Abstract:
Endophytes are organisms that inhabit plant organs and colonise plant tissues without
causing obvious signs of disease. Much research has been done to elucidate the effects that
endophytes have on their hosts, but the majority of these studies have been done on grass
species that are considered model organisms. Evidence shows that endophytes evolved
from closely related pathogenic fungi, because many endophytes are latent pathogens or
saprobes that only sporulate when their hosts are stressed or dying. Hence, it is important to
understand the principles surrounding endophyte biology and the effects that they could have
on their hosts. There are specialised mechanisms involved enabling endophyte-host
interactions to exist and these have co-evolved over millions of years. Endophytic symbionts
affect the growth and fitness of their hosts, as well as their ability to tolerate biotic and abiotic
stressors. In most cases, however, the ecological role and basis for the interaction between
plants and their diverse assemblage of endophytes remain obscure and this is especially true
for trees. Given the prominent presence of endophytes and the large part of biological
diversity that they represent, further work to clarify these roles is urgently needed. This
review aims to establish an understanding of the theory surrounding fungal endophytes,
endophyte-host interactions, modes of infection, the influence of endophytes on their hosts,
the co-evolution of life-history traits and why endophytes are important in their environments.
