PLANT PATHOLOGYCOURSE WORK: TEST 1: 10% TEST 2: 10% TEST 3: 10% QUIZES: 10%

LAB REPORT/ASSIGNMENT: 20%

CARRY MARKS: 60% + FINAL EXAM: 40% TOTAL: 100%

INTRODUCTION TO PLANT PATHOLOGY• The Concepts• “Phytopathology” derived the Greek words• “phyton meaning plant.• “Pathos” = suffering/disease• “Logos” = reason/study

• Def: Pathology is the study about the diseases.

• Plant pathology @ phytopathology = the study about the plant diseases

• Plant pathology is an interdisciplinary science that includes knowledge of botany, microbiology, crop science, soil science, ecology, genetics, biochemistry, molecular biology, and physiology. 

Plant pathology is the study of:– The microorganisms (pathogen) and of the environmental

factors (abiotic agents) that cause disease in plants - causal agents.

– of the mechanisms by which these factors induce disease in plants – infection mechanisms.

– of the methods of preventing or controlling disease and reducing the damage it causes - disease controlling/preventing.

• Pathogen is the organisms that cause the diseases.• Parasite is the organism that lived in the other living organism. • Obligate parasite = the parasite that lived only in the living

host. Eg: bacteria, virus, nematode• Non obligate parasite (Facultative parasite) = the parasite

that live either in the living or dead host. Eg: fungi and bacteria.

The concepts of disease in plants

• The plant is “healthy” (normal) when it can carry out its physiological functions to the best of its genetic potential.

• Normal physiological functions include: – normal cell division, differentiation and

development; – absorption of water and minerals from

soil and translocation of these substances throughout the plant;

– photosynthesis and translocation of the photosynthetic products to areas of utilization or storage;

– metabolism or synthesized compounds reproduction;

– storage of food supplies for over wintering or reproduction.

• The “sick” plant is when all its physiological functions are disturbed that caused the cells or tissues weakened or destroyed and thus can disturb the plant growth and die.

Disease is A malfunctioning of host cells and tissues that results from their continuous irritation by a pathogenic agent or environmental factor and leads to the development of symptoms. 

Disease is a condition involving abnormal changes in the form, physiology, integrity or  behavior of a plant. Such changes may result in partial impairment or death of the plant or its parts.”

Plant diseases can be classified into 2 types:• Infectious diseases = the diseases that caused by the pathogens or

biotic agent such as fungi, bacteria, virus/viroid, mycoplasmas, nematode etc.

• Non infectious diseases = the diseases that caused by the abiotic agents or environmental factors such as:– Too low or too high a temperature– Lack or excess of soil moisture– Lack or excess of light– Lack of oxygen– Air pollution– Nutrient deficiencies– Mineral toxicities– Soil acidity or alkalinity (pH)– Toxicity of pesticides– Improper cultural practices.

• Noninfectious diseases, perhaps more appropriately called disorders, do not spread from plant to plant.

• These disorders result from the plant's exposure to such factors as unfavorable weather, mechanical damage, nutrient deficiencies, excess salts or toxic chemicals.

• Although disorders can predispose plants to infection by pathogens, disorders are not directly treated using pesticides.

History of plant pathology

The Early Belief • Theophrastus (370 – 286 B.C)• Greek philosopher

– The first to study and write about diseases of trees, cereals and legumes.

– Observed that diseases generally were more severe in lowlands than on hillsides and the rust was more common on cereals than on legumes.

– His approach was observational and speculative rather than experimental.

• Romans era– Rust diseased on grain crops, they believed that diseases

is the punishment of god to the man behavior (good and bad)

– They become so painfully aware of the devastating effects of the rust of grain crops that they created a special rust god, “Robigo” to protect them from these diseases.

– In the spring of each year, just before the rust appeared they celebrated the “Robigalia”, a special holiday that involved sacrifices of red dogs and sheep in an attempt to appease Robigo.

• During these times they believed in “Theory of Spontaneous Generation” of lower plants and animals.

• This theory passed down from century to century. Theory of Spontaneous generation stated that an organism is formed or created from where it exists or from where it comes from. For example frogs live in pond, so the frog was created there at the pond! The supposed development of living organisms from nonliving matter, as maggots from rotting meat.

• The theory of spontaneous generation for larger organisms was easily shown to be false, butthe theory was not fully discredited until the mid-19th century with the demonstration of theexistence and reproduction of microorganisms.

• Louis Pasteur (1822-1895) demolished the theory of spontaneous generation and established the germ theory. Prior to Pasteur it was generally accepted that some life forms arose spontaneously from non-living matter. Pasteur experiments disproved the theory of spontaneous generation and demonstrated that microorganisms occur everywhere even in the air.

Overview the beginning of scientific study

Anton von Leeuwenhoek (1675)• constructed a microscope• he was able to view organisms, including protozoa and

bacteria, which cannot visible to the naked eye (1683)

Robert Hook (1635-1703) • developed simple microscope which was used to study of

minute structure of fungi.

