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Diseases Caused by Fungi (Including disease by ‘lower fungi’)

Diseases Caused by Fungi (Including disease by ‘lower fungi’). What are Fungi?. Fungi are small, generally microscopic, eukaryotic, usually filamentous, branched, spore-bearing organisms that lack chlorophyll. Mycelium.

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Diseases Caused by Fungi (Including disease by ‘lower fungi’)

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  1. Diseases Caused by Fungi (Including disease by ‘lower fungi’)

  2. What are Fungi? Fungi are small, generally microscopic, eukaryotic, usually filamentous, branched, spore-bearing organisms that lack chlorophyll.

  3. Mycelium Have a filamentous, vegetative body called mycelium. pl.= mycelia.

  4. Hyphae and Septa Individual strands of mycelium are call hyphae (sing. = hypha). Hyphal cell walls are made of chitin. Hyphae in some fungi are partitioned into cells by cross walls called septa. septa

  5. Fungi • Hyphae that do not have septa are said to be coenocytic. • Fungi reproduce mainly byspores.

  6. Asexual Reproduction in Fungi • Spores may be produced within a sac called a sporangium. The spores within the sporangium are called sporangiospores.

  7. Asexual Reproduction Conidia are asexual spores that are not produced within a sac, but are produced by cutting off terminal or lateral cells from special hyphae called conidiophores.

  8. Asexual Reproduction • Conidia may be produced naked (not in a structure or in several different types of structures. • These structures include acervuli, pycnidia, synnemata, and sporodochia.

  9. Examples of naked conidia

  10. Acervulus (pl. acervuli) – mat of hyphae containing short conidiophores and conidia where the structure surrounding them is made of host tissue.

  11. Pycnidium (pl. pycnidia) – A hollow structure made of fungal tissue that contains short conidiophores and conidia.

  12. Sporodochium (pl. sporodochia) – a cushion shaped structure made of fungal tissue and covered with conidiophores.

  13. Synnema (pl. synnemata) – a group of long conidiophores fused or cemented together to form a spore bearing structure.

  14. Chlamydospores – thick wall spores formed from terminal or intercalary cells of hyphae. They can also form in cells of conidia.

  15. Sexual Reproduction • Occurs in most fungi • May involve fusion of two cells or to specialized gametangia (sing. = gametangium).

  16. Sexual Reproduction Zygosporangium – a sporangium containing a zygospore that develops from the fusion of two gametangia.

  17. Sexual Reproduction Ascus – a saclike cell usually containing a definite number of ascospores (8) formed usually after karyogamy and meiosis.

  18. Sexual Reproduction Basidium - structure bearing on its surface a definite number of basidiospores (4) that usually are formed following karyogamy and meiosis.

  19. Kingdom: Fungi • Has zygosporangia – Zygomycetes • Has asci – Ascomycetes • Has basidia - Basidiomycetes

  20. Fungal Like Organisms • Have some of the characteristics of fungi • Kingdom Protozoa – parasitic slime molds • Kingdom Stramenopila (Chromista) • are referred to as the water molds • were called Oomycetes (Oomycota)

  21. Oospores Gametangia are oogonium and antheridium Sporangia may be function as conidia or contain motile sporangiospores called zoospores.

  22. Reading Assignment: Chapter 10 and Pages 91-94 of Chapter 11

  23. Oomycetes – fungal like members of the Stramenopila • Have elongated mycelium containing cellulose and glucans but no septa. • Oospores are produced via sexual reproduction and are resting spores • Asexual reproduction is by sporangia • Sporangia may contain zoospores.

  24. Plasmodiophoromycetes – Parasitic Slime Molds Body is plasmodium (an amoeboid mass of protoplasm that has many nuclei and no cell wall). Clubroot of cabbage Potato Scab

  25. Club Root of CabbagePlasmodiophora brassicae • Occurs on cruciferous plants such as cabbage, cauliflower, and radish • Obligate biotroph • Control: rotate (3-5 yrs) with nonhost; avoid diseased transplants and contaminated equipment; increase pH to 7.2 is useful, but limits crop options.

  26. Plasmodiophora brassicae

  27. Plasmodiophora brassicae

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