Culturable fungal endophytes in Australian macadamia nursery plants

Macadamia is a high value tree nut crop that is endemic to subtropical Australia and grown commercially worldwide. Frequency of pathogen-induced crop loss is increasing globally. The role that nursery plants play in disease occurrence in macadamia is limited and therefore, this article provides baseline information on fungal endophytes in nursery plants. Fungi were isolated from plant parts (root, stem and leaf) of 3-month-old germinated seedlings and 18-month-old potted plants of the rootstock cv. H2. Fungal identification barcode to the genus level was performed using DNA sequencing of the internal transcribed spacer (ITS) gene region. The most frequently isolated genus was Penicillium sensu lato from germinated seedlings (48%), whereas Pestalotiopsis was from potted plants (19%). The diversity of fungal genera that include plant pathogens was highest in leaves of potted plants compared with germinated seedlings. Thus, growth stage and plant parts influenced the occurrence and diversity of endophytes in healthy macadamia plants. Genera containing beneficial and potentially pathogenic fungal species including Trichoderma, Penicillium, Curvularia, Muscodor and Colletotrichum were isolated as endophytes in germinated macadamia seedlings and potted plants. Fungal genera (Diaporthe, Pestalotiopsis, Cladosporium, Lasiodiplodia and Neofusicoccum) containing species of known pathogens that cause diseases in macadamia trees were also isolated from nursery plants. The role of the endophytic fungal community of seedlings and potted plants in macadamia nursery are discussed.

Automated summary

This article provides baseline information on fungal endophytes in nursery plants of Macadamia, discussing how growth stage and plant parts influence the occurrence and diversity of endophytes. Furthermore, the study isolates both beneficial and potentially pathogenic fungal species in germinated seedlings and potted plants, highlighting the importance of understanding the endophytic fungal community in nursery settings for this high value tree nut crop.