Project Summary

I approached MLA in 2016 to see if my previous experience with dieback might be useful for determining what is causing this syndrome in pastures across Queensland. Having previously done biological consulting I had some experience in setting up this small project. My experience extended to a talent for being able to explain complex scientific protocols and concepts to collaborators with a variety of backgrounds, including cattle breeders, corporate executives and council members

I proposed conducting a multiplex microbial sequencing analysis of the microbiome associated with healthy and dieback-affected pasture species. This was based on the final chapter of my PhD thesis wherein I describe a potential workflow for diagnosing dieback in plants

This would investigate the importance of beneficial endophytes (microbes living in plants) and also focus on pathogens that may exist in pasture, or that are introduced by insects like mealybugs

We used next-generation Illumina MiSeq sequencing at QUT's CARF (one of only a few such platforms in Australia available for commercial use), to sequence specific genes that target the fungi and bacteria living in healthy pasture grass and soil, and compared these species to those living in dieback-affected grass. We also sequenced genes from a group of fungi-like organisms called Oomycetes which are renowned for causing dieback in other plants, but have not yet been found to associate with grasses

The raw data produced by the MiSeq platform (in the form of millions of DNA bases) were put through a data analysis pipeline which assigned the identities of the sequenced microorganisms by comparing each DNA sequence with the publicly available genetic database, GenBank. The data analysis pipeline also converted the raw sequence data to relative abundance data. 

Knowing which species are found in dieback-affected grass and how prevalent they are will help to identify the species associated with dieback-occurrence. The results will show what pathogens are most likely involved, whether there may be “protective” or “beneficial” microorganisms protecting the healthy grass. These could be the focus of management options

At this stage, the causal agent of pasture dieback is pointing to a tiny soil-dwelling mealy bug (Heliococcus sp.) as the likely cause. The data from the sequencing was added to all other analyses to try to work out correlations with dieback occurrence (publications pending) and what a management options are available.