2 Bioefficacy of Endophytes in the Control of Plant Diseases
25
shown that VOCs from other Arabidopsis native rhizospheric bacteria induced the
expression of MYB72. Strikingly, the induction of iron deficiency markers (FRO2 and
IRT1) was only observed when plants were inoculated with ISR-inducing bacteria,
while the inoculation with similar bacteria that do not induce ISR was unable to
induce the expression of iron management genes. This indicates a close relationship between the induction of ISR and the activation of iron management response
(Zamioudis et al. 2015). It is important to mention that both the induction of MYB72
and the iron-related genes by VOCs is independent of the availability of iron in roots,
but it is dependent on signals from above-ground parts of the plant (Zamioudis et al.
2015).
Recently, it has been shown that the induction of the iron-deficiency response
mediated by WCS417 does not depend on iron nutrition. In this trend, the plant
growth promotion effect triggered by this bacterium was also observed under iron
limitation conditions (Verbon et al. 2019). Since the response triggered in the roots
by WCS417 inoculation showed to be dependent on shoot-to-root signaling, the
authors evaluated if iron content in the leaves could affect this response. However,
they demonstrated that iron content in the aerial parts of the plant did not affect the
WCS417-induced response on roots. Also, this response was independent of the iron
transport in the phloem mediated by the phloem-specific iron transporter (OPT3)
(Verbon et al. 2019). Altogether, the information generated in these works confirms
that the induction of ISR triggered by beneficial microbes is intimately related to an
activation of the iron metabolism and this response is independent of the iron content
that requires shoot-to-root signaling. More research is needed to determine the exact
mechanisms involved in this process.
As described early, some endophytic fungi can diminish disease symptoms caused
by pathogens. This is the case of an endophyte strain of Colletotrichum tropicale that
reduces the infection provoked by P. palmivora in cocoa plants (Christian et al. 2017).
Recently, the authors analyzed the uptake and distribution of nitrogen in response to
endophyte and pathogen inoculation by pulsing the soil with nitrogen-15 (
15 N) and
then tracing
15 N uptake and its subsequent distribution to whole plants and individual
leaves. They demonstrated that endophyte-inoculated plants showed significantly
greater
15 N uptake than endophyte-free plants. However, the total nitrogen amount
did not vary in each treatment (Christian et al. 2019). Moreover, pathogen inoculation
did not affect the
15 N content, but the co-inoculation with the endophyte and the
pathogen showed a correlation between the
15 N content and the pathogen damage
(Christian et al. 2019). These results suggest that endophyte colonization can modify
nutrient acquisition and affect N distribution within plant tissues under pathogenic
conditions.
2.5 Conclusions
The main goal of the research in the field of biocontrol is to provide new and improved
tools for the development of biotechnological products for disease management.
25
shown that VOCs from other Arabidopsis native rhizospheric bacteria induced the
expression of MYB72. Strikingly, the induction of iron deficiency markers (FRO2 and
IRT1) was only observed when plants were inoculated with ISR-inducing bacteria,
while the inoculation with similar bacteria that do not induce ISR was unable to
induce the expression of iron management genes. This indicates a close relationship between the induction of ISR and the activation of iron management response
(Zamioudis et al. 2015). It is important to mention that both the induction of MYB72
and the iron-related genes by VOCs is independent of the availability of iron in roots,
but it is dependent on signals from above-ground parts of the plant (Zamioudis et al.
2015).
Recently, it has been shown that the induction of the iron-deficiency response
mediated by WCS417 does not depend on iron nutrition. In this trend, the plant
growth promotion effect triggered by this bacterium was also observed under iron
limitation conditions (Verbon et al. 2019). Since the response triggered in the roots
by WCS417 inoculation showed to be dependent on shoot-to-root signaling, the
authors evaluated if iron content in the leaves could affect this response. However,
they demonstrated that iron content in the aerial parts of the plant did not affect the
WCS417-induced response on roots. Also, this response was independent of the iron
transport in the phloem mediated by the phloem-specific iron transporter (OPT3)
(Verbon et al. 2019). Altogether, the information generated in these works confirms
that the induction of ISR triggered by beneficial microbes is intimately related to an
activation of the iron metabolism and this response is independent of the iron content
that requires shoot-to-root signaling. More research is needed to determine the exact
mechanisms involved in this process.
As described early, some endophytic fungi can diminish disease symptoms caused
by pathogens. This is the case of an endophyte strain of Colletotrichum tropicale that
reduces the infection provoked by P. palmivora in cocoa plants (Christian et al. 2017).
Recently, the authors analyzed the uptake and distribution of nitrogen in response to
endophyte and pathogen inoculation by pulsing the soil with nitrogen-15 (
15 N) and
then tracing
15 N uptake and its subsequent distribution to whole plants and individual
leaves. They demonstrated that endophyte-inoculated plants showed significantly
greater
15 N uptake than endophyte-free plants. However, the total nitrogen amount
did not vary in each treatment (Christian et al. 2019). Moreover, pathogen inoculation
did not affect the
15 N content, but the co-inoculation with the endophyte and the
pathogen showed a correlation between the
15 N content and the pathogen damage
(Christian et al. 2019). These results suggest that endophyte colonization can modify
nutrient acquisition and affect N distribution within plant tissues under pathogenic
conditions.
2.5 Conclusions
The main goal of the research in the field of biocontrol is to provide new and improved
tools for the development of biotechnological products for disease management.