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TAMU PLPA 301 Final Exam Review – Study Guide, Practice
Questions & Plant Pathology Exam Prep 2026
bacilli - ANS ✔✔rod shaped bacteria phytophthora infestans - ANS ✔✔effect of low temperature on spore germination pathogen of bacterial canker of stone fruits is aided by - ANS ✔✔ice nucleation activity xanthomonas oryzae - ANS ✔✔rice bacterial blight holy fire/saint anthony - ANS ✔✔lsd and ergotamine texas male sterile germplasm - ANS ✔✔southern corn leaf blight god robigus - ANS ✔✔spontaneous generation theory fire blight of pear (erwinia amylovora) - ANS ✔✔pears, apples, and hawthorn are hosts propagule - ANS ✔✔inoculum southern bacterial wilt - ANS ✔✔potato now grown in idaho latent period - ANS ✔✔symptomless infection
facultative parasite - ANS ✔✔primarily saprophyte marshall ward - ANS ✔✔coffee rust of ceylon/disease forecasting prokaryote - ANS ✔✔lack of nuclear membrane eukaryote - ANS ✔✔multiple cell organelles dikaryon - ANS ✔✔hyphae with two nuclei in a single cell puccinia graminis - ANS ✔✔cereal rusts smuts - ANS ✔✔order ustilaginales rhizoctonia solani - ANS ✔✔brown patch of saint augustine grass dutch elm disease - ANS ✔✔spread by beetles microcyclic - ANS ✔✔two spore stages sporangia - ANS ✔✔indirect germination heteroecious - ANS ✔✔two alternate hosts sclerotium - ANS ✔✔interwoven hyphae for overwintering kingdom protozoa - ANS ✔✔single celled eukaryotes, vector viruses
homothalllic - ANS ✔✔same strains for same mating types chemotropism - ANS ✔✔movement towards chemicals autotropism - ANS ✔✔movement towards same species thigmotropism - ANS ✔✔movement towards touch describe three features (diploid vs, haploid hyphae coenocytic vs. septate hyphae, chitin vs. glucan) for ascomycetes and basidiomycetes - ANS ✔✔ascomycetes: haploid hyphae, septate hyphae, chitin and glucan basidiomycetes: dikaryotic hyphae, septate hyphae, chitin phytophthora infestans is the causal agent for the disease commonly known as ______ and is translated from latin as "phyto is _____, phthora is ______, infestans is _______" - ANS ✔✔late potato blight; plant; death; infection name the three most general ways by which most pathogens penetrate a host - ANS ✔✔direct penetration, natural openings, and wounds what are the three components of the disease triangle? - ANS ✔✔virulent pathogen, susceptible host, and favorable environment potato irish famine happened primarily due to which component of the disease triangle? - ANS ✔✔environment
name four structural elements of a bacterial cell - ANS ✔✔DNA, LPS, plasmid, and ribosomes one common feature of smuts is that they all replace kernels by the end of the growing season that they infect with - ANS ✔✔teliospores sexual reproduction relies on cell divisions called ______ and asexual reproduction relies on cell division called _______ - ANS ✔✔meiosis; mitosis the three major groups of plant pathogenic basidiomycetes are - ANS ✔✔rusts, smuts, and wood-rotting fungi two primary genera that cause disease called "damping-off" are - ANS ✔✔pythium and phytophthora describe at least three major characteristics of the rust fungi - ANS ✔✔obligate parasites, local lesions, can have two hosts what's similar between pythium and downy mildew? - ANS ✔✔both are in kingdom protozoa, phylum oomycota, and have obligate parasites what's different between downy mildews and pythium? - ANS ✔✔downy mildew: above ground, biotroph, narrow host range pythium: below ground, necrotroph, many hosts bordeaux mixture is called a mixture because it contains ______ that's toxic to microorganisms and _________ to prevent phytotoxicity - ANS ✔✔copper sulfate and lime
demise? what were the social and environmental factors? - ANS ✔✔characteristics: genetic uniformity of crop social factors: reliance on staple crop and grain given to english landlords as payment environmental factors: cool, moist environments and continuous overcast/rain for six weeks list, in proper order, koch's postulates - ANS ✔✔observe pathogen symptoms isolate the pathogen inoculate the healthy plant with pathogen reisolate the pathogen (same symptoms as #2) what kind of pathogens cannot be tested using koch's postulates? - ANS ✔✔obligate parasites, smuts, rusts, viruses, and downy mildews name four major general disease control strategies against bacterial pathogens? - ANS ✔✔biological control, chemical control, vector control, and sanitation of tools choose four examples of the major disease epidemics of a historic proportion and explain what we did wrong that helped epidemics occur for each particular disease - ANS ✔✔southern corn leaf blight - detasseling coffee rust of ceylon - kept in large acres
