Quick viewing(Text Mode)

The Kingdom Fungi: A. Chytridiomycota: Synchytrium, B

The Kingdom Fungi: A. Chytridiomycota: Synchytrium, B

THE FUNGI A. : , B. : , COELOMOMYCES C. : SAKSANAEA, PILOBOLUS,

Dr. Basudha Sharma KINGDOM FUNGI

• Fungi are eukaryotic, unicellular or multicellular non vascular organisms and have a filamentous structure , mesh like structure () except yeast the cells. • Fungi possess a wall made up of and polysaccharides, and store food in the form of starch. • They reproduce by means of spores. • Fungi exhibit the phenomenon of alternation of generation. • Fungi lack chlorophyll and hence cannot perform photosynthesis. • Biosynthesis of chitin occurs in fungi. • The mode of reproduction is sexual or asexual. • Some fungi are parasitic and can infect the host. CHYTRIDIOMYCOTA

• Chytridiomycota is the only among the kingdom Fungi that possesses motile cells at least once in its cycle. • They can be found in terrestrial and aquatic ecosystems • They are morphologically relatively simple and distinguished from other groups of fungi due to the presence of a single on the posterior end. • Most of the members are parasites or grow on organic matter • They do not form colonies of branched hyphae (mycelia) like non- fungi, but produce multinucleate spheroidal bodies referred to as thalli • These spheroidal bodies absorb nutrients from their surroundings, and are transformed into sporangia that release when nutrients become limiting. SYNCHYTRIUM ( WART/BLACK SCAB OF POTATO) Diseased potato tubers appear as dark brown or black cauliflower like outgrowths. Galls or tumours may be formed on aerial parts as well. The parasite thrives in cool and moist climate. India, it has been reported from the Darjeeling district (West Bengal), regions of Himachal and Uttrakhand This can survive for many years (up to 30 years) in the soil in the form of a cyst (survival spores) is a holocarpic endoparasite. It occurs as a parasite in the epidermal cells of the host. LIFE CYCLE OF SYNCHYTRIUM

• There are two different sporangia, the winter sporangia and the summer sporangia • Winter sporangia ( resting sporangia): are mostly spherical, thick-walled, present in small aggregates or crumbs of soil. Summer sporangia: are thin-walled and transparent. Zoospores may be visible within the summer sporangia. • The zoospores have a single whiplash type of flagella Zoospores swell into prosori (aseptate, smooth, thick walled, light golden brown, 40-50 μm in diameter, present at the bottom of the infected cell) and then develop into sorus (spherical haploid, containing 1-9 hyaline, thin-walled summer sporangia, which release zoospores causing new infection sites) • When conditions become unfavourable, zoospores can fuse together forming a zygote. At this point, the host cell containing the zygote does not swell, but divides, forming an outer layer to the winter sporangia • The resting spores induce hypertrophy of the infected tissue resulting in the so-called warts. This tissue will rot down in the soil during the winter months to release the resting spores into the soil. BLASTOCLADIOMYCOTA

• These are aquatic fungi that produce posterior uniflagellate zoospores. • Blastocladiomycota live in freshwater habitats, mud, and soil where they operate as saprotrophs decomposing plant and debris or parasitize • these fungi show an alternation of a haploid gametophytic generation and a diploid saprophytic generation. These also show the presence of mycelia. These are eucarpic with extensive vegetative growth ALLOMYCES

• Allomyces are saprotrophs that form separate haploid and diploid colonies with an unusual morphology. • The thallus is a mycelium which is attached to the substratum called rhizoidal hyphae. The mycelium undergoes dichotomous branching on which the reproductive organs are borne terminally. • Allomyces has an alteration of generation. It spends part of its life as haploid thallus and part as diploid. Haploid and diploid colonies look the same, but when nutrients become limited, the hyphae stop extending and produce different types of reproductive structures at their tips. • Haploid thallus bears male and gametangia. Male and female fuse to form zygote which later forms the diploid thallus. The diploid thallus produces two types of sporangia, megasporangia and mitosporangia. The megasporangia releases zoospores which form the haploid thallus, which later bear gametangia, whereas the mitosporangia release zoospores which undergo asexual reproduction. LIFE CYCLE OF ALLOMYCES COELOMOMYCES

