Oral Presentation Australian Microbial Ecology 2022

Diversity, biogeography and plant growth promotion potential of native Australian seed microbiomes (#23)

Allison Mertin 1 , Marlien Van der merwe 2 , Edward C.Y. Liew 2 , Douglas Brumley 3 , Linda L Blackall 4
  1. University of Melbourne & Royal Botanic Gardens Sydney, Petersham, NSW, Australia
  2. Research Centre for Ecosystem Resilience, Royal Botanic Gardens Sydney, Sydney, NSW, Australia
  3. School of Mathematics and Statistics, University of Melbourne, Melbourne, VIC, Australia
  4. School of Biosciences, University of Melbourne, Melbourne, VIC, Australia

Seed microorganisms are dispersed with the plant seed and are already present at the first stages of a seedling. Seed endophytes (microorganisms within seed tissues) therefore, form the primary inoculum for the initial plant microbiome. Seed endophytes can increase germination and root development but can also be latent pathogens and some can cause seed decay. As many plants within restored sites have low rates of germination, it is important to identify key members of the seed microbiome. Research is focussed on agricultural plants, with knowledge for natural ecosystems lacking, limiting their application to restoration. 

We studied the taxonomic and functional diversity of seed microbiomes of one native Australian tree (Melaleuca quinquenervia) and two native grasses (Microlaena stipoides and Themeda triandra), which are used in restoration. We sampled from fifty-two sites in NSW and the ACT. We identified fungi and bacteria from metabarcoding of the ITS2 region of rRNA (fungi) and the V4 region of the 16S rRNA gene (bacteria). Our results uncovered a diverse seed microbiome representing two fungal phyla (223 families) and 20 bacterial phyla (159 bacterial families), from the host species combined. M. quinquenervia was dominated by the bacteria Lichenihabitans and Pseudomonas, and the fungi Pestalotiopsis and Crustomyces. Microlaena stipoides and T. triandra were similar, dominated by the bacteria Pantoea and Pseudomonas, and the fungi Alternaria. 

To identify factors that may shape the seed microbiome we are determining whether populations show biogeographical structuring and whether sites that are geographically and abiotically more similar house more similar seed microbiomes. We also have a pure culture collection isolated from the seed (520 fungal and 450 bacterial) and are phenotyping them for plant growth promotion traits to provide insight into their potential role in plant fitness and for improving restoration efforts for these plant species. We show that many of the isolates demonstrate the ability to produce indole-acetic-acid and ACC-deaminase, compounds which can improve mineral acquisition for the host plant.