eChapters

DEFINITION

The term Plant Pathology is derived from Greek words- pathos (suffering) + Logos (study) i.e. the study of the suffering plant. Plant Pathology has two phases broadly-

• Science- understanding of the disease i.e. the theoretical consideration of the suffering plants and how do pathogens invade, how do plants defend themselves, what causes symptoms etc.
• Art- the application of the science to the field problems i.e. Diagnosis and Control.

Plant pathology or phytopathology is the branch of agricultural, botanical or biological science which deals with the cause, etiology, resulting in losses and management methods of plant diseases.

Plant pathology can also be defined as the study of the nature, cause and prevention of plant diseases. Plant pathology is related to most of the old and new sciences like biology, physics, chemistry, physiology, mathematics, genetics, soil science, biochemistry, biotechnology etc.

Study of plant pathology includes the study of sciences viz, microbiology, bacteriology, virology, mycology, nematology, protozology, phycology, unfavorable environmental factors, nutritional deficiencies and flowering plant parasites.

Prologue: The Issues

Farmers lose a significant portion of their income when their crops and products become infested with various insects, diseases and weeds, resulting in much lower crop productivity and lower actual yields than the attainable yield of crops. Yield losses due to pests, pathogens and weeds are responsible for 20-40% losses in global agricultural productivity. India reports crop losses of 20-25% annually due to pest infestations. Without the use of crop protection solutions, there could be a 78% loss in fruit production, 54% loss in vegetable production and 32% loss in cereal production. According to the Ministry of Agriculture, India loses INR 1.48 billion worth of agricultural production annually due to pests, weeds and plant diseases.

Important Points to be Remember

• Father of Indian plant pathology – E.J.Butler
• Father of Plant virology – Beijerinck
• Wheat rust is associated with Indian scientist – K.C.Mehta
• Kresek phase of rice is due to – Bacterial leaf blight
• Bakanae disease of rice is also known as – Foot rot and Foolish seedling disease

1. ………… is the father of plant pathology.

   a) T J Burril

   c) Anton De Barry

   b) Needham

   d) E J Butler

2. ……… first time reported that plant diseases are caused by bacterium.

   a) Robert Koch

   c) Kuhn

   b) E F Smith

   d) T J Burril

Plant physiology is a sub-discipline of botany concerned with the functioning, or physiology of plants. Closely related fields include plant morphology (structure of plants), plant ecology (interactions with the environment), phytochemistry (biochemistry of plants), cell biology, genetic, biophysics and molecular biology. Fundamental processes such as photosynthesis, respiration, plant nutrition, plant hormone functions, tropism, nastic movements, photoperiodism, photo-morphogenesis, circadian rhythms, environmental stress physiology, seed germination, dormancy, stomata function and transpiration, both parts of plant water relations, are studied by plant physiologists. The field of plant physiology includes the study of all the internal activities of plants those chemical and physical processes associated with life as they occur in plants. This includes study at many levels of scale of size and time. At the smallest scale are molecular interactions of photosynthesis and internal diffusion of water, minerals, and nutrients. Major sub disciplines of plant physiology include phytochemistry (the study of the biochemistry of plants) and phytopathology (the study of disease in plants). The scope of plant physiology as a discipline may be divided into several major areas of research.

Basic LabTechniques - This laboratory is intended to:

(1) Provide an introduction to basic techniques used in biology labs

(2) provide some experience with the equipment employed in future labs

2.1 Microscopy

The compound light microscope is a veryimportant tool in the study of biology. Typical compound light microscopes allow specimens to be viewed at 400 to 1000 times their actual size (total magnification is determined by multiplying the objective lens magnification by the ocularlens magnification). Thelight microscopeis made up of a system of lenses aligned in such a way thatallows magnification, as well as improved resolution. The resolution obtainable is also dependent on contrastin the specimen. Contrast can be adjusted with the iris diaphragm, located below the condenser lens,and can also be enhanced by the addition of stains to the specimen.

