130
A. Ghasemnezhad et al.
Table 6.3 Endophyte
classification
Non-clavicipitaceous (NC)
Clavicipitaceous (C)
Fusarium
Colletotrichum
Phomopsis
Xylaria
Atkinsonella
Balansia
Balansiopsis
Echinodothis
Epichloe
Myriogenospora
Neotyphodium
Parepichloe
active and fights with fungal agents, the fungus will not be able to colonize plant
tissues (De Silva et al. 2019; Kusari et al. 2012; Suryanarayanan et al. 2016). Further,
plants produce an array of secondary metabolites against weeds and pathogens. As
known, fungi and bacteria produce specialized enzymes and secondary metabolites
to overcome these plant defense barriers and defend to cause disease, if pathogenic.
For example, endophytic fungi produce toxic compounds, while plants produce antifungal metabolites such as condensed tannins (Schulz et al. 1999; Randriamanana
et al. 2018).
Some endophytes become pathogens when they are influenced by certain intrinsic
and environmental factors to express the factors that lead to pathogenesis (Kusari
et al. 2012). The above said phenomenon is common due to excessive moisture or
nutrient deficiencies that alter the susceptibility of the host to the natural conditions
(De Silva et al. 2019; Fisher and Petrini 1992). Endophyte, such as Epichloe festucae
express the mitogen-activated protein kinase (sakA) gene to maintain interaction
with the host Lolium perenne (perennial ryegrass). If the fungus is unable to express
the gene, the endophyte becomes pathogenic and or disadvantaged in environmental
conditions (De Silva et al. 2016). It has recently been observed that gene conferring
secondary metabolite production in fungi is non-expressible in pure culture and can
be activated in dual experiments with antagonist microbes (De Silva et al. 2019).
Fungi act as stimulator for host defense via two mechanisms: (i) acquired systemic
resistance (SAR) and (ii) inducible systemic resistance (ISR) (De Silva et al. 2019;
Busby et al. 2016). Other various mechanisms of antagonistic activity of an BCA
have been described as mycoparasitism, lytic and/or antibiotic production, induction
of plant defense, and competition for nutrients and ecological niches (De Silva et al.
2019; Busby et al. 2016). Plant defense responses include altering the biochemistry
of cell wall, producing pathogenesis-related proteins (PR), and/or generating specific
resistance ISR.
In natural conditions, BCAs must tolerate a wider range of climatic factors
(temperature, humidity, UV light), soil (soil type), and biotic agents (antagonists),
that are not ruling-out under laboratory conditions (Chow et al. 2019). As a result, the
levels of defense enzymes are unlikely remain stable at elevated levels and are likely
to decrease after several hours or days (Chow et al. 2019). Evidence suggests that
endophyte colonization reproduces plant gene expression, reducing physiological
A. Ghasemnezhad et al.
Table 6.3 Endophyte
classification
Non-clavicipitaceous (NC)
Clavicipitaceous (C)
Fusarium
Colletotrichum
Phomopsis
Xylaria
Atkinsonella
Balansia
Balansiopsis
Echinodothis
Epichloe
Myriogenospora
Neotyphodium
Parepichloe
active and fights with fungal agents, the fungus will not be able to colonize plant
tissues (De Silva et al. 2019; Kusari et al. 2012; Suryanarayanan et al. 2016). Further,
plants produce an array of secondary metabolites against weeds and pathogens. As
known, fungi and bacteria produce specialized enzymes and secondary metabolites
to overcome these plant defense barriers and defend to cause disease, if pathogenic.
For example, endophytic fungi produce toxic compounds, while plants produce antifungal metabolites such as condensed tannins (Schulz et al. 1999; Randriamanana
et al. 2018).
Some endophytes become pathogens when they are influenced by certain intrinsic
and environmental factors to express the factors that lead to pathogenesis (Kusari
et al. 2012). The above said phenomenon is common due to excessive moisture or
nutrient deficiencies that alter the susceptibility of the host to the natural conditions
(De Silva et al. 2019; Fisher and Petrini 1992). Endophyte, such as Epichloe festucae
express the mitogen-activated protein kinase (sakA) gene to maintain interaction
with the host Lolium perenne (perennial ryegrass). If the fungus is unable to express
the gene, the endophyte becomes pathogenic and or disadvantaged in environmental
conditions (De Silva et al. 2016). It has recently been observed that gene conferring
secondary metabolite production in fungi is non-expressible in pure culture and can
be activated in dual experiments with antagonist microbes (De Silva et al. 2019).
Fungi act as stimulator for host defense via two mechanisms: (i) acquired systemic
resistance (SAR) and (ii) inducible systemic resistance (ISR) (De Silva et al. 2019;
Busby et al. 2016). Other various mechanisms of antagonistic activity of an BCA
have been described as mycoparasitism, lytic and/or antibiotic production, induction
of plant defense, and competition for nutrients and ecological niches (De Silva et al.
2019; Busby et al. 2016). Plant defense responses include altering the biochemistry
of cell wall, producing pathogenesis-related proteins (PR), and/or generating specific
resistance ISR.
In natural conditions, BCAs must tolerate a wider range of climatic factors
(temperature, humidity, UV light), soil (soil type), and biotic agents (antagonists),
that are not ruling-out under laboratory conditions (Chow et al. 2019). As a result, the
levels of defense enzymes are unlikely remain stable at elevated levels and are likely
to decrease after several hours or days (Chow et al. 2019). Evidence suggests that
endophyte colonization reproduces plant gene expression, reducing physiological