Endophytic fungi in the invasive weed Impatiens glandulifera: a barrier to classical biological control?

Amanda Currie, Alan Gange, Nadia Ab Razak, Carol Ellison, Norbert Maczey, Suzy Wood

Research output: Contribution to journalArticlepeer-review


The rust fungus, Puccinia komarovii var. glanduliferae has been introduced into the UK for biological control of the invasive weed, Impatiens glandulifera (Himalayan balsam). However, establishment of the pathogen has differed across the country, which may be partly explained by variation in plant genotype. The aim of this study was to examine whether there is a further layer of phenotypic resistance, provided by indigenous foliar endophytic fungi. Culturable endophytes were isolated from a number of different balsam populations and the commonest species were inoculated into ‘clean’ balsam plants, to test their interactions with the rust. We found that endophyte communities within balsam are low in diversity, and become more dissimilar with increasing distance between populations. Three endophytes (Colletotrichum acutatum, Alternaria alternata and Cladosporium oxysporum) were common and appeared to be antagonistic to the rust, reducing pustule number and mitigating the effect of the pathogen on plant biomass. I. glandulifera thus partially conforms to the Endophyte-enemy release hypothesis, in that as an introduced species it has an impoverished endophyte complement, acquired from the local environment. However, these endophytes represent a potential barrier to effective biological control and future weed control strategies need to find strains of rust that can overcome plant genetic resistance and the overlaying phenotypic resistance, conferred by endophytes. Future classical biological control programmes of weeds must therefore take into account the fungal bodyguards that invasive species may acquire in their introduced ranges.
Original languageEnglish
Pages (from-to)50-59
Number of pages10
JournalWeed Research
Issue number1
Early online date9 Dec 2019
Publication statusPublished - Feb 2020


  • asymptomatic fungi
  • endophyte
  • invasive species
  • pathogen
  • Puccinia komarovii var. glanduliferae
  • resistance
  • rust fungus

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