Romano, Ida (2021) Development of innovative microbial-based biostimulants from agri-food waste for sustainable agricultural productions- Versione dscurata fino al 12-2024. [Tesi di dottorato]

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Collection description

The use of beneficial microbes as inoculants able to improve fitness, growth and health of plants also in stress conditions is an attractive low-cost and eco-friendly alternative strategy to harmful chemical inputs. Thirteen potential plant growth-promoting bacteria were isolated from the rhizosphere of wheat plants cultivated under drought stress and nitrogen deficiency. Among these, the two isolates TL8 and TL13 showed multiple plant growth promotion activities as production of indole-3-acetic acid (IAA), siderophores, ammonia, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production, the ability to solubilize phosphate as well as exerted antimicrobial activity against plant pathogens as Botrytis spp. and Phytophthora spp. The two selected strains were identified as Kosakonia pseudosacchari by sequencing of 16S rRNA gene. They resulted also tolerant to abiotic stress and were able to efficiently colonize plant roots as observed in vitro assay under fluorescence microscope. Based on the best PGP properties, the strain K. pseudosacchari TL13 was selected to develop a new microbial based formulate. A sustainable and environmentally friendly process for inoculant production was developed using agro-industrial by-products for microbial growth. Moreover, the application of K. pseudosacchari TL13- based formulates in pot experiment improved growth performance of maize plants. In a second case study, sixteen bacteria were isolated from the Moroccan oat rhizosphere and were screened for their putative P-solubilization by semi-quantitative agar spot method. The two strains MS1B15 and MS1B13, identified as Streptomyces roseocinereus and Streptomyces natalensis, respectively, showed the maximum phosphate solubilization index (PSI = 1.75 and PSI = 1.63). After quantitative assay to determine phosphate solubilization activity, S. roseocinereus MS1B15 was selected for evaluating its putative plant growth promotion activities including production of siderophores, indole-3-acetic acid (IAA) and amino-cyclopropane-1-carboxylate (ACC) deaminase, nitrogen fixation and antimicrobial activity against soil-borne plant pathogens. Based on the best PGP properties, the strain S. roseocinereus MS1B1 was tested to develop a new microbial based formulate. Then, were evaluated alternative strategies for sustainable agriculture to manage soil microbiome. It was investigating the impact of leguminous pre-crops, fertilization and potato genotypes on soil and plant-associated microbiomes. To identify the best performing genotypes under reduced and conventional tillage, standard agronomic parameters such as grain/straw yield, grain protein and grain N/P content will be assessed. Furthermore, it was investigate the effect of different genotypes, crop rotation and fertilization regime on the abundance, community structure and functionality of the soil microbiome. The following molecular biology and chemical analyses were foreseen: abundance of bacteria and fungi (qPCR of the marker genes16S/18S), fungal community structure (ITS amplicon sequencing), abundance of functional genes (qPCR) and activity of soil enzymes (enzymatic assays) involved in N/(P) cycling. Thanks to this study, it was possible to provide evidence for the influence of cultivars, combined stresses and pre-crop on microbial activity and fungal community composition. The goal of this complex experimental design was to select one or more potato genotypes that combined with the right sequential cropping can stimulate microbial activities to address more effectively water and nitrogen limitations. This study demonstrated that the experimental variables affect differently the response variables. Comparison with other field experiments performed by project partners with same design but in other countries (e.g., Hungary) as well as further investigations (16 S and AMF amplicon sequencing) are necessary to deepen evaluate the effects on plant and on microbial community in detail.

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