Fungi as biocontrol agents, Mushroom cultivation, Mycorrhiza application in agriculture and plant growth
Fungi as biocontrol agents:-
> Fungi possess a number of characteristics that make them potentially ideal bio control agents.
i. Firstly, many saprophytic species antagonize, representatives of all the pest organisms, including plant pathogenic fungi, weeds and insects.
ii. Secondly, fungi can be readily grown in culture so that large quantities can be economically produced for release, mainly as spores or mycelial fragments, into the environment.
> These inoculants then germinate or grow to produce active mycelium which can parasitize or otherwise inhibit the pest without damaging the non-target organisms.
> Fungi also survive for relatively long periods as resting bodies, and can then germinate to grow and control the target population thereby making continual re-inoculation with the bio-control agent unnecessary.
1. Use of Fungi to Control Fungal diseases:-
> Example of Bio Control Agents Used Commercially:-
i. Trichoderma harzianum:- White rot onion.
ii. Phlebia gigantean:- Heterbasidion root rot pine.
iii. Sporidesmium sclerotivorum:- Lettuce drop lettuce.
iv. Talaromyces flavus:- Damping off sugarbeet.
> Trichoderma species reduces the growth of all the four soil borne pathogens:-
i. Sclerotium rolfsii
ii. Fusarium solani
iii. Rhizoctonia solani
iv. Sclerotionia sclerotiorum
- Therefore, can be incorporated for integrated disease management of soil borne plant pathogens.
- Hence, Trichoderma species can be used as a potential biocontrol agent against these pathogens.
- However, its efficacy against Sclerotium rolfsii (a fungal Plant pathogen in tobacco plant) was found to be more in comparison to others.
- Trichoderma sp. was found to be effective against Sclerotium rolfsii causing the damping-off, root rot, and seed rot disease in mung bean and sunflower, and moreover, it also increased the plant growth.
- Several strains of Trichoderma are commercially available to control plant disease in environmentally friendly agriculture. Fungal formations made from T. harzianum and T. viride cultures to prevent the growth of pathogen soilborne fungi responsible for leaf-falling disease in several crops.
> The fungus Ampelomyces quisqualis is a naturally occurring hyperparasite of powdery mildews. It infects and forms pycnidia (fruiting bodies) within powdery mildew hyphae, conidiophores (specialized spore-producing hyphae), and cleistothecia (the closed fruiting bodies of powdery mildews). This parasitism reduces growth and may eventually kill the mildew colony.
2. Use of Fungi to Control Nematodes:-
> Fungi that parasitise nematodes (nematophagus fungi) can be divided into nematode- trapping fungi, endoparasitic species and fungi that parasitise nematode eggs.
> Nematode trapping fungi capture nematodes with specialized structures such as constrictive and non- constrictive rings, adhesive knobs or, lastly, by producing an adhesive material along the entire mycelial surface.
> Endoparasitic nematophagous fungi live in soils where they produce adhesive spores. These become attached to body of the nematode, on germination, a germ tube enters the body where it grows and consumes the host.
> Egg parasites, as their name suggests, are nematophagous fungi that parasitise the eggs of nematodes.
> Root-knot nematode (Meloidogyne incognita) is a limiting factor causing yield reduction in FCV tobacco crop. As an alternative to nematicides of chemical origin, beneficial fungi such as Paecilomyces lilacinus and Glomus fasciculatum significantly reduced the number of egg masses/g root and final soil nematode population.
3. Use of Fungi to Control Insect Pest:-
> An entomopathogenic fungus is a fungus that can act as a parasite of insects and kills or seriously disables them.
> Since they are considered natural mortality agents and environmentally safe, there is worldwide interest in the use and manipulation of entomopathogenic fungi for biological control of insects and other arthropod pests.
> Over 400 species of fungi attack insects and mites, so there is great potential for the use of these organisms as biological insecticides.
> As insect bio control agents, fungi are markedly superior to other microorganisms because they are generally non-specific in their action and are useful against a wide range of insect pests.
> Most of the so-called entomopathogenic fungi are phycomycetes and Deuteromycetes.
> Spores of these fungi attack either the external or gut cuticle of their insect hosts. They then germinate and hyphae penetrate the haemocoel. Death may result from the production of a toxin by the fungus.