Scientific drawings of specimens observed under the light microscope are often used to provide a record of what was viewed. Proper scientific drawings should be neatly drawn,with smooth lines, in pencil (they should never be in colour). More than one cellshould be drawn to illustrate the cellularassociation to the observer(e.g.found singly or as part of a tissue). Labels should be added using straight horizontal lines to the right side of the drawing, and care should be taken with singular and plural forms of structural terminology. To demonstrate differences in density of specific structures, use stippling rather than shading. A figure caption thatindicates the specimen viewed, how viewed, and the to right side of the drawing, and care should be taken with singular and plural forms of structural terminology. To demonstratedifferences in densityof specific structures, use stippling rather than shading. Afigure caption thatindicatesthe specimen viewed, how viewed, and the magnification of the drawing is always necessary.

Significance in Agriculture

The Green Revolution resulted in many fold increase in the food grain production. Crop yields have increased steadily over time, but continuing these increases above the current high levels would be difficult. But in order to meet the demands of the increasing population, the crop production must increase in a sustainable manner. Sustainable increase in the total production without increasing cultivated area represents a huge challenge that can only be met by integrative investigations at the whole plant-plant community level. Improvement of crop production systems will require a thorough understanding of basic principles of yield production. This involves the study of the plant processes responsible for the growth, development and production of economic yield by crop plants, focusing on whole plants and plant communities and not individual plant parts, organs, or cells because most of the processes that control yield operate at the whole plant-plant community level.

The processes responsible for the primary productivity of crop communities are photosynthesis, respiration, transpiration, nutrient utilization and how the products of these processes are converted to economic yield and morphogenetic processes.

Crop physiology is the study of plants at the whole-plant and plant-community level of organization and Agronomy is the study of crops and cropping systems at the farm level over a period of time. At this level of organization, the complexity of the system is so large that comprehensive attempts are to be made to examine the mechanisms underlying the crop responses to management or climate.

The scientific approach to agriculture has been to isolate (i.e., the experiments in which everything else is equal except the studied phenomenon) and to reduce (i.e., the process by which, a phenomenon is quantified in terms of one or more essential molecular processes), because the production system is too complex. Whereas the unraveling of crop production systems to simple chemical and physical phenomena has improved our general understanding of the system, it is necessary to understand how these chemical and physically processes interact within a whole plant grown from seed to maturity under natural conditions for this information to be useful in agronomy.

1. A man supplied excess fertilizer and water the grass well. After sometime the leaves turn brown because

   a) Due to water logging

   b) It decreases photosynthesis

   c) Fertilizer is drained in lower layer of soil

   d) Osmosis occurs in root and root dies

2. If roots of plant are removed and plant is placed in water, then what will be happen?

   a) Passive absorption will continue

   b) Imbibition will continue

   c) Active absorption will continue

   d) None of these

Plant pigments impart colour to the different components like leaves, flowers, fruits etc. They in turn are responsible for the colour of raw food, we eat. Pigments like chlorophyll, anthocyanins, flavonoids, tannins, xanthones etc. are the different pigments that are present in plants. The primary function of pigments in plants is photosynthesis, which uses the green pigment chlorophyll along with several red and yellow pigments that help to capture as much light energy as possible. Other functions of pigments in plants include attracting insects to flowers to encourage pollination.

1. Chlorophylls

Chlorophyll can be regarded as a true representation of health of green plants. This presumption is based on the fact that chlorophyll is most commonly and immensely influenced by biotic and abiotic stress conditions in addition to events like pathogenic invasion, pollution, mineral deficiencies as well as mineral toxicity. This is the reason that estimation of chlorophyll is considered to be one of the most important parameters in plant physiological studies.

Eukaryotic plant cells possess many types of ‘reserves’, one of them is plastid. A plastid, that contains green colour is known as chloroplast and the green colouration of a chloroplast is mainly due to the presence of a pigment to which we call as chlorophyll. Normally, chlorophyll constitutes about 4% of chloroplast dry weight.

Chlorophyll ‘a’ and ‘b’ are the most abundantly found in all autotrophic higher plants. However, there are other chlorophylls also such as ‘c’, ‘d’, ‘e’, bacteriochlorophyll and bacterioviridin which have restricted presence in blue-green, brown and red algae.

