2022 Solved Old Paper (BOT - 201) New
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Heterothallism:-
> A. F. Blakeslee, an American Geneticist, in 1904 made an important observation with Mucor, which resulted in the discovery of Heterothallism.
> Heterothallism, according to Whitehouse (1949) can be caused by the absence of the morphological sex organs of the opposite type (morphological heterothallism) or by the absence
of genetically-different nuclei (physiological heterothallism). Whatever be the reason for heterothallism, the fact remains that different thalli are needed for sexual reproduction.
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Types of Hetrothallism:-
i. Bipolar Heterothallism:- Fungi in this category have two mating types, each containing genetically different nuclei. The sexual compatibility is controlled by a pair of genetic factors A and a located at the same locus on different chromosomes. This is, therefore, also called as ‘two allele heterothallism’.
ii. Tetrapolar Heterothallism:- Fungi in this group form thalli of four mating types. This type of heterothallism is governed by two pairs of compatibility factors Aa and Bb, located at different chromosomes, which segregate independently during meiosis. If crossing over occurs between the mating type loci, four types of segregations (AB, Ab, aB, ab) are possible depending on the chromosomal arrangement.
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Mycorrhiza:- It is a symbiotic association of fungi with roots of higher plants. Their major role is to enhance nutrient and water uptake by the host plant by exploiting a larger volume of soil than roots alone can do. the large mass of fungal hyphae acts as a virtual root system for the plants, increasing the amount of water and nutrients that the plant may obtain from the surrounding soil. In reverse, the roots provide essential nutrients for the growth of the fungi.
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Clamp Connections (क्लैम्प कनैक्शन):- Topical growth is found in Basidiomycetes class. In all Basidiomycetes members except rusts, the apical cells of the secondary mycelium divide with the help of a lateral tubular structure.
(Basidiomycetes वर्ग में शीर्षस्थ वृद्धि पायी जाती है। Rusts को छोड़कर शेष सभी Basidiomycetes सदस्यों में द्वितीयक कवकजाल की शीर्षस्थ कोशिकाएं एक पार्श्व ट्यूबनुमा संरचना की सहायता से विभाजित होती है।)
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Ascocarp (एस्कोकार्प):- It consists of very tightly interwoven hyphae and millions of embedded asci.
(इसमें बहुत कसकर उलझे हुए कवक तन्तु और लाखों धँसी हुई एस्कस होती हैं।)
Paraphyses (पैराफाइसिस):- Sterile hyphae present in between of asci are called as paraphyses.
(एस्कस के बीच- बीच में मौजूद बंध्य कवक तंतुओं को पैराफाइसिस कहा जाता है।)
Hymenium (हाइमेनियम):- Paraphyses and asci together form a fertile layer which is called as hymenium.
(पैराफाइसिस और एस्कस मिलकर एक उर्वर परत बनाते हैं जिसे हाइमेनियम कहा जाता है।)
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Antibiotics:- Antibiotics are the metabolic product of some micro-organisms which are active against other microorganism. Wonder drug Penicillin from Penicillium notatum, and drug Fusidin (Fusidic acid) from Fusidium coccineum.
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Hallucinogenic fungi:-
> The group of hallucinogenic mushrooms (species of the genera Conocybe, Gymnopilus, Panaeolus, Pluteus, Psilocybe, and Stropharia) is psilocybin-containing mushrooms. These "magic", psychoactive fungi have the serotonergic hallucinogen psilocybin.> Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine) is the active chemical in hallucinogenic mushrooms. This chemical is found in approximately 190 species of edible mushrooms that are indigenous to tropical and subtropical regions of South America, Mexico, and the United States.
> Ergot fungus can produce hallucinations and psychosis, so it is a mind-altering substance. However, it is extremely dangerous to take it recreationally. A related substance, lysergic acid diethylamide (LSD), is a semi-synthetic ergot alkaloid. It is not the same as ergot fungus but contains some similar compounds.
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Heterokaryosis:-
> Heterokaryosis is the main source of variation in the anamorphic (imperfect) fungi, which lack
sexual reproduction. The term Heterokaryosis was proposed by Hansen and Smith in 1932, who
reported it for the first time in Botrytis cinerea.
> The presence of genetically-different nuclei in an individual is called heterokaryosis, and the
organism heterokaryon.
> Essentially, a heterokaryon possesses two sets of chromosomes, just like a diploid organism, but
instead of being contained in a single nucleus, the two sets of chromosomes lie in separate
nuclei, sharing the same cytoplasm.
