To study about the general study of different structures of fungi || plant pathology practical manual || BSc agriculture

 

 

1.    Rhizomorphs: ( rhiza=root, morph=shape)

 Thick strands of somatic hyphae in which the hyphae loose their individuality and form complex tissues that are resistant to adverse conditions and remain dormant until favourable conditions return. The structure of growing tip of rhizomorphs resemble that of a root tip, hence the name rhizomorph. Eg. Armillariella mellea

 

2.    Sclerotium: (skleron=hard)

 pl.sclerotia: It is a hard, round ( looks like mustard seed)/ cylindrical or elongated (Claviceps) dark coloured ( black or brown )resting body formed due to aggregation of mycelium, the component hyphae loose their individuality , resistant to unfavourable conditions and remain dormant for a longer period of time and germinate on the return of favourable conditions. Eg. Sclerotium, Rhizoctonia Fig. 6.1. Sclerotium, Rhizoctonia

 

3.    Stroma: (stroma=mattress)

pl.stromata. A stroma is a compact, somatic structure or hyphal aggregation similar to a mattress or a cushion, on which or in which fructifications of fungi are usually formed. They may be of various shapes and sizes. Hyphal masses like acervuli, sporodochia, pionnotes etc. are the fertile stromata, which bear sporophores producing spores. Eg.Claviceps, Cercospora

 

4.    Haustorium: ( hauster=drinker)

pl.haustoria. It is a outgrowth of somatic hyphae regarded as special absorbing organ produced on certain hyphae by parasitic fungi for obtaining nourishment. They may be knob like (Albugo), elongated ( Erysiphe, Uncinula), finger like ( Peronospora ).

 

5.    Rhizoids: (rhiza=root, oeides=like)

These are slender root like branched structures found in the substratum produced by some fungi which are useful for anchoring the thallus to substratum and for obtaining nourishment from the substrate.

 Eg. Rhizopus stolonifer.

 

6.    Appresorium: (apprimere=to press against)

 pl.appressoria A flattened tip of hyphae or germ tube acting as pressing organ by attaching to the host surface and gives rise to a minute infection peg which usually grows and penetrates the epidermal cells of the host.

 Eg. Puccinia, Colletotrichum, Erysiphe.

Read More

To study about the Koch’s postulates || plant pathology practical manual || BSc agriculture

 

Experiment no. 4

To study about the Koch’s postulates.

 

Koch’s postulates for plant pathogens

Introduction

 During the late 19th century a bacteriologist called Robert Koch laid down a set of rules for confirming that an organism is the cause of a disease. These are now known as ‘Koch’s postulates’.

When a plant becomes infected with a fungus (or any other disease causing microorganism), it is likely to become weakened and therefore more susceptible to infection by other microbes. So how do us plant pathologists work out what pathogen has caused a particular disease? We have to apply Koch’s postulates to the disease.

To determine Koch’s postulates:

(a) the organism must be consistently associated with the lesions of the disease;

(b) the organism must be isolated from the lesions and grown in pure culture;

(c) the organism from pure culture must be re-inoculated into the healthy host and must cause the same disease as was originally observed;

(d) the organism must be re-isolated into culture and shown to be identical to the organism originally isolated.

 Aim:

To demonstrate Koch’s postulates using apples infected with the brown rot fungus, Monilinia fructigena,.

 

Koch’s postulates: brown rot

To determine which microbe caused that fuzzy stuff on your apple you must:

 1. Describe the symptoms you see on the infected apple and isolate the suspected fungus pathogen responsible.

2. Isolate the fungus in pure culture (this means grow the fungus on its own, away from the host plant (apple) and without any contaminating microorganisms).

 3. Use the fungus that you isolated in pure culture to inoculate a healthy apple.

4. Record the symptoms that develop on the healthy apple following infection with the cultured fungus. Are your observations the same as recorded previously?

 5. Re-isolate the fungus and check that it is the same as observed initially.

Materials needed

1. Apples infected with Monilinia fructigena

2. Slides and coverslips

3. Cotton blue stain

4. Stereo & compound microscope

5. Imersion oil

6. Sterile scalpels

7. Potato dextrose agar (PDA) plus antibiotic

8. Fresh apples

Session 1

 You are provided with:

· An apple infected with the fungus Monilinia fructigena;

 · Three plates of Potato dextrose agar (PDA) supplemented with antibiotic (to control bacteria);

· Microscopes, slides, cover slips and cotton blue stain

 

Method:

1. Carefully record the symptoms of the disease. Examine the fruit externally. What do you see?

2. Slice through the infected apple. Are there any colour and texture changes in the infected fruit? Observe the symptoms using a microscope and compare them with a healthy apple (control).

