42
A. Dahiya et al.
characterized 31 indigenous and culturable bacterial endophytes from three switchgrass leaf cultivars: (Cave-in-Rock, Blue Jacket, and Tecumseh). Bacterial endophytes were identified as Microbacterium testaceum, Curtobacterium flaccumfaciens, Bacillus subtilis, Bacillus pumilus, Pseudomonas fluorescens, Sphingomonas
parapaucimobilis, Serratia sp., and Pantoea ananatis. Various positive attributes
viz. high biomass production, efficient water use, relatively low demand for nutritional inputs, and less use of agrochemicals were also reported in these endophytes
that contributed to the adaptation of switchgrass leaf cultivars to marginal soils
(Sanderson et al. 2006). Kang et al. (2018) isolated 30 endophytic and non-endophytic
isolates from Medicago sativa. Other plant growth-promoting traits such as phosphate solubilization and production of indole-3-acetic acid (IAA) were also exhibited
by most of the tested strains during colonization of plant tissues and soil. Schmidt
et al. (2018) isolated endophytes from Miscanthus x giganteus. Genera Pantoea
ananatis and Pseudomonas savastanoi exhibited as the predominant bacteria in
leaves, whereas other pseudomonads prevailed in roots. Chinnaswamy et al. (2018)
isolated Gram-positive, endophytic bacterium B. megaterium NMp082 from root
nodules of Medicago polymorpha. The isolate co-inhabited nodules with the symbiotic Ensifer medicae, the nif H and nodD genes in the B. megaterium NMp082 were
100% identical to those of Ensifer meliloti. Although the endophyte possessed nodulation and nitrogen fixation genes, the bacterium failed to form effective nodules.
However, it induced nodule-like unorganized structures in alfalfa roots.
Many fungi belonging to different groups have also been reported as plant endophytes. The first group includes fungal species with a broad range of host plants,
and the second group includes a smaller number of specialized fungal species that
colonize some monocotyledonous hosts. Most of the endophytic fungi belong to
the phylum Ascomycota and Glomeromycota whereas some fungi belong to phylum
Basidiomycota and Zygomycota. The fungi from the genera Acremonium, Alternaria,
Chaetomium, Cladosporium, Cryptocline, Cryptosporiopsis, Leptostroma, Phoma,
Phomopsis, Phyllosticta, and Trichoderma are well represented in endophyte assemblages. Fungal endophytes within the host may inhabit different tissues of roots,
stems, branches, leaves, flowers, fruits, seeds, twigs, bark, and petioles, including
xylem of all available plant organs. These endophytes are classified into four classes.
Class 1 endophytes form systemic associations with the aboveground tissues of
grasses and are defined as the Claviciptaceous endophytes (including Balansia spp.
and Epichloe spp.) (Johnson et al. 2013). These species are one of the most economically important examples of plant–endophyte interactions. The diverse class 2 endophytes include both Ascomycota and a few Basidiomycota. Their most exclusive
characteristic is the ability to colonize roots, stems, and leaves, and form extensive
plant infections. Class 3 comprises endophytes that form highly localized infections
in aboveground tissues, such as in the leaves of tropical trees and non-vascular and
vascular plants. The dark septate endophytes (DSE) constitute class 4 and these
facultative biotrophic fungi colonize plant roots and have the distinguishing feature
of having melanized dark septate hyphae (Jumpponen 2001; Rodriguez et al. 2009;
Lugtenberg et al. 2016). Fungal endophytes play a major role in habitat adaptation
A. Dahiya et al.
characterized 31 indigenous and culturable bacterial endophytes from three switchgrass leaf cultivars: (Cave-in-Rock, Blue Jacket, and Tecumseh). Bacterial endophytes were identified as Microbacterium testaceum, Curtobacterium flaccumfaciens, Bacillus subtilis, Bacillus pumilus, Pseudomonas fluorescens, Sphingomonas
parapaucimobilis, Serratia sp., and Pantoea ananatis. Various positive attributes
viz. high biomass production, efficient water use, relatively low demand for nutritional inputs, and less use of agrochemicals were also reported in these endophytes
that contributed to the adaptation of switchgrass leaf cultivars to marginal soils
(Sanderson et al. 2006). Kang et al. (2018) isolated 30 endophytic and non-endophytic
isolates from Medicago sativa. Other plant growth-promoting traits such as phosphate solubilization and production of indole-3-acetic acid (IAA) were also exhibited
by most of the tested strains during colonization of plant tissues and soil. Schmidt
et al. (2018) isolated endophytes from Miscanthus x giganteus. Genera Pantoea
ananatis and Pseudomonas savastanoi exhibited as the predominant bacteria in
leaves, whereas other pseudomonads prevailed in roots. Chinnaswamy et al. (2018)
isolated Gram-positive, endophytic bacterium B. megaterium NMp082 from root
nodules of Medicago polymorpha. The isolate co-inhabited nodules with the symbiotic Ensifer medicae, the nif H and nodD genes in the B. megaterium NMp082 were
100% identical to those of Ensifer meliloti. Although the endophyte possessed nodulation and nitrogen fixation genes, the bacterium failed to form effective nodules.
However, it induced nodule-like unorganized structures in alfalfa roots.
Many fungi belonging to different groups have also been reported as plant endophytes. The first group includes fungal species with a broad range of host plants,
and the second group includes a smaller number of specialized fungal species that
colonize some monocotyledonous hosts. Most of the endophytic fungi belong to
the phylum Ascomycota and Glomeromycota whereas some fungi belong to phylum
Basidiomycota and Zygomycota. The fungi from the genera Acremonium, Alternaria,
Chaetomium, Cladosporium, Cryptocline, Cryptosporiopsis, Leptostroma, Phoma,
Phomopsis, Phyllosticta, and Trichoderma are well represented in endophyte assemblages. Fungal endophytes within the host may inhabit different tissues of roots,
stems, branches, leaves, flowers, fruits, seeds, twigs, bark, and petioles, including
xylem of all available plant organs. These endophytes are classified into four classes.
Class 1 endophytes form systemic associations with the aboveground tissues of
grasses and are defined as the Claviciptaceous endophytes (including Balansia spp.
and Epichloe spp.) (Johnson et al. 2013). These species are one of the most economically important examples of plant–endophyte interactions. The diverse class 2 endophytes include both Ascomycota and a few Basidiomycota. Their most exclusive
characteristic is the ability to colonize roots, stems, and leaves, and form extensive
plant infections. Class 3 comprises endophytes that form highly localized infections
in aboveground tissues, such as in the leaves of tropical trees and non-vascular and
vascular plants. The dark septate endophytes (DSE) constitute class 4 and these
facultative biotrophic fungi colonize plant roots and have the distinguishing feature
of having melanized dark septate hyphae (Jumpponen 2001; Rodriguez et al. 2009;
Lugtenberg et al. 2016). Fungal endophytes play a major role in habitat adaptation