1 Fungi As Plant Pathogens Anubhav Vinayak Lisa Tofil Heather Rice Introduction Definitions: • Parasite – organism that gains all or part of its nutritional requirements from the living tissues of another organism – the host. • Pathogen – organism that causes disease. A pathogen almost always a parasite but not all parasites cause diseases. Pathogens • Pathogens – Necrotrophic – (kill the host tissues usually by directly invading them or by producing toxins or degradative enzymes and then feed on the tissues that they kill) – Biotrophic – (feed on living host tissues by producing special nutrient-absorbing structures that tap into host’s tissues) Pathogens Pathogen Necrotroph Biotroph Host-specialized Non-specialized Host-specialized Seed rots and seedling pathogens • Athelia rolfsii – One of the most devastating seedling pathogens in the warmer parts of the world where rainfall is seasonal Source: http://www.agroatlas.ru/content/diseases/Olee/Olee_Athelia_rolfsii/Olee_Athelia_rolfsii.jpg Seedling pathogens (cont) • Rhizoctonia solani – Common seedling pathogen that attacks the basal stem tissues of plants – Examples Source:http://www.ctahr.hawaii.edu/nelsons/Misc/ 1_potato_sore_shin_rhizoctonia_1.jpg Source: http://www.turffiles.ncsu.edu/diseaseID/diseasedetail.aspx?disease=RHISL
7
Embed
Fungi As Plant Pathogens - Youngstown State Universitycrcooper01.people.ysu.edu/Fungi Ch14 presentation Final.pdf · Fungi As Plant Pathogens Anubhav Vinayak Lisa Tofil Heather Rice
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
Fungi As Plant Pathogens
Anubhav Vinayak Lisa Tofil
Heather Rice
Introduction
Definitions:
• Parasite – organism that gains all or part of its nutritional requirements from the living tissues of another organism – the host.
• Pathogen – organism that causes disease.
A pathogen almost always a parasite but not all parasites cause diseases.
Pathogens
• Pathogens – Necrotrophic – (kill the host tissues usually by
directly invading them or by producing toxins or degradative enzymes and then feed on the tissues that they kill)
– Biotrophic – (feed on living host tissues by producing special nutrient-absorbing structures that tap into host’s tissues)
Pathogens
Pathogen
Necrotroph Biotroph
Host-specialized Non-specialized Host-specialized
Seed rots and seedling pathogens
• Athelia rolfsii – One of the most devastating seedling pathogens
in the warmer parts of the world where rainfall is seasonal
• Dilemmas of endophytes – Produce mycotoxins – Mycotoxins harm grazing animals – endophytes increase stress tolerance – endophytes prevent insect damage over other
grasses
Fungal Endophytes and Their Toxins Cont.
• Types of mycotoxins and effects – loliterm B- saturated aminopyrrolizidine alkaloids--
“ryegrass staggers” disease of grazing sheep and cattle. Staggers are loss of coordination and/or tremors occur at times
– Egrovaline- causes “fesuce foot” and “fescue toxicosis” where the animal can experience hyperthermia, weight loss, reduced pregnancy rates, decreased milk production, and for horses birth defects or abortions
– Peramine- tripeptide that is repellent and toxic to insects, but not mammals
• Phytophthora infestans – Heterothallic fungi – Originated in Central Mexico, both mating types
present there (A1 and A2) – Moved over to Europe by 1840’s causing Potatoe
Blight – Only A1 was dominantly present outside Central
Mexico, but in 1980 began to spread
Phytophthora Diseases Cont.
• Phytophthora infestans Cont. – Symptoms
• Black spreading lesions on foliage • Cool humid conditions allow black lesions to produce
sporangiophores that emerge from leaf stomata • Potato tubers become infected later (spread of motile zoospores) • Tubers rot then destroyed by secondary bacteria invaders • May also be spread by wind born sporangia or splashed sporangia
• Phytophthora ramorum: sudden oak death – First found in Germany and Netherlands in 1993 – Described as P. ramorum in 2001 – Now found in coastal fog belt of northern California
and southern Oregon – European mating type is A1 – North American mating type is A2 – Separate origin of sources
Phytophthora Diseases Cont. • Phytophthora ramorum: sudden oak death cont.
– Part of Ascomycota cause problems throughout all seasons, especially when dry and hot and if not treated with fungicides
– Common types • powdery mildew of roses (Sphaerotheca pannosa) • powdery mildew of gooseberries (S. mors-uvae) • powdery mildew of hawthorn bushes (Podosphaera
clandestina)
– This species undergoes multiple cycles of infection in one season like rust fungi
7
Biotrophic Plant Pathogens Cont. • Downy mildews
– Part of Oomycota – haustorial biotroph act like rust fungi and
powdery mildew fungi, but need humid conditions for infection
– Examples • Blemia lactucae of lettuce • Plasmopara viticola on grape vines • Pseudoperonospora humuli on hops
• What structure do pectic enzymes degrade in plant cells? A. Primary wall B. Middle lamella C. Secondary wall D. Plasmodesmata
Question 2
• What is the name of the signal molecule that mediates systemic acquired resistance? A. Jasmonic acid B. Xylanase C. Ethylene D. Salicylic acid
Question 3
• Which of the following is not a defense mechanism used by plants to prevent invasion by necrotrophic pathogens? A. Phytoanticipins B. Cutinase enzyme C. Oxidative burst D. Phytoalexins
Question 4
• What type of fungi has multiple life cycles including uredospore, teliospores, basidiospores, and aeciospores? A. Powdery Mildew Fungi B. Rust Fungi C. Blemia lactucae D. Phytophthora ramorum
Question 5
• Which type of fungi has two types found in the US (A1 and A2) A. Phytophthora infestans B. Phytophthora ramorum C. Blemia lactucae D. Pseudoperonospora humuli