Serendipita Species from Australian Native Orchids and their Impacts on Tomato Growth and Protection Against Powdery Mildew

Serendipita Species from Australian Native Orchids and their Impacts on Tomato Growth and Protection Against Powdery Mildew

Most plants form symbiotic associations with mycorrhizal fungi, which provide water and inorganic nutrients to the host and in exchange obtain plant-derived carbohydrates for their own growth. Fungi in the Serendipitaceae form mycorrhizal associations with a wide variety of plant species including grasses, orchids, ericoids and bryophytes. Serendipita indica is the most extensively studied species in the Serendipitaceae, due to its ease of culture on artificial media and its ability to colonise the roots of various plant species. Previous studies have shown that colonisation with S. indica enhances the growth of the shoots and roots of many plants and protects plants against biotic and abiotic stresses. The first aim of this project was to isolate and identify Serendipita spp. from native Australian orchids including Caladenia spp. and Bulbophyllum spp. in south east Queensland. Five known Serendipita spp. were isolated from seven Caladenia species and identified using morphological and molecular methods. Two likely new species of Serendipita were also isolated from Bulbophyllum schillerianum and B. bracteatum. The fungal isolates from B. minutissimum and B. shepherdii also included endophytic Preussia and Tulasnella respectively. Inoculating plants with a recently described Serendipita species, S. whamiae, increased the fresh weight of tomato and improved immunity against the powdery mildew pathogen, Golovinomyces lycopersici. Semi-quantitative RT-PCR analysis showed no difference in the expression of nutrient transporters between Serendipitacolonised tomato and non-colonised plants. In Serendipita-colonised plants challenged with powdery mildew, there was inconsistent expression pattern of a β-1,3-glucanase gene and no expression in chitinase, callose 11 synthase, phenylalanine ammonia lyase and JA-Lipoxygenase genes. Serendipita inoculants may represent an alternative eco-friendly and non-chemical approach for enhancing plant growth and pathogen control in agriculture and horticulture.

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