Introduction to pathology by muhammad asif

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  • 1. PLANT PATHOLOGY INTRODUCTION By Muhammad Asif
  • 2. INTRODUCTION
    • Plants make up the majority of earths living environment
    • Plants are the only organisms that convert the suns energy to food
    • All animals including humans depend on plants for food
    • Plants as do people get “sick”
    • The causal agents are similar to human
  • 3. INTRODUCTION
    • Disease causing organisms include;
    • Viruses
    • Bacteria
    • Fungi
    • Protozoa
    • Nematodes
    • Or unfavorable environmental conditions
  • 4. INTRODUCTION
    • Plant pathology is the study of microorganisms and environmental factors that cause plant disease
    • The way they work
    • The way they are avoided or controlled
    • The cost of control must be less than the profit
    • Environment friendly materials must be used
  • 5. INTRODUCTION
    • A plant is considered healthy if it functions to the best of its genetic ability
    • When a plant function is interfered with by a microorganism or environmental factor the plant is diseased
    • The visible changes are the symptoms
    • Some pathogens affect only one variety of plant while others affect many species
  • 6. History of Plant Disease
    • The Romans were so aware of famine they created a special rust god, Robigo who was responsible to protect people from famine
    • These beliefs lasted about 2000 years
    • The compound microscope was invented in the 1600’s
  • 7. CLASSIFICATION OF DISEASES
    • Infectious disease
      • Diseases caused by fungi
      • Diseases caused by prokaryotes (bacteria & mollicutes
      • Diseases caused by parasitic plants
      • Diseases caused by viruses and viroids
      • Diseases caused by nematodes
      • Diseases caused by protozoa
  • 8. Non Infectious diseases
    • Diseases caused by low or high temperature
    • Diseases caused by lack or excess soil H 2 O
    • Diseases caused by lack or excess light
    • Diseases caused by lack of oxygen
    • Diseases caused by air pollution
    • Diseases caused by nutrient deficiencies
    • Diseases caused by mineral toxicities
  • 9. Non infectious plant diseases
    • Diseases caused by soil acidity or alkalinity
    • Diseases caused by toxicity of pesticides
    • Diseases caused by improper cultural practices
  • 10. The Birth of Plant Pathology
    • The fungus found on potatoes was first described by Dr. C Montagne, a French doctor with Napoleon’s army
    • He shared his observation with Rev. M. J. Berkely who thought it might be connected with the disease
    • Dr. John Lindley, a rival did not believe there was a connection
  • 11. The Birth of Plant Pathology
    • Was the fungi the cause or the effect?
    • Grain was used as an export to raise $
    • Sir Robert Peel used the blight as an excuse to repeal the protectionist trade laws to import corn from America to feed the starving Irish. It was called Peel’s Brimestone” because the recipients were considered ungrateful
  • 12. The Birth of Plant Pathology
    • During a 15 year period 1 million Irish died of disease and starvation and another 1.5 million left to go to the U.S. or Canada
    • The scientist of the time were unable to save the crops but there came an understanding of plant disease
    • Anton deBary, a German Botanist performed experiments that proved the role of fungus in the blight
  • 13. The Birth of Plant Pathology
    • For 200 years people thought the disease causing organisms were the result , not the cause
    • The theory of spontaneous generation was abandoned for the germ theory in 1863
    • It was originally named Botrytis infestans by Montagne but was changed to Phytophthora infestans by deBary because he realized they were not related
  • 14. The Birth of Plant Pathology
    • Phyto= plant
    • Phthora =destroyer
    • Phytophthora= plant destroyer
    • Infestans=devastating infestation
    • Usual microorganisms do not have common names since only scientist talk about them
  • 15. Proof of pathogenicity Koch’s postulates
    • The symptoms and any evidence of the pathogen in the diseases host are carefully described
    • The suspected pathogen is isolated from the host, a description is made.
