6 Microbial Endophytes: New Direction to Natural Sources
127
ecosystem processes and are important for the structure, function, and health of the
plant community (Molina-Montenegro et al. 2015) (Table 6.2).
6.3 Classification of Endophytic Fungi
Fungal endophytes are a diverse group of microorganisms that are broadly divided
into two groups, clavicipitaceous (C) and non-clavicipitaceous (NC) based on their
life cycle, evolutionary dependence, host plant range, and ecological class function (De Silva et al. 2019). On the other hand, Clavicipitaceous endophytes (family
of Clavicipitaceae) including Atkinsonella, Balansia, Balansiopsis, Echinodothis,
Epichloe, Myriogenospora, Neotyphodium, and Parepichloe are usually associated
with the herbaceous plants of the Poaceae family (De Silva et al. 2019). Nonclavicipitaceous endophytes such as Fusarium sp., Colletotrichum sp., Phomopsis sp.
and Xylaria sp. are associated with several plants and does not spend their complete
life cycle inside the host plant (De Silva et al. 2019; Rodriguez et al. 2009; Jayawardena et al. 2016). A significant attention on endophytes includes various disciplines
because of their ability to switch between endophytic, pathogenic, and saprophytic
lifestyles (De Silva et al. 2019; Rodriguez et al. 2009) (Table 6.3).
Clavicipitaceous endophytes, live as intracellular symbionts are mainly transmitted from mother plants to off-spring and systematically grow in the leaves and
stems, by vertical transfer from the mother plant to their off-spring. The off-spring are
seed-borne and have systemic growth within the plant’s tissues (De Silva et al. 2019;
Arnold et al. 2003; Santangelo et al. 2015). In contrast, endophytes associated with
the foliage of woody plants are transmitted horizontally by sexual or asexual spores
(De Silva et al. 2019; Arnold et al. 2003). The above examples confirm about the
importance of endophytic fungi that are biological control agents. The next important
question arises how endophytes reduce disease and pests.
6.4 Plant Defense Responses in Relation
to Endophyte-Pathogen and Host Plant
Sustainable agriculture can be achieved by reducing or eliminating chemical fertilizers and agrochemicals, which are resulting in harmful environmental impact.
Recently, application of antagonist endophytes as biological control agents (BCA)
has gained momentum and received special attention for plant diseases management with comparatively low negative impacts on the environment (De Silva et al.
2019). Symptom-free colonization of endophytes can be explained by the hypothesis
of “balanced antagonism” (Kusari et al. 2012). Balanced adaptation between host
and endophyte is maintained by avoiding activation of host defense, activation, and
production of toxic metabolites by host. On the other hand, if plant defense becomes
127
ecosystem processes and are important for the structure, function, and health of the
plant community (Molina-Montenegro et al. 2015) (Table 6.2).
6.3 Classification of Endophytic Fungi
Fungal endophytes are a diverse group of microorganisms that are broadly divided
into two groups, clavicipitaceous (C) and non-clavicipitaceous (NC) based on their
life cycle, evolutionary dependence, host plant range, and ecological class function (De Silva et al. 2019). On the other hand, Clavicipitaceous endophytes (family
of Clavicipitaceae) including Atkinsonella, Balansia, Balansiopsis, Echinodothis,
Epichloe, Myriogenospora, Neotyphodium, and Parepichloe are usually associated
with the herbaceous plants of the Poaceae family (De Silva et al. 2019). Nonclavicipitaceous endophytes such as Fusarium sp., Colletotrichum sp., Phomopsis sp.
and Xylaria sp. are associated with several plants and does not spend their complete
life cycle inside the host plant (De Silva et al. 2019; Rodriguez et al. 2009; Jayawardena et al. 2016). A significant attention on endophytes includes various disciplines
because of their ability to switch between endophytic, pathogenic, and saprophytic
lifestyles (De Silva et al. 2019; Rodriguez et al. 2009) (Table 6.3).
Clavicipitaceous endophytes, live as intracellular symbionts are mainly transmitted from mother plants to off-spring and systematically grow in the leaves and
stems, by vertical transfer from the mother plant to their off-spring. The off-spring are
seed-borne and have systemic growth within the plant’s tissues (De Silva et al. 2019;
Arnold et al. 2003; Santangelo et al. 2015). In contrast, endophytes associated with
the foliage of woody plants are transmitted horizontally by sexual or asexual spores
(De Silva et al. 2019; Arnold et al. 2003). The above examples confirm about the
importance of endophytic fungi that are biological control agents. The next important
question arises how endophytes reduce disease and pests.
6.4 Plant Defense Responses in Relation
to Endophyte-Pathogen and Host Plant
Sustainable agriculture can be achieved by reducing or eliminating chemical fertilizers and agrochemicals, which are resulting in harmful environmental impact.
Recently, application of antagonist endophytes as biological control agents (BCA)
has gained momentum and received special attention for plant diseases management with comparatively low negative impacts on the environment (De Silva et al.
2019). Symptom-free colonization of endophytes can be explained by the hypothesis
of “balanced antagonism” (Kusari et al. 2012). Balanced adaptation between host
and endophyte is maintained by avoiding activation of host defense, activation, and
production of toxic metabolites by host. On the other hand, if plant defense becomes