 3. Using a sterile scalpel blade, carefully remove a pustule (containing reproductive structures of the fungus) from the infected apple and place it on a microscope slide. Place a drop of cotton blue stain onto the pustule and cover with a coverslip. Lightly press down the cover slip and use a circular motion to squash the pustule. This is best done using the end of a pencil. Take care not to crack the coverslip. Record your observations.

4. Using a sterile scalpel blade isolate small pieces of tissue from the edge of the infected apple and place one piece of tissue at the centre of each plate of PDA.

Session 3:

1. Compare the symptoms of disease in the inoculated apples with those recorded in session 1. Are they identical, or are there differences?

 2. You must now re-isolate the micro-organism from the apple inoculated in session 2, to show that it is identical to the organism originally isolated.

The plates will be incubated at 25o C and returned in session 4.

Session 4

. 1. Carefully examine the cultures.

2. Use the skills that you have learnt in the previous sessions to examine the cultures using microscopy.

3. Look for the characteristic spore bearing structures.

Read More

To study about the microscope with diagram in details || plant pathology practical manual || BSc agriculture

 

Read More

To study about the preparation of PDA media || plant pathology practical manual || BSc agriculture

 

Boiling potatoes	Boiling agar	Potato extract + agar+ sugar

 

Sterilization	PDA media	Pouring in Petri plates

 

Read More

To study about the acquaintance with various laboratory equipment's || plant pathology practical manual || BSc agriculture

 

Read More

Soil – Pedological and Edaphological concepts || lecture - 1 soil science || bsc agriculture pdf

01. Soil – Pedological and Edaphological concepts

Soil science is the study of soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.

Sometimes terms which refer to branches of soil science, such as pedology (formation, chemistry, morphology and classification of soil) and edaphology (influence of soil on organisms, especially plants), are used as if synonymous with soil science. The diversity of names associated with this discipline is related to the various associations concerned. Indeed, engineers, agronomists, chemists, geologists, physical geographers, ecologists, biologists, microbiologists, sylviculturists, sanitarians, archaeologists, and specialists in regional planning, all contribute to further knowledge of soils and the advancement of the soil sciences.

 

Soil scientists have raised concerns about how to preserve soil and arable land in a world with a growing population, possible future water crisis, increasing per capita food consumption, and land degradation.

Soil occupies the pedosphere, one of Earth's spheres that the geosciences use to organize the Earth conceptually. This is the conceptual perspective of pedology and edaphology, the two main branches of soil science. Pedology is the study of soil in its natural setting. Edaphology is the study of soil in relation to soil-dependent uses. Both branches apply a combination of soil physics, soil chemistry, and soil biology. Due to the numerous interactions between the biosphere, atmosphere andhydrosphere that are hosted within the pedosphere, more integrated, less soil-centric concepts are also valuable. Many concepts essential to understanding soil come from individuals not identifiable strictly as soil scientists. This highlights theinterdisciplinary nature of soil concepts.

 

Soil Science

“The science dealing with soil as a natural resource on the surface of the earth, including Pedology (soil genesis, classification and mapping), physical, chemical, biological and fertility properties of soil and these properties in relation to their management for crop production.”

Soil Science has six well defined and developed disciplines

Soil fertility:        Nutrient supplying properties of soil

Soil chemistry:        Chemical constituents, chemical   properties and the chemical reactions

Soil physics:        Involves the study of physical properties Soil microbiology:        Deals with micro organisms, its population, classification, its                                    role in transformations

Soil conservation:        Dealing with protection of soil against physical loss by erosion or against                                        chemical deterioration i.e excessive loss of nutrients either natural or                                                artificial means.

Soil Pedology:        Dealing with the genesis, survey and classification

Views on Soil (Science)

The term SOIL was derived from the Latin Word “SOLUM” Means FLOOR

·         For a Layman soil is dirt or debris

·         For an Agriculturist soil is a habitat for plant growth (to grow crops)

·         For a Mining Engineer soil is a debris covering the Rocks

·         For a Civil Engineer soil is a material on which road bed or house bed is formed

·         For a Home Owner soil is a mellow or loamy or hard material

Definitions

Generally soil refers to the loose surface of the earth as identified from the original rocks and minerals from which it is derived through weathering process.

