2019 Solved Old Paper (BOT - 201) New
Ans.
> Fungi:- These are heterotrophic, eukaryotic and thallophytic plants, which reproduce asexually by mitospores.
> L.- fungarum = grow fast
> Mycology:- It is the branch of biology concerned with the study of fungi.
Gr.- mykes = mushroom
logos = study
> Father of Mycology:- P. A. Micheli (Italian botanist)
> Father of Indian Mycology:- E. J. Butler (Irish mycologist and plant pathologist)
> Father of modern Mycology:- de Bary (German surgeon, botanist, microbiologist, and mycologist)
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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
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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.
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
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i. Early Blight of Potato:-
ii. Downy Mildew of Grapes:-
Pathogen:- Alternaria solani
Pathogen:- Plasmopara viticola
iii. Blast disease of Rice:-
Pathogen:- Pyricularia grisea (P. oryzae)
iv. Red Rot of Sugarcane:-
Pathogen:- Glomerella tucumanensis. (Older name = Colletotrichum falcatum)
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Plant quarantine:- The process of ensuring that seeds, propagules and plant products imported from outside are free from diseases, pests and weeds, is called plant quarantine. The DIP (Destructive Insects & Pests) Act was passed in 1914. There are 4 plant quarantine centres in India -
· NBPGR, New Delhi:- For plant species related to Agriculture and Horticulture.
· FRI (Forest Research Institute), Dehradun:- For forest trees.
· IBS (Indian Botanical Survey), Kolkatta:- For other plants.
· DPPQS (Directorate of Plant Protection, Quarantine and Storage), Faridabad, Haryana:- For food materials.
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Sexual reproduction:-
> It takes place by the union of two isogametangia and their coenocytic contents, and resembles essential features of the sexual reproduction of Mucor mucedo. But, in this case, the gametangia are somewhat club-shaped and they meet in such a way that they resemble a pair of tongs.
> A coenocytic zygospore is formed, by their union, at the point of contact, and it appears as a bud and occupies, as if, a terminal position.
> P. crystallius is heterothallic, and the formation of a zygospore is dependent upon the union of mycelia of two sexual strains, ( + ) and (-).
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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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Tomato Mosaic Virus:-
Pathogen:-
> Tomato mosaic virus (ToMV) is a member of family tobamoviridae and belongs to the genus tobamovirus, which is a plant pathogenic virus.
> It is found worldwide and affects tomatoes and many other wide host range plants including many agricultural crops and weeds such as tobacco and beans, all of which can serve as inoculum sources.
> The tomato crop is highly susceptible to the Tomato mosaic virus (ToMV).
> The symptoms vary from tiles, wrinkle, reduction and curvature of leaflets, and irregular ripening of fruits.
> This disease requires attention because of its easy dissemination by contact, cultural practices, or contaminated seed.
Symptoms:-
> Tomato mosaic virus symptoms can be found at any stage of growth and all parts of the plant may be infected.
> ToMV causes yellow mosaic symptoms on the leaves and tomato fruits.
> Tomato mosaic virus symptoms are seen as a general mottling or mosaic appearance on foliage.
> Light and darker green mosaic leaf mottle, sometimes with distortion of younger leaves; this is the most common reaction in summer in glasshouses.
> In winter, with low light intensity, short days and temperatures not above 20°C, plants are often severely stunted and leaves distorted to ‘fern-leaf’ or tendril shape, but mottling may be slight.
> Plants are less vigorous, and fruit yield is reduced by 3 to 23%.
> Tomato mosaic virus strains occur in Chenopodium murale in the USA, causing severe stunting, distortion and necrosis, and in pear associated with a diffuse chlorotic leaf spotting.
Management:-
> Treating mosaic virus is difficult and there are no chemicl controls like there are for fungal diseases.
> Tomato mosaic virus has been found to survive for up to 50 years in desiccated plant detritus! So tomato mosaic virus control then leans less on eliminating the disease and more on reducing and eliminating the virus sources and insect infestations.
> Control is mainly based on the use of virus-free seeds.
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Downy Mildew of Grapes:-
Pathogen:- Plasmopara viticola
Symptoms:-
> Irregular, yellowish, translucent sports on the upper surface of the leaves.
> Correspondingly on the lower surface, white, powdery growth on leaves.
> Affected leaves become, yellow, brown and gets dried.
> Premature defoliation.
> Dwarfing of tender shoots.
> Brown, sunken lesions on the stem.
> White growth of fungus on berries which subsequently becomes leathery and shrivels.
> Later infection of berries result in soft rot symptoms.
> No cracking of the skin of the berries.
> Spread:- Through sporangia by wind, rain etc.
