Dynamics of native AMF communities in maize roots as affected by plant genotype, starter fertilization and a seed-applied biostimulant

Sustainable intensification of crop production may be implemented by a promising strategy involving the utilization of beneficial root-associated microorganisms, such as plant growth-promoting (PGP) bacteria and arbuscular mycorrhizal fungi (AMF). The aim of this study was to investigate whether a seed-applied biostimulant, containing a PGP strain of Bacillus amyloliquefaciens, and nitrogen (N)-phosphorus (P) starter fertilization, can shape the communities of native root-colonizing AMF in two maize genotypes differing for early vigor. A factorial growth chamber experiment was set up in natural soil, and plants were harvested at two time points: at 13 (emergence) and 49 (5-leaf stage) days after sowing. Mycorrhizal colonization of maize roots by native AMF communities at the 5-leaf stage ranged between 5% and 54%, with a significant negative effect of NP fertilization, regardless of host genotype. Accordingly, mineral fertilization was the major driver of native AMF communities colonizing maize roots, as assessed by PCR–Denaturing Gradient Gel Electrophoresis separation of the 18S ribosomal RNA gene and amplicon sequencing. Here, for the first time, we described significant interactions between conventional NP fertilization and a biostimulant containing B. amyloliquefaciens IT-45, that affected native AMF, although the combined effects of the two factors were modulated by maize genotype. Amplicon sequencing allowed the identification of the predominant AMF in maize roots, represented by Glomus, Funneliformis and Rhizoglomus species. Funneliformis mosseae appeared to be resilient across all treatments in both maize hybrids, while populations of the genus Rhizoglomus were more affected by the interaction between microbial biostimulant and NP fertilization. The results of this study increase our understanding of how plant genotypes, PGP bacterial strains and NP fertilization can interact, altering the dynamics of native AMF communities in maize. Present findings pave the way for the implementation of beneficial root-associated microorganisms in sustainable and resilient agroecosystems.