the roots as well as on systemic effects within the plant shoots. We could show via microscopy that S. herbamans builds a very dense hyphal mat around the roots which inhibits the spores of the pathogen from infecting the roots. In addition to that, S. herbamans activates the plant's defence system within the stem where a second defence line of the plant is created. The second effect is further increased by adding mycorrhiza to the system. The findings of this project can be used to develop much more sustainable plant protection strategies with less input of pesticides.