> Heterokaryons show dominance and, thus, resemble diploids in many respects. Heterokaryosis is
a major factor in natural variability and sexuality.
> The heterokaryotic condition can arise in a fungus by three methods, viz., (1) Mutation, (2)
Anastomosis i.e., fusion between genetically-different hyphae, and (3) Diplodization-fusion
between haploid nuclei to form diploid nuclei.
> Mutations occur frequently in fungi, and a homokaryotic mycelium is frequently converted into a
heterokaryotic one. Anastomosis between spores and hyphae is a universal feature of higher
fungi and certainly must be a potential source of heterokaryosis and, thus, of variability.
> Whether nuclei migrate from one thallus to another is a debated point but the hyphae having
nuclei of both parents arise at the point of fusion.
> Heterokaryosis is often accompanied by parasexual cycle.
Parasexual Cycle:-
> Until 1944, the sexual cycle was the only means of exchange of genetic material.
> It is to the credit of microbial geneticists that a series of novel methods of genetic recombination are now known in bacteria, which do not involve karyogamy and meiosis.
> These are transformation, conjugation, transduction, lysogeny, and sexduction which differ from the standard sexual cycle.
> A similar alternative to sexual reproduction was discovered in the imperfect fungus, Aspergillus nidulans, in 1952 by Pontecorvo and Roper Glasgow. They called this parasexual cycle.
> In this, genetic recombination occurs in somatic cells by the mechanism of mitotic crossing over, which brings the same result as is achieved by the meiotic crossing over.
> The parasexual cycle involves the following steps:
i. Formation of heterokaryotic mycelium
ii. Nuclear fusions and multiplication of the diploid nuclei
iii. Mitotic crossing over during division of the diploid cells
iv. Sorting out of the diploid strains
v. Haplodization
i. Formation of Heterokaryotic Mycelium:- The methods of formation of heterokaryotic mycelium are described earlier under ‘heterokaryosis.
ii. Nuclear Fusions and Multiplication of the Diploid Nuclei:-
- Nuclear fusion in somatic heterokaryotic hyphae was first noted by Roper (1952) in Aspergillus nidulans.
- Nuclear fusion may occur between genetically similar and dissimilar nuclei, resulting in the formation of homozygous and heterozygous diploid nuclei, respectively.
- Diploid heterozygous nuclei are formed very rarely (at a frequency of one in a million).
- In such hyphae, five types of nuclei are present- 2 types of haploid nuclei, their two types of homozygous diploids, and the one type of heterozygous diploids.
iii. Mitotic Crossing Over:-
- Crossing over is a phenomenon which occurs during meiosis and gives rise to new linkage of genes, gene recombination. A similar mitotic crossing over occurs during the multiplication of the diploid heterozygous nuclei, though at a low frequency of 10-2 per nuclear division.
- However, in some other fungi e.g., Penicillium chrysogenum and Aspergillus niger, the frequency of mitotic crossing over is as high as during meiosis in sexual reproduction. (Both species lack sexual reproduction.) Mitotic crossing over is the most important, or ‘key’ event in the parasexual cycle, as it is during this step that genetic recombination occurs.
iv. Sorting Out of Diploid Strains:- The segregation of the diploid strains occurs when uninucleate diploid conidia are formed. The colonies that are formed by diploid conidia are recognized by various methods, e.g., higher DNA content and bigger size of the conidia and certain phenotypic characters of the colony.
v. Haplodization:-
- The diploid colonies show appearance of sectors on the Petri plate, which produce haploid conidia. This indicates that some diploid nuclei must have undergone haplodization, forming haploid nuclei, which later get sorted out in haploid conidia.
- Some of these haploids are genetically different from the original haploid parental nuclei. This is because of the recombination that occurred during the mitotic crossing over.
- Haplodization occurs at a constant frequency of 10-3 per nuclear division. The haplodization occurs not by a reduction division (meiosis), but by aneuploidy, a phenomenon in which chromosomes are lost during mitotic divisions.
- It happens in the following manner. During mitosis of the diploid nucleus, the chromatids fail to separate (non-disjunction) in the anaphase stage.
- One daughter nucleus gets one chromosome more (2n + 1), while the other gets one chromosome less (2n – 1) than the normal 2 sets of chromosomes (2n). Both the daughter nuclei are called aneuploidy. The deficient aneuploid nucleus (2n – 1) may lose more chromosomes in the successive mitotic division and finally reduce to haploid state (n).
- Mitotic crossing over and haplodization also occur with the diploid homozygous nuclei, but since the two nuclei are similar, crossing-over products or the haploid nuclei formed by haplodization, are genetically no different from the haploid parent nuclei.
