Distinct effects of phyllosphere and rhizosphere microbes on invader Ageratina adenophora during its early life stages

Abstract

Microbes strongly affect invasive plant growth. Interactions between soil microbes and invasive plants have received widespread attention; however, it remains to be determined how phyllosphere and rhizosphere soil microbes affect seedling mortality and the growth of invasive plants across ontogeny under varying soil nutrition levels. In this study, we used the invader Ageratina adenophora to evaluate these effects in plant growth chambers. We found that leaf litter harboured more potential pathogens and thus had more adverse effects on seed germination and seedling survival than soil inoculation. Microbial inoculation at different growth stages altered the microbial community and functions enriched in seedlings, and earlier inoculation had a more adverse effect on seedling survival and growth. In most cases, the soil nutrient level did not affect microbe-mediated seedling growth and the relative abundance of the microbial community and functions involved in seedling growth. Some microbial genera have distinct effects on seedling survival from those on growth. Moreover, fungal strains isolated from dead seedlings inoculated with litter exhibited significant phylogenetic signals to seedling mortality, in which strains of Allophoma and Alternaria caused high seedling mortality. Our study stresses the essential role of A. adenophora litter microbes in population establishment by regulating seedling density and growth.