Intercropping wheat and aromatic crops: Impacts on the root associated microbiome

The root microbiome plays a crucial role in plant health, growth, and yield promotion. Under draught stress, the important roles played by root associated bacteria and arbuscular mycorrhiza (AMF) are more pronounce. Mixed cropping which involves the cultivation of different crops enables the efficient utilization of nutrient by combining deep rooters and shallow rooting plants during a production time period. This enables increased plant diversity and hence diversity of root exudates. The composition of root associated microbiome is controlled by the production of root exudates. The extent of the effects of mixed cropping/intercropping involving wheat and medicinal aromatic plants on the root microbiome is not well studied.

In the TRIO project intercropping of wheat-aromatic crops (wheat-coriander, wheat-caraway) and monocrops (wheat, caraway, and coriander) will be investigated to determine the effects of intercropping systems on the root associated microbiome. The project involves two experimental fields under ecological and two experimental fields under conventional agricultural management system in Hesse. The field trials in the four experimental fields will be carried out under randomized complete block experimental design. Each field has 20 plots with 12 plots under monocrops of wheat, caraway, and coriander. For mixed crops eight plots are studied, four plots with wheat-coriander and four plots with wheat-caraway combinations. Annual and perennial crop production will be studied. The microbial diversity and community composition in bulk soil (at sowing and flowering of herbs) and rhizosphere and roots samples at flowering of wheat and herbs will be compared.

Our first hypothesis is that mixed cultures have a positive effect on the bacterial diversity and affect nutrient uptake. To answer this hypothesis, the bacterial communities will be analysed by 16S rRNA gene amplicon next generation sequencing. We also hypothesize that crop diversity in mixed crops positively affect AMF colonization benefitting perennial as compared to annual crops. To answer this, fluorescence microscopy of plant in monocrops and mixed will be carried out to determine the colonization abundances of AMF. Quantification of root colonizing AMF using qPCR and diversity analysis using amplicon sequencing will be carried out in parallel.