A chlorophyll molecule contains ‘Tetrapyrrole’ skeleton formed into a ring with an atom of magnesium (Mg⁺⁺) in the centre. A so-called ‘Pyrrole’ molecule contains four carbon and one nitrogen atoms arranged in a ring. Four such pyrrols arranged in a ring form the ‘Head’ of chlorophyll molecule. Attached to this is ‘porphyrin ring’, at one point, is a ‘phytol’ tail- a long chain of linked carbon.

Biological pigments, also known simply as pigments or biochromes are substances produced by living organisms that have a colour resulting from selective colour absorption. Biological pigments include plant pigments and flower pigments. Many biological structures, such as skin, eyes, fur and hair contain pigments such as melanin in specialized cells called chromatophores.

Pigment colour differs from structural colour in that it is the same for all viewing angles, whereas structural colour is the result of selective reflection or iridescence, usually because of multilayer structures. For example, butterfly wings typically contain structural colour, although many butterflies have cells that contain pigment as well.

Plant pigments impart colour to the different components like leaves, flowers, fruits etc. They in turn are responsible for the colour of raw food, we eat. Pigments like chlorophyll, anthocyanins, flavonoids, tannins, xanthones etc. are the different pigments that are present in plants. The primary function of pigments in plants is photosynthesis, which uses the green pigment chlorophyll along with several red and yellow pigments that help to capture as much light energy as possible. Chlorophyll is green in colour. Carotenoids like a, b, and g, carotenoids are yellow in colour. Lycopene is red in colour. Flavones and falvonols are also yellow in colour. Anthocyanins are purple and magenta in colour. Other functions of pigments in plants include attracting insects to flowers to encourage pollination. The assay of pigments is mostly based on their native colour.

Crop Stand Establishment

Good crop establishment is one of the most important features in better crop production. The better crop establishment is in turn expressed as optimum plant population in fields.

Plant population is the number of plants per unit area in a cropped field. It indicates the size of the area available for individual plant.

Optimum Plant Population

It is the number of plants required to produce maximum output or biomass per unit area. Any increase beyond this stage results in either no increase or reduction in biomass.

Crop geometry is the pattern of distribution of plant over the ground or the shape of the area available to the individual plant, in a crop field.

Introduction

In agriculture and public health sectors, a variety of pesticides are still in uses that are toxic chemicals and having broad-spectrum actions. They kill target species but also harm the ecosystem seriously by affecting desirable organisms, thus, badly impairing prey-predator relationship. Most of these pesticides are persistent or non-biodegradable and hence exhibit biological magnification by accumulating at higher concentration in the organism, which are on the top of the food chain. The other drawbacks of repeated use of pesticides are eradication of natural enemies of pests, increased level of pesticide residues in soil, water, food and fodder crops, resistance of pests to pesticides and resurgence of minor pests in addition to the environmental pollution. It is clear that once used pesticide may persist, somewhere causing serious harm to the mankind and his ecosystem.

The increasing incidence of pesticide harms is fueling the need for new pesticides, which are toxicologically safe, more selective and efficacious and environment-friendly. Now the natural compounds, thus, have increasingly become the focus of those interested in discovery of pesticides. Tens of thousands of secondary products of plants have been identified and there are estimates that hundreds of thousands of these compounds exist. There is growing evidence that most of these compounds are involved in the interaction of plants with other species-primarily the defense of the plants from plant pests. Thus, these secondary compounds represent a large reservoir of chemical structures with biological activity. This resource is largely untapped for use as pest management agents^3, 4. The extraction of such chemicals from plants and derivatives of potent compounds are being encouraged all over the world under the Integrated Pest Management (IPM) approaches. The natural compounds and their synthetic derivatives are more selective in action, completely biodegradable and environment-friendly. In short, natural ways of pests control have already been established and are receiving much attention these days.