Pier Antonio Micheli (1729)• Italian botanist • Observed that dust particles taken from a fungus and

placed on freshly cut slices of melon generally reproduced the same kind of fungus.

• Concluded that the dust particles were the seeds (spores) of fungus.

• Is the first observation of fungal infection of plant diseases.

Tillet (1755)• France scientist• Study about infectious diseases • Study on wheat smut/bunt• Diseases can be reduced by seed treatment.

Prevost (1807)• Proved that bunt is caused by a fungus• He study on spores, their production and germination• Able to control the disease by dipping the seed in copper sulphate

solution.• Pointed out the importance of the environment in induction and

development of the disease.

1840s• Devastating epidemics of late blight of potato in Northern Europe

particularly Ireland, results in the death of hundreds of thousands of people and emigration of more than one and a half million people from Ireland to the United States.

• Rise the concern to the plant disease cause by fungus

Overview the beginning of scientific study …..con

Heinrich Anton de Bary (1853)• Germany botanist• Proved experimentally that potato late blight disease caused by

the fungus Phytophthora infestans• Known as “father of modern pathology”

Brefeld (1875,1883,1912)• contributed greatly to plant pathology• introducing and developing modern techniques for growing

microorganisms in pure culture.

1878 – Downy Mildews of grape was introduced from US and spread rapidly and threatened to ruin the vineyards of Europe.

Prof Millardet (1885)• From Bordeaux University• Create the first fungicide (CuSO4 + hydrated lime)• Known as “Bordeaux mixture”

Pasteur and Koch (1876)• Studied about antrax disease on animal caused by bacterium

Burril (1878)• Showed that fire blight of pear and apple is caused by

bacterium

Needham (1743)• Observed nematode within wheat gall. (kernels)

Cobb (1913 – 1932)• Studies on plant parasitic nematodes and contributed

greatly to nematode taxonomy, morphology and methodology.

• 1965 – the first systemic fungicide was created (Carboxin)

Definition and terms

• Parasite: An organism living upon or in another living organism (the host) and obtaining the food from the invading host.

• Pathogen: An entity, usually a micro-organism that can cause the disease.

• Pathogenicity: The relative capability of a pathogen to cause disease.

• Pathogenesis: It is a process caused by an infectious agent (pathogen) when it comes in contact with a susceptible host.

• Virulence: The degree of infectivity of a given pathogen.

• Infection: The initiation and establishment of a parasite within a host plant.

• • Primary infection: The first infection of a plant by the over wintering or

over summering of the pathogen.

• Inoculum: That portion of pathogen which is transferred to plant and cause disease.

• Invasion: The penetration and spread of a pathogen in the host. • Colonization: The growth of a pathogen, particularly a fungus, in the host

after infection is called colonization. • Symptoms: The external and internal reaction or alterations of a plant as a

result of disease. • Incubation period: The period of time between penetration of a pathogen

to the host and the first appearance of symptoms on the plant. • Disease cycle: The chain of events involved in disease development. • Single cycle disease (Monocyclic): This type of disease is referred to those

caused by the pathogen (fungi) that can complete only one life cycle in one crop season of the host plant. e.g. downy mildew of rape seed, club root of crucifers, sclerotinia blight of brinjal etc.

• Multiple cycle disease (Polycyclic): Some pathogens specially a fungus, can complete a number of life cycles within one crop season of the host plant and the disease caused by such pathogens is called multiple cycle disease e.g. wheat rust, rice blast, late blight of potato etc.

• Cop Damage: It is defined as any reduction in the quality or quantity of yield or loss of revenue resulting from crop injury.

• Deficiency: Abnormality or disease caused by the lack or subnormal level of availability of one or more essential nutrient elements.

• Alternate host: Plants not related to the main host of parasitic fungus, where it produces its different stages to complete one cycle (heteroecious).

• Predisposition: The effect of one or more environmental factors which makes a plant vulnerable to attack by a pathogen.

• Symbiosis: A mutually beneficial association of two or more different kinds of organisms.

• Mutualism: Symbiosis of two organisms that are mutually helpful or that mutually support one another.

• Antagonism: The counteraction between organisms or groups of organisms.

• Mutation: An abrupt appearance of a new characteristic in an individual as a result of an accidental change in genes present in chromosomes.

• Disease: Any deviation in the general health, or physiology or function of plant or plant parts, is recognized as a disease.

Significance of plant diseases• All of our food, much of our clothing, building materials, and much of

the beauty in nature is provided by plants.

• Plant diseases are a constant threat to the world’s food and fiber crops, forests, and landscape plants.

• Plant diseases are significant to humans because they cause: 1. Kinds and amounts of losses

damage to plants and plant products on which humans depend for food, clothing, furniture and environment.

2. Limit the kinds of plants and industries in an area3. Reduce the quality and quantity of plant produce

Destroy the beauty of environment by damaging plants around homes, along streets, in parks and in forests.

