Abstract
The application of chitin as a soil amendment has recently attracted considerable interest due to its potential to enhance plant growth, improve plant stress resilience, and alter soil microbiomes.
Lettuce (Lactuca sativa), being the world's most widely eaten leafy vegetable, holds significant economic importance. Due to its high demand, producers frequently resort to the use of synthetic fertilizers, which negatively affects both human and environmental health. Commonly eaten raw in salads, lettuce is susceptible to microbial contamination, influenced by environmental conditions, farming practices, and its inherent physical traits. This susceptibility makes it a potential vector for foodborne diseases. Considering these industry challenges, lettuce serves as an ideal subject for evaluating the effects of chitin soil amendments. This comprehensive study investigates the effects of chitin soil amendments on lettuce growth across different soil types, its effects on soil microbes and the immune response of lettuce.
Transcriptomic analysis revealed significant changes in over 300 genes in lettuce roots after chitin soil amendments. Gene Ontology (GO) enrichment analysis revealed an overrepresentation of GO terms related to photosynthesis, pigment metabolism, and phenylpropanoid metabolism. Metabolomic analysis indicated increased levels of salicylic acid, chlorogenic acid, ferulic acid, and p-coumaric acid in lettuce grown in chitin amended soil. These findings suggest that chitin soil amendments may activate induced resistance through transcriptional modifications.
During our experiments, lettuce was cultivated in both peat substrate and mineral soil that had been amended with chitin. We monitored physiological changes on a bi-weekly basis over an eight-week growth period. The results of the study demonstrated that the application of chitin to the soil resulted in an increase in the chlorophyll content, leaf number, and fresh weight of lettuce. The increase in fresh weight was most pronounced in the peat substrate, where a 50% increase was observed at harvest, and in the mineral soil, where a 30% increase in fresh weight was recorded. Furthermore, we explored the microbial dynamics in response to the chitin treatment. The presence of chitin notably influenced the abundance of specific microbial taxa, including a significant increase in Mortierellaceae family members in peat substrate but not in mineral soil. Our findings suggests that soil type profoundly affects microbial responses and, consequently, plant growth outcomes.
We tested a beneficial fungal strain, Linnemannia hyalina (previously classified as Linnemannia elongata), which demonstrated a pronounced effect on lettuce growth when present. While chitin soil amendments promote lettuce growth, the overall effectiveness can vary considerably depending on soil type and the composition of the soil microbiome. This emphasises the necessity of considering local soil characteristics and microbial communities in the utilisation of chitin as a sustainable alternative to synthetic fertilisers and pesticides
Kaufmann, Moritz