Response of the strawberry rhizosphere microbiome to chitin andbiochar in function of plant health: expanding towards metatranscriptomics and DNA-SIP (BIOCHI)

To reduce the amounts of mineral fertilizers and plant protection products in horticulture, ILVO has investigated several organical alternatives, such as chitin and biochar. We have shown previously that both amendments, either extracted from crab shells (chitin) or as waste product of biomass pyrolysis (biochar) have beneficial effects on plant growth and/or plant defense. The mode of action of both amendments is however not known and examined in this project. 

We hypothesize that the effects of chitin and biochar could either be directed to an increase in nutrion for the plants (and a higher uptake of nutrients), and/or could be due to the active attraction to the plant roots of plant growth promoting microorganisms that induce growth and plant defense. Therefore, we set up a large-scale greenhouse experiment of 600 plants and measured the nutritional values of potting soil and plant leaves, looked into plant growth promotion, studied defense gene expression of the plant by RNA sequencing and extensively studied the microbial community by metabarcoding. 

There is evidence of complex relationships among the measured indicators. Biochar by itself has no effect on the growth and production of strawberry plants, but it does strongly influence disease resistance to powdery mildew on strawberries. This is a relevant finding: This could mean fewer failures in strawberry cultivation. At the consumer level, the fruits would keep longer qualitatively. Unlike biochar, chitin does have a positive effect on plant growth. The explanation may have to do with the higher amounts of nitrogen in the leaves and potting soil, but also with the presence of some interesting fungi around the plant root. Thus, mainly for plants grown for their leaf material, such as lettuce, chitin could be an interesting alternative to mineral fertilization.