4. Make plants poisonous to humans and animals Diseased plant produce poisons and unfit to human and animals

5. May cause financial losses Can cause economic losses to growers Results in increased prices of products to consumers

• Throughout history, plant diseases have been responsible for the death and suffering of millions of people and countless animals.

• A few examples of devastating diseases are:

1. Potato Late Blight2. Ergot of Rye3. Black Stem Rust of Wheat 4. Southern Corn Leaf Blight5. Dutch Elm Disease6. Bacterial Canker on Citrus7. Plum Pox Virus on Stone Fruit

• All of these are infectious diseases caused by plant

pathogens.

Late Blight of PotatoLate Blight of PotatoCaused by the fungus Phytophthora infestans

• The fungus killed most of the potatoes grown in Ireland during the mid 1800’s.

• Potatoes were the main source of food for the Irish people.

• This plant disease resulted in the Irish Potato Famine of 1845

1 million people died1.5 million people left Ireland -USA

Late Blight on Potato TubersLate Blight on Potato Tubers

Ergot of RyeErgot of RyeCaused by the fungus Claviceps purpurea

The pathogen produces a structure called a sclerotium that grows in place of the rye kernel. This sclerotium contains poisons that are very harmful to man and animals.

The sclerotium is harvested with the rye grain. The grain is ground into flour, made into bread and is eaten by people. Eating the contaminated bread results in a disease called ErgotismErgotism. .

ERGOTISM OFTEN RESULTS IN DEATH.ERGOTISM OFTEN RESULTS IN DEATH.

Ergot of RyeErgot of Rye(note dark sclerotia)(note dark sclerotia)

Ergot of RyeErgot of Rye

• The scelotia also contains hallucinogenic compounds. People that eat ergot often see Fire.

• In the middle ages, people called the vision of fire induced by Ergot as “Holy Fire” or “St. Anthony’s Fire”

• Ergotism can also cause abortions and gangrene.

• THIS PLANT DISEASE IS STILL KILLING PEOPLE IN THE WORLD TODAY!

Black Stem Rust of WheatBlack Stem Rust of Wheat1916 - Destroyed 300 million

bushels of wheat in the United States and Canada

1935 - Destroyed 135 million bushels in Dakotas and Minnesota

• SPORATIC EPIDEMICS STILL COST NORTH AMERICAN FARMERS BILLIONS OF DOLLARS

Wheat rust in United State• In southern US the people faced the severe

wheat rust and stop planting the wheat and change to corn thus, affected their food where they change to corn bread

Black Stem Rust of WheatBlack Stem Rust of Wheat

• Coffee rust in Ceylon (1870an)– Ceylon well known to its coffee industry and

most of them were exported to Europe

– Then the coffee rust affect their coffee industry and the British people cannot get the source of coffee thus they change to tea.

• SALB (South America Leaf Blight) in South America– This disease caused the damage of rubber

industry in Brazil.– Rise the development of synthetic rubber

The relations of plant pathology with other areas

• Many areas of science and agriculture are involved in the study of plant diseases.– Plant pathology began as an offshoot of botany, the study of plants. – To understand diseases and development management methods, one must

study the physiology, anatomy, taxonomy and growth of plants.– The following sciences also contribute to understanding of the causes of plant

diseases: Agronomy: the science of field crop production and soil management

Bacteriology: the study of bacteria, because bacteria can cause plant diseases.

Biochemistry: the chemistry of plant and animal life.

Biotechnology: the collection of processes and techniques, many at the molecular and cellular levels that involve understanding and modification of biology systems, including genetically engineered microorganisms, plants and animals.

Botany: the study of plants and their structure, function, classification and ecology (anatomy and physiology) – characteristics of diseases.

Chemistry: the study of composition, properties and structure of substances, important in disease treatment because most of fungicide need certain chemical formulation.

Ecology; the study of the relations between organisms and their environment.

Economy: the study of trade and value. the diseased plant product will reduce it economical value and yield so income will reduce.

Engineering: the study of machines and engines; also the practical application of scientific principles. Important in built the pesticide equipments – disease control

Entomology: the study of insects, because most of the insects are the vectors of the plant pathogens such as virus

Forestry: the science of plating and taking care of forests

Genetics and plant breeding: the study of sexual reproduction and inheritance in plants, important in plant breeding to get the disease resistant plants

Horticulture: the science of cultivating flowers , fruits, vegetables or ornamentals plants

Mycology: the study of fungi, because most of the fungi are plant pathogen

Nematology: the study of nematode because most of the nematodes are plant pathogens

Physics: the study of matter and energy and their interaction, to use the microscope (light and electron) in the study of pathology to see the cells and hyphae of fungi need to know the physics.

soil science : the study of soil, most of the pathogens that infect the root live in soil

virology: the study of virus, because virus also plant pathogens

Weed science: the study of weeds and their control, because weed in the secondary host for the pathogens.