    • A healthy host is inoculated, described
    • The pathogen is isolated and must be the same as original
    • When all four steps are complete= proof
  • 16. The Birth of Plant Pathology
    • Even though the cause was discovered, they did not know how to treat it
    • The last major famine was 1916
    • Copper was then known to protect crops but it was needed to make bullets for the war
    • 700,000 Germans died from starvation
  • 17. Arrival of the potato in Europe
    • The potato was from the highlands of South America’s, Lake Titicaca
    • It was discovered by the Spanish Conquistadors while looking for gold
    • The crop dates back to 400 B.C.
    • The first potatoes reached Europe about 1570
  • 18. The Birth of Plant Pathology
    • New cultivars were developed
    • The potato was resistant for a few years
    • Then the blight returned
    • The blight develops a new race to attack each new cultivar
    • The boom and bust cycle is the result
  • 19. Lessons from the potato famine
    • The disease triangle, plant, pathogen, environment
    Disease Susceptible Host Favorable environment Virulent Pathogen
  • 20. HISTORY OF PLANT PATHOLOGY
      • Tribes settled and began farming
      • In wet or dry years, small crops led to famine
      • Plant diseases are mentioned in the Bible (c750B.C.)
      • Sin was blamed for plant diseases
      • The Greek philosopher Theophrastus (c 300B.C.)was the first to study and write about plant disease
  • 21. History of Plant Pathology
      • Nomadic tribes had to find enough healthy food
    • Homer (c.1000 B.C.) mentioned the therapeutic properties of sulfur on plant disease
    • Democritus (c. 470 B.C.) mentioned the control of blight by sprinkling olive grounds on plants
    • Most control was festivals and sacrifices
  • 22. History of Plant Pathology
    • Magnus A.D. 1200, Germany, proposed that mistletoe was a parasitic plant but no one followed up on this.
    • French farmers (1600’s) and Connecticut farmers (1700’s) noticed that wheat rust was worse near barberry bushes.
    • (Alternate hosts)
    • Around 1667, Hooke (England) observed the spores with a microscope.
  • 23. History of Plant Pathology
    • In Italy, Micheli (1729) described the structures of fungi and noted that when he put the structure on fresh cut melon, they reproduced the same. He proposed that fungi arose from their own spores but no one believed him.
  • 24. History of Plant Pathology
    • In 1775 Tillet, in France showed that;
    • Wheat smut increased with the addition of spores to the seeds
    • The smut was reduced in seeds treated with copper sulfate
    • He thought it was a poison rather than a microorganism
  • 25. History of Plant Pathology
    • Provost, 1807 repeated Tillet’s work and determined it was the spores that caused the fungus but the Science Academy would not believe him
    • The thought they were the result rather than the cause
  • 26. History of Plant Pathology
    • Nematodes were first associated with disease by Needham in 1743
    • In 1855 the second nematode was observed in cucumber root galls
    • Several more were discovered in the next 4 years
  • 27. History of Plant Pathology
    • In 1876 Pasteur and Koch in France showed that anthrax was caused by a bacterium
    • In 1878 Burill showed that fire blight was caused by bacterium
    • Acceptance was slow
    • In 1890’s Smith showed crown gall to be caused by bacterium
    • In 1980 the process of crown gall was finally explained, excessive hormone produce growth
  • 28. History of Plant Pathology
    • Viruses
    • In1886 Mayer reproduced tobacco mosaic by injecting juice from a diseased plant into a healthy one, he thought it was a bacteria
    • In 1892 Ivanowski showed that it was not a bacteria because it could go through a bacteria sieve
  • 29. History of Plant Pathology
    • In 1898 Beijerinck concluded that the mosaic was caused by a living fluid which he called a virus
    • In 1935 Stanley separated the virus as sediment in a flask
    • The first virus was seen with an electron microscope in 1939 by Kausche
    • In 1956, Gierrer and schramm removed protein from the virus and showed RNA
  • 30. History of Plant Pathology