Plant Propagation

Plant propagation involves the formation and development of new individuals, which are used in establishment of new plantings. It is simply the reproduction or multiplication of a plant from a source that is often referred to as a mother plant. In general, two methods are employed: 1) sexual and 2) asexual. Sexual propagation is multiplication of plants from seed and asexual or vegetative propagation involves starting a new plant from some vegetative part of a plant. Propagation by seed results in seedling variability. It is an extreme disadvantage for a nursery operator trying to produce a uniform crop containing chosen desirable characteristics. Seed propagation is not practiced in fruit nursery as plants raised by this method fail to bear true to type fruits.

Germination of seed

The activation of the metabolic machinery of the embryo leading to the emergence of a new seeding plant is known as germination. Germination is essentially a quickening of the growth of the embryo. As germination proceeds, the growing points of the radical and plumule divide rather rapidly Usually the radical emerges from the seed coat first, proceeds downward, and develops into the root system, the plumule proceeds upward and develops into the shoot system. Germination is entirely a food utilization process. Processes going on in seed during germination are: 1) Absorption of water; 2) Secretion of enzymes and hormones; 3) Hydrolysis of stored food into soluble form; and 4) Translocation of soluble foods and hormones to the growing points. These processes are either wholly or in part influenced by the food reserves, hormone supply, water supply, oxygen supply and temperature level.

Pomegranate is emerging as one of the important fruit crops for semiarid and arid areas of India with the identification of superior varieties like Ganesh, Mrudila, Arka Ruby, and Bhagwa the area under pomegranate is increasing fast. Therefore the demand for elite planting material is also increasing fast. Pomegranate is propagated vegetatively either by cutting or air layering since ages. However now a day’s orchards raised from tissue culture are also very common. Nursery as a business preposition can also be as profitable as raising a crop. 

Types of Nurseries According to Marketing
    1.    Wholesale nurseries
    2.    Garden centers
    3.    Nurseries for large-scale gardening (municipals etc.)
    4.    Regular nurseries

Plant structure

• Peach – In leaf axils is called – as (blind bud).
• Pecans and walnut, 2-4 buds development at one bud.
• Plants which grow from adventitious buds on the roots are called suckers.
• Some are broad-leaved evergreen: Citrus, mango, litchi, avocado.
• Narrow-leaved evergreen – (coniferous trees)
• Deciduous plants: apple, pears, grape, apricots, pecans.
• Monoecious: Walnut, pecan nut, hazelnut, Tung coconut, cucurbits.
• Dioecious: Papaya, date palm, pistachio nut muscadine grape pointed and snake gourds asparagus.
• Spike inflorescence: Banana
• Catkin: is a spike pecan nut, oak, mulberry, dates and walnut.
• Raceme: Pear
• Corymb: Cherry, pear, candytuft.
• Fascicle Inf.: Phlox and apple.
• Panicle: Mango, grape, litchi.
• Self-pollination (autogamy)
• Cross-pollination (autogamy) (gait gamy)
• Dischongamy: Walnut, pecan nut, macadamia nut.
• Self sterility: Almond, some fruit, onion, marigold.
• Incompatibility: Mango, ber, loquat, apple.
• Wind pollination: Walnut, pecan, nuts, coconut, dates.
• Insect pollination: Apple, mango, peach, fig, coconut.
• Birds: Pineapple and banana.
• Water: Water lily, water chestnut.
• Seedless fruits: Banana, pineapple.
• When plants set and mature fruits without pollination, it is called as vegetative parthenocarpy. Banana, Japanese person, fig, orange, grapefruit.
• Monocarpic: One crop of seed and then dies.
• Polycarpic: One crop of seed and then does not die.
• Media for propagation: 5.5-6.5 pH.

Introduction

After the green revolution, India achieved significant strides in agricultural output, but productivity is still poor owing to climate change and the interference of old agriculture techniques. In order to fulfill the world’s food demand in 2050, global output will have to grow by 70 % (FAO, 2020). Man has devised technical techniques for growing crops round the year.

Crop propagation is a natural process that is enhanced via the use of modified and regulated settings. These conditions are altered to guarantee that the crop in question grows to its full potential. The purpose of propagation structures is to build environments that can be changed and controlled.