Enhancing cucumber plantlet growth and rhizosphere microbial communities with chitin and gelatin biostimulants

Biostimulants emerged as a versatile tool to modify plant biological processes, by enhancing growth, improving nutrition, increasing stress tolerance, and enhancing crop quality. Among various biostimulant compounds, chitin and gelatin have shown promise in promoting plant growth and enhancing microbial communities. In this study, we investigated the biostimulant effects of chitin, gelatin, and their mixture on cucumber plantlets and associated rhizosphere microbial communities during plantlet production. Cucumber seeds were sown in seedling substrate amended with gelatin, chitin, or a mixture of both biostimulants. Plants were grown at 25°C/21°C with a 16/8 h photoperiod and 75 % humidity. Unamended samples served as controls, while urea was used as a mineral fertilizer control. After 8, 11 and 15 days, rhizosphere samples were collected, DNA was extracted, and the bacterial and fungal communities were assessed by high-throughput sequencing of the 16 S rRNA gene and the ITS region, respectively. Our findings revealed that the application of these biostimulants significantly improved cucumber plantlet growth, with the most pronounced effects 15 days after germination. Gelatin had significantly superior performance compared to chitin. The microbial communities with those amendments were enriched with microbes of genera Cellvibrio, Catenulispora, Arthrobacter, Mortierella, and Penicillium, all known for their production of hydrolytic enzymes such as chitinases, cellulases, and proteases. Overall, this research contributes to a deeper understanding of the biostimulant-mediated interactions between plants and their associated microbial communities, offering potential applications to enhance crop productivity, especially at the plantlet stage while promoting circular economy and environmental sustainability in agriculture.