    • In 1971 Diener discovered that potato spindle tuber disease was a naked single strand circular molecule of infectious RNA which he called a viroid
    • An even smaller infectious agent was discovered by Prusiner in 1982 which he called a prion
    • Three human diseases are caused by prions, non so far discovered in plants
  • 31. History of Plant Pathology
    • Protozoa were observed in Euphorbiaceae by Lafont in 1909
    • 1931 Stahel found flagellates in coffee trees
    • 1963 Vermeulen found evidence of pathogenicity of flagellates in coffee trees and coconut
  • 32. History of Plant Pathology
    • Mollicutes were discovered in 1967
    • Doi and assoc observed wall-less mycoplasmic bodies infecting plant exhibiting witches broom
  • 33. History of Plant Pathology
    • There are many severe diseases for which no cause has been found
    • Forest decline
    • Citrus blight
    • Spear rot of oil palm
    • Mango malformation
    • All have unknown causes
  • 34. History of Plant Pathology the experimental phase
    • The importance of plant pathology was realized and added to the USDA offices in the late 1800’s
    • As knowledge accumulated, experimentation grew rapidly on ways to control or avoid plant disease
  • 35. History of Plant Pathology the etiological phase
    • Involved observation and experiments to prove the causes of plant disease
    • This developed techniques for pure cultures to satisfy Koch’s postulates
    • This phases depended on the development of instrumentation and methodology
  • 36. History of Plant Pathology The search for disease control
    • Even though the early people made sacrifices to the gods , they did choose plants that were more resistant to disease
    • Recommendations for disease control have been found as early as 1000B.C. Homer, Democritus 470 B.C., and Theophrastus 300 B.C.
    • The 1600’s show the first reports of resistant varieties
  • 37. History of Plant Pathology
    • There were a lot of worthless cures recommended but a few actually worked such as sulfur
    • Seed saved from a ship wreck (1600’s)had less smut disease than other plants so they started a seed pre-treat with brine
    • Later this was changed to copper sulfate
    • This is still used today
  • 38. History of Plant Pathology
    • In the 1800’s lime sulfur was discovered.
    • The story is a grape farmer made the mixture to look like bird drops which he sprayed on his grapes so people walking by the edge of the field would not eat them.
    • He soon noticed the plants that were sprayed would not get diseased so he sprayed everything
  • 39. History of Plant Pathology
    • In 1913 organic mercury compounds were developed as seed treatments until mercury was banned in the 1960’s
    • 1934 a series of fungicides were developed; ferbam, zineb, maneb
    • 1965 the first systemic, carboxin was discovered
    • Antibiotics were discovered in 1950 & ‘67
  • 40. History of Plant Pathology
    • In 1954 resistant bacteria strains were discovered
    • 1963 resistant fungi were discovered
    • 1970’s new races of fungal pathogens appeared
  • 41. History of Plant Pathology
    • Public concern developed in the 1950’s
    • Some pesticides such as DDT were found to be harmful to animals, especially birds
    • It did not break down into harmless materials as did most other pesticides
    • It and many others have since been banned
    • A book, The Silent Spring by Rachel Carson raised public awareness
  • 42. History of Plant Pathology
    • By the 1960’s all mercury was banned
    • DDT and chlorinated hydrocarbons
    • Since 1980’s 80% of previous materials have been banned
    • Damages, research, supply have raised costs
  • 43. Alternative controls
    • Cultural practices
      • Clean up debris
      • Use certified seed
      • Remove infected plant parts
      • Rotate crops
      • Destroy weeds
      • Irrigate, etc
      • I.P.M.
  • 44. Alternative controls
    • 1928 Fleming reported that certain soil borne fungi (Penicillium) inhibited the growth of other fungi and bacteria
    • 1930’s it was found if you inoculated a plant with a mild form of virus, it would protect the plant from the severe strain
  • 45.
