Land Use History Influences Recruitment Of Soilborne Microbes To Seeds, And Seed Germination, Of Prosopis Velutina (velvet Mesquite)

A better understanding of interactions between native plants and endophytic microbes can help improve regional strategies for revegetation of damaged lands. One native plant of interest for revegetation in the Sonoran Desert is Prosopis velutina (velvet mesquite). I used a field experiment to evaluate how communities of microbes that recruit to seeds in soil might differ between more natural, riparian soils and degraded, post-agricultural soils. I exposed surface-sterilized P. velutina seeds to soils in Tucson, Arizona; isolated microbes associated with seed interiors; and evaluated germination frequency in vitro. Regardless of soil type, infection frequency increased after exposure to soil. This increase was due to an increase in fungal infections, not bacterial infections. Germination frequency was negatively associated with fungal isolation frequency, but not bacteria, and germination was particularly poor in seeds exposed to degraded soils. The most abundant fungal morphotypes differed between the soil types (Fusarium brachygibbosum in riparian soil; Aspergillus tubingensis in degraded soil). Together these findings provide a first perspective on soilborne microbes that infect seeds of an economically and ecologically important plant and set the stage for experiments to measure the effects of focal microbes on seed germination and establishment under field conditions