Agriculture has been an important sector globally. One of the main reason why it is so much important it reduces poverty, improve food security.it is also important to economic growth ( agriculture accounts for 4% of the global gross product). Because of the industrialization of agriculture sector for more economic growth rather than solving the food security within the country, use of chemicals , pesticides, herbicides, fungicides etc have increased. Eventhough it increases the productivity rate of yield and increased the export rate, it actually caused a negative impact to the environment and also increased the risk of health of living entities. So it is really necessary to increase the sustainable mode of agriculture and improve new agriculture methods for the safer environment condition to persist. One best way to achieve this is the utilisation of microorganisms (bacteria, fungi etc) . Among these fungi contribute a lot to solve the problems through their unique properties.
Fungi
Fungi are eukaryotic,
spore bearing ,achlorophyllous ,heterotrophic organisms whose cell wall is
made up of chitin and developed a
branched tubular body called mycelium.It exist
as saprobes,parasites or mutualists for example , plants
(mycorizzhae)or algae (lichens).
Even if
it causes a lot of diseases to
plants and reduce the yield,
it contain many features
which actually helps the plants to grow much better. About 1.5 million of
fungi were estimated and of these 148000 were described and
these all were one or
the other way important to
plants. One of the main
feature is that it decompose
organic matter and make it
available to the plants wit the
help of mycelium. Other functions
include mineral and water
uptake,chemical change, stomatal movement, biosynthesis of copounds to
enhance flexibility,cope up with environmental stress. Several species
( Trichoderma, Alternaria,
Aspergillus etc) manufacture
organic compounds which helps in the maintanence of organic
matter present in the soil.
Mainly fungi have both positive and negative aspects.
Positive aspects include:-
1-
As
decomposers
2-
As
mycorrhizae
3-
As
phosphate solubilizing fungi
4-
As
bio control agents
5-
In
soil health management
Fungi is commonly known by the name ‘natural scavengers’ .
mainly saprophytic fungi helps in the
decomposition of dead plants and wastes thereby converting complex organic
matter into simpler ones by secreting
enzymes and will return back to
environment and can be used by plants again.it
also plays a crucial role in biogeochemical cycles and in food webs.
Fungi also degrade certain contaminants present in the
environment and this process is known as mycoremediation.
eg- A.niger ,A.terreus degrade endosulfan
Candida- degrade formaldehyde
Gibeberella- degrade cyanide
White rot fungi- degrade organic pollutants in
soil and effluents and
decolorize kraft black liquor(Phanerochaete
chrysosporium) ; can degrade DDT ,TNT..
Picture courtesy- https://www.shutterstock.com/search/white-rot-fungi
It is the fungal
association with the roots of higher plants.it decompose organic matter
,thereby enhancing soil fertility.
Functions :-
1-
raised
nutrient uptake
2-
production of growth promoting substances
3-
tolerance to
drought , salinity interactions with other beneficial microorganisms.
4-
improve soil characters and phytoremediation
5-
improve
resistance against different abiotic strength
6-
Enhance water holding capacity of soil
7-
Providing stability and productivity in agro ecosystems
Eg- Ammantia, Boletus ,Tricholoma
Arbuscular mycorrizhal fungi-
Arbuscular mycorrizhal
fungi are a group of fungi which
inhabit in the soil
thereby increases the soil fertility. It also provide resistance against
pathogens and environment stress(as bioprotector).enhances water uptake
capacity.
Other functions include:-
1-
Increase crop
productivity .
2-
Enhancing plant
performance and soil quality .
3-
In the symbiosis
plant-AMF, the fungi facilitate uptake and translocate some mineral nutrients from the soil,
alleviating nutrient defciency, and increasing plant health and yield.
4-
AMF can be used such
as biofertilizers improving plant nutrition.
5-
As bioregulators
interfering in the phytohormone balance of host plants infuencing plant
development.
6-
AMF as a
biofertilizer.
7-
As bioregulators
Picture courtesy- https://i.redd.it/05jys2xnyp281.png
Phosphate
is a macronutrient present in the soil and it is present in ample amount .But
the uptake by the plants is so low. This problem can be solved with the help of phosphate solubilizing fungi. Application of PSM has
shown up to 40% reduction in the need of chemical fertilizers when applied
alone .
PSMs are the microbial
inoculants or biological active products with formulations containing one or
more beneficial strains of fungi in an
easy to apply and effcient carrier material which either add, conserve, or mobilize
phosphate in soil .
