Kingdom Fungi and PhytoPathology – A Unique Perspective

Fungi are small, generally microscopic, eukaryotic, usually filamentous, branched, spore-bearing organisms that lack chlorophyll. Fungi have cell walls that contain chitin and glucans (but no cellulose) as their skeletal components.

OUTLINE OF THE TOPIC

a) Introduction
b) Phylum Chytridiomycota
c) Phylum Zygomycota
d) Phylum Ascomycota
e) Phylum Basidiomycota
f) Phylum Oomycota
g) Phylum Hypochytriomycota

h) Phylum Labirynthiomycota

i) Phylum Plasmodiophoromycota

j) Phylum Dictyosteliomycota

k) Phylum Acrasiomycota
l) Phylum Myxomycota

m) References
n) Read more…
o) You May Also Like to Read…

Alexopoulos et. al., 1996 has divided Kingdom Fungi into following phyla;

1) PHYLUM CHYTRIDIOMYCOTA

 

Spore producing Bodies: Zoosporangia (asexual), Oogonia (sexual – female repoductive part)

 

Types of Spores: Zoospores (asexual), Oospores (sexual)

Host range: vascular plants, mosses, phytoplanktons, VAM fungi, Ascomycetes, Basidiomycetes.

Examples: Synchytrium endobioticum causes Potato wart diseases.

Physoderma maydis causes Physoderma brown spot of corn.

Olpidium is vector of at least 6 viruses including tobacco necrosis virus and lettuce big vein virus.

2) PHYLUM ZYGOMYCOTA

Spore producing Bodies: Zygosporangia (sexual), Sporangiola (asexual; smaller sporangia), Sporangia (asexual)

Rhizopus Stolonifer

Types of Spores: Zygospores (sexual), sporangiospores (asexual)

Host range: vascular plants, mosses, mushrooms. (weak endoparasites)

Diseases: Rhizopus and mucor are common bread mold cause soft rot of fleshy fruits, vegetables, flowers, bulbs, corms and seeds.

Examples: Rhizopus stolonifer casuses Soft rot of sweet potato.

Choanephora cucurbitum causes Choanophora wet rot of squash.

3) PHYLUM ASCOMYCOTA

Spore producing Bodies: Ascus (sexual), Conidiophores (asexual; conidiogenous cell bearing hyphal branches)

 

Types of Ascocarps (sexual fruiting bodies):

 

 

• Naked Asci
• Cleistothecium (rounded, globose ascocarp)
• Perthecium (pear-shaped ascocarp)
• Apothecium (saucer-shaped ascocarp)

Types of Spores: Ascospores (sexual), Chlamydospores (asexual), Conidia (asexual), Soredia (in lichens; vegetative propagules)

Parasexual life cycle is an exception in Aspergillus nidulans.

Host range: crop plants, timber plants and ornamental plants.

Diseases:

• Capnodium casuses sooty mold on plants. it is not parasitic but live off the honey dew particles left by aphids, insects, etc.
• Taphrina cause leaf, flower and fruit deformations in stone fruits and forest trees such as leaf curl in peach and nectarin, leaf curl and Witches’ broom on cherries, Plum pocket on plums, and leaf blister of oak.
• Cochilobolus sp cause various leaf spots, blights and root rots of most cereals and grasses
• Mycosphaerella graminicola causing Septoria leafspots of cereals
• Alternaria cause leaf spots, blights, damping-off of seedlings, stem-rots, tuber and fruit rots of onions, cucurbits, cherry, sour cherry; core rots of apple, and rots of lemons and oranges.
• Cercospora leaf spots of various shapes and sizes are common on almost all plants including grasses, many field crops, vegetables, ornamentals and tree. Cercospora early blight of celery, leaf spots of beets and peanuts, leaf spots of beans and soybeans; gray leaf spots of corn are very common and severe.
• Bipolaris oryzae cause brown spot disease of rice.

Anthracnose: Diplocarpon, Discula, Elsinoe and Gnomonia cause anthracnose in strawberry, dogwood, grapes, and walnut and many forest and shade trees respectively.

Stem and Twig Cankers: cankers of different plants are caused by Ascomycetes are:

• Botryosphaeria dothidea cause on apple, peach, almond, pecan.
• Fusarium circinatum, causes pitch canker of pines.
• Nectria galligena on apple, pear and many forest trees.

Powdery mildews: of various plants are caused by different pathogens;

• Blumeria, B. graminis cause powdery mildew of cereals and grasses
• Erysiphe, cause in Begonia, Chrysanthemum, and cucurbits
• Levillula taurica on tomato
• Microsphaera, M. alni cause on many shade trees and ornamental plants
• Oidium neolycopesicum causes in tomato
• Phyllactinia spp. cause in shade and forest trees
• Podosphaera, P. leucotricha cause in apple, pear and quinch; P. oxyacanthae on apricot, cherry, peach and plum and P. xanthii on cucurbits
• Sphaerotheca, S. macularis on strawberry; S.mors-uvae on goose- berry and currant; S.pannosa on peach and rose and S. fuligena on sugar beets.
• Uncinula necator on grapes,
• Uncinuliella flexousa on horsechestnut.

Fuarium sp.

Examples:

• Ophiostoma novo-ulmi causese Dutch elm disease.
• Blumeria graminis tritici causes Powdery mildew of wheat.
• Pyricularia oryzae cause rice blast disease.
• Fusarium oxysporium cv. lycopersici cause Fusarium wilt of tomato.

