Native plant microbes and soil AMF+accompany microbiome promote growth of modern cultivars of chrysantemum, but the response is cultivar-dependent

Plant Growth-Promoting Microbes (PGPM) have the potential to contribute to more sustainable agriculture, but there is still a limited understanding of how the complex interplay between plant genetic variability, the native soil community, and soil nutrients affects PGPM recruitment. To address this challenge, we investigated the impact of bacterial isolates and arbuscular mycorrhizal fungi (AMF) plus accompany microbiome from a wild relative of chrysanthemum on the growth of five different commercial chrysanthemum cultivars (Chic, Chic-45, Chic-Cream, Haydar, and Barolo) and their rhizosphere microbiome in a nutrient-rich, complex substrate environment. Our screening of PGPM from wild chrysanthemum identified 23 bacterial strains capable of producing siderophores, 14 strains capable of producing Indole-3-acetic acid, and 18 strains capable of solubilizing phosphate, while the AMF plus accompany microbiome comprised six AMF species, and bacteria and fungi from different phyla. Using generalized joint models, we investigated the impact of the three most effective bacterial strains and the AMF plus accompany microbiome on plant growth (shoot and root dry mass) while integrating information on plant genotype, environment, and microbes. The impact of PGPM inoculation varied from positive to negative effects depending on the cultivar, with Chic Cream showing the highest increase in root biomass after inoculation with both SMF006 (57%) and AMF plus accompany microbiome inoculation (79%). Our study demonstrates that PGPM isolated from wild relative can impact the growth and assembly of the root microbiome of chrysanthemum, but this impact is cultivar-dependent. Furthermore, inoculation with a complex AMF community induced greater change in the rhizosphere microbiome profiles than with a single bacterial isolate. Our study emphasizes the need for a comprehensive understanding of plant-microbiome-environment interactions in developing effective microbial inoculants.