- The parasexual cycle, thus, like the sexual cycle, involves plasmogamy, karyogamy and haplodization, but not at a specified time or place. Every step differs drastically.
Significance of Parasexuality:-
- Parasexual cycle is of importance in industrial processes.
- Several fungi which are used in various industrial processes belong to fungi imperfecti or Deuteromycetes and in these fungi only parasexual cycle operates.
- New and better strains of these fungi are obtained by mutation through parasexual cycle.
- The strains of desirable characters can be developed through mitotic recombination.
- Parasexuality can also be applied in the analysis of genetic and physiologicaln processes of perfect and imperfect fungi.
- Parasexual cycle has also been successfully employed in genetic control of pathogenicity and host-range in several species of Fusarium.
Pontecarvo’s (1958) idea of parasexual cycle
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Sub-division: Zygomycotina:- It includes 2 classes -
a. Zygomycetes:-
> The class zygomycetes derives its name from the thick-walled resting spores, the zygospores formed as a result of the complete fusion of the protoplasts of two equal or unequal gametangia.
> It comprises 450 species which are grouped under 70 genera.
> They all are terrestrial molds which show a wide range in their habit.
> Most of them are saprobes. Among these some are soil saprophytes and others coprophilous (growing on dung).
> The parasitic species include pin molds which attack fungi, insects or protozoa. Some are facultative weak parasites (Rhizopus sexualis) of higher plants. A few are specialized parasites of animals. A very few occur as obligate parasites of other Zygomycetes.
> The members are saprobes or weak parasites on plants to specialized parasites on animals. A few occur on dung thus coprophilous in nature.
> The thallus usually consists of well developed, branched, filamentous, and coenocytic mycelium; some members possess very much reduced septate mycelium. In some cases, the coenocytic mycelium produces rhizoids and adheres to hard surfaces with their help.
> The cell wall is mainly composed of chitosan-chitin.
> The asexual reproduction takes place usually by means of non-motile sporangiospores, called aplanospores, but some also reproduce by chlamydospores or by oidia formation.
> The sexual reproduction takes place by means of gametangial copulation, resulting in the formation of thick-walled zygospores.
> The zygospore germinates by producing a germ sporangiophore that terminally bears a germ sporangium.
b. Trichomycetes:-
> Trichomycetes, includes organisms that are clearly protozoans though they were mistakenly classified as fungi for a long time, and are still called fungi by many people who should know better.
> These extremely common organisms live only in the digestive tracts of insects and other arthropods, generally as commensals, sometimes as pathogens or symbionts (mutualists), which are associated with, although not penetrating, the cuticle lining the digestive tracts of the host animal.
> Their hosts include terrestrial, marine and freshwater arthropods, most commonly midges (Chironomidae), mosquitoes (Culicidae), black flies (Simuliidae), beetles (Coleoptera), stoneflies (Plecoptera), and mayflies (Ephemeroptera), as well as several millipedes (Diplopoda) and crustaceans.
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Ustilago:-
जनन या जीवन चक्र (Reproduction or Life cycle):-
i. टेल्यूटोबीजाणु (Teleutospores):-
ii. बेसिडिओबीजाणु / संक्रमण तन्तु (Basidiospores / Infection threads):-
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Role of fungi in industries:-
1. Alcohol Production:- Alcoholic fermentation by fungi is the basis of brewing industry. The enzyme zymase of microorganisms like yeast is responsible for alcohol production. Wines are produced from grapes or other fruits by Saccharomyces ellipsoideus with about 14% alcohol concentration. Beer is brewed from barley malt by Saccharomyces cerevisiae with 3-8% alcohol production.
2. Organic acid Production:- Many fungi are used in the commercial production of different organic acids.
3. Antibiotics:- Antibiotics are the metabolic product of some micro-organisms which are active against other microorganism. Wonder drug Penicillin from Penicillium notatum, and drug Fusidin (Fusidic acid) from Fusidium coccineum.
4. Fungi as Food:- Fungi are used as food by humans from a long time ago.
> Fruit bodies of some fungi, like Mushroom and truffles are used as food due to their high protein content (21-30% on dry weight) and have good amount of lysine, an amino acid; minerals like Na, Ca, K and P; Vitamins like B, C, D and K and very little amount of fat. These are recommended as ideal foods for heart patients and diabetes.
> The above-mentioned fungi can grow artificially at the commercial level. Mushroom cultivation has recently gained considerable popularity and has contributed to the national economy in some East Asian
countries.
