As an alternative to chemically synthesized plant protection products, bio-effectors without their own substantial mineral content have produced initial positive results in the field and greenhouse. Direct pathogen resistance has not yet been proven, but a growth-stimulating effect can be observed.

Silicon has multiple protective effects in plants, both in response to abiotic (Moradtalab et al., 2018) and biotic stress. The disease-suppressing effects have already been well studied in many crops, although the exact mechanisms are often still unclear.

Symbiosis and N2 fixation are apparently hardly affected by bio-effectors or silicon, but rather promoted (Herrmann et al., 2022).

The aim is to quantitatively and mechanistically determine the protective effects of bio-effectors and silicon through prophylactic and/or targeted treatment of legumes (soybean, field bean) on the infestation pressure with pathogens (especially soybean and bean rust) and their effects on N2-fixation performance.

Greenhouse trials with defined pest infestations will be used to develop practical instructions for the field and to identify mechanisms involved in the protective effect.

In greenhouse trials, soybeans and field beans inoculated with suitable rhizobia are treated with bio-effectors and/or silicon. In the following, the biomass yield in different vegetation stages, the number of root nodules and their N content as well as the seed yield will be measured. Some of the plants will be infected with pathogens and later the physiological parameters of plant defense will be recorded and compared in order to obtain a complete picture of the mechanisms of defense and the reactions to pathogen attack.

The expected research results are quantitative protection of soybeans and field beans by silicon and bio-effectors as well as a correlation of the resulting changes in metabolites and plant hormones with protective effects.