3 Microbial Endophytes: Sustainable Approach …
53
3.7 Inoculation Responses of Endophytes on Plants
Numerous reports exist regarding the application of endophytic bacteria in the growth
promotion of wheat, rice, canola, potato, tomato, etc. (Mei and Flinn 2010; Sturz and
Nowak 2000) (Table 3.2). Most of the studies involve the growth promotion potential
of the endophytes isolated from the same plants or the plants which are very closely
related to their natural host (Long et al. 2008). However, some endophytic bacteria
have been reported to cause growth promotion on non-host or diverse host plants
(Sessitsch et al. 2005; Ma et al. 2011), indicating contrasting observations about the
host specificity of endophytes. The broad-host-range of endophytes makes a powerful
tool in agriculture biotechnology and, therefore, endophytes have a great potential
to be used as biofertilizers and biopesticides in sustainable agrobiological practices.
Our understanding of endophyte communities and the ability to predict the success
of endophytes to promote plant growth under field conditions is limited. Various
soil, plant, and microbial factors have been reported to affect the survival, colonization, and compatibility of the endophyte to survive within the root. Moreover,
the plant growth-promoting ability of endophytic microbes can be influenced by
the genotype of the plant host. Bacterial genotype has been found to strongly influence the growth-promoting effects on host plants. Trognitz et al. (2008) demonstrated that different strains of B. phytofirmans differed markedly in their abilities
to promote the growth of the same potato cultivar. Few decades back, Dong et al.
(1994) reported that four strains of endophytic Salmonella enterica colonized alfalfa
roots and hypocotyl differently. Hence, plant colonization and growth promotion
by the endophytic bacteria are controlled by the genetic factors of both partners.
Long et al. (2008) observed that PGP bacteria of Solanum nigrum proved highly
host-specific, where these bacteria were unable to produce growth enhancement in
Nicotiana attenuate, a non-host plant. However, the broad-host-range of endophytic
bacteria has been demonstrated in the case of B. phytofirmans PsJN, isolated from
onion roots (Pillay and Nowak 1997), which can promote the growth of A. thaliana,
grape, maize, potato, switchgrass, tomato, and wheat (Sessitsch et al. 2005; SheibaniTezerji et al. 2015). Also, Thomas and Upreti (2014) demonstrated that endophytic
bacterial isolates of crop plants could inhibit wilt pathogen Ralstonia solanacearum
and also suppressed the disease effects of Ralstonia solanacearum on a non-host
tomato plant. Moreover, endophytic bacteria from tomato grown in different agricultural soils, were able to promote canola growth under gnotobiotic conditions (Rashid
et al. 2012). Afzal et al. (2015) showed that endophytic bacteria selectively isolated
from Cannabis sativa rhizosphere induced growth promotion of canola. Thus, these
reports suggested that endophytic bacteria have a broad-host-range potential in plant
growth and development.
Earlier, Wu and Guo (2008) observed that inoculation of Saussurea involucrata
with a DSE fungus promoted plant growth and especially plant height similar in
case of DSE inoculation in pigeon pea. Fakhro et al. (2010) inoculated tomato with
Penicillium indica and observed the colonization of tomato roots by P. indica. The
inoculation resulted in increased biomass of the leaves up to 20% and also reduced the
53
3.7 Inoculation Responses of Endophytes on Plants
Numerous reports exist regarding the application of endophytic bacteria in the growth
promotion of wheat, rice, canola, potato, tomato, etc. (Mei and Flinn 2010; Sturz and
Nowak 2000) (Table 3.2). Most of the studies involve the growth promotion potential
of the endophytes isolated from the same plants or the plants which are very closely
related to their natural host (Long et al. 2008). However, some endophytic bacteria
have been reported to cause growth promotion on non-host or diverse host plants
(Sessitsch et al. 2005; Ma et al. 2011), indicating contrasting observations about the
host specificity of endophytes. The broad-host-range of endophytes makes a powerful
tool in agriculture biotechnology and, therefore, endophytes have a great potential
to be used as biofertilizers and biopesticides in sustainable agrobiological practices.
Our understanding of endophyte communities and the ability to predict the success
of endophytes to promote plant growth under field conditions is limited. Various
soil, plant, and microbial factors have been reported to affect the survival, colonization, and compatibility of the endophyte to survive within the root. Moreover,
the plant growth-promoting ability of endophytic microbes can be influenced by
the genotype of the plant host. Bacterial genotype has been found to strongly influence the growth-promoting effects on host plants. Trognitz et al. (2008) demonstrated that different strains of B. phytofirmans differed markedly in their abilities
to promote the growth of the same potato cultivar. Few decades back, Dong et al.
(1994) reported that four strains of endophytic Salmonella enterica colonized alfalfa
roots and hypocotyl differently. Hence, plant colonization and growth promotion
by the endophytic bacteria are controlled by the genetic factors of both partners.
Long et al. (2008) observed that PGP bacteria of Solanum nigrum proved highly
host-specific, where these bacteria were unable to produce growth enhancement in
Nicotiana attenuate, a non-host plant. However, the broad-host-range of endophytic
bacteria has been demonstrated in the case of B. phytofirmans PsJN, isolated from
onion roots (Pillay and Nowak 1997), which can promote the growth of A. thaliana,
grape, maize, potato, switchgrass, tomato, and wheat (Sessitsch et al. 2005; SheibaniTezerji et al. 2015). Also, Thomas and Upreti (2014) demonstrated that endophytic
bacterial isolates of crop plants could inhibit wilt pathogen Ralstonia solanacearum
and also suppressed the disease effects of Ralstonia solanacearum on a non-host
tomato plant. Moreover, endophytic bacteria from tomato grown in different agricultural soils, were able to promote canola growth under gnotobiotic conditions (Rashid
et al. 2012). Afzal et al. (2015) showed that endophytic bacteria selectively isolated
from Cannabis sativa rhizosphere induced growth promotion of canola. Thus, these
reports suggested that endophytic bacteria have a broad-host-range potential in plant
growth and development.
Earlier, Wu and Guo (2008) observed that inoculation of Saussurea involucrata
with a DSE fungus promoted plant growth and especially plant height similar in
case of DSE inoculation in pigeon pea. Fakhro et al. (2010) inoculated tomato with
Penicillium indica and observed the colonization of tomato roots by P. indica. The
inoculation resulted in increased biomass of the leaves up to 20% and also reduced the