Effects of indigenous soil cyanobacteria on seed germination and seedling growth of arid species used in restoration

Background and aims Cyanobacteria from biocrusts can enhance soil function and structure, a critical objective when restoring degraded dryland ecosystems. Large-scale restoration of biodiversity requires direct seeding of native plant species, and bio-priming seeds with cyanobacteria is a potential method of initiating enhanced soil functioning. The utility of cyanobacteria for improving soil is therefore dependent on whether target plant species remain unaffected during its application. Methods Cyanobacteria from the genera Microcoleus and Nostoc were isolated from locally-sourced biocrust samples, and cultured under controlled conditions. A two-factor laboratory experiment was conducted including cyanobacteria and the culture growth medium (BG11) as factors. We bio-primed seeds of five species native to Western Australia, commonly used in dryland restoration, by soaking them in the cultures developed, and assessed germination and growth. Results We found significant positive effects of seeds bio-primed with cyanobacteria on germination and seedling growth of two species, Senna notabilis and Acacia hilliana, respectively. Importantly, no significant negative effects of cyanobacteria were found for any of the species studied. Conclusions Few studies of cyanobacteria effects on regeneration of native species exist. We found that the potential benefits of applying indigenous bacteria via bio-priming seeds would not inhibit plant establishment, and indeed may be beneficial for some species used in dryland restoration.