What is mycorrhizae & types of mycorrhiza; Ectomycorrhizae, Endomycorrhizae: Mycorrhizae is a symbiotic association between a fungus and plant roots. They belong mainly to the genera Basidiomycetes and Zygomycetes.
What is mycorrhizae: Ectomycorrhizae, Endomycorrhizae
Mycorrhizal associations divided into two broad groups, the ectomycorrhizae, and the endomycorrhizae, according to the way the hyphae of the fungi are arranged within the cortical tissues of the root.
Ectomycorrhizae are formed predominantly on forest species by mushroom and puffball producing basidiomycetes and by some as compactly. The fungus forms a large hyphal not or mantle on the root surface and invades the cortex, giving the root a characteristic thickened and branched appearance. The thickness of the mantle varies from 1 or 2 hyphal diameters to as may as 30 to 40.
These fungi enter the roots, but they only grow around the cortical cells, replacing part of the middle lamella between the cells, and forming so-called hurting net. Ectomycorrhizae appear as white, brown, yellow, or black depending on the color of the fungus growing on the root. Spores of the most ectomycorrhizae fungi are produced aboveground and are wind disseminated.
Endomycorrhizae is found on the roots of many plant species it is very common. Endomycorrhizae roots eternally appear as similar to nonmycorrhizae root in sheep and color, but internally grow into the cortical cells of the feeder toot either by forming specialized feeding hyphae (Haustouia like structures) arbuscles or by forming vesicles (terminal food-staring hyphal swelling).
Most endomycorrhizae contain both vesicles and arbuscules, so they are called vesicular-arbuscular mycorrhizae. The mycelial net of the vesicular-arbuscular mycorrhizal fungus can extend for a considerable distance into the surrounding the soil, creating mycorrihizaphise with hazarding the shizenpheare by entering the capacity to uptake the nutrients from the soil.
Endomycorrhizae is not surronded by a dense fungal mantle. Endonycare is produced on most cultivated plants and on the same forest trees, mostly by zygomycetes, primarily of the genus Glomus but also by other fungi such as Aeaulospora. Some are produced by Banidioncelis
Plant root colonization
Colonization implies the ability to adhere and recognize plant roots, penetrate the plant, and withstand toxic metabolites produced by the plants in response to invasion by a foreign organism, whether pathogen or not.
- Plants react against fungal invasion by synthesizing and accumulating phytoalexins, flavonoids and terpenoids, phenolic derivatives, aglycones, and other antimicrobial compounds. Some authors have defined Trichoderma strains as plant symbiont opportunistic avirulent organisms, able to colonize plant roots by similar mechanisms of mycorrhizal fungi and to produce compounds that stimulate growth and plant defense mechanisms [Harman et al., 2004].
- Mycorrhizae are formed as the result of the mutual relationship between fungi and plants and the mycorrhizal fungi colonize the roots of their host suppress many phytopathogenic fungi (Dehne, 1982). Among them, some are ectomycorrhizal fungi that are capable of lysing phytopathogenic fungi (Kope and Fortin, 1990) and some are vesicular-arbuscular mycorrhizal fungi (VAM, also known as arbuscular mycorrhizal/ endomycorrhizal fungi). Those are all members of the Zygomycota and the current classification contains one order, the Glomales, encompassing six genera into which 149 species have been classified (Morton and Benny 1990).
- The ectomycorrhizae proliferate outside the root surface and form a sheath around the root by the combination of the mass of root and hyphae called a mantle. Disease protection by ectomycorrhizal fungi may involve multiple mechanisms including antibiosis, synthesis of fungistatic compounds by plant roots in response to mycorrhizal infection, and a physical barrier of the fungal mantle around the plant root (Duchesne 1994). Ectomycorrhizal fungi like Paxillus involutus effectively controlled root rot caused by Fusarium oxysporum and Fusarium moniliforme in red pine. Inoculation of sand pine with Pisolithus tinctorius, another ectomycorrhizal fungus, a controlled disease caused by Phytophthora cinnamomi (Ross and Marx 1972).
- Various mechanisms also allow VAM fungi to increase a plant’s stress tolerance. This includes the intricate network of fungal hyphae around the roots which block pathogen infections. The mechanisms involved in these interactions include physical protection, chemical interactions, and indirect effects (Fitter and Garbaye 1994).
- The other mechanisms employed by VAM fungi to suppress plant pathogens include enhanced nutrition to plants especially phosphorus and micronutrients; morphological changes in the root by increased lignification; changes in the chemical composition of the plant tissues like antifungal chitinase, isoflavonoids, etc. (Morris and Ward 1992); alleviation of abiotic stress and changes in the microbial composition in the mycorrhizosphere (Linderman 1994). For example, inoculation of apple-tree seedlings with the VAM fungi Glomus fasciculatum and G. macrocarpum suppressed apple replant disease caused by phytotoxic myxomycetes (Catska 1994).
- Methods have been developed of binding mycorrhizal fungi to bloated clay and sowing the resulting granules together with the seed (Dehne and Baltruschat, personal communication). A similar product is already in the market (Nutrilink@). High costs currently restrict its use to particularly profitable crops.