> Survival:- As oospores present in the infected leaves, shoots and berries. Also as dormant mycelium in infected twigs.
> Optimum temperature:- 20-22°C
> Relative humidity:- 80-100 per cent
Management:- Spray Bordeaux mixture 1 % or Metalaxyl + Mancozeb 0.4 %.
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1. Synchytrium:-
> Synchytrium is a soil borne fungus which do not possess mycelium and is designated as holocarpic.
> It is worldwide in distribution, occurring in tropical, temperate and arctic zones.
> It has been found present even at higher altitudes of above 11000 ft.
> All the species are parasitic and infect algae, mosses, ferns and most commonly flowering plants.
> It causes Black wart disease in Potato. As a result potato tubers are affected and become malformed due to formation of warts on them.
> There are 200 species of Synchytrium, but about 60 species have been reported from India.
> The most common species is S. endobioticum, well known for disease on potato. It mainly infects solanaceous plants.
> The body of the fungus is composed of a single uninucleate cell with definite cell wall.
> The fungus resides in the potato tuber in most part of its life cycle and produces many uniflagellate motile zoospores. These zoospores are the carrier of fresh infection in healthy tubers.
> The fungus induces the host tissue to multiply in number and to grow in size. Due to this, many warts develop in the tubers; hence the disease is known as wart disease.
> Although, wart is more common disease in Europe. Fortunately, it is not found in our country, but it has been reported from Darjeeling district of W. Bengal.
> Warts on infected tubers burst at later stage and release putrid liquid as exudates. This liquid contains zoospores in large number having single posterior flagellum. They swim in the film of water and move to other potato tubers.
2. Plasmodiophora:-
> Plasmodiophora has single species, Plasmodiophora brassicae.
> It is intracellular parasite in the roots of members of family brassicae like cabbage, turnips etc.
> It causes disease club roots or linger-and toe disease. In this disease the roots are swelled and become club like.
> This fungus is present in the form of mass of protoplasmic bodies in the infected roots.
> Each plasmodium contains thirty nuclei. These nuclei are haploid.
Ans.
Life cycle:- There are 5 types of spore stages found in Puccinia-
i. Uredospores:- They are dikaryotic and are found on wheat.
ii. Teleutospores:- They are dikaryotic and are found on wheat.
iii. Basidiospores:- They are monokaryotic and are found in soil.
iv. Pycnidiospores:- They are monokaryotic and are found on barberry.
v. Aecidiospores:- They are dikaryotic and are found on barberry.
i. Uredospores:-
ii. Teleutospores:-
iii. Basidiospores:-
iv. Pycnidiospores:- These are also called spermatia.
Spermatization:- The mature spermatia are released from the ostiole along with the drop of nectar. Nectar attracts insects due to which spermatia stick to the legs and mouthparts of insects. When these insects come in contact with the receptive fungal hyphae of opposite strain, spermatia stick to it. Due to the desolution of the contact wall, both the nuclei enter the receptive fungal hyphae.
v. Aecidiospores:-
Note:- The formation of secondary mycelium by germination of aesidiospore takes place only on mountains because there, wheat and barberry plants are located close to each other. There are no barberry plants in the plains, so aesidiospores are not formed here.
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Plant Disease control by Physical methods:-
> The hot water treatment method of Jensen was developed in 1887 which was used to control loose smut disease of wheat, barley and Oats. Until the development of systemic fungicide hot water treatment was the only method to control loose smut. Hot water treatment is also effective in the control of nematodes.
> Solar energy treatment to control loose smut was first developed by Lutlzra. In this method seeds are first rinsed or soaked in water for 4-5 hrs. before drying them in scorching sun.
> Hot air treatment for the control of virus in propagating stocks was first developed by Kunkal in Peach yellow.
Plant Disease control by Chemical methods:-
> Chemical barrier to protect the host plant and/or eradicate an existing infection.
> Pesticides typically cannot “cure” heavily diseased plants.
> Types of pesticides:- fungicides, bactericides, nematicides, insecticides, biocides.
> Contact fungicide:- effective only at the site of application (protectant) must be applied before pathogen infects the plant; new growth emerging after application is not protected. examples: mancozeb, coppers, chlorothalonil, captan.
> Systemic fungicide:- absorbed & translocated (moved from application site) by the plant locally systemic = moves short distances (towards leaf margin) within the plant from the site of application (e.g., benomyl, triforine) systemic = moves further within the plant from the site of application (e.g., metalaxyl moves from roots up to shoots and foliage).
