Fungi Reproduction PDF

Leila Geagea, PhD 1 CHAPTER III FUNGI Leila Geagea, PhD 2 General characteristics  Fungi belong to the kingdom of “Fungi” (Myceteae): small, generally microscopic eukaryotic, usually filamentou...

Leila Geagea, PhD 1 CHAPTER III FUNGI Leila Geagea, PhD 2 General characteristics  Fungi belong to the kingdom of “Fungi” (Myceteae): small, generally microscopic eukaryotic, usually filamentous, branched, spore-bearing organisms.  They lack chlorophyll.  They have cell walls that contain chitin and glucans as the skeletal components. Leila Geagea, PhD 3 General characteristics  Fungi can be saprophytic symbiotic parasitic Leila Geagea, PhD 4 Morphology and structure Most fungi have a filamentous vegetative body mycelium that branches out in all directions hyphae or the individual branches of the mycelium. emerging from the elongation of the germ tube results from the germination of the smallest reproductive body: spore Leila Geagea, PhD 5 Morphology and structure Leila Geagea, PhD 6 Morphology and structure  Types of hyphae septate partitioned by cross walls (septa) Aseptate (coenocytic) Leila Geagea, PhD 7 Modification of hyphal structure  Chlamydospores terminal or intercalary cells of a hypha enlarge, round up and form a thick wall. vegetative cells helping in pathogen survival.  Rhizomorphs rootlike aggregation of hyphae. involved in mycelium migration and food transport. Leila Geagea, PhD 8 Modification of hyphal structure  Sclerotia a compact mass of hyphae. survival structure under unfavorable environmental conditions.  Appressorium swollen tip of a hypha or germ tube that facilitates attachment and penetration of the host by a fungus Leila Geagea, PhD 9 Modification of hyphal structure  Haustorium a simple or branched projection of hyphae into host cells. an absorbing organ for food and water. Leila Geagea, PhD 10 Modification of hyphal structure Leila Geagea, PhD 11 Reproduction of fungi  Fungi reproduce chiefly by means of spores. Spores consist of one or a few cells. Spores may be formed  asexually like buds produced on a twig.  or as the result of sexual fertilization. Leila Geagea, PhD 12 Reproduction of fungi  Asexual reproduction also called vegetative or imperfect it represents the main source of pathogen dissemination  an increase in the number of individuals is observed. it is repeated several times during the pathogen’s life or within the same season. Leila Geagea, PhD 13 Reproduction of fungi  Asexual reproduction Fragmentation of hyphae  separation of hyphae on small segments. each segment turns into a spore that will grow and form a new individual. Leila Geagea, PhD 14 Reproduction of fungi  Asexual reproduction Fission of individual cells  Cells divide by mitosis Yeast Leila Geagea, PhD 15 Reproduction of fungi  Asexual reproduction Budding of cells  small growths produced from a vegetative cell that would contain a nucleus. Leila Geagea, PhD 16 Reproduction of fungi  Asexual reproduction Production of asexual spores  unicellular spores  multicellular spores  uninucleated  multinucleated.  There are two types of asexual spores:  Sporangiospores  Conidia Leila Geagea, PhD 17 Reproduction of fungi  Asexual reproduction Production of asexual spores  Sporangiospores ✓produced inside a sac called a sporangium carried by sporangiophores. ❖Pythium sp., Phytophthora sp. Leila Geagea, PhD 18 Reproduction of fungi  Asexual reproduction Production of asexual spores  Sporangiospores ✓Some sporangia are produce from a naked, amoeboid, multinucleate body called plasmodium instead of mycelium. Leila Geagea, PhD 19 Reproduction of fungi  Asexual reproduction Production of asexual spores  Sporangiospores: two types ✓Zoospores swim by means of flagella ❖ Pythium, Phythophthora, Plasmopara. Leila Geagea, PhD 20 Reproduction of fungi  Asexual reproduction Production of asexual spores  Sporangiospores: two types ✓Aplanospores lacking flagella ❖ Rhyzopus stolonifer Leila Geagea, PhD 21 Leila Geagea, PhD 22 Reproduction of fungi  Asexual reproduction Production of asexual spores  Conidia ✓ produced by 95% of fungi and carried by conidiophores Leila Geagea, PhD 23 Reproduction of fungi  Asexual reproduction Production of asexual spores  Conidia ✓ hyaline or ✓ dark color ✓ unicellular or ✓ multicellular Leila Geagea, PhD 24 Reproduction of fungi  Asexual reproduction Production of asexual spores  Conidia ✓ Conidiophores can be ❖distinct based directly on mycelium ❖ in acervuli ❖ in pycnidia Leila Geagea, PhD 25 Leila Geagea, PhD 26 Reproduction of fungi  Sexual reproduction It represents the genetic recombination and produces the survival structures. It is an alternation between haploid and diploid state. It produces 4 types of spores.  