10 Endophytic Actinobacteria Associated …
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to more frequent drought events that threaten crop productivity and global food security (Anjum et al. 2011; Fahad et al. 2017). Crop yields in more than 70% of global
arable lands are affected by water deficits especially in Africa and Asia (Eke et al.
2019). About 85% of damage and loss in agriculture from 2010 to 2016 are related
to drought with an estimated economical value of at least USD 29 billion (FAO
2018). For these reasons, drought is emerging as the most deleterious abiotic stress
to crop production and yields worldwide. This chapter aims to summarize the current
information on the diversity of actinobacteria associated with arbuscular mycorrhizal
spores and their beneficial applications to promote plant growth. Special attention
has been given to actinobacteria associated with Funneliformis mosseae spores and
their ability to promote rice growth under drought conditions.
10.2 Endophytic Actinobacteria from Mycorrhiza
Mycorrhizal fungi interact with several actinobacteria in all stages of their life cycle
(Frey-Klett et al. 2007). This associated actinobacterial population has a versatile
role in health promotion in positive ways by way of root colonization, stimulate
hyphal, and spore germination of their mycorrhizal host (Roesti et al. 2005). In turn,
mycorrhizal fungi support the growth of associated bacteria by providing habitat and
nutrients. However, the exact role of these associated bacteria is yet to be established.
Endophytic bacteria adhere to the arbuscular mycorrhiza hyphae (Bianciotto et al.
1996; Manfeld-Giese et al. 2002) and or embeded within the outer AM spore wall
layer (Walley and Germida 1996) or penetrate inner layer of spore (Roesti et al.
2005).
Actinobacteria frequently found inside the mycorrhizal spores. Mycorrhizal
spore-associated actinobacteria have been isolated, characterized, and applied to
the plants for their growth as summarized in Table 10.1. Most of the actinobacteria
isolated from mycorrhizal spores are filamentous including species of Amycolatopsis,
Intrasporangium, Nocardioides, Pseudonocardia, Streptomyces, Streptoverticillium,
etc. From all filamentous genera, Streptomyces spp. remained the most abundant actinobacteria found from several mycorrhizae for example Glomus mosseae (Mohandas
et al. 2013), Rhizophagus intraradices (Battini et al. 2016), and F. mosseae (Lasudee
et al. 2018). Other nonfilamentous actinobacteria including Arthrobacter, Cellulomonas, Corynebacterium, Curtobacterium, Leifsonia, Mycobacterium, Nocardia,
Propionibacterium, and Streptosporangium (Bharadwaj et al. 2008b; Poovarasan
et al. 2013; Battini et al. 2016; Long et al. 2017) were also found invarious genera
of mycorrhizal spores.
The standard isolation methods for actinobacteria occurring inside mycorrhizal
spores generally involve 3 steps (i) surface sterilization of mycorrhizal spores, (ii)
destruction of the spore cell wall, and (iii) cultivation of actinobacteria on selective
media. For surface sterilization, different chemicals were used including 2% Clorox
(Lee and Koske 1994), chloramine (Mohandas et al. 2013), 4% (w/v) chloramine
T trihydrate (Chaiya et al. 2019), 2% sodium hypochlorite, and 70% (v/v) ethanol
231
to more frequent drought events that threaten crop productivity and global food security (Anjum et al. 2011; Fahad et al. 2017). Crop yields in more than 70% of global
arable lands are affected by water deficits especially in Africa and Asia (Eke et al.
2019). About 85% of damage and loss in agriculture from 2010 to 2016 are related
to drought with an estimated economical value of at least USD 29 billion (FAO
2018). For these reasons, drought is emerging as the most deleterious abiotic stress
to crop production and yields worldwide. This chapter aims to summarize the current
information on the diversity of actinobacteria associated with arbuscular mycorrhizal
spores and their beneficial applications to promote plant growth. Special attention
has been given to actinobacteria associated with Funneliformis mosseae spores and
their ability to promote rice growth under drought conditions.
10.2 Endophytic Actinobacteria from Mycorrhiza
Mycorrhizal fungi interact with several actinobacteria in all stages of their life cycle
(Frey-Klett et al. 2007). This associated actinobacterial population has a versatile
role in health promotion in positive ways by way of root colonization, stimulate
hyphal, and spore germination of their mycorrhizal host (Roesti et al. 2005). In turn,
mycorrhizal fungi support the growth of associated bacteria by providing habitat and
nutrients. However, the exact role of these associated bacteria is yet to be established.
Endophytic bacteria adhere to the arbuscular mycorrhiza hyphae (Bianciotto et al.
1996; Manfeld-Giese et al. 2002) and or embeded within the outer AM spore wall
layer (Walley and Germida 1996) or penetrate inner layer of spore (Roesti et al.
2005).
Actinobacteria frequently found inside the mycorrhizal spores. Mycorrhizal
spore-associated actinobacteria have been isolated, characterized, and applied to
the plants for their growth as summarized in Table 10.1. Most of the actinobacteria
isolated from mycorrhizal spores are filamentous including species of Amycolatopsis,
Intrasporangium, Nocardioides, Pseudonocardia, Streptomyces, Streptoverticillium,
etc. From all filamentous genera, Streptomyces spp. remained the most abundant actinobacteria found from several mycorrhizae for example Glomus mosseae (Mohandas
et al. 2013), Rhizophagus intraradices (Battini et al. 2016), and F. mosseae (Lasudee
et al. 2018). Other nonfilamentous actinobacteria including Arthrobacter, Cellulomonas, Corynebacterium, Curtobacterium, Leifsonia, Mycobacterium, Nocardia,
Propionibacterium, and Streptosporangium (Bharadwaj et al. 2008b; Poovarasan
et al. 2013; Battini et al. 2016; Long et al. 2017) were also found invarious genera
of mycorrhizal spores.
The standard isolation methods for actinobacteria occurring inside mycorrhizal
spores generally involve 3 steps (i) surface sterilization of mycorrhizal spores, (ii)
destruction of the spore cell wall, and (iii) cultivation of actinobacteria on selective
media. For surface sterilization, different chemicals were used including 2% Clorox
(Lee and Koske 1994), chloramine (Mohandas et al. 2013), 4% (w/v) chloramine
T trihydrate (Chaiya et al. 2019), 2% sodium hypochlorite, and 70% (v/v) ethanol