review - BTNY 301 Exam#3 Review Session Nov. 10,...

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Unformatted text preview: 11/8/10 BTNY 301 Exam #3 Review Session Nov. 10, 2010 Basidiomycetes Viruses Plant Parasi3c Nematodes (Rusts, Smuts and Mushrooms) •  Sexual fruiFng organ is a basidium. May or may not be in a basidiocarp. •  Sexual spore is a basidiospore (1N); typically produce 4 per basidium Basidiomycetes RD Martyn, Purdue University 2 1 11/8/10 Basidiomycetes •  In the rust and smut fungi, the sexual spore is considered the teliospore because that is where karyogamy occurs (N+N 2N). The teliospore overwinters and then germinates to form a probasidium. Meiosis occurs (2N 1N) and 4 basidiospores (1N) are formed on the basidium. •  Basidiomycetes spend most of their life cycle in the dikaryoFc state (N + N) Basidiomycetes – Rust Fungi •  No basidiocarp, but they do have a basidium •  Complex life cycle with mulFple spore stages –  Macrocyclic (3 – 5 spore stages) –  Microcyclic (<3 spore stages) •  May require two hosts to complete life cycle –  Autoecious (one host) –  Heteroecious (two hosts) •  Alternate host (infected by basidiospores) •  Primary host (infected by aeciospores from alternate host if present; host on which the teliospore forms) RD Martyn, Purdue University 4 2 11/8/10 •  Obligate parasites •  Plasmogamy occurs between pycniospores and recepFve hyphae in the pycnidium Rust Fungi •  Karyogamy occurs in the developing teliospore •  Meiosis occurs in the germinaFng teliospore / probasidium. RD Martyn, Purdue University 5 Black stem rust of wheat (Puccinia graminis f. sp. tri-ci) •  Macrocyclic / heteroecious •  Five spore stages (IV, 0, I, II, III) IV  ­ Basidiospore (1N) 0  ­ Pycniospore (1N) I  ­ Aeciospore (N + N) II  ­ Urediospore (N + N) III  ­ Teliospore (2N) RD Martyn, Purdue University 6 3 11/8/10 Black stem rust of wheat (Puccinia graminis f. sp. tri-ci) –  Alternate host is barberry •  Infected by basidiospores  ­ IV (1N) •  Forms a pycnidium, pycnidiospores  ­ 0 (1N) and recepFve hyphae (Plasmogamy) •  Forms an aecium and aeciospores ­ I (N+N) RD Martyn, Purdue University 7 Black stem rust of wheat (Puccinia graminis f. sp. tri-ci) •  Primary host is wheat –  Infected by aeciospores –  Forms uredinia and urediniospores  ­ II (N+N) •  Urediniosproes are the repeaFng spore stage. Can reinfect wheat. –  Forms telia and teliospores  ­ III (2N) – Karyogamy •  Teliospores are the overseasoning spore –  Basidium forms from germinaFng teliospore. Produces basidiospores (1N)  ­ Meiosis RD Martyn, Purdue University 8 4 11/8/10 Black Stem Rust of Wheat (Puccinia graminis f. sp. tritici) Barberry (Berberis vulgaris) Alternate host (Barberry) Primary host (Wheat) RD Martyn, Purdue University 9 Puccinia graminis f. sp. tritici – Strain Ug99 •  Identified in Uganda, 1999 •  Virulent on all wheat varieties grown around the world. •  Has spread to Middle East and likely reach India and Europe and eventually the U.S. •  Has potential to reduce yields by as much as 70% RD Martyn, Purdue University 10 5 11/8/10 Soybean Rust – Phakopsora pachyrhizi Rupe, J. and L. Sconyers. 2008. Soybean Rust. The Plant Health Instructor. DOI: 10.1094/PHI-I-2008-0401-01 •  Autoecious – microcyclic rust fungus •  Only has two spores stages – Urediniospores and Teliospores. •  Wide host range - alternative hosts. Not to be confused with ‘alternate hosts’. –  Many legume species –  Kudzu (Important as a overseasoning host in the South) RD Martyn, Purdue University 11 Rust Diseases •  Disease management –  Most rust diseases are best managed with resistant varieFes, when available; however, new races or strains of the fungus ocen evolve –  When economics allow, fungicides are used –  EradicaFon of alternate hosts may reduce the development of new strains –  ScouFng fields and/or senFnel plots RD Martyn, Purdue University 12 6 11/8/10 Basidiomycetes  ­ Smuts •  Typically produce only teliospores and basidiospores •  No basidiocarp (similar to rust fungi) •  Ocen afack the ovaries of cereal grains and kill the ovary and producing large amounts of inoculum or fungal Fssue RD Martyn, Purdue University 13 Mathre, D.E. 2000. SFnking smut of wheat. The Plant Health Instructor. DOI: 10.1094/PHI ­I ­2000 ­1030 ­01 hfp:// SFnking Smut (Bunt) of Wheat (Tille-a tri-ci) M. M. Tillet – 1755 RD Martyn, Purdue University 14 7 11/8/10 Corn Smut – Us-lago maydis RD Martyn, Purdue University 15 Us-lago maydis Teliospores (2N) Basidium Basidiospore (1N) Teliospore RD Martyn, Purdue University 16 8 11/8/10 Armillaria Root Rot  ­ Shoestring Root Rot (Armillaria mellea and other species) Worrall, J. 2004. Armillaria root