    • 1972 inoculation with non pathogenic forms of bacteria and fungi prevent the infection by pathogenic forms
    • 1980’s genetic engineering replaced the former method
    • A new method is the use of microorganisms or chemicals to form lesions which stimulate natural defense
  • 46. Interest in the Mechanisms by Which Pathogens Cause Disease
    • Once it was realized the fungi etc caused the disease instead of the result, the mechanisms were studied
    • 1886 deBary noticed that host cells of Sclerotinia died in advance of the pathogen
    • This was the discovery of toxins and enzymes produced by the pathogen
  • 47. Interest in the Mechanisms by Which Pathogens Cause Disease
    • 1905 cytolytic enzymes were reported by L.R. Jones
    • 1925 it was suggested that Pseudomonas tabaci produced a toxin which caused wildfire disease of tobacco
    • 1934 it was confirmed
    • It was the first toxin to be isolated 1950’s
  • 48. Interest in the Mechanisms by Which Pathogens Cause Disease
    • Many toxins and enzymes have since been found
    • There have been many studies about the mechanisms by which the toxins or enzymes affect plants and,
    • Many studies about the defense mechanisms
  • 49. Interest in the Mechanisms by Which Pathogens Cause Disease
    • 1939 IAA was discovered, a growth regulator produced by a fungus Gibberella
    • It is now used in plant propagation
    • 1970’s-80’s Agrobacterium tumefaciens induces crown gall which does a natural DNA transplant
    • It is now used in research and the production of pharmaceuticals
  • 50. Genetic inheritance of Resistance and Pathology
    • 1894 Eriksson discovered different biological races of Puccinia graminis
    • They cannot be differentiated by sight but by their hosts
    • 1905 Biffen reported inherited resistance
    • 1909 Orton distinguished between disease escape, endurance, and resistance
  • 51. Interest in the Mechanisms by Which Pathogens Cause Disease
    • 1911 Barrus showed genetic variability within a pathogen species
    • 1914 Stakmen et al explain resistance and susceptibility of the same species in different geographical areas
    • 1946 Flor showed that for each gene in the host for resistance there was a gene in the pathogen for virulence (gene-for-gene)
  • 52. Interest in the Mechanisms by Which Pathogens Cause Disease
    • 1963 Vanderplank described vertical resistance
      • Few genes, strong but only effect against a few races
    • Horizontal resistance, weaker but effective against all races
  • 53. Interest in the Mechanisms by Which Pathogens Cause Disease
    • 1946 Gaumann proposed hypersensitivity whereas and area around the site dies and protects the rest of the plant
    • 1960’s anti microbial substances was proposed to exist
  • 54. Epidemiology of Plant Disease Comes of Age
    • 1944 Mills developed a table showing rain and temperature and hoe it affected the development of apple scab
    • 1963 Vanderplank wrote Plant Diseases: Epidemics and Control, establishing and important field of study
    • It is now possible to predict epidemics by keeping records
  • 55. Epidemiology of Plant Disease Comes of Age
    • 1969 first computer simulation for early blight of tomato and potato
    • Since 1970’s many disease modeling and computer simulations have been developed for many diseases
  • 56. Molecular Plant Pathology
    • Since 1980’s most functions of genes have been mapped and gene transfers have been made to provide resistance
    • Early beginnings from 1956 when RNA of tobacco mosaic virus was shown to be responsible for plant cell infection
    • 1960’s study showed full genetic code for a certain amino acid
  • 57. Molecular Plant Pathology
    • It was shown that two genes could be removed and replaced and expressed by the plant cells
    • Whole plants could be produced from a single cell
    • This is called tissue culture or propagation
  • 58. Molecular Plant Pathology
    • Foreign DNA can be moved to another plant by using a virus or bacteria as a vector
    • Since 1980’s segments of DNA have been marked with radioactive isotopes and tracked
    • We now have many genetically engineered plants such as corn and soybeans
  • 59. Development of Plant Pathology Worldwide
    • Origins in late 1800’s
    • 1891Netherlands Society of Plant Pathology
    • 1895 Netherlands Journal of Plant Pathology
    • 1911 International journal named Phytopathology
  • 60. Development of Plant Pathology Worldwide