ergot of wheat and rye - didn't separate clean vs. infected seed irish potato famine - monoculture describe four mechanisms by which plant pathogens can attack a host - ANS ✔✔plugging substances - interference with transport plant growth regulators - altered genetic control cell wall degrading enzymes - loss of plant cell integrity and toxins which groups of genes are deleted when you want to insert a desired gene into Ti plasmid for biotechnology purposes? - ANS ✔✔T-DNA liebig's law of minimum - ANS ✔✔the total yield or biomass of any organism will be determined by the nutrient present in the lowest concentration in relation to the requirements of that organism shelford's law of tolerance - ANS ✔✔the occurrence and abundance of organisms in an environment are determined not only by nutrient, but also by various physiochemical factors characteristics of non-infectious disease - ANS ✔✔no pathogen involved caused by lack of or excess of something that supports life differ in symptoms from biotic agents that cause more random patterns (abiotic stress cause more damage)
moisture - low relative humidity - ANS ✔✔combines with wind/temperature = wilting, scorching leaves radiators in house moisture - high soil moisture - ANS ✔✔soil becomes anaerobic: plant stress, root death, and loss of selective permeability of plant cells under anaerobic conditions = alter metabolism and compounds toxic to plants oxygen - ANS ✔✔inadequate oxygen can also occur in the centers of fleshy fruits/vegetables during periods of high respiration ex. blackheart of potato: high temperature stimulates high respiration; cells die due to lack of oxygen and cell constituents are oxidized lack of light - ANS ✔✔retards chlorophyll production etiolation: pale green seedlings excessive light - ANS ✔✔rare to have damage, usually combined with high temperature low pH values - ANS ✔✔calcium, phosphorus, and magnesium become less available to the plant high pH values - ANS ✔✔phosphorus and most of micronutrients become less available
pH 5.0 to 5.5 - ANS ✔✔azaleas, rhododendrons, blueberries, and conifers thrive best in this soil pH pH 5.8 to 6.5 - ANS ✔✔vegetables, grasses, and most ornamentals thrive best in this soil pH pH extremes affect growth - ANS ✔✔denature enzymes affect protein structure and activity hydrolyze proteins pH affects energy-yielding reactions by affecting organelle function - ANS ✔✔cytoplasm, mitochondria, and chloroplast primary elements - ANS ✔✔nitrogen, phosphorus, and potassium secondary elements - ANS ✔✔magnesium and calcium minor elements - ANS ✔✔boron, sulfur, iron, zinc, copper, manganese, molybdenum toxic minerals - ANS ✔✔sodium, boron, manganese, copper, aluminum, iron air pollution - ANS ✔✔ethylene, herbicides, chlorine gas, ammonia, heavy metals, sulfuric acid, and hydrogen sulfide
unpolluted rain = pH of 5.6 to 7. lemon juice = 2. interactions - ANS ✔✔air pollutants may be synergistic obligate parasites likely to be suppressed by air pollution facultative parasites tend to be encouraged by air pollution herbicides - ANS ✔✔distorted, yellow leaves broad-leaved gene-for-gene theory - ANS ✔✔for every resistance gene (R gene) in the host, there's a corresponding gene for avirulence (Avr gene) in the pathogen gene-for-gene interaction - ANS ✔✔leads to abortion of compatibility between the host and the pathogen avirulence genes - ANS ✔✔single genes in the pathogen that trigger host resistance mechanisms and limit the pathogens ability to cause disease on certain host genotypes resistance genes - ANS ✔✔single genes in the host that allow recognition of certain pathogen genotypes R gene resistance - ANS ✔✔most common
against all types of pathogens encodes a receptor hypersensitive response - ANS ✔✔programmed cell death process triggered in response to incompatible pathogens very rapid response that invariably leads to cell and tissue death within 24 hours after pathogen infection causal role in resistance sufficient not attacked by opportunistic necrotrophic organisms types of genetic resistance - ANS ✔✔cultivar specific vs. cultivar nonspecific monogenic vs. polygenic qualitative vs. quantitative gene-for-gene type vs. non gene-for-gene type dominant vs. recessive
involves several genes (polygenic) expression of minor genes for R, less strong difficult for the pathogen to overcome influenced more by the environment suppression of symptoms: longer incubation period, fewer lesions, smaller lesions, ability of susceptible plant to halt systemic spread R gene management - ANS ✔✔single gene, R gene pyramiding, gene mixtures, multiline cultivars, geographic deployment, and gene rotation
