Plant-Microorganism Interactions: Effects on the Tolerance of Plants to Biotic and Abiotic Stresses - Crop Improvement: New Approaches and Modern Techniques - page 229

of research that can be an effective option for increasing plant tolerance to biotic
and abiotic stresses. Beneficial microorganisms that promote plant growth and con-
fer a protective effect against soil pathogens are considered to be of great value to
production systems.
Despite of more than 120 years, since the first descriptions and hypotheses about
the functionality of the mycorrhizal associations, it is suspected that the deeper im-
pact of this symbiosis is yet to be revealed.
The effort by the potentiation of AMF in the field, as well as by the generation of
related techniques, demand studies incorporating multiplication protocols of AMF.
Implies consider this component in long-term studies that seek to detect not only
its impact on the growth and development of a plant, but about the magnitude of its
contribution to global events and structure of plant communities.
With the perspective opened by molecular techniques, there are the opportu-
nity to understand mechanisms of evolution of plant species and the symbiosis. It
remains to researchers in AM extend your range of research in a multidisciplinary
effort, even because, without this approach, it will not possible to understand the
full dimension of this formidable symbiosis.
The AMF and the symbiotic association process require an interaction between
root and fungi, so far not clarified with regard to the mechanism for the recognition
of symbiotic partners and interaction, or the moment from which it is recognized as
an association.
The symbiosis between plants and AMF results in the reduction of losses by
stresses and consequently faster growth, with economic inputs and the reduction
of environmental contamination. Furthermore, AMF can act as potential biological
control agents, reducing the effects or damage caused by plant pathogens through
indirect means, enhanced plant nutrition, or increased resistance in the root system.
Little is known about the physiological and molecular mechanisms responsible
for greater tolerance of mycorrhizal plants. The knowledge that one of the physi-
ological responses to biotic and abiotic stress in plants mediated by AM consists
in the increase of the activity of an oxidative stress set of enzymes (SOD, APX,
POD), in the production of compounds with antimicrobial activity (phenols, qui-
nones, phytoalexins ) and the activation of enzymes that catalyze the reactions for
the production of compounds that act as chemical or physical barriers. Furthermore,
increased activity and induction of new isoenzymes that participate in the antioxi-
dant system in inoculated plants can allow the plant to tolerate excess superoxide
radicals generated during the prevalence of stress conditions.
Know the community structure of the AMF of a particular environment or bi-
ome, and evaluate the functional diversity of these symbionts are of fundamental
importance when you want to explore the potential of these fungi to increase the
plants tolerance to biotic and abiotic stress. There are few works that examine in
detail the factors that affect the survival of AMF in their natural habitats. On the
contrary, the effects of physical and chemical factors on plants are widely reported.
Studies on the factors that may regulate the establishment and functioning of
AM and changes biochemical, physiological and molecular in both symbionts dur-
ing biotic and abiotic stress conditions have been made in recent years. However,