plant defense may be similar to other fungal phytopathogens that use LysM effector
molecules in modulating host immunity (Cen et al. 2017). Artificial wounding of
above-ground maize tissues enhanced the persistence of B. bassiana inoculum in the
rhizosphere suggesting signal transduction and a strategy by the plant to cope with
herbivory (McKinnon et al. 2018). Raad et al. (2019) reported the upregulation of
molecular pattern recognition receptors and changes in transcriptional factors of
plant defense pathway in B. bassiana-inoculated Arabidopsis thaliana, suggesting
MAMP-triggered immunity. These reports provide evidence that suggests Beauveria
spp. may play a role in plant growth and defense modulation under stress conditions.
Field-based studies will be necessary to confirm that observations from laboratory
and greenhouse experiments occur in the field.
Plants can regulate the production of secondary metabolites for enhanced
defense. For example, endophytic colonization by B. bassiana enhanced the biosynthesis of terpenes in tomato leaves that may lead to the production of biologicallyactive metabolites (Shrivastava et al. 2015). Terpenes are considered to be chemical
defense molecules that plants use to alert other plants of the presence of herbivory
(Ahern and Whitney 2014; Reid and Purcell 2011).
EIPF from other genera have been reported to induce defense in plant hosts under
various stress conditions. For example, proteomic analysis revealed that date palm
colonized with L. dimorphum and L. cf. psalliotae showed differential induction of
stress and defense-related proteins (Gómez-Vidal et al. 2009).
13.5 EIPF in Nutrient Exchange
One of the strategies that some plant-associated microbes have evolved is nutrient
exchange, in which the endophyte provides some benefit to the plant host, such as
plant growth promotion, in exchange for nutrients from the host plant. Some
endophytes aid in nutrient absorption and assimilation possibly by affecting root
morphology directly or indirectly. Accessible nitrogen is one of the most important
nutrients for plants and accessible carbon is the limiting nutrient for soil fungi (Smith
et al. 2009). Genes associated with metabolic pathways of nitrogen and carbon in
plants and EIPF may affect root colonization by EIPF (Liao et al. 2013). PaungfooLonhienne et al. (2015) demonstrated that nitrogen concentration in growth media
can strongly affect the abundance of EIPF in the fungal community of the rhizosphere. The source and fertility of the plant growth medium are a major growth
determining factor and plants can shift their association with EIPF according to their
needs. For example, the detection of M. anisopliae and B. bassiana was less variable
in sterile vermiculite compared with sterile soil:sand:peat growth medium
suggesting an effect due to variability in nutrients due to greater competition in a
non-sterile environment (Parsa et al. 2018). Non-sterile growth environments may
also reduce endophytic colonization efficiency of EIPF possibly due to competition
with other microbes (Parsa et al. 2018; Tefera and Vidal 2009).
Some Metarhizium spp. appear to promote plant growth through nutrient transfer
(reviewed in Vega 2018). Behie et al. (2017) and Behie et al. (2012) reported that
13 The Role of Endophytic Insect-Pathogenic Fungi in Biotic Stress Management
387
molecules in modulating host immunity (Cen et al. 2017). Artificial wounding of
above-ground maize tissues enhanced the persistence of B. bassiana inoculum in the
rhizosphere suggesting signal transduction and a strategy by the plant to cope with
herbivory (McKinnon et al. 2018). Raad et al. (2019) reported the upregulation of
molecular pattern recognition receptors and changes in transcriptional factors of
plant defense pathway in B. bassiana-inoculated Arabidopsis thaliana, suggesting
MAMP-triggered immunity. These reports provide evidence that suggests Beauveria
spp. may play a role in plant growth and defense modulation under stress conditions.
Field-based studies will be necessary to confirm that observations from laboratory
and greenhouse experiments occur in the field.
Plants can regulate the production of secondary metabolites for enhanced
defense. For example, endophytic colonization by B. bassiana enhanced the biosynthesis of terpenes in tomato leaves that may lead to the production of biologicallyactive metabolites (Shrivastava et al. 2015). Terpenes are considered to be chemical
defense molecules that plants use to alert other plants of the presence of herbivory
(Ahern and Whitney 2014; Reid and Purcell 2011).
EIPF from other genera have been reported to induce defense in plant hosts under
various stress conditions. For example, proteomic analysis revealed that date palm
colonized with L. dimorphum and L. cf. psalliotae showed differential induction of
stress and defense-related proteins (Gómez-Vidal et al. 2009).
13.5 EIPF in Nutrient Exchange
One of the strategies that some plant-associated microbes have evolved is nutrient
exchange, in which the endophyte provides some benefit to the plant host, such as
plant growth promotion, in exchange for nutrients from the host plant. Some
endophytes aid in nutrient absorption and assimilation possibly by affecting root
morphology directly or indirectly. Accessible nitrogen is one of the most important
nutrients for plants and accessible carbon is the limiting nutrient for soil fungi (Smith
et al. 2009). Genes associated with metabolic pathways of nitrogen and carbon in
plants and EIPF may affect root colonization by EIPF (Liao et al. 2013). PaungfooLonhienne et al. (2015) demonstrated that nitrogen concentration in growth media
can strongly affect the abundance of EIPF in the fungal community of the rhizosphere. The source and fertility of the plant growth medium are a major growth
determining factor and plants can shift their association with EIPF according to their
needs. For example, the detection of M. anisopliae and B. bassiana was less variable
in sterile vermiculite compared with sterile soil:sand:peat growth medium
suggesting an effect due to variability in nutrients due to greater competition in a
non-sterile environment (Parsa et al. 2018). Non-sterile growth environments may
also reduce endophytic colonization efficiency of EIPF possibly due to competition
with other microbes (Parsa et al. 2018; Tefera and Vidal 2009).
Some Metarhizium spp. appear to promote plant growth through nutrient transfer
(reviewed in Vega 2018). Behie et al. (2017) and Behie et al. (2012) reported that
13 The Role of Endophytic Insect-Pathogenic Fungi in Biotic Stress Management
387