Inter- and infraspecific plant-soil feedbacks of grass species

Plants continuously interact with soil microbiota. These plant-soil feedbacks (PSFs) are considered a driving force in plant community dynamics. However, most PSF information comes from inter-family studies, with limited information on possible causes. We studied the variation of PSFs between and within grass species and identified the soil microbes that are associated with the observed PSFs effects. We grew monocultures of ten cultivars of three grass species (Lolium perenne, Poa pratensis, Schedonorus arundinaceus) using a two-phase PSF experiment. We measured plant total biomass to determine PSFs between and within species and correlated it with sequenced rhizosphere bacteria and fungi. In the soil conditioning phase, grass species developed microbial legacies that affected the performance of other grass species in the feedback phase.  We detected overall negative interspecific PSFs. While we show that L. perenne and P. pratensis increased their performance respectively in conspecific and heterospecific soils, S. arundinaceus was not strongly affected by the legacies of the previous plant species. Contrary to our expectation, we found no evidence for intraspecific variation in PSFs. Bacterial taxa associated with PSFs included members of Proteobacteria, Firmicutes, Verrucomicrobia and Planctomycetes whereas fungal taxa included members of Ascomycota. Our results suggest differences in PSF effects between grass species, but not between cultivars within species. Thus, in the studied grass species, there might be limited potential for breeding on plant traits mediated by PSFs. Furthermore, we point out potential microbial candidates that might be driving the observed PSF effects that could be further explored.