> In particular, the asexual phases of Ascomycota (Beauveria spp., Lecanicillium lecanii, Metarhizium spp., Paecilomyces spp. and others) are under intense scrutiny due to the traits favouring their use as biological insecticides.
Mushroom cultivation:-
Mushroom:-
> Mushrooms are the eukaryotic, spore bearing organisms, macro-fungi lacking chlorophyll and
grow on dead decomposed matter as saprophytes.
> They derive nutrients through their mycelia. This mycelium forms the fleshy structures, the fruit bodies, which are generally called the mushrooms.
> There are more then 10,000 verities of mushroom out of which only 200 verities identified as edible variety.
Varieties of Mushrooms:- We can grow four varities of mushroom depending upon the climatic condition as:
i. Oyster Mushroom (Sept-April)
ii. Paddy Straw Mushroom (May-Sept)
iii. Milky Mushroom (Sept-April)
iv. Button Mushroom (Nov-Feb)
Cultivation of Button mushroom:- The most popular kind of mushrooms are button mushrooms, often referred to as white mushrooms, baby mushrooms, and cultivated mushrooms. These mushrooms can be consumed raw or cooked, and are frequently added to salads, soups, and as toppings for pizza. In the sixteenth century, button mushrooms were first grown. Button mushrooms make up 85% of the annual production of mushrooms.
Following is a process to grow mushroom:-
1. Compost:-
> The first stage in cultivating button mushrooms is composting.
> This procedure is carried out in public.
> On neat concrete platforms, button mushrooms are raised.
> Compost is prepared in the two types listed below:
a. Natural compost:-
- Natural compost is produced by nature.
- When producing compost for button mushrooms, some natural ingredients are wheat straw, horse manure, gypsum, and chicken manure.
- The compost yard should be evenly covered with a mixture of all the components.
- After that, moisten the prepared compost with a water sprayer.
b. Synthetic Compost:-
- For synthetic compost, we needed urea, gypsum, wheat straw, bran, and ammonium nitrate / ammonium sulphate.
- To begin, trim the staw to a length of 8 to 20 cm.
- Now cover the compost with a fine layer of cut straws and mist it with water.
- You must now thoroughly combine the bran, calcium nitrate, urea, gypsum, and other ingredients.
2. Filling the compost trays:-
> The compost that has been processed is a deep brown tint.
> The compost shouldn't be too damp or too dry when you put it in trays.
> Spray some water on the compost if it's dry.
> Allow some water to evaporate if it is excessively wet.
> You can choose the size of the compost-spreading trays to suit your needs.
> The depth must be between 15 and 18 cm.
> Make sure the trays are constructed of softwood as well.
> Compost must be poured into the trays to the rim and spread out evenly.
3. Spawning:-
> Spawning is the following stage in the cultivation of button mushrooms.
> It entails planting mycelium in the beds.
> There are two methods for spawning:
i. The first is to distribute compost on the tray bed.
ii. The second is to mix mycelium with compost before spreading it on the tray.
> After sprinkling the tray with water and spawning, you must cover it with newspaper to keep the moisture there.
4. Casing:-
> The tray must now be covered with a heavy layer of dirt.
> This soil can be created by mixing garden soil and decomposing cow manure.
> Casing soil is the term for this soil. This casing soil may hold a lot of water.
5. Harvesting:-
> The cap should be gently torn off during harvest.
> To do this, hold it gently between your forefingers, press it into the ground, and then twist it off.
> Cut off the base of the stalk where mycelial threads and dirt granules adhere.
Mycorrhiza application in agriculture and plant growth:-
> Mutually beneficial relationship between the root of a plant and a fungus that colonizes the plant root.
> Mycorrhizal spores germinate when in contact with plant roots and form filaments (hyphae), which create a symbiotic relationship increasing the plants ability to uptake fixed nutrients and water, improving plant performance.
> Mycorrhizal fungi increase the surface absorbing area of roots 100 to a 1,000 times, thereby greatly improving the ability of the plant to access soil resources.
> Mycorrhizal fungi increase nutrient uptake not only by increasing the surface absorbing area of the roots, but also release powerful enzymes into the soil that dissolve hard-to-capture nutrients, such as organic nitrogen, phosphorus, iron and other “tightly bound” soil nutrients.
