2 Bioefficacy of Endophytes in the Control of Plant Diseases
21
classification proposed by Rodriguez et al. (2009). In these interactions, fungi inside
plant tissues can produce ergot alkaloids that prevent against parasitoid infections,
mainly represented by herbivores insects (Bacon et al. 1986; Torres et al. 2008). These
plant-fungal interactions affect directly the insect abundance with consequences in
the balance of the food-web dynamics (Omacini et al. 2001). Also, a recent study
has demonstrated another protective mechanism involved in Epichlöe-grass systems
that are based on the alteration of the plant odor to attract aphid predators (Fuchs
and Krauss 2019).
Endophytes-grass interactions have been described as mutualism. In this sense,
Clay (1988) has described endophyte-grass interactions as a “defensive mutualism.”
Further studies have demonstrated that the effects of these interactions depend on
global factors, such as plant genotype and environmental conditions, leading to
neutral situations or turning into a pathogenic outcome (Faeth and Fagan 2002;
Müller and Krauss 2005; Saikkonen et al. 2006).
The research conducted on endophyte-grass interactions is oriented to a better
understanding of the effects on all the components of the ecosystem. For example,
it has been studied the relation between grass-endophytes, growth and fecundity of
their hosts, and the further reconstruction of the plant community with the implication
in the restoration of prairies (Moore et al. 2019). On the other hand, some studies
analyzed the effect of endophytes on other soil microorganisms such as mycorrhizal
fungi (Kalosa-Kenyon et al. 2018), and the cattle in agro-ecosystems (Bultman et al.
2018).
Since transmission of grass-endophytes occurs horizontally as well as vertically,
it protects all the plant tissues in every plant generation (Rodriguez et al. 2009).
This phenomenon would help the establishment of certain plant species in particular environments, which denotes the evolutionary impact of this kind of interaction,
in which the permanence of plant species may be a consequence of the interaction
with particular fungal endophytes (Saikkonen et al. 2004). Thus, grassland protection conferred by endophytes makes these microbes beneficial for augmenting integrated pest management programs and considering sustainable agriculture premises
(Kauppinen et al. 2016).
2.3.2 Non-Clavicipitaceous Fungal Endophytes
Despite most research on fungal endophytes is represented by the grass-endophytes
interactions, there is increasing interest in fungal endophytes belonging to the NonClavicipitaceous group, as these fungal endophytes are also able to impair the proliferation of pathogens and decrease the severity of symptoms by direct interaction
(Arnold et al. 2000). Interestingly, fungal endophytes can reduce pathogenic infections even when both organisms are closely related. For example, Colletotrichum
magna can infect Cucumis sativus and confer protection against C. orbiculare and
F. oxysporum (Redman et al. 1999). This evidence demonstrates that despite the
pathogenic role of certain fungi, such as Fusarium species, they are also able to
21
classification proposed by Rodriguez et al. (2009). In these interactions, fungi inside
plant tissues can produce ergot alkaloids that prevent against parasitoid infections,
mainly represented by herbivores insects (Bacon et al. 1986; Torres et al. 2008). These
plant-fungal interactions affect directly the insect abundance with consequences in
the balance of the food-web dynamics (Omacini et al. 2001). Also, a recent study
has demonstrated another protective mechanism involved in Epichlöe-grass systems
that are based on the alteration of the plant odor to attract aphid predators (Fuchs
and Krauss 2019).
Endophytes-grass interactions have been described as mutualism. In this sense,
Clay (1988) has described endophyte-grass interactions as a “defensive mutualism.”
Further studies have demonstrated that the effects of these interactions depend on
global factors, such as plant genotype and environmental conditions, leading to
neutral situations or turning into a pathogenic outcome (Faeth and Fagan 2002;
Müller and Krauss 2005; Saikkonen et al. 2006).
The research conducted on endophyte-grass interactions is oriented to a better
understanding of the effects on all the components of the ecosystem. For example,
it has been studied the relation between grass-endophytes, growth and fecundity of
their hosts, and the further reconstruction of the plant community with the implication
in the restoration of prairies (Moore et al. 2019). On the other hand, some studies
analyzed the effect of endophytes on other soil microorganisms such as mycorrhizal
fungi (Kalosa-Kenyon et al. 2018), and the cattle in agro-ecosystems (Bultman et al.
2018).
Since transmission of grass-endophytes occurs horizontally as well as vertically,
it protects all the plant tissues in every plant generation (Rodriguez et al. 2009).
This phenomenon would help the establishment of certain plant species in particular environments, which denotes the evolutionary impact of this kind of interaction,
in which the permanence of plant species may be a consequence of the interaction
with particular fungal endophytes (Saikkonen et al. 2004). Thus, grassland protection conferred by endophytes makes these microbes beneficial for augmenting integrated pest management programs and considering sustainable agriculture premises
(Kauppinen et al. 2016).
2.3.2 Non-Clavicipitaceous Fungal Endophytes
Despite most research on fungal endophytes is represented by the grass-endophytes
interactions, there is increasing interest in fungal endophytes belonging to the NonClavicipitaceous group, as these fungal endophytes are also able to impair the proliferation of pathogens and decrease the severity of symptoms by direct interaction
(Arnold et al. 2000). Interestingly, fungal endophytes can reduce pathogenic infections even when both organisms are closely related. For example, Colletotrichum
magna can infect Cucumis sativus and confer protection against C. orbiculare and
F. oxysporum (Redman et al. 1999). This evidence demonstrates that despite the
pathogenic role of certain fungi, such as Fusarium species, they are also able to