230
K. Lasudee et al.
analysis, the actinomycetes group of organisms is now renamed as actinobacteria.
They are widely distributed in natural environments and established in cells and
tissues of plants. Members of actinobacteria in particular Streptomyces spp. are
major producers of antimicrobial agents and bioactive compounds, some of which
are being used today as antibacterial, antifungal, anticancer, or cholesterol-lowering
drugs (Barka et al. 2016). On the other hand, they have the potential to produce
plant growth-promoting compounds and have biocontrol properties (Singh et al.
2018; Suarez-Moreno et al. 2019; Liotti et al. 2019). Actinobacteria can be used to
improve plant growth and promote growth of plants under both abiotic and biotic
stresses. Similar to other PGP bacteria, they can promote plant growth via direct
and indirect mechanisms (Olanrewaju et al. 2017; Sathya et al. 2017; Vurukonda
et al. 2018). Nitrogen fixation, phytohormones production, phosphate solubilization, siderophore production, etc., are considered as direct (Glick 2012; Hamadi
and Mohammadipanah 2015; Vurukonda et al. 2018). Whereas indirect mechanisms
include antibiotics production (Dinesh et al. 2017; Singh and Dubey 2018) and
production of lytic enzymes to degrade the cell wall of fungal pathogens (Singh
and Gaur 2016; Sathya et al. 2017; Gasmi et al. 2019). Thus, actinobacteria are
attractive microorganisms with high potential for agricultural applications in terms
of environmental sustainability and safety.
The term mycorrhiza (from the Greek “mycos” meaning fungus and “rhiza”
meaning root) was coined to describe the symbiotic association between plant root
and fungi (Parniske 2008; Bonfante and Anca 2009). To date, at least 50,000 fungal
species are suggested to form mycorrhizal associations with 250,000 plant species
(van der Heijden et al. 2015). Arbuscular mycorrhiza (AM) is a type of endomycorrhiza in which the fungal hyphae penetrate host root cells. It is widespread in natural
environments and can be found in more than 80% of living land plant species, liverworts, ferns, woody gymnosperms, angiosperms, and grasses (Bonfante and Anca
2009). Arbuscular mycorrhizal fungi (AMF) are obligate symbionts (Owen et al.
2015) and meant to improve the plant’s nutrient uptake and in turn plant provides
AM fungi with carbon sources and habitat (Smith and Smith 2011).
Several microbial taxa including members of both Gram-negative bacteria (Xavier
and Germida 2003; Bharadwaj et al. 2008a, b; Battini et al. 2016; Lasudee et al.
2017) and Gram-positive bacteria including actinobacteria of the genus Streptomyces
(Schrey et al. 2012; Mohandas et al. 2013; Poovarasan et al. 2013; Battini et al.
2016; Lasudee et al. 2018; Chaiya et al. 2019) associated with AM fungal spores
have recently been reported. These mycorrhizal associated bacteria usually exhibited
interesting biocontrol and plant growth-promoting activities (Mohandas et al. 2013;
Poovarasan et al. 2013; Battini et al. 2016) thus make them attractive for application
in sustainable agriculture.
Drought stress induces damage to the biochemical and physiological processes of
plants thus interfere with their normal functions (Pandey and Shukla 2015). Moreover, drought influences the nutrient availability and transportation in soil (GontiaMishra et al. 2016; Vurukonda et al. 2016). Currently, climate change is causing a
reduction in precipitation and changed rainfall patterns. This changing climate leads
K. Lasudee et al.
analysis, the actinomycetes group of organisms is now renamed as actinobacteria.
They are widely distributed in natural environments and established in cells and
tissues of plants. Members of actinobacteria in particular Streptomyces spp. are
major producers of antimicrobial agents and bioactive compounds, some of which
are being used today as antibacterial, antifungal, anticancer, or cholesterol-lowering
drugs (Barka et al. 2016). On the other hand, they have the potential to produce
plant growth-promoting compounds and have biocontrol properties (Singh et al.
2018; Suarez-Moreno et al. 2019; Liotti et al. 2019). Actinobacteria can be used to
improve plant growth and promote growth of plants under both abiotic and biotic
stresses. Similar to other PGP bacteria, they can promote plant growth via direct
and indirect mechanisms (Olanrewaju et al. 2017; Sathya et al. 2017; Vurukonda
et al. 2018). Nitrogen fixation, phytohormones production, phosphate solubilization, siderophore production, etc., are considered as direct (Glick 2012; Hamadi
and Mohammadipanah 2015; Vurukonda et al. 2018). Whereas indirect mechanisms
include antibiotics production (Dinesh et al. 2017; Singh and Dubey 2018) and
production of lytic enzymes to degrade the cell wall of fungal pathogens (Singh
and Gaur 2016; Sathya et al. 2017; Gasmi et al. 2019). Thus, actinobacteria are
attractive microorganisms with high potential for agricultural applications in terms
of environmental sustainability and safety.
The term mycorrhiza (from the Greek “mycos” meaning fungus and “rhiza”
meaning root) was coined to describe the symbiotic association between plant root
and fungi (Parniske 2008; Bonfante and Anca 2009). To date, at least 50,000 fungal
species are suggested to form mycorrhizal associations with 250,000 plant species
(van der Heijden et al. 2015). Arbuscular mycorrhiza (AM) is a type of endomycorrhiza in which the fungal hyphae penetrate host root cells. It is widespread in natural
environments and can be found in more than 80% of living land plant species, liverworts, ferns, woody gymnosperms, angiosperms, and grasses (Bonfante and Anca
2009). Arbuscular mycorrhizal fungi (AMF) are obligate symbionts (Owen et al.
2015) and meant to improve the plant’s nutrient uptake and in turn plant provides
AM fungi with carbon sources and habitat (Smith and Smith 2011).
Several microbial taxa including members of both Gram-negative bacteria (Xavier
and Germida 2003; Bharadwaj et al. 2008a, b; Battini et al. 2016; Lasudee et al.
2017) and Gram-positive bacteria including actinobacteria of the genus Streptomyces
(Schrey et al. 2012; Mohandas et al. 2013; Poovarasan et al. 2013; Battini et al.
2016; Lasudee et al. 2018; Chaiya et al. 2019) associated with AM fungal spores
have recently been reported. These mycorrhizal associated bacteria usually exhibited
interesting biocontrol and plant growth-promoting activities (Mohandas et al. 2013;
Poovarasan et al. 2013; Battini et al. 2016) thus make them attractive for application
in sustainable agriculture.
Drought stress induces damage to the biochemical and physiological processes of
plants thus interfere with their normal functions (Pandey and Shukla 2015). Moreover, drought influences the nutrient availability and transportation in soil (GontiaMishra et al. 2016; Vurukonda et al. 2016). Currently, climate change is causing a
reduction in precipitation and changed rainfall patterns. This changing climate leads