Rhizosphere microbiome as affected by plant species, Fe nutrition and growth substrates
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Introduction. Plant-associated microorganisms can stimulate plants growth and influence both crops yield and quality by nutrient mobilization and transport. Rhizosphere microbiome appears to be one of the key determinants of plant health and productivity. Plant roots can influence their surrounding microbiology, the so called rhizosphere microbiome, by creating of specific chemical niches through the release of phytochemicals (i.e. root exudates) that depends on several factors, such as plants genotype, soil properties, plant nutritional status, climatic conditions.Objectives. The aim of the study is to investigate the influence of plant species and the nutritional status on the structure of the rhizosphere microbial communities in two Italian calcareous soils.Materials and Methods.Two different crops (barley and tomato), with different strategies for Fe acquisition, have been grown in the RHIZOtest system in either complete or Fe-free nutrient solution to induce Fe starvation. Afterwards, plants were cultivated for 6 days on two different calcareous soils. Total DNA was extracted from soil and subjected to pyrosequencing.Results. NMDS plot well separated microbial communities patterns as indicated by the goodness of fit (0.1) of the stress value for the ordination with two dimensions. The analysis of the bacterial communities confirmed that the two bulk soils showed different structures. The presence of the two plant species, as well as the nutritional status (Fe-deficiency and Fe-sufficiency), could promote a differentiation of the rhizosphere microbiome. Alphaproteobacteria, Actinobacteria, Chloracidobacteria, Thermoleophilia, Betaproteobacteria, Saprospirae, Gemmatimonadetes, Gammaproteobacteria, Acidobacteriawere the most represented classes in all the samples analyzed even though their relative abundance changed as a function of the soil, plant species and nutritional status.Conclusions. To our knowledge, this research demonstrates for the first time that different plants species with diverse nutritional status can promote thedevelopment of a peculiar rhizosphere microbiome, depending on the growth substrate.