Plant Pathogenic Fungi PDF

17/09/2024 Phyla under Kingdom Fungi with Plant Pathogens 1. Phylum Chytridiomycota...

17/09/2024 Phyla under Kingdom Fungi with Plant Pathogens 1. Phylum Chytridiomycota Different Orders of Plant 2. Phylum Zygomycota 3. Phylum Ascomycota Pathogenic Fungi 4. Phylum Basidiomycota 5. Phylum Oomycota 37 36 37 1. Phylum Chytridiomycota Important Plant Pathogenic Chytrids ▪ Contains a single class: Chytridiomycetes 1. Olpidium brassicae 2. Synchytrium - root disease of crucifers endobioticum ▪ The mycelium or thallus has no septa. (vector of lettuce big vein virus) - black wart of potato ▪ About 150 genera; 1000 species ▪ The only member of Kingdom Fungi that form motile cells (zoospores or gametes) 38 39 38 39 Important Plant Pathogenic Chytrids 2. Phylum Zygomycota 3. Synchytrium psophocarpi 4. Physoderma maydis ▪ Class Zygomycetes - orange galls of winged bean - brown spot of corn ▪ no zoospores ▪ Produce resting spore – zygospore Order Mucorales: - Produce zygospore - non-motile sexual spore 40 41 40 41 1  17/09/2024 Examples: 3. Phylum Ascomycota ▪ sac fungus - sexual spores (ascospores) formed within a ▪ Mucor sp. - cause rotting of fruits sac known as ascus and vegetables during storage ▪ Teleomorph - the sexual or perfect stage of ascomycetes ▪ Rhizopus nigricans and R. ▪ Anamorph - the asexual or conidial or imperfect stage stolonifera - cause soft rot of ▪ During the growing season, plant pathogens exist as fruits and vegetables mycelia/conidia ▪ Choanephora cucurbitarum - ▪ Perfect stage occurs only at end of growing season causes soft rot of squash ▪ Sexual reproduction through an ascogonium (female) fertilized by antheridium or spermatium (male), a minute 42 male sex spore 43 42 43 Deuteromycetes or Imperfect Fungi - the imperfect stage of Phylum Ascomycota. Many plant pathogens Three groups of Deuteromycetes or Imperfect Fungi belong to this class. 1. Hypomycetes - fungi that produce conidia on free Asexual or conidial forms of most of the Phylum conidiophores or groups of conidiophores Ascomycota and rarely of the Phylum Basidiomycota 2. Coelomycetes - fungi that produce acervuli or belongs to Deuteromycetes pycnidia that bear conidia and conidiophores Sexual reproduction and sexual structures are lacking 3. Mycelia sterilia - no asexual nor sexual spores; or unknown produced sclerotial bodies 44 45 44 45 46 47 46 47 2  17/09/2024 4. Phylum Basidiomycota – Orders under Phylum Basidiomycota Class Basidiomycetes a. Order Uredinales rusts ▪ Club and mushroom fungi most rust fungi are very specialized ▪ Sexual spores are basidiospores produced externally on a club-like, one- or attack only certain genera, varieties ▪ four-celled spore producing structure called a basidium Formae speciales ▪ Most are fleshy Puccinia graminis f.sp. tritici = attacks wheat only ▪ Includes rusts and smuts Puccinia graminis f.sp. hordei = attacks barley only Pathogenic (Physiogenic) race = P.g. f.sp. tritici attacks some varieties of wheat (within crop species) 48 49 48 49 B. Order Ustilaginales Examples of Diseases smuts attack varies of grains, develop in them and in the 1. Peanut rust - Pucinnia arachidis fruit or kernel 2. Corn rust - Puccinia maydis, P. polysora some attack leaves, stems and floral parts 3. Coffee rust - Hemileia vastatrix Cells affected are destroyed and replaced by black spores 4. Soybean rust - Phakopsora pachyrizi Examples of Diseases 5. Bean rust - Uromyces phaseoli 1. Corn smut - Ustilago maydis 2. Corn headsmut and sorghum smut - Sporisorium reilianum 3. Sugarcane smut - Ustilago scitaminea 50 51 50 51 C. Order Exobasidiales no basidiocarp d. Order Agaricales the mushrooms Examples 1. Armillaria causes root rots of trees 2. Marasmius 3. Pleurotus causes white rot on forest trees 4. Amanita – poisonous 52 5. Calvatia - puffball 53 52 53 3  17/09/2024 d. Order Aphyllophorales 5. Phylum Oomycota Polyporus causes root and stem rot of many trees, rotting of logs ▪ The oomycetes, also known as “water molds”, are a group of several hundred organisms that include some of the most Stereum causes wood decay and devastating plant pathogens. silver leaf disease of trees ▪ The diseases they cause include seedling blights, damping-off, Fomes causes heart rot of many root rots, foliar blights and downy mildews. trees ▪ Some notable diseases are the late blight of potato, downy mildew of grape vine, sudden oak death, and root and stem rot of soybean. ▪ Because of their filamentous growth habit, nutrition by absorption, and reproduction via spores, oomycetes were long 54 regarded by plant pathologists as lower fungi. 55 54 55 a. Order Pythiales (Family Pythiaceae) Pythium – have sporangia that looks like a swollen hyphae or globose opportunistic pathogens especially in young plants. Phytophthora – have lemon shaped, ovoid, pyriform, obpyriform or globose, sporangia 56 57 56 57 4