Major advantage is
that it is very easy to use, non-toxic and cost-effective
PSMs can solubilize
the insoluble P complex into the bioavailable form through chelation,
ion-exchange reactions, and acidification
Aspergillus,
Penicillium are the major groups used as phosphate
solubilizing fungi.
picture
courtesy- https://www.aquast.org/pdf.php?id=503
Biological
control- it is the suppression of
damaging activities caused by one
organism by another organism. Various
microoranisms are used as
biocontrol agents like
bacteria,fungi etc. fungi are the best one to be used as biocontrol agents because
of its properties like high
specificity,dispersal efficiency.it could be used against birds, weeds,
plant parasite nematodes etc.
Mechanisms
include direct antagonism ,antibiosis and competition. Direct antagonism is the
direct attack of fungal organism against pathogenic phytopathogens
Eg-
eg- Cladosporium myxosporum (capacity
to parasitize powdery mildew pathogens)
Antibiosis-
it is a mechanism of secretion of antimicrobial compounds by antagonist
fungi to supress pathogenic
fungi.
Eg-
Trichoderma sp produce secondary metabolites against Rhizoctoni
asolani.
Competition-
limited resources actually cause the organism to result for a competition which
actually act as a biocontrol measure.
Eg- Botrytis cinerea
Biocontrol
of pest
Fungi
attacking insects- entamogenous.
Several
hyphomycetes are there which are effective against different insect pests and
it can be used in agri-ecosystems.
Phycomycetes
and Deuteromycetes are more considered.
eg-Aspergillus
,Hirsutella, Verticillium.
Biocontrol
of weeds:-
Fungal
BCA can be exploited and for weed management using
fungal pathogens but it is still on
a learning phase .
Eg- Alternaria macrospora was evaluated
and reported as a
mycoherbicide to control spurred anoda Anoda
crisatata in cotton field
in USA.
Biocontrol
of plant-parasitic nematodes:-
Trichoderma
harzianum was reported significantly reduced the level of disease caused by nematode Melaidogyne javanica
It
mainly affects establishment developmentand
reproduction of Melaidogyne
javanica.
Soil health is mainly controlled by the presence of soil microbiota
including fungi. Fungi can increase the health of the soil and quality soil can support
the productivity of the crop plants. They are very successful
inhabitants of the soil. Due to
high plasticity and capacity to adopt various forms in response to unfavourable conditions
owing to
produce a wide variety of extracellular enzymes. Fungi breakdown
organic matter(lignin,cellulose) ,decompose soil components and thereby
regulate the balance of carbon and
nutrients in soil. Basiodiomycetes are the major groups which helps in the soil
management.
Picture courtesy- http://website.nbm-mnb.ca/mycologywebpages/NaturalHistoryOfFungi/Puffballs.html
Negative aspects
1-Negative aspects mainly include diseases. Fungi
are one of the greatest groups of
organisms which cause majority of
the diseases in plants. It causes major
economic loss. Started with the first reported case of irish famine of 1845 , fungal
diseases are still a major concern in
agricultural sector. Major phyto-pathogenic fungi belong to
Ascomycetes and Basidiomycetes.
Two types
of deleterious fungal species were
identified.It could be Biotrophic fungus or Necrotrophic fungus.
Biotrophic- obtain nutrients from living host
cells.
Eg- Powdery mildew
Picture courtesy- https://extension.umn.edu/disease-management/powdery-mildew-cucurbits
Necrotrophic- kill the host tissue and then
obtain the nutrients from the dead host cells.
Eg – Rice blast
Picture courtesy-
https://ars.els-cdn.com/content/image/3-s2.0-B9780128143834000086-u08-35-9780128143834.jpg
Some of the major diseases caused by
fungi are:-
Rust diseases- Puccinia sp
Smut diseases- Ustilago sp
Blight diseases- Phytophthora sp
Damping off
diseases- Pythium sp
Ergot disease of rye
2-
another negative aspect it degrade the
wood components. Species like Fusarium, Polyporous, Serpula etc when
grown on wood reduce the mechanical strength and make them useless.
3- Several fungal species like Mucor, Penicillium, Rhizopus etc cause spoilage in foods and crops.
Conclusion
Agriculture is one of the major sector in the world . to increase the economic value , farmers use chemical pesticides , fertilizers etc. and this causes lots of environmental damages and health hazards to living beings. So to decrease that microorganisms are being used nowadays. Among these fungi are more capable .eventhough it cause diseases and damages to plant species, it can be used to increase production and yield due to certain properties.
References
1- S, Jyoti & Singh, D P. (2016). Fungi as Biocontrol Agents in
Sustainable Agriculture.
2- Yadav, A.N. (Ed.).
(2021). Recent Trends in Mycological Research. Fungal Biology.
3- Yuvaraj, M., &
Ramasamy, M. (2020). Role of Fungi in Agriculture. Biostimulants in Plant
Science. doi:10.5772/intechopen.89718
4- https:// www.legit.ng
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