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by: Ms. Mina Leuschke


Ms. Mina Leuschke
OK State
GPA 3.94


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Class Notes
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This 0 page Class Notes was uploaded by Ms. Mina Leuschke on Sunday November 1, 2015. The Class Notes belongs to PLP 3343 at Oklahoma State University taught by Staff in Fall. Since its upload, it has received 19 views. For similar materials see /class/232869/plp-3343-oklahoma-state-university in Pathology at Oklahoma State University.




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Date Created: 11/01/15
Lecture 17 Parasitic Plants amp Oomycetes Oomycetes General Characteristics Downy mildews White rusts Pythium diseases Phytophthora diseases Oomycetes General Characteristics Downy Mildews White Rusts Pythium Diseases Phytophthora Diseases Characteristics of Oomycetes Water molds high humidity and soil moisture will favor these diseases Similarities of Oomycetes with True Fungi Absorptive nutrition Vegetative filamentous hyphae Production of spores However although morphologically similar they share no close phylogenetic relationships to fungi Characteristics of Oomycetes Kingdom Stramenopila Chromista Hams Oomycetes Protists m up Bacteria Mollicutes 39 EUKARYOTA quotmum 302mm opisthokunts Animals Nematodes amp lnseds D h l MVmQWIdao Myxogastridae Slime Molds PTOIOZoa39 Amm green red algae 39 glmcophylas WWW oomycetes Stramenopiles phaeaphvles39 waxes alveolales J Plasmodiophorids parasitic slime molds kneloglasllds Characteristics of Oomycetes Taxonomy Kingdom Stramenopila Chromista Phylum Oomycota Class Oomycetes Order Saprolegniales Family Saprolegniaoeae root rots Genus Aphanomyces Order Peronosporales Family Pythiaceae root rots and foliar blights Genus Pythium Phytophthora Family Peronosporaceae Downy Mildews Genus Plasmopara Peronospora Bremia Pseudoperonospora Peronosclerospora Sclerophthora Sclerospora Family Albuginaceae White Rusts Genus Albugo Plant Pathogenic Oomycetes Oomycetes E E s u E o a 5 u k os 121am 5P Z 39i 1 le V 42 Phytcphthora Albugu E 95 9 m 3 9 3P 5quot Q i Sp E 5 5 a 5 D 1 E s s 5 k as Plasmopara Bremia Pamncspara Vseudcpevonospova sdemspma Oomycetes vs True Fungi CHARACTER OOMYCETES TRUE FUNGI Sexual Heterogametangia Meiospore zygospore reproduction meiospore oospore ascospore or basidiospore Nuclear state of vegetative mycelia Diploid 2n Haploid 1n or dikaryotic nn Cell Wall Composition pglucans cellulose Chitin rarely cellulose Zoospore flagella Posterior whiplash Anterior tinsel ciliated Chytrids posterior whiplash only Vegetative hyphae Aseptate coenocytic Chytrids Zygos aseptate Ascos Basidios septate Mitochondria Tubular cristae Flatten cristae Characteristics of Oomycetes Mycelium contains cellulose and 3glucans Cell Walls of FLO s and Fungi CELL WALL POLYSACCHARIDES l Myxo mycetes Cellulose resting spores Plasmodiophorids F JNG TRUE FUNGI Cellulose resting spores Characteristics of Oomycetes Aseptate coenocytic hyphae No cross walls in actively growing hyphae May find septa at the base of sporangiophores and in old hypha Characteristics of Oomycetes Sexual meiospores oospores Greek oon egg spora seed spore Diploid thallus meiosis occurs in developing heterogametangia Antheridia 8 Oogonia S Sexual Structures meiospores oospores Homothallic selffertile A e ridiu qg Heterothallic opposite mating types required for sexual reproduction A1A2 Resting Spores Oospores Sexual meiospores x L Chlamydospores Asexual mitospores Characteristics of Oomycetes Asexual mitospores sporangia zoosporangia and zoospores Characteristics of Oomycetes Zoospores Zoospores possess 2 flagellae Anterior tinsel ciliated flagellum Posterior whiplash flagellum Sporangia germination and Zoospore encystment Sporangia Direct germination Zoosporangia Zoospore formation Zoospore Encystment and substrate penetration Encystment and amp emer ence Up to 5 times Multiple chances to find host http heios bto ed ac ukbtomicrobeszoospore htm towards root exudates ht pn s helios bto ed ac uksbto microbess zoospore htm h tpn s hel os bto ed ac uksbtos39microbess zoospore htm Oomycete Diseases 1 Foliaraerial Diseases leaves young stems and branches fruits Phytophthora Pythium white rusts and