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FR Symbiosis between plants and fungi: the advantages of Trichoderma harzianum
More than 90% of plants have symbiotic relationships with fungi, with mechanisms that can vary from simple opportunistic links to an exclusive relationship, in the absence of which there is no plant development, or sub-optimal growth.
The symbiotic relationship between the two organisms is mutually beneficial. The fungus extracts water and mineral elements from the soil and protects the plant from hostile organisms, the plant provides the fungus with sugars and starches that the fungus is unable to produce.
There are also other fungi that are either occasional symbionts (Trichoderma), or live alone, obtaining their nourishment simply by obtaining it from the breakdown of organic materials of various kinds.
Trichoderma harzianum: what it is and why it is important
Trichoderma harzianum is a very common species, found at virtually all latitudes, from the equator to subpolar regions. The fast-growing colonies are green in colour, very intense, so much so that the fungus has earned the nickname Green Mold.
It produces a huge quantity of spores and therefore spreads very quickly.
Fig. 1 Fully mature Trichoderma harzianum colony.
Trichoderma harzianum demonstrated a great ability to adapt, even to difficult climatic conditions. Its ability to adapt to environments with a high presence of pollutants is also positive. Whether chemicals or heavy metals, the fungus manages to grow, sometimes with relative ease, other times with more difficulty, but only rarely did it fail to grow at all and always at very high pollutant concentrations.
These qualities alone determine its interest, but added to this is its characteristic of also being an opportunistic symbiont.
Unlike other fungi whose link with plants is unbreakable, Trichoderma harzianum is able to live independently, but prefers symbiosis with the plant, acting on it both as a growth promoter and as a defence against pathogens. The fungus in fact wraps its hyphae around the root, thus preventing pathogens from gaining access, and then expands into the soil in search of nutrients and water. The hyphae penetrate the cortical layer of the roots, with a mechanism similar to that of a pathogen, but without going any further, and in doing so they make the connection between the fungus and the plant.
The advantages of using mycorrhizae in agriculture
Fig. 2 Plant-mushroom interaction Trichoderma
The symbiosis between the two organisms is not as strong as in mycorrhizae, which often penetrate inside the root cells, but it allows the plant to grow very well, which is also able to overcome stressful situations more easily, such as water shortages or less accessible nutrients. The advantage of using the fungus lies both in its ease of use and in the possibility of being able to operate on it alone without needing a host plant to develop it.
