Poster Presentation Australian Microbial Ecology Conference 2024

Fungal antagonists and agonists of Austropuccinia psidii isolated from leaves of Rhodamnia rubescens (#34)

Karishma D. Kuar 1 , Ashish Kumar Sarker 1 2 , Isobel Nelson 1 , C.Oliver Morton 1 , Colin M. Stack 1 , Jonathan M. Plett 3 , Michelle C. Moffitt 1
  1. School of Science, Western Sydney University, Campbelltown, NSW, Australia
  2. Department of Pharmacy, Pabna University of Science and Technology, Pabna-6600, Rajshahi, Bangladesh
  3. Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia

Rhodamnia rubescens (scrub turpentine) is highly susceptible to myrtle rust (Austropuccinia psidii) disease. Due to this disease, it experienced huge population decline and is currently declared as a critically endangered plant species in Australia.  However, plants have evolved to utilise ecological interactions with beneficial symbiotic microorganisms and some microbes can influence plants resistance against pathogens. Therefore, this research, investigates the endophytic and leaf surface fungi inhabiting the myrtle rust infected and uninfected R. rubescens plants and potential antagonism against A.psidii.  Leaf surface and endophytic fungi were isolated from infected and uninfected R. rubescens leaves through leaf washes and maceration of sterilised entire leaf tissue and growth on chloramphenicol enriched Plant Broth Media (PBA), Czapek Dox Agar (CDA) and Potato Dextrose Agar (PDA) media. The isolated fungi were identified based on ITS gene sequences. Co-culture antagonism assays against plant pathogens Stagonosporopsis cucurbitacearum, Fusarium oxysporum and Botrytis cinereal pinus were performed and active isolates were further tested on A.psidii urediniospores. Variations in the fungal genera obtained from infected and uninfected leaves of Rhodamnia rubescens plants as well as between leaf surface and endophytic fungi were observed. Yeast isolates showed no significant decrease in the mean percentage germination of A.psidii urediniospore in vitro with leaf surface and endophytic yeasts. Screening of all fungal isolates indicates that there are some potential antagonists. Further screening and co-culture assays will reveal the effect of the isolates against A.psidii urediniospores. Given the current challenges of managing myrtle rust population in the wild and conserving susceptible Myrtaceae, there's an urgent need to investigate the natural properties of fungal endophytes and their compounds for conservation and preservation of the at-risk and endangered species.