Endophytes of horopito (Pseudowintera colorata) and their bioactive properties

Abstract

Medicinal plants are valued for the naturally bioactive compounds they produce. International research has demonstrated that these plants also contain endophytic communities of microorganisms that, through close interaction with the plant's physiology, contribute to the production of host metabolites either directly or via involvement in biochemical pathways. Some endophytes have been shown to produce bioactive compounds which are either the same or similar to those originating from their host plants. Pseudowintera colorata (horopito or NZ pepper tree), an endemic New Zealand plant used in traditional Maori medicine (rongoa), is recognized for its antimicrobial properties. The biologically active chemical constituent polygodial is used for treating candidiasis. Endophyes were recovered from surface sterilized stems, leaves and roots from horopito collected from two sites in the South Island. From this collection 22 endophytic actinobacteria were assessed for their ability to inhibit the phytopathogens Neofusicoccum parvum, Neofusicoccum luteum, Ilyonectria liriodendri and Nectria galligena using a dual culture technique. Inhibition zones greater than 3 mm were considered a positive result. Out of the isolates tested strain PRY2BA2 showed activity against all test pathogens. Strains PRY2RB1 and PRY2RC1 were active against three test pathogens and four other isolates were active against at least one test pathogen. The endophyte collection recovered from horopito included known pathogenic fungi and further experiments are planned to discover the role of these actinobacteria in protecting horopito. Future work will also determine if any endophytes produce the antimicrobial agent polygodial.