• These are obligately parasitic fungi that have a complex life cycle involving an alternation of sexual (gametophytic) and asexual (sporophytic) generations. As a pathogen of mosquitoes, Coelomomyces has been explored as a biocontrol agent • Coelomomycesis unique among the entomopathogenic fungi in that it requires two different hosts to complete its life cycle. The insect hosts are usually mosquito larvae, while the other are aquatic arthropods (microcrustaceans) such as copepods and ostracods. LIFE CYCLE OF COELOMOMYCES • Life cycle of fungal parasite Coelomomyces dodgei: (A) Biflagellate zygote infects mosquito larva, producing hyphagens, which form hyphae. (B-C) Hyphae form sporangia, which are released after larva dies. (D) Meiospores infect copepod, producing gametophytes (E), each of which forms a (F), which releases gametes. (G) Copepod may contain either male (dark) or female (uncolored) gametes, or both. (H) Garnets fuse, forming zygote ZYGOMYCOTA

• Zygomycota, are true fungi, and produce cell walls containing chitin. They grow primarily as mycelia, or filaments of long cells called hyphae • Zygomycota form hyphae which are generally coenocytic because they lack cross walls or septa. • Unique character of the Zygomycota is the zygospore. Zygospores are formed within a zygosporangium after the fusion of specialized hyphae called gametangia during the sexual cycle. They also undergo a specialized process conjugation Zygomycota typically undergo prolific asexual reproduction through the formation of sporangia and sporangiospores • Zygomycota are arguably the most ecologically diverse group of fungi, functioning as saprophytes on substrates such as fruit, soil, and dung (), as harmless inhabitants of guts (), as plant mutualists forming ectomycorrhizae (), and as pathogens of , , amoebae, and especially other fungi

SAKSANAEA

• Saksenaea was discovered in 1953 by Dr. S. B. Saksena from Patharia forest (Assam) soil of India. • They belong to Mucorales (a group which includes Rhizopus, Mucor, Saksanae) . These organisms are morphologically filamentous with broad, nonseptate hyphae with branches occurring at right angles • Saksenaea vasiformis is an infectious fungus (human pathogen) associated with cutaneous or subcutaneous lesions • Saksenaea vasiformis very rapidly grows in growth media, producing sterile hyphae. Saksenaea is characterised by the formation of flask-shaped sporangia with columellae and simple, darkly pigmented rhizoids. • On maturity the sprorangiospores are released from the sporangia. • Since it is a rare parasitic fungi, much information is not available. REPRODUCTIVE STRUCTURE PILOBOLUS

• These are coprophilous group of mucorales which grow on the dung of herbivores mainly, cow and horse. These shoot their spores out, with great speed to reproduce. • The spores of these fungi only germinate once they pass through a digestive tract, so the goal of the fungus is not to disperse directly to fresh dung, but to vegetation that will be consumed by their counterpart. • These fungi create a water filled subsporangial vesicle that is under a black . The sporangium of this species is much larger than the spores of other fungi, and is covered in calcium oxalate crystals. These hydrophobic crystals help the fungi adhere to moist vegetation as causes the sporangium to flip on to its sticky side. • Once clung to a blade of grass it is consumed by a grazing horse. The environment of the lower digestive system stimulates the sporangium into germination. Unlike other coprophilous fungi, it does not have to search for dung, it already has dung which it can completely colonize and transform it into usable sugars PILOBOLUS • The fungus grows directed towards the light. • The subsporangial vesicle acts as a lens ensuring that the spore are released up in the air unimpeded, instead of directly into the ground FUNGI AS BIOCONTROL AGENTS