Whitney (1892): Soil is a nutrient bin which supplies all the nutrients required for plant growth

Hilgard (1892): Soil is more or less a loose and friable material in which plants, by means of their roots, find a foothold for nourishment as well as for other conditions of growth” Dokuchaiev (1900): Russian scientist - Father of soil science - Soil is a natural body composed of mineral and organic constituents, having a definite genesis and a distinct nature of its own.

Joffe (1936): “Soil is a natural body of mineral and organic constituents differentiated into horizons - usually unconsolidated - of variable depth which differs among themselves as well as from the underlying parent material in morphology, physical makeup, chemical properties and composition and biological characteristics”.

Jenny (1941): Soil is a naturally occurring body that has been formed due to combined influence of climate and living organisms acting on parent material as conditioned by relief over a period of time.

Ruffin and Simonson (1968): Soil is a mixture of Earth’s uppermost mantle of weathered rock and organic matter

Buckman and Brady (1969 ): Soil is a dynamic natural body on the surface

of the earth in which plants grow, composed of mineral and organic materials and living forms

Soil Science Society of America (1970)

(i)    Soil is the unconsolidated mineral matter on the surface of the earth that has been subjected to and influenced by genetic and environmental factors of parent material, climate (including moisture and temperature effects), macro and microorganisms and topography, all affecting over a period of time and producing a product, that is “SOIL” that differs from the material from which it is derived in many, physical, chemical, biological and morphological properties and characteristics.

(ii)   The unconsolidated mineral material on the immediate surface of the earth that serves as a natural medium for the growth of land plants.

Dr W.E.H. Blum

Soils not only serve for agriculture and forestry, but also for filtering, buffering and transformation activities between the atmosphere and the groundwater, protecting the food chain and drinking water against pollution and biodiversity

As soil provides nutrients, water, air and anchorage and supports life on Earth, it can be called as Soul Of Infinite Life (SOIL)

List of International Soil Scientists

1. Van Helmont (1577 – 1644)

2.      Theoder De Saussure

3.      John Woodward

4.      Boussingault (1802 – 1882) 5. J.V. Liebig (1803 – 1873)

6. J.B.Laws & J.H. Gilbert (1855) 7. J.T.Way (1856)

8.      R.Warrington (1876)

9.      E.W. Hilgard (1860)

10. V.V. Dokuchaiev (1846-1903)

11.  K.D.Glinga (1914)

12.  C.F.Marbut (1927)

13.  Hens Jenny (1941)

Indian Scientists

1.      J.W.Leather (1906)

2.      Madam Scholasky (1932)

3.      Wadia et al. (1935)

4.      Viswanath & Ukil (1943)

Soil as a three dimensional body

Soil is a three dimensional body having length, breadth and depth. They form a continuation over the land surface and differ in properties from place to place. Its upper boundary is air or water and lower boundary is the rock lithosphere.

Composition of soil on volume basis (Soil 

components)

Mineral matter: 45%

Organic matter: 5%

Soil water: 25%

Soil air: 25%

Soil can be compared to various systems of animals 

Digestive system : Organic matter decomposition Respiratory system: Air circulation & exchange of gases Circulatory system (blood): Water movement within the soil Excretory system: Leaching out of excess salts

Brain: Soil clay

Colour: Soil colour

Height: Soil depth

Approaches of Soil Study

Two Concepts: One treats soil as a natural body, weathered and synthesized product in nature (Pedology) while other treats soil as a medium for plant growth (Edaphology).

Pedological Approach: The origin of the soil, its classification and its description are examined in Pedology. (From Greek word pedon, means soil or earth). Pedology is the study of soil as a natural body and does not focus on the soil’s immediate practical use. A pedologist studies, examines and classifies soil as they occur in their natural environment.

Edaphological Approach: Edophology (from Greek word edaphos, means soil

or ground) is the study of soil from the stand point of higher plants. Edaphologists consider the various properties of soil in relation to plant production. They are practical and have the production of food and fibre as their ultimate goal. They must determine the reasons for variation in the productivity of soils and find means for improvement.

Read More