Plant Pathology: Fundamentals and Advancements, Exams of Biology

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PLPA 3003 Test 1 with complete solutions

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Theophrastus - ANSWER-1st to study and publish articles on plant diseases (Greek Philosopher) Micheli - ANSWER-determined dust particles were seeds of fungi and reproduced the fugus Prevost - ANSWER-proved bunt caused by fungus Tillet - ANSWER-- demonstrated bunt of wheat was a contagious disease spread by infected seed

• Primary treatment: pigeon manure, sheep manure, night soil, horse manure, nothing
• Secondary treatment: seed blackened with bunt, sea salt and lime, lime, clean seed DeBary - ANSWER-- Phytophtora infestans
• worked with rusts and smuts; discovered alternate hosts
• pathogen produced enzymes and toxins to kill plant, then fungus obtains the nutrients Brefeld - ANSWER-developed technique for growing microbes in pure culture

Millardet - ANSWER-vines sprayed with copper sulfate and lime retained leaves (Bordeaux mixture)

• control of down mildew on grape
• systemic pesticides Riehm - ANSWER-seed treatments of organic mercury compounds Tisdale - ANSWER-developed dithiocarbamate (Thiram) fungicide; ferbam, zineb, and maneb E.F. Smith - ANSWER-- established role of bacteria cause disease in plants
• in conflict with Fisher
• showed crown gall caused by bacteria and linked to cancer Alfred Fisher - ANSWER-studied under DeBary; rejected bacteria as cause of plant disease N.A. Cobb - ANSWER-"Father of nematology" Plant disease - ANSWER-malfunctioning of host cells and tissues that results from their continuous irritation by a pathogen agent or environmental factor
• classification: symptoms, organ affected, types of plants affected, pathogen infectious disease causing agents - ANSWER-fungi, prokaryotes, parasitic higher plants, viruses & viroids, nematodes, protozoa non-infectious disease causing agents - ANSWER-abnormalities, lack of oxygen, air pollution, nutrient deficiencies, soil acidity, toxicity of pesticides, improper cultural methods symptom - ANSWER-external and internal reaction or alternation plant as a result of disease

sign - ANSWER-the pathogen or its parts or products seen on host Koch's postulates - ANSWER-When a disease is associated with a pathogen to verify cause

1. Associate (pathogen found associated with all infected plants)
2. Isolate (isolate pathogen in pure culture and describe morphologically)
3. Inoculate (inoculate healthy plants with pathogen from pure culture
4. Reisolate (reproduce symptoms of disease and resolute pathogen in pure culture- must be identical) diseases triangle - ANSWER-pathogen, environment, host disease cycle - ANSWER-1. inoculation: pathogen/plant contact
5. pre-penetration: spores germinate, nematodes hatch, pathogen attaches
6. penetration: direct or through natural openings/wounds
7. infection: pathogens contact susceptible cells/tissues and take nutrients
8. invasion: subcuticular, surface, intracellular mycelium, local, systemic
9. growth/reproduction of pathogen: spores, fission, replicate, eggs
10. dissemination of pathogen
11. overwintering: on seeds, plants, organs, debris as spores and mycelium primary inoculum - ANSWER-causes initial infection secondary inoculum - ANSWER-produced by primary inoculum and cause secondary infection latent infection - ANSWER-doesn't produce symptoms immediately local infection - ANSWER-infection that involves a single cell or small area of plant systemic - ANSWER-pathogen spread from initial point throughout plant

saprophytes - ANSWER-use dead, organic matter as food facultative parasites - ANSWER-live most of life cycle on dead plants but under certain circumstances attack living plants obligate parasites - ANSWER-grow and reproduce in nature only on living hosts (biotrophs) facultative saprophytes - ANSWER-live most of life as parasite but may grow saprophytically on dead organic matter (semi-biotrophs) growth regulators - ANSWER-- naturally occurring compounds that act as hormones

• auxins, gibberellins, cytokinins, ethylene
• act in very small concentrations
• cause difference in plant growth host specific toxins - ANSWER-produced by pathogen and are toxic only to host non-host specific toxins - ANSWER-produce disease on pants not usually attacked by pathogen maceration - ANSWER-softening of plant tissues and separation of individual cells which die; facilitates invasion and provides nutrients to pathogen mechanical attack on pants - ANSWER-nematodes stylets, fungi appressorium chemical attack on plants - ANSWER-enzymes, toxins, growth regulators enzyme attack on plants - ANSWER-large proteins that catalyze reactions toxins - ANSWER-poisonous substance effective in low concentration that injures host cells permeability membrane, inactivating enzymes

abscisic acid - ANSWER-inhibition of growth, closure of stomata, stimulates germination of fungal spores, stunting in plants (tobacco mosaic virus, verticillium wilt) auxins - ANSWER-(IAA)

• continually produced in growing tissue
• cell elongation and differentiation
• permeability of membrane
• increase respiration, protein synthesis crown gall gibberellins - ANSWER-- synergize with IAA
• stem and root elongation
• promotes flowering/fruit growth
• 1st isolated from Gibberella fujikuroi (foolish seedling disease of rice) cytokinin - ANSWER-- cell growth and differentiation
• inhibit breakdown proteins and nucleic acids
• inhibit senescence
• increases clubfoot galls, crown galls, smut, rust infected beans ethylene - ANSWER-- chlorosis
• leaf abscission
• epinasty
• fruit ripening
• produced by fungi and bacteria
• premature defoliation diseases hypersensitivity - ANSWER-mechanism, used by plants, to prevent the spread of infection by microbial pathogens. Characterized by the rapid death of cells in the local region surrounding an infection

monocyclic - ANSWER-1 disease cycle per year polycyclic - ANSWER-many disease cycles per season (explosive epidemics) polyetic - ANSWER-multi year life cycle (dutch elm disease) parasitic enzymes of cell wall - ANSWER-cutinase, pectinase, cellulase, hemicellulase, ligninase appressorium - ANSWER-swollen tip of hyphae penetration peg - ANSWER-haustorium cytoplasmic parasitic enzymes - ANSWER-proteinases, amylases, lipases