5. Fungi as Fodder:-
> Yeast that is used as animal feed it is a microbial proteins synthesized by yeast in which digestibility amino acid content higher than an animal routine does has a high biological value as compared to other feed.
> Inactive dry yeast fodder increases bioavailability of protein as they contain essential amino acid.
> Composition of fodder yeast contain 10 essential amino acid. On the content of amino acids fodder yeast similar to proteins of animal origin
> Feed yeast contain Vitamin B (rgulate fat metabolism) rich source of Vitamin D2 (5000-12000 IU/Kg Fd .yst).
> Ash of fodder yeast also contain valuable animals and birds macro and micro elements P, K, Ca, Fe, Mg, S, Na, Cu and others.
> Yeast commonly used commercially strain of Candida utilis,(torula yeast) often called as Torulopsis utilis.
> Other yeast used commerically or studied extensively in laboratory include C.tropicalis and Saccharomyces cerevisea.
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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.
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Sub-division: Deuteromycotina:- It includes 1 class -
Class - Deuteromycetes:-
> Deuteromycetes occur mostly as saprophytes on a wide range of substrates, but a large number of them are parasites on plants and animals (including humans) and cause a variety of diseases.
Leaf- spots, blights, blotch, wilts, rots, anthracnose, etc. are the important diseases of plants, while diseases like meningitis, candidiasis, skin diseases, nail diseases, dermatomycosis as ringworms, athlete’s foot, etc. occur in animals (including humans).
> The mycelium is made up of well-developed, profusely branched and septate hypha that possess multinucleate cells and simple pore septa.
> The hyphae may be inter- or intracellular, and their cell wall chiefly contains chitin-glucan.
> Deuteromycetes reproduce only asexually. The asexual reproduction may take place by hyphal fragments, budding (common in Blastomycetes), arthrospores (flat-ended asexual spores formed by the breaking up of cells from the hypha), chlamydospores (thick-walled modified cells functioning as resting spores), or most commonly by conidia or conidiospores (nonmotile spores formed externally on the surface of hyphae or on specialized hyphal branches called conidiophores).
> The cell of conidiophore that produces conidia is called conidiogenous cell and the conidia may be produced either at the tip or side of the conidiogenous cell either singly or in chains.
> The conidiophores are either frees from one anther (mononematous) or they may be aggregated to form specialized structures such as synnemata and sporodochia.
In large number of Deuteromycetes, the conidiophores are formed in more specialized and organized fruiting layers present within the specialized fruiting bodies called conidiomata (sing. Conidioma; formerly called conidiocarps). The conidiomata may be acervulus or pycnidium.
> Sexual reproduction lacks, but a parasexual cycle or parasexuality generally operates in their life to fulfil the requirements of sexuality.
> Classification:- It includes 3 sub-classes -
1. Blastomycetidae:-
2 Orders:-
a. Sporobolomycetales:- Eg.- Sporobolomyces
b. Cryptococcales:- Eg.- Cryptococcus
2. Coelomycetidae:-
2 Orders:-
a. Sphaeropsidales:- Eg.- Sphaeropsis, Phoma, Septoria
b. Melanconiales:- Eg.- Melanconium, Colletotrichum
3. Hyphomycetidae:-
2 Orders:-
a. Moniliales:- Eg.- Alternaria, Cercospora, Trichoderma, Helminthosporium, Fusarium, Drechslera
b. Agonomycetales:- Eg.- Rhizoctonia
Mycorrhiza:- It is a symbiotic association of fungi with roots of higher plants. Their major role is to enhance nutrient and water uptake by the host plant by exploiting a larger volume of soil than roots alone can do. the large mass of fungal hyphae acts as a virtual root system for the plants, increasing the amount of water and nutrients that the plant may obtain from the surrounding soil. In reverse, the roots provide essential nutrients for the growth of the fungi.
It is further divied into 2 types:-
Ectomycorrhiza:- It is a type of mycorrhiza, typical of temperate and Boreal trees, in which the fungus forms a layer on the outside of the roots of the plant. Here the fungal hyphae does not penetrate the cortical cells of the plant root. It occur only in about 3 per cent of plant species, majority of which are forest trees. Eg.- Amanita, Boletus, Tricholoma
Endomycorrhiza:- It is a type of mycorrhiza, most common among vascular plants, in which the fungus grow inside the tissues of the roots of the plant. the fungal hyphae penetrates the cortical cells of the plant root and make arbuscules and vesicles, hence also called as Vesicular Arbuscular Mycorrhiza (VAM). Eg.- Glomus
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.