Types of Mycorrhiza:-
1. Ectomycorrhiza:- Ectomycorrhizal fungi do not penetrate into the root cell walls, they form a sheath around the root known as a fungal mantle as nutrient exchange network. Ectomycorrhizal fungi are mainly in forests ecosystems.
Examples:-
a. Arbutoid Mycorrhiza:-
> Arbutoid mycorrhiza are a type of endomycorrhizal fungi that look similar to ectomycorrhizal fungi.
> They form a fungal sheath that encompasses the roots of the plant; however, the hyphae of the arbutoid mycorrhiza penetrate the cortical cells of plant roots, differentiating it from ectomycorrhizal fungi.
b. Ectotrophic Mycorrhiza:-
> The fungi involved in this mycorrhizal association are from the Ascomyota and Basidiomyota families.
> They are found in many trees in cooler environments.
> Unlike their wood-rotting family members, these fungi are not adapted to degrade cellulose and other plant materials; instead, they derive their nutrients and sugars from the roots of their living plant host.
2. Endomycorrhiza:- Endomycorrhiza forms symbiotic relationship with about 85% of plants, they penetrate into the root cortexs and form nutrient exchange structures within the root cells.
Examples:-
a. Orchid Mycorrhiza:-
> Some orchids cannot photosynthesize prior to the seedling stage. Other orchids are entirely non-photosynthetic.
> All orchids, however, depend on the sugars provided by their fungal partner for at least some part of their lives.
> Orchid seeds require fungal invasion in order to germinate because, independently, the seedlings cannot acquire enough nutrients to grow.
> In this relationship, the orchid parasitizes the fungus that invades its roots.
> Once the seed coat ruptures and roots begin to emerge, the hyphae of orchidaceous mycorrhiza penetrate the root’s cells and create hyphal coils, or pelotons, which are sites of nutrient exchange.
b. Arbuscular Mycorrhiza:-
> Arbuscular mycorrhiza are the most widespread of the micorrhiza species and are well known for their notably high affinity for phosphorus and ability for nutrient uptake.
> They form arbuscules, which are the sites of exchange for nutrients such as phosphorus, carbon, and water.
> The fungi involved in this mycorrhizal association are members of the zygomycota family and appear to be obligate symbionts. In other words, the fungi cannot grow in the absence of their plant host.
c. Ericaceous Mycorrhiza:-
> Ericaceous mycorrhizae is generally found on plants of the order Ericales and in inhospitable, acidic environments.
> While they do penetrate and invaginate the root cells, ericoid mycorrhiza do not create arbuscules.
> They do, however, help regulate the plant’s acquisition of minerals including iron, manganese, and aluminum.
> Additionally, mycorrhizal fungi form hyphal coils outside of the root cells, significantly increasing root volume.
Benefits in agriculture:-
> Mycorrhizae induce plants to absorb more nutrients and water from the soil.
> They also increase plant tolerance ability to various bad environmental stresses.
> In addition to this, Mycorrhizae also play an important role in soil structure process and stimulate beneficial microbial activity.
> We divided functions into two parts:
a. For Soil:-
i. Increase soil’s water & nutrition holding capacity.
ii. Improve soil porosity and permeability.
iii. Develop soil microenvironment, promote higher microbial activity and nutrient cycling.
b. For Plants:-
i. Increase roots establishment and survival at seeding or transplanting.
ii. Improve the plant’s mineral absorption capabilities, access many extra nutrient sources share with colonized plants.
iii. Increase plants resistance ability to soil diseases, virus, drought & salt stress and pests etc.
iv. Increase plants root system healthy development.
Simliar Products:- The optimum supplements to mycorrhizae is Bacillus subtilis, Trichoderma harzianum.
> Mycorrhizae’s ability is to regulate biological diversity in soil, develop positive microenvironment.
> Bacillus subtilis can improve plants uptake nutrients efficiency, increase roots growth and protect roots away from soil pathogens.
> Trichoderma harzianum have super soil adaptability. Good effect on soil conditioner and control soil borne diseases. Also can increase root systems development.
> In general, the more biological diversity of microorganisms, the more advantageous it is for growing.