 

4) PHYLUM BASIDIOMYCOTA

Spore producing Bodies: Basidium (sexual), Basidiocarp (sexual fruiting body)

Types of Spores: Basidiospores (sexual), Conidia (asexual), Oidia (asexual), Arthrospores (asexual), Urediospores or urediniospores (asexual; similar in function to conidia; in rust fungi)

Host range: Cereals (rusts and smuts), forest and shade trees, timber plants, ornamental plants

 

Diseases: Rusts and smuts are major diseases causing most damage to plants.

 

Rusts: Rust are caused by member of order Uredinales; appear on stem, leaves as orange, yellow, brown or white spots and rupture the epidermis. Some form swellings and galls. These may be caused by;

Puccinia graminis (wheat, and all other small grains), P. striiformis (yellow or stripe rust of wheat, rye, barley), P. triticina (leaf or brown rust of wheat and rye); P. hordei (leaf rust of barley); P. purpurea (sorghum rust); P. sacchari and P. melanocephala (sugar cane rust) and P. stakmani (rust of cotton) and many other.

Smuts: 2nd most destructive diseases after rusts; caused by member of Ustilaginales; 1200 species have been reported; many smuts attack the ovary of grain and develop in them and hence destroy the fruit.

• Ustilago, causing corn smut (U. zeae (= U. maydis), loose smut of cereals (U. nuda, U. avenae and U. tritici) and sugarcane smut (U. scitaminae)
• Tilletia, causing covered smut or bunt of wheat [T. caries = (T. tritici) and T. laevis (=T. foetida)]
• Sphacelotheca, causing the sorghum smuts (S. sorghi, S. cruenta and S. reiliena)
• Urocystis, causing onion smut (U. cepulae)
• Neovossia, causing kernal smut of rice (N. barclayana)
• Entyloma, causing leaf smut of rice (E. oryzae)

Examples:

• Puccinia graminis tritici causes stem rust of wheat.
• Ustilago spp. causes smuts of cereals.
• Armillaria spp. cause root rots of trees and shrubs.
• Ganoderma spp. cause root and basal rots of conifers and hardwoods; in palms and other tropical plantations.
• Polyporus spp. cause heart rot of living trees and rot of dead log.
• Crinipellis perniciosa cause Witches’ broom of cocoa.

 

5) PHYLUM OOMYCOTA

Spore producing Bodies: Zoosporangium (asexual), Oogonium (sexual)

Types of Spores: Biflaellated zoospore (asexual), Oospore (sexual; oogomous)

Host range: vascular plants, agronomically important crops, grasses

Diseases:

• Pythium sp., cause seed-rot, seedling damping-off, root rot of all plants and soft-rots of fleshy fruits in contact with soil.
• Phythophthora sp. cause late blight of potato, root rots, frut rots and blights of many annuals and perennial plants, and roots and stem rots, cankers and diebacks of trees.
• Peronoslerospora, Sclerophthora and Sclerospora causing downy mildew diseases of monocots such as corn, sorghum, and sugar cane.
• Albugo cause white rust disease of cruciferous plants.

Phytophthora infestans

Examples:

• Phytophthora infestans cause Late blight of potatoes
• Plasmopara viticola causes downy mildews of grapes
• Pythium aphanidermatum and P. ultimum cause Pythium blight of turf grasses
• Phytophthora cinnamomi is known to cause diseases in nearly 1000 different species of plant.

6) PHYLUM HYPHOCHYTRIOMYCOTA

[Very small group consists only 23 species]

Spore producing Bodies: Zoosporangium (asexual); sexual reproduction not yet reported.

Types of Spores: Zoospores (asexual)

Host range: parasitic on algae and fungi and saprobic on plant and insect debris

Examples:

• Anisolpidium ectocarpi parasitize a marine algae, Ectocarpus mitchellae.
• Rhizidiomyces apophysatus is parasitic on the oogonia of water mold (Oomycetes) of family Saprolegniaceae and on chrysophyte alga, Vaucheria.

7) PHYLUM LABYRINTHIOMYCOTA

 

(NET SLIME MOLDS)

 

 

Spore producing Bodies: Sporangium (asexual), sexual life cycle not yet defined.

 

Types of Spores: Biflagellate, heterkont Zoospores (asexual; with eye-spots)

Host range: saprobes of organic debris or weak parasites of vascular plants, algae in nearshore or estuarine environments

Examples: Labyrinthula sp. lives in association with an alga in Black Sea.

Thraustochytrium genus was discovered from association with benthic algae.

8) PHYLUM PLASMODIOPHOROMYCOTA

 

(ENDOPARASITIC SLIME MOLDS)

 

 

Spore producing Bodies: Zoosporangium (asexual). Studies regarding nuclear cycle are incomplete.

Types of Spores: Zoospores (asexual)

Host range: necrtoic endoparasites of vascular plants and stremanopiles (a major group of eukaryotes) causing hypertrophy and hyperplasia.

Diseases: Plasmodiophora causeClubroot of crucifers, Polymyxa cause root diseases of cereals and vegetable,

Examples: Plasmodiophora brassicae causes clubroot or finger-and-toe disease of cabbage.

Spongospora subterranea causes powdery scab of potatoes.