    • 1916 Phytological Society of Japan
    • Began publishing 1918
    • Canada 1930
    • India 1947
  • 61. Development of Plant Pathology Worldwide
    • 1968 International Society of Plant Pathology was founded
    • Most parts of the world have plant pathologists but a few parts have none and do not practice controls so losses are great
    • 1940’s Rockefeller foundation started to help Mexican government
  • 62. Development of Plant Pathology Worldwide
    • With great success in the program many were soon to follow
    • It was impossible to have such foundations in every country so international centers were formed
  • 63. Development of Plant Pathology Worldwide
    • International Rice Institute, 1960 Philippines
    • International Maize and Wheat Improvement Center, 1966 Mexico
    • International Institute of Tropical Agriculture, 1968 Nigeria
    • International Center of Tropical Agriculture, 1969 Columbia
  • 64. Development of Plant Pathology Worldwide
    • More foundations were needed so a consortium of donors was set up with the World Bank…Consultative Group on International Agriculture Research
    • Numerous centers were established in many countries
    • Tropical countries are in special need because the weather promotes pathogens
  • 65. Trends in Teaching and Training in Plant Pathology
    • First course in Plant Pathology was offered at Harvard by M.A. Farlow in 1875
    • Textbooks became common
    • Duggar 1906
    • Stevans and Hall 1921
    • Heald 1926 & ‘43
    • Walker 1950
    • Many specialized books appeared
    • B.S., M.S., and Ph.D. are available in Plant Path
  • 66. Education and Information Technology in Plant Pathology
    • Many advances have been made in developing, collecting, organizing and transmitting information by researchers, teachers etc.
    • Many data bases have been established
  • 67. Plant Disease Clinics
    • Most states have plant disease clinics operated by plant pathology departments and county extension agents
    • Since 1970 every state has at least one plant disease clinic
    • Most are run by M.S. or Ph.D.’s
    • Most are run by the state department of agriculture
  • 68. Plant Pathology: The Practice
    • Most discoveries were and are made by graduate students working on advance degrees
    • The actual practice of plant pathology is carried out at a lower level by technicians etc. who use the knowledge and techniques of the researchers
    • The knowledge etc. is transferred through the county extension agents
  • 69. Plant Pathology: The Practice
    • Most growers receive limited information
    • In the last 20 years, pesticide licensing has increased the professional level of the landscaper
    • The author of your textbook predicts there will be plant doctors on the same level as medical doctors.
    • We have plant doctors now but are basically Ph.D’s
  • 70. Plant Pathology: The Practice
    • In the 1960’s-70’s licensing began
    • Many horticulture/landscape associations have established certification programs
    • There is an American Registry of Plant Pathologists governed by a board of directors
  • 71. Plant Pathology: The Practice
    • To be a certified plant pathologist you must have:
    • B.S. + 5 years professional experience
    • M.S. + 3 years of professional experience
    • Ph.D. + 1 year of professional experience
    • Or complete a recommended course of study
  • 72. Kinds and amounts of losses
    • Plant disease is important because of the losses of food, fiber and other products
    • Plant loss affects the economy
    • People may starve to death
    • Damage parks, recreational areas and building
    • Billions of pounds of pesticides are produced and applied
  • 73. Plant Pathology: The Practice
    • Plant diseases may limit the kinds of plants and industry in an area
    • Chestnut eliminated by blight
    • Elm eliminated by Dutch elm disease
    • White birch only does well in the north
    • European grape cannot be grown in southern U.S
    • Plant disease has created whole new industry of pesticides and other business
  • 74. Plant Pathology: The Practice
    • Some plant disease makes the plant poisonous to humans and animals such as ergot of rye and wheat
    • Several fungi will make hay poisonous
    • May contain nematodes which carry virus
    • Plant disease causes great financial loss from a few % to total crop
    • The cost of disease control must be less than cost of crop loss