this will lead to 4 main classes of fungi. Leila Geagea, PhD 27 Reproduction of fungi  Sexual reproduction Three phases of development  Plasmogamy union of two cytoplasms bringing the nuclei close together and within the same cell. ✓ haploid nucleus of a donor cell (+) penetrates the cytoplasm of a recipient cell (-). Leila Geagea, PhD 28 Reproduction of fungi  Sexual reproduction Three phases of development  Karyogamy fusion of the two nuclei.  formation of a dikaryon: a binucleate cell containing two nuclei from each parent. ✓ the two nuclei fuse to form a diploid nucleus. Leila Geagea, PhD 29 Reproduction of fungi  Sexual reproduction Three phases of development  Meiosis  diploid nucleus gives rise to haploid nucleus. ✓ Sexual spores: some (+), some (-), some recombinants ✓ Four sexual spores used to classify fungi into divisions. Leila Geagea, PhD 30 Reproduction of fungi  Sexual reproduction Oospores  they are produced when two gametes of unequal size fuse: antheridium and oogonium.  they are thick-walled survival structures.  they should remain dormant for a certain period of time before germination.  they are characteristics of Oomycetes. Leila Geagea, PhD 31 Reproduction of fungi  Sexual reproduction Oospores Leila Geagea, PhD 32 Life cycle of Oomycetes Leila Geagea, PhD 33 Reproduction of fungi  Sexual reproduction Zygospores  two cells (gametes) of similar size and appearance unite and produce a zygote.  they are thick walled cells.  they are characteristics of Zygomycetes. Leila Geagea, PhD 34 Life cycle of Zygomycetes Leila Geagea, PhD 35 Reproduction of fungi  Sexual reproduction Ascospores  they are produced within a sac- like zygote cell, the ascus. in each ascus, there are 8 ascospores. ✓ they result from a meiosis followed by a mitosis  they are characteristics of Ascomycetes. Leila Geagea, PhD 36 Reproduction of fungi  Sexual reproduction Ascospores  Asci could be naked inside a fruiting body: ascocarp ✓ apothecium (disc-shaped) ✓ perithecium (flask-shaped) ✓ cleistothecium (spherical) Leila Geagea, PhD 37 Leila Geagea, PhD 38 Life cycle of Ascomycetes Leila Geagea, PhD 39 Reproduction of fungi  Sexual reproduction Basidiospores  they are produced on the outside of a club-like zygote cell called the basidium.  four sterigma are formed  they are exogenous  they are characteristics of Basidiomycetes. Leila Geagea, PhD 40 Life cycle of Basidiomycetes Leila Geagea, PhD 41 Leila Geagea, PhD 42 Leila Geagea, PhD 43 Dissemination  Two types of dissemination Active dissemination  Fungi move by themselves  Movement for only very short distances (a few millimeters or centimeters, perhaps).  Zoospores (as they have flagella). Leila Geagea, PhD 44 Dissemination  Two types of dissemination Passive dissemination  An agent is responsible of the disseminating the fungi  wind, water, birds, insects, other animals and humans.  Movement can occur over long distances. Leila Geagea, PhD 45  Concerning the classification of fungi, we have seen that usually they are classified based on the sexual spores they form.  You have to know that all fungi produce asexual spores but not all produce sexual spores.  The fungi producing asexual spores only are classified under the Deuteromycetes. Leila Geagea, PhD 46 Control of fungal diseases of plants  A combination of measures is usually necessary for the satisfactory control of most diseases.  An integrated approach to disease management and control is a must for most fungal diseases of plants.  Cultural and biological control use of resistant plant varieties; use of pathogen-free seed or propagating stock; destruction of plant parts; destruction of volunteer plants or alternative hosts of the pathogen; Leila Geagea, PhD 47 Control of fungal diseases of plants  Cultural and biological control use of clean tools and containers; proper drainage of fields; aeration of plants; crop rotation; use of microorganisms antagonistic or pathogenic to the fungus causing the plant disease.  Soil treatment solarization, with steam or with fumigants. Leila Geagea, PhD 48 Control of fungal diseases of plants  Chemical control application of fungicides on the plants, on seeds, or into the soil where the plants are to be grown.  Seed treatment treatment of the seed with fungicides that are absorbed and are distributed through the plant or the hot water.  Controlling vectors control of the insect vectors may be helpful or the only available possibility.