Termite–gut-associated actinomycetes as biological control agents against phytopathogen Pyrrhoderma noxium

Abstract

Brown root-rot disease is caused by phytopathogenic white-rot basidiomycete fungus, Pyyrhoderma noxium. Currently, it is causing significant issues for the Brisbane hinterland in Queensland, Australia and killing many tree species throughout the greater Metropolitan area, including park and street trees located in Shorncliffe, Taringa, New Farm, Eagle Farm, West End, Hamilton, Indooroopilly, Brisbane River, and the City Centre. Brisbane trees being attacked are figs, poinciana, jacarandas, Chinese elms, Moreton Bay eucalypts, kauris, and hoop pines and these include both public and privately owned trees. A joint study between the University of the Sunshine Coast (UniSC) and the Brisbane City Council (BCC) aimed to assess the efficacy of different biological control agents to control infections in the region. In a substudy presented here, termite gut-associated actinomycetes were evaluated to determine their antifungal abilities against the pathogen.

In vitro biological control of Pyrrhoderma noxium using volatile compounds produced by termite gut-associated streptomycetes

“…The pathogen has also now been found to cause significant damage across the city of Brisbane in the state of Queensland, Australia. The culturally important heritage fig trees ( Ficus macrophylla ) found in many of the city’s parks and roadsides have been infected with P. noxium resulting in brown root-rot the pathogen induces ( Adra et al., 2022 ; Panchalingam et al., 2022 ). Historically, plant protection from fungal pathogens has been achieved using chemical fungicides.…”

Identification of Acetomycin as an Antifungal Agent Produced by Termite Gut-Associated Streptomycetes against Pyrrhoderma noxium

“…Due to the decay within the roots, the trees easily fall down, which can be a threat to public safety [8]. Currently, the city of Brisbane in Queensland, Australia, is facing the spread of this pathogen and the subsequent destruction of many of the amenity trees [9,10]. Numerous privately owned and park trees are being killed, including the heritage Moreton Bay fig trees, poinciana, jacarandas, and hoop pines [9,11].…”

“…Currently, the city of Brisbane in Queensland, Australia, is facing the spread of this pathogen and the subsequent destruction of many of the amenity trees [9,10]. Numerous privately owned and park trees are being killed, including the heritage Moreton Bay fig trees, poinciana, jacarandas, and hoop pines [9,11]. As chemical control methods are deemed no longer suitable, particularly within public locations due to their harmful effects and persistent nature, alternative methods are required [12].…”

“…One such resource is from insect guts that contain communities of transient and symbiotic microorganisms [20]. Termites feed mostly on wood and litter tissue, meaning they would frequently encounter various fungal pathogens and would, therefore, require defense mechanisms to protect themselves against invading pathogens [9,21]. It has also been reported that actinomycetes are among the most dominant taxonomic group within the guts of termites, with a majority of the actinomycetes belonging to the genus Streptomyces [22].…”

“…The objective of this study was to identify bioactive antifungal compounds as potential biological control agents to control the plant pathogen P. noxium infecting heritage fig trees in Brisbane City, Australia. As part of the ongoing research on antifungal natural products derived from termite gut-associated Streptomyces isolates [9,27], this paper reports the identification of acetomycin (compound 1) as a key component of the bioactive compounds in several termite gut-associated Streptomyces isolates with inhibitory activity towards plant fungal pathogen P. noxium.…”