downy mildews 2 Soilborne Diseases roots lower stems tubers seeds fleshy fruits lying on the soil Aphanomyces Pythium and Phytophthora 5 5m if f 1 a a it L Seedling A I Seed rot damping off Root and stem rot Blight Tuber rot Soft rot Oamycetes y 1 Upper 21 side quot7 x u t l 7 Oospoes on Mildews soybean seed White rust Downy mildews Vegetables fruits cereals ornamentals Obligate parasites Symptoms Upper leaf surface yellow patches Lower leaf surface white sporulation of the pathogen First fungicide Bordeaux Mixture Millardet 1885 Grape downy mildew Plasmopara viticola quotDilspotquot lesion develops on top of leaves Zoospores with two flagella O are released from sporangium Zoospore eno yrsls near stoma andthe germ tube penetrates Zoospore differentiate Leaf lnfemon W1 in sporangium 5 i f V a 39 Dospores are released gt quotK from decaying leaves onthevineyard floor Sporanglum are dispersed V by wind or rain splash Asparangium is produced from the oospore in spring L24 Sporangia are produced onthe berries and the undersides of leaves through stomata 39 I Antheridium Crosssection of leaf tissue with oospora Dogonia are formed and fertilized in the leaf Downy mildews w a Management Minimize leaf wetness quot Air circulation Avoid overhead irrigation Sanitation remove dead leaves prune out diseased branches Genetic resistancetolerance Fungicide program Disease forecasting DMCast Protectivesystemic hllpANwwhesgechelArchivesa llesA magesperonosporam jpg l mu Wab 39el org om he ArthelQQBRos39e yl mm White rust Albugo spp Obligate parasites Vegetables field crops weeds Symptoms Upper leaf surface chlorotic spots Emmmmwkmmny7 Lower leaf surface and stems white pustules Frequently appear in concentric rings Hypertrophied flower hllp wwww apan Zyrgs un Ine Arch Si owtu I185 hint White rust o Locally a problem on spinach and canola 0 Management Some tolerant cultivars Crop rotation Forecasting model Fungicides Morning39glory Diseases caused by Pythium and Aphanomyces Seedling blights damping off Root rots Fruit rot Pythium blight of turfgrass Damping off or seedling blight iEa mmrlg 3 A hanoh aggs V Pythium Aphanomyces Seeds and young seedHngs Death or stunting of plants Losses vary with soil moisture and Young or older Mild to severe root 39 Stunted or chlorotic 39 Reduced yield or temperature Root rots Reot rot vAphan39ofinyce s r 39 Pythium Aphanomyces plants necrosis plants unmarketable Fruit rots Pythium aka cottony leak fruit decay Symptoms Watersoaking and leaking of fruits White mycelial growth Fruit necrosis Bad smell hII so Pythium and Aphanomyces Management Resistance or tolerance Seed treatments Fungicides Cultural Planting date Get the fruit off the ground Deep tillage Crop rotation Improve drainage Pythium blight of turfgrass aka cottony blight greasy spot Coolseason turfgrasses are the most susceptible Hot humid weather Small 15 inch irregular spots May observe streaks in the direction of water movement or mowers 1O Pythium blight of turfgrass 0 Grass blades water soaked and have a greasy or slimy feel and appearance 0 Upon drying dead areas are brown or strawcolored and may have a reddish tinge Pythium blight otfas 39 r f o Pythium spp 0 May observe fungal mycelium under high humidity 0 Diagnosis large oospores in the roots APS Press from the Compendium of Turlgrass Diseases 2nd Edition lntncllon Encyatea I tampons V l Germina a lion t Zoospms Germina lion Zoosporanglum 39 Oran um with zoospores ZOOSpore p g Z quot Spreading mycelium Ooapora Germinatloln I 39 Oospore 739 quota 1 939 4 39 quot39L39v39v 392 I Blighlad plan Fertilization 39 r 01 ooganiurn quotvquot z in iamp l r3939 Coenocytic mycelium Dead and sexual pm mproduclwe structures Life cycle of Pythium blight of turfgrass Pythium spp 11 Pythlum Eight of Turfgrass Disease Management Plant treated seed at establishment Cultural Water early in the day Increase drainage Balanced fertilizer with gypsum CaSO4 Avoid mowing when turf is wet Plant moderately resistant cool season grasses httpwwwnteporg Diseaseforecasted fungicides T gt30 C RH gt90 for 14hday Ave nighttime TRH 2150 Lab Today Parasitic Plants Specimens and slide Oomycetes Videos Isolations on selective media Zoospore demo Specimens and slides 12


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