Page 69 - ACCB 2020

Arbuscular Mycorrhizae Fungi: A Tool For Sustainable Agriculture. Varaprasad Kolla et al

with Faba bean inoculated with AMF increase the per- Light
centage of N transfer to the cereal and the percentage of Light is known to infl uence mycorrhizal colonization
N in the cereal derived from the Faba Bean. (60). signifi cantly. Plants exposed to sunlight show higher
hyphal colonization rate, higher number of arbuscules
Interactions of AM Fungi and Plant Pathogens and the higher number of vesicles per fi eld of micros-
AMF are known to affect rhizosphere interactions by cope, thus enhancing mycorrhizal symbiosis in plant
altering root morphology and activity (39). Suppression roots exposed to sunlight compared to those in the sha-
of the pathogenic activities is due to morphological, de (101). High intensity of light enhances the root co-
biological, and physiological changes that take place in lonization as well as AMF spore production. These
host plant. Lignifi cation that is induced by AMF in- characteristics make mycorrhizal fungi a strong tool to
creases the thickness of the cell walls and the produc- be used in the sustainable management of the environ-
tion of polysaccharides which prevent the penetration ment. (102-103).
and growth of pathogens like Fusarium oxysporum,
Meloidgyne incognita, etc., thus decreasing the rate Elevated CO
2
and severity of diseases caused due to the pathogens Global warming majorly alters the atmospheric CO
2
penetrating the soil (86). The arbuscules formed on the concentrations, soil temperature, and drought stress,
interaction of AM-Phytophthora prevent the penetration which have indirect effects on symbiotic associations
of cortical cells. Mycorrhizal plants in symbiosis with between plant and microorganisms and ultimately in-
AMF have a stronger vascular system that imparts grea- fl uence crop productivity.
ter mechanical strength, increases the nutrient supply
and decreases the effect of vascular pathogens, thus in- The response of plant species and its functional groups
creasing the tolerance to pathogen infection (9, 27, 54, to elevated levels of CO is highly variable (104), it to
2
87). some extent dependent on the patterns of C allocation
within the plant (105-106). Under increased C alloca-
AMF reduce the number of pathogenic fungi in roots by tion AM fungi strains are positively infl uenced by in-
interference competition and exploitation competition creased growth in the rhizosphere, and enhanced co-
(28, 88, 89). Phosphorus plays an important role in root lonization, thus promoting plant growth by increasing
exudation that reduces the germination of pathogenic nutrient uptake (107-108). Experiments showed that the
spores. (27, 90, 91). forage quality in alfalfa leaves and nutritional quality
in strawberry onion bulbs were enhanced by the inte-
CLIMATIC FACTORS raction between humic substances, the mycorrhiza, and
Temperature elevated CO (109-110).
2
The effect of temperature or global warming is plant
species and AMF strain dependent (92-95).The varia- Drought
tion in climatic factors affects the AMF present in the Water defi cit is an important factor that affects crop
soil as well as their symbiotic activity. This may alter growth, survival, and yield. The effect of drought on
the C allocation to the root zone, root exudation, nu- AMF is strain dependent (111). Drought conditions in-
trient availability (C/N ratio), etc. The optimum tem- fl uence and alter the type of mycorrhizae colonization
perature for the function of AMF is similar to the ran- and, in many cases different crops such as strawberry,
ge required for plant vegetation. AMF promotion was wheat, barley and sweet potato, the benefi cial effect of
observed at temperatures below 27 degrees C (96). AMF is evident under low water conditions (112-114).
Extremely low or high temperature lessens the popula- Studies by Auge et al. suggest that drought resistance in
tion of AMF in the soil.(97). Mohan et al summarized plants can be enhanced in the presence of AMF. Thus,
that mycorrhizal abundance increased in 63% of works emphasizing the capability of AMF to adapt to clima-
with no effect on 20% at elevated temperatures, thus tically stressed conditions and facilitate the survival of
concluding that elevated temperatures have a positive plants, increasing their root shoot ratio and biomass.
impact on the growth of external hyphae and diversity AMF symbiosis aids seedling establishment in the har-
of mycorrhizae.(98) The AMF adapt to higher tempe- sh desert environment by improving nutrient uptake and
ratures by altering the structure of their hyphal network, regulating phytohormone concentration (115-116). Fur-
to a more extensive extra-mycorrhizal type to facilitate ther, studies by Mena-Violante et al, 2006 showed that
higher respiration and quicker C allocation (99,100). compared to non-mycorrhizae plants, in conditions of

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Rev. Asoc. Col. Cienc.(Col.), 2020; 32: 63-76.