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No. 9, January 2011
Endophytes: novel weapons in the IPM arsenal
Alexandra zum Felde
CGIAR Systemwide Program
on Integrated Pest
Management (SP-IPM) is a
global partnership that draws
together the diverse IPM
research, knowledge and
expertise of the international
agricultural research centers
and their partners to build
synergies in research outcomes
and impacts, and to respond
more effectively to the needs
of farmers in developing
countries.
What are endophytes?
Endophytes are microorganisms that live in plant tissue for part or all of their lifecycle (Sikora et al. 2007), and
can be classified as beneficial, neutral, or detrimental, depending on the nature of their interaction with their host
plant. Though not initially identified or recognized as such, many well-known and studied organisms are in fact
endophytes: arbuscular mycorrhizal fungi and rhizobia, for example, are beneficial endophytes, whereas the
Fusarium spp. causing wilt are examples of detrimental endophytes.
Microbial and fungal endophytes have been
isolated from a broad range of plants,
including grasses, herbs, and trees, and
from various plant tissues (Backman &
Sikora, 2008). Mutualistc endophytes have
been defined as beneficial microorganisms
that protect plants from pests and diseases
and can enhance plant growth. They are
especially interesting for IPM as innovative
biological control agents (BCAs).
Endophytes to enhance plant defense and growth: Fusarium spp. (left)
and Trichoderma spp. (right). – A. zum Felde
How do mutualistic endophytes work?
A lot of research has recently focused on exposing the modes of action of mutualistic endophytes. What has
become clear from these studies is that some endophytes activate their host plant’s existing defense
mechanisms, sometimes before pests/pathogens are introduced into the system and sometimes afterwards (Vu
et al. 2006; Paparu et al. 2008). Other endophytes seem to directly antagonize pests/pathogens, either by
producing metabolites detrimental to the pest/pathogen in question (Hallmann & Sikora 2006), or by competing
with it for nutrients (Olivain et al. 2006).
Further research into the subject may identify additional modes of action though it is already known that greater
plant protection can be achieved when plants are inoculated with multiple endophytes (zum Felde et al. 2009;
Sikora et al. 2010). However, when studied, the effects of inoculating multiple endophytes versus single
endophytes were neither synergistic nor additive. This may be due to the inoculated endophytes having similar
modes of action. If endophytes with different modes of action were inoculated, control levels would feasibly be
additive. For this reason, the search for the perfect combination of endophytes to mimic the natural conditions
found in suppressive plants should be a research priority.
SP-IPM Technical Innovation
Briefs present, in short, IPM
research findings and
innovations for the
management of pests, diseases
and weeds in agricultural
production.
This and other IPM Briefs are
available from
www.spipm.cgiar.org
Why use endophytes?
A major advantage of endophytes is that their use
circumvents many of the problems traditionally
associated with inundative inoculations of conventional
BCAs on fields. For example, endophytes can be applied
solely to seeds (i.e., in seed coating/dressing) or to
seedlings (especially tissue culture plants or seedlings in
rooting trays). Thereby the need to treat huge quantities
of surface soil or large numbers of already established
plants in the field is avoided. This requires large amounts
of BCA propagules, and exposes the BCA to other
Banana seedlings in rooting tray dipped in endophyte spore
suspension. – A. zum Felde