• Biological control is the process which decreases the inoculum density of the pathogenic mirobes, present in dormant state by the other microbes. It is involves either the genetically modified microbes which reduce the effect of pests of pathogen and disease. • Species of Trichoderma are used to control root disease of many crops, stem blight of peanuts, dry bubble cotton wilt, and silver leaf of plums, Verticillium to control cotton wilt, Shaperllopsis to control disease on a number of plants, These belong to mycofungicides. • Biological control is an eco-friendly method employed to control the plant disease, with the aim of developing a sustainable system in agriculture • Bacillus subtilius after the harvest but before storage or shipping. This bacterium produces an antifungal metabolite that is toxic to Monilinia fruticolawhich causes brown rot of peach ENTOMOPTHORA

• These are pathogenic fungi belonging to Zygomycetes. It causes fatal disease in flies especially in houseflies and can be used as biocontrol agents. • Dying flies, their bodies riddled by the fungus usually crawl into exposed situations -- where the fungal infection bursts through the insects' exoskeleton and produces tightly-packed masses of sporangiophores • The life cycle of Entomopthora includes a conidial cycle an resting spore cycle. The conidial cycle results in spread of disease, whereas resting spore results in survival in unfavorable condition. Infection is caused due to conidia which attach on to the cuticle of insect and then enter the body of host by forming a penetration tube. The fungi colonizes the abdomen of insect and absorbs the nutrients from the insects body. At this stage the fungi starts producing conidiophores which break the cuticle of the insects body by mechanical force. The condiophores form the primary conidia. These germinate to form secondary conidia which are more virulent then the primary conidia. Some of the primary conidia may form a thick wall and act as resting spore. ENTOMOPTHORA • Germination of multinucleate primary infectious conidia on multiple locations on the host surface, producing hyphae and secondary conidium or multiple secondary conidia • . Infected fly in an intermediate stage of incubation with interior hyphal bodies in insect blood and tissues within the body cavity • . Death grip of actively sporulating cadaver (corpse), fungal conidiophores with young primary conidia emerging from membranous areas of host abdominal cuticle . • Mummified fly cadaver as a potential reservoir for overwintering resting spores. C House fly after most conidial discharge is complete. QUESTIONS

• 1. What are Zygomycetes. Give their salient features. • 2. What are the features of chrytridiomycota. Give their salient features. • 3. Write a note o the black scab of Potato. • 4. What are Blastocladiomycota. Give their salient features • 5. Write a note on Allomyces • 6. Write a note on Coelomyces. • 7. What are biological Control agents. Give few examples of Biological Control agents • 8. What are coprophilous fungi. Write a note on Pilobolus REFERENCES

• http://www.biologydiscussion.com/fungi/synchytrium-endobioticum-symptoms-and-thallus- structure-disease/63189 • https://www.cabi.org/isc/datasheet/52315 • https://www.sciencedirect.com/topics/immunology-and-microbiology/blastocladiomycota • Alexopoulos, C. J. 1966. Introductory . 1st ed. John Wiley and Sons. New York. • http://www.biologydiscussion.com/fungi/allomyces-occurrence-and-life-cycle-fungi/63210 • Federici B A, Fetter-Lasko J, Soares G and Tsao P (1980) Fungi show promise in biological control. California Agriculture • University of Adelaide's Mycology Website. http://thunderhouse4- yuri.blogspot.com/2015/11/saksenaea-vasiformis-complex.html • P. Gryganskyi, Andrii; A. Mullens, Bradley; Gajdeczka, Michael T.; A. Rehner, Stephen; Vilgalys, Rytas; E. Hajek, Ann (2017): Life cycle of Entomophthora muscae infecting a muscoid fly.. PLOS Pathogens. F • "Fungi as biocontrol and its types"[www.researchgate.net.co.in] and [www.angelfire.com] 5."Role of fungi as biocontrol agents"[www.researchgate.com] Thank You

Top View