Effects of the commercial biostimulant BC204 on the rhizosphere microbial community of Solanum lycopersicum L.

Abstract

The biostimulant BC204 is a commercially available biostimulant based on an extract from Citrus aurantium, comprising a mixture of bioflavonoids, other plant extracts and organic acids. In this study, the potential of BC204 to cause positive effects on plant growth and overall plant health by altering the rhizosphere microbial community of Solanum lycopersicum L. was investigated. Mycorrhizal colonization of plant roots was analysed by trypan blue-staining and light microscopy, followed by polymerase chain reaction (PCR) amplification of a region of the 18S rRNA gene conserved among arbuscular mycorrhizal fungi. No difference in mycorrhizal colonization of roots was observed between control and treated plants. The structural and functional diversity of rhizosphere bacteria between different treatment groups was assessed using 16S rRNA gene restriction fragment length polymorphism (RFLP) analysis and community-level physiological profiling (CLPP), respectively. Nearest sequence matches for three isolates from the rhizosphere of plants treated with BC204 as a soil drench in soil supplemented with Mycoroot™ revealed bacterial genera which play a role in promoting plant growth. Furthermore, the microbial community from this treatment group showed increased richness of substrate utilization on Biolog EcoPlates™. These results indicate some form of interaction between BC204 and Mycoroot™ which causes a shift in the structural and functional diversity of the rhizosphere bacterial community.