Fungi used as a Fungicide

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=====Biotroph===== =====Biotroph=====
-Biotrophic relations are more complicated and are not as clear as necrotrophic ones. For a biotrophic mycofungicide to be useful, it required a very dominant relation of the parasite on its hosts<ref name="textbook fungi">Moore ''et al.''</ref>. The host is denied access to main nutrient such as nitrogen and phosphorus and its vegetative growth or ability to build reproductive structure is inhibited <ref name="agricultural applications"> Elad Y., Freeman S.(2002). The Mycota: AGgricultural Applications. Esser K, Bennett J.W. & Kempken F.(Eds.), ''Biological Control of Fungal Plant Pathogens''(pp.93-104 ). Berlin: Springer-Verlag.</ref> +Biotrophic relations are more complicated and are not as clear as necrotrophic ones. They require the host's cytoplasm to stay healthy althought it has a very restricted food source<ref name="textbook fungi">Moore ''et al.''</ref>. For a biotrophic mycofungicide to be useful, it required a very dominant relation of the parasite on its hosts<ref name="textbook fungi">Moore ''et al.''</ref>. The host is almost fully denied access to main nutrient such as nitrogen and phosphorus and its vegetative growth or ability to build reproductive structure is inhibited <ref name="agricultural applications"> Elad Y., Freeman S.(2002). The Mycota: Agricultural Applications. Esser K, Bennett J.W. & Kempken F.(Eds.), ''Biological Control of Fungal Plant Pathogens''(pp.93-104 ). Berlin: Springer-Verlag.</ref>. This will cause, in return, the prevention of the spread of the disease. There are three type of biotroph: intracellular, haustorial and fusion <ref name="textbook fungi">Moore ''et al.''</ref>. Intracellular involve a total penetration of the parasite in the host and require lower fungi parasites like oomycete. The haustorial biotrophs develop hyphae called haustoria that do not fully invade the hosts cells. Finally the fusion biotroph will accomplish anastamosis with the hosts which will allows a share of cytoplasm between the two organisms <ref name="textbook fungi">Moore ''et al.''</ref>.
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====Pesticide Preparation==== ====Pesticide Preparation====

Revision as of 10:40, 22 March 2013

Fungi have the ability to undergo autolysis when then environment they are growing in becomes depleted from the nutrients they need[1]. They are required to digest their own cell wall in order to reach the nutrient contained inside the hyphae. Thus, most if not all fungi are capable of synthesizing lytic enzyme such as chitinase and glucan-1,3-B-glucosidase [2] that will allow this destructive behavior to occurs. Mycofungicides are making use of this ability to destroy nuisible fungal pests using different strategies.

Contents

Processes

For a mycofungicide to be useful, the antagonistic fungi needs to be able to parasite an host. Mycoparasitism occurs widely in nature [3] and the two possible interactions that are in use for mycofungicides are the necrotroph and biotroph ones. The attack of a parasitic fungi on its host happens in four stages [2][4].

  1. Chemotropism. The parasitic specie is attracted to its potential host by the detection and reaction to a chemical released by that host. As in many form of taxis, the parasite follows the increase in concentration, the gradient, as it gets closer to the host [4]. This gradient might be made of amino acids or sugar molecules[4].
  2. Recognition. The recognition procedures are triggered by different gene-regulated mechanisms[1]. It is a short period that will determine if the parasite attach to the host, which will decide if the invasion happens or not. In Trichoderma spp. for example, the lectin carbohydrates are known to play a role in this critical stage of adhesion [4].
  3. Attachment and coiling. The parasitic fungi grows an appresorium around or along the host to prepare its invasion[4]. The appressorium structures will provide the turgour pressure needed to penetrate or invaginate the host cells during the penetration stage.
  4. Penetration and digestion. The antagonist fungi uses a variety of lytic enzymes to degrade the cell wall of the host and penetrate it. For example, Tricoderma spp. uses four family of enzymes: B-glucanases, cellulases, chitinases and proteinases to accomplish this step[4].


Once they mycoparasite is infecting the hosts, one of the two main type of relationship will occur: necrotrophy or biotrophy.

Necrotroph

Necrotroph fungi will kill the host it is invading. The parasite typically starts to feed from the nutrients contained in the hyphae of the host. This will reach a point where the host cannot survive and will die from this relation. This can occur in two different way. The first one is by simple contact where the parasite releases enzymes without fully penetrating the hosts [1]. The second one is said to be invasive and involve a full penetration of the host by the parasite[1]. In this case, the death of the host occurs quicker and involves the destruction of the host hyphae[1].

Biotroph

Biotrophic relations are more complicated and are not as clear as necrotrophic ones. They require the host's cytoplasm to stay healthy althought it has a very restricted food source[1]. For a biotrophic mycofungicide to be useful, it required a very dominant relation of the parasite on its hosts[1]. The host is almost fully denied access to main nutrient such as nitrogen and phosphorus and its vegetative growth or ability to build reproductive structure is inhibited [5]. This will cause, in return, the prevention of the spread of the disease. There are three type of biotroph: intracellular, haustorial and fusion [1]. Intracellular involve a total penetration of the parasite in the host and require lower fungi parasites like oomycete. The haustorial biotrophs develop hyphae called haustoria that do not fully invade the hosts cells. Finally the fusion biotroph will accomplish anastamosis with the hosts which will allows a share of cytoplasm between the two organisms [1].

Pesticide Preparation

Specific example

Trichoderma harzianum

Mycoparasitic Trichoderma viride as a biocontrol agent against Fusarium oxysporum f. sp. adzuki and Pythium arrhenomanes and as a growth promoter of soybean, Rojan P. Johna R.D. Tyagia, D. Prévostb, Satinder K. Brara, Stéphan Pouleurb, R.Y. Surampallic


Pythium`oligandrum it is a water mould, but often they are studied as fungi and I have few reason why to put it in this cateroy


Gliocladium roseum

Notes and References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Moore D., Robson G.D., Trinci A.P.J. (2011). 21st CENTURY GUIDE TO FUNGI. Cambridge University Press:New York.
  2. ↑ 2.0 2.1 Boland, G. J., & Kuykendall, L. (1998). Plant-microbe interactions and biological control / edited by Greg J. Boland, L. David Kuykendall. New York : Marcel Dekker, c1998.
  3. ↑ Jeffries P. (1995). BIOLOGY AND ECOLOGY OF MYCOPARASITISM. Canadian Journal of Botany. (73):S1284-S1290
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Steyaert J.M., Ridgway H.J., Elad Y., Stewart A.(2003). GENETIC BASIS OF MYCOPARASITISM: A MECHANISM OF BIOLOGICAL CONTROL BY SPECIES OF TRICHODERMA. New Zealand Journal of Crop and Horticultural Science. (31):281-291.
  5. ↑ Elad Y., Freeman S.(2002). The Mycota: Agricultural Applications. Esser K, Bennett J.W. & Kempken F.(Eds.), Biological Control of Fungal Plant Pathogens(pp.93-104 ). Berlin: Springer-Verlag.
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