disease. The Plant Health Instructor. DOI:10.1094/PHI ­I ­2004 ­0706 ­01 hfp:// RD Martyn, Purdue University 17 Viruses as Plant Pathogens •  Tulip Break disease (1630s) •  Tobacco mosaic virus –  First virus shown to be infecFous –  First virus shown to reproduce in vivo –  First virus crystalized from infected plant –  First virus to be seen (electron microscope) –  First virus to be characterized (protein & NA) 9 11/8/10 The Intrinsic ProperFes of Viruses •  •  •  •  •  •  Infec3ous – Adolf Mayer Extremely small size – D. Ivanowski Reproduce in plants  ­ M. Willem Beijernick Contain protein – Wm. Stanley Contain nucleic acid (RNA) – F. C. Bawden Nucleic acid (RNA) is infec3ous en3ty – H. Frankel ­Conrat 19 RD Martyn, Purdue University Viruses •  Contain a nucleic acid surrounded by a protein coat •  The nucleic acid may be either DNA or RNA and either single stranded or double stranded •  Most (but not all) plant viruses contain ssRNA •  Most (but not all) animal viruses contain dsDNA 10 11/8/10 Viruses •  Have mulFple morphologies (shapes) A. Rigid rod, B. Flexuous rod, C. Icosahedral (spherical), D. Bacilliform, membrane-bound Viruses •  Only contain a few genes, but at least 3 that code for: –  Replicase (polymerase) –  Coat protein –  Movement protein Replicase Movement protein Coat protein 11 11/8/10 Viruses •  All viruses are obligate parasites •  Viruses infect the phloem Fssue of plants •  Move from cell ­to ­cell thru plasmodesmata with the aid of the movement protein Transmission of plant viruses •  Most plant viruses are transmifed by insect vectors •  Insects in the Hemiptera order are most important –  Family Aphididae (aphids) •  Potyviruses, BYDV –  Family Cicadellidae (leaf hoppers) –  Family Aleyrodidae (whiteflies) •  Gemini viruses Order Thysanoptera (thrips) •  TSWV 12 11/8/10 Insect Transmission of Plant Viruses •  Nonpersistent transmission (stylet ­borne transmission) •  Persistent transmission (circulaFve transmission) •  Persistent, circulaFve propagaFve transmission RD Martyn, Purdue University 25 Tobacco Mosaic Virus •  1st virus to be purified; shown to cause disease, characterized, EM micrograph – rigid rod •  Symptoms are mosaic and mofling paferns and necrosis, leaf distorFon, stunFng •  Transmifed mechanically, no specific insect vector •  Wide host range 13 11/8/10 Barley Yellow Dwarf Virus   Infects cereal grasses (barley, wheat, rice, maize) •  Vectored by aphids – persistent and circulaFve (T.F. Mann) •  Icosahedral parFcle shape (spherical); ssRNA Tomato Spofed Wilt Virus •  •  •  •  Very wide host range (650 different plants) Vectored by thrips Icosahedral parFcle shape Spopng and wilFng symptoms and necrosis 14 11/8/10 Plant ParasiFc Nematodes Nematode Biology / ClassificaFon •  Phylum Annelida – Segmented round worms (earthworms) •  Phylum Platyhelminthes – Flat worms (many human and animal parasites) •  Phylum Nematoda – Non ­segmented round worms (many plant parasites) A. Earthworm B. Tapeworm C. Lesion nematode 15 11/8/10 Plant ParasiFc Nematodes •  Obligate parasites •  Mostly affect roots but leaves and stems also may be infected by some species. •  May be ectoparasicitc or endoparasiFc •  May be sedentary or migratory •  All PPN have a stylet Ectoparasitic Endoparasitic Plant ParasiFc Nematodes •  Three stages in life cycle: egg, juveniles (J1 – J4), adult •  J2 is the only stage that can infect plants Usually occurs inside egg Occurs on plant Infective stage RD Martyn, Purdue University 32 16 11/8/10 Plant ParasiFc Nematodes •  Three most economically important PPN –  Root knot (Meloidogyne incognita; M. hapla) –  Soybean cyst (Heterodera gylcines) –  Lesion (Pratylenchus spp.) Root Knot Nematode (Meloidogyne incognita, M. hapla) •  •  •  •  •  Wide host range Sedentary / endoparasiFc Female induces plant to make ‘giant cells’ upon which she feeds Body swells into a large egg mass Feeding causes large galls (knots) on roots 17 11/8/10 Soybean Cyst Nematode (Heterodera glycines) •  •  •  •  •  Sedentary / endoparasiFc Same basic life cycle as root knot (eggs J1 ­J4 adult) Female induces feeding site “syncyFum” Female body swells with eggs, becomes a hard cyst. Cysts fall to ground & overseasons; release eggs in spring. Lesion Nematode – Potato Early Dying Disease (Pratylenchus spp.) •  Wide host range; over 400 dicots & moncots •  Migratory / endoparasiFc •  Symptoms are lesions; not galls 18 11/8/10 PPN Field Symptoms Management of Nematode Diseases •  •  •  •  •  Resistant varieFes when available Crop rotaFon to a nonhost Field flooding Soil fumigaFon Biological control (nematode ­trapping fungi) 19 ...
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