Biodegradability and interactions with plants and microorganisms

The FocusLab greenRelease serves to develop a technology that reduces the overall input of agrochemicals. A more precise and efficient application of active ingredients will relieve the environment while still delivering the necessary protection to the desired crop. This concept requires to validate the technology’s biocompatibility and sustainability itself.

One part of biocompatibility is testing the complete product, the active agent (in our test case copper salts) and ingredients of the gel for their impact on plant growth. All of those should finally facilitate plant growth through the delivered active agent, but the greenRelease delivery system itself should not impact plant growth on its own. To test for possible effects, which may be rather little, it is useful to monitor growth of numerous plants side by side in a controlled environment before and after application of test substances. Within CG Schurr at FZJ, there are possibilities to perform such experiments using high-throughput phenotyping installations such as the “ScreenHouse” (Fig. 1).

This installation can record images of up to 120 plants on a regular basis using a portal crane system to transport pots between an imaging station and their growth position. From the images projected leaf area is measured, which can be used as a proxy for total leaf area and shoot weight. Those are good traits to be compared between test plants to assess changes in growth and therefore potential effects of the applied substances. In our tests with barley and sugar beet, we could show that neither copper-loaded nor unloaded greenRelease microgels have a negative effect on overall plant growth, while certain other copper salts not used for our technology show effects. We will continue testing updated greenRelease formulations on plants also in comparison to other commercially available formulated copper salts.

Another part of testing for biocompatibility and general sustainability is the assessment of possible effects on the soil- and leaf-associated microbiome (CG Knief). Soil microorganisms can largely contribute to plant health and development while also representing an important factor to consider when evaluating the environmental impact and fate of a substance. We assess these impacts in field and laboratory experiments. Soil was e.g. incubated with different components of the greenRelease technology to monitor possible effects on microbial community composition and activity using high-throughput community profiling approaches and respiration measurements. The specific increase in relative abundance of bacterial strains over time along with temporally increased respiratory activity in response to the incubation with some of the greenRelease components point to degradation potential. In ongoing experiments, we aim to validate these results.

So far, our experiments support that the greenReleasetechnology is a promising candidate for the application of agrochemicals with no substantial impact on plant growth or the surrounding environment.

We are also testing the effects of greenRelease microgels on epiphytic microbes, i.e., the ones inhabiting plant surfaces. They are an important indicator for the biocompatibility of any foliar application system, as epiphytes are directly exposed to it. In a field trial, microgels loaded with copper were applied to apple trees in order to counteract the pathogenic fungus Venturia inaequalis, the cause of apple scab (Fig. 2). In ongoing analyses, we are evaluating the impact of these applications on different aspects of the epiphytic microbial community structure.

Involved Core Groups

Prof. U. Schurr
Dr. F. Fiorani
Dr. H. Lenz
IBG-2: Plant sciences
Forschungszentrum Jülich

Prof. C. Knief
J. Zierul
INRES – Molecular Biology of the Rhizosphere
Universität Bonn