Agriculture Reference
In-Depth Information
INR-7 effectively induced downy mildew resistance in pearl millet. The histochem-
ical analysis of
B. pumilus
INR-7-mediated systemic resistance indicated that IR
was associated with the expression of hypersensitive response (HR), enhanced
lignification, callose deposition, and H
2
O
2
in addition to the increased expression
of the defense enzymes
β
-1,3-glucanase, chitinase, phenylalanine ammonia lyase
(PAL), peroxidase (POX), and polyphenol oxidase (PPO). The HR was rapidly
expressed in the resistant pearl millet. The further microscopic investigation of
inoculated pearl millet tissues showed the presence of significantly higher levels of
lignin, callose, and H
2
O
2
in resistant and induced resistant seedlings. Accumulation
of various defense enzymes (e.g.,
β
-1,3-glucanase, chitinase, PAL, POX, and PPO)
located in vascular bundles was an immediate response to
Sclerospora graminicola
infection and preceded the development of induced resistance elicited by strain
INR-7. This study clearly demonstrated that the differences between the responses,
susceptibility, INR-7 treated, or resistant pearl millet seedlings exhibited variations
in the speed, intensity, and pattern of different histochemical responses to
S. graminicola
infection (Raj et al.
2012
).
10.4 Conclusion
Naturally abundant yet functionally diverse rhizosphere microorganisms have
immense potential in sustainable crop production and have shown significant
increase in crop yields both directly and indirectly under fluctuating field environ-
ments. Besides supplying soluble P to plants and increasing crop production
directly, phosphate-solubilizing microorganisms also promote plant growth and
yields (primary effect) indirectly by suppressing the plant diseases (secondary
effect) caused by so many phytopathogens. In some cases, the secondary effect is
more obvious and effective than the primary ones. Therefore, the simultaneous
biocontrol activity and other plant growth-promoting properties of PS organisms
provide one of the better options to replace pesticides and chemical fertilizers in
sustainable agriculture practices. From the disease management point of view, more
researches aimed at finding quality biocontrol PS organisms with multiple growth-
promoting activities are urgently required. Moreover, understanding the precise
mode of action and the ecophysiology of the PSM in relation to other soilborne
inhabitants is important which may help in developing the appropriate inoculants
for their efficient use under different production systems. Further investigations
including efficacy test under field conditions are however needed to consolidate the
role of PS organisms as proficient biofertilizers. If the field trials show promising
results, this could allow further exploiting the full potential of PS organisms as
multifaceted beneficial bio-inoculants at commercial scale for increasing the
growth and health of plants which in turn is likely to reduce problems associated
with the use of toxic chemicals in agriculture practices.