Methods:-
a. Seed treatment:- With fungicide before transplanting.
i. Soil treating chemicals:- It is used for controlling such soil borne diseases which attack on seeds or seedlings. The examples of such chemicals are – Formaldehyde, Captan, Thiram, Zineb, Organo-mercurials, PCNB, Ethylene dibromide, vapam etc.
ii. For Externally seed borne diseases, chemicals such as formalin, copper carbonate, captan, organo-mercurials (Agrosan GN and Ceresan) are used for seed treatment.
iii. For Internally seed borne diseases (i.e. loose smut), hot water treatment and solar treatment are used.
iv. Systemic Organic Compounds are effective chemicals for controlling both externally and internally seed borne diseases eg. Oxanthin derivatives (Plantvax and Vitavax), Benlate, Bavistin, Demosan.
v. For controlling air borne diseases, foliar application of chemicals is more effective.
vi. The common copper fungicides are: Perenox, Perelan, Blitox, Cuprokyt, Cuprosanand Fytolan. Its use is comparatively better than that of Bordeaux mixture.
b. Seed dressing:- With organomercurials and systemic fungicides.
Plant Disease control by Biological methods:- Biological control involves the use of one living organism to control another.
Biological Control Agents:-
a Parasitoids
b. Pathogens
c. Predators
d. Antagonists of Plant Diseases
a Parasitoids:-
> Each parasitoids requires only one host, which it kills for its development into a free living adult.
> Parasitoids are of the same size as the hosts , or sometimes even smaller.
> Mechanism:-
- The Female parasitoid lays eggs inside or on an insect host.
- Legless larva on hatching feed on the hosts internally or externally.
- Many adult parasitoids feed on nectar or pollen and serve as important pollinators.
> Examples:- Trichogramma,Ichneumoid,Scelionoid,Braconid, Encryrtid,Eulophid,Chalcid wasps and Tachinid Flies.
> Revolution of Trichogramma chilonis:-
- Trichogramma chilonis has been successfully released in Jammu & Kashmir, Himachal Pradesh, Punjab, Haryana, Gujrat , Uttrakhand , Uttar Pradesh, Bihar , Karnataka, Tamil Nadu ,Maharashtra and few other states.
- It has given 56-82% protection against the sugarcane tissue borers.
b. Pathogens:-
> Pathogens are disease causing organisms e.g. Bacteria, Fungi, Viruses ,Protozoa and Nematodes in Insect Pests which kill their host or debilitate the future generation.
> Mechanism:-
- The infected insects are unable to feed properly ,remain stunted, lose their body colour and get paralysed.
- Dead insects are often found hanging on the plants, or a fungal growth on the body of dried insect could be easily located in the field.
- Caterpillar, Pseudoplusia includens , killed by entomopathogenic fungus Nomuraea rileyi , white-disease in soybean crop.
c. Predators:-
> These are free living and larger in size than their prey, requiring several preys to complete their life cycle.
> Some smaller predators release a powerful poison, use a trap or hunt in groups to be more effective.
> Mechanism:-
- Green lacewings (very common and important predator of crop pests).
- The female lays small pale green, oval shaped eggs at the end of long silken stalks, which ultimately turns grey.
- The larva have well developed legs and pincer like jaws with which they suck the body fluids from the prey.
d. Antagonists of Plant Diseases:- The microorganisms used in biological suppression of plant diseases which grow in association with plant diseases are termed as antagonists.
An antagonist microorganism adversely affects the disease causing organism by following:-
i. Competition:- The competition which takes place between two organisms in terms of nutrients etc.
ii. Antibiosis:- An association between organisms that is injurious to one of them. Antibiosis, is provided by marigold (Tagetes species) roots, which release terthienyls, chemicals that are toxic to several species of nematodes and fungi.
iii. Hyperparastism:- The parasitic habit of one species upon another parasitic species which is harmful to one of them.
iv. Mycoparasitism:- A parasitism of a fungus(host) by another fungus(mycoparasite). Trichoderma harzianum, used as seed treatment against pathogenic fungus(Sclerotium rolfsii) on chickpea and sugarbeet.
Plant Disease control by Resistant varieties:- Using resistant varieties is the most efficient way of controlling vegetable diseases. Make an effort to buy resistant varieties when they are available.
> The following terms are important in a discussion of crop resistance:
i. Immunity
ii. Resistance
iii. Tolerance
> Immunity is the rule in the plant kingdom; most plants are immune to most pathogens. Therefore, one does not have to worry that the black spot on roses will appear next year on the garden tomatoes.
> Resistance, strictly speaking, refers to the lower disease levels seen in some cultivars or varieties of a particular crop species compared to other susceptible cultivars. Always choose resistant varieties when available.
> Tolerance refers to varieties or cultivars that appear to be just as heavily diseased as standard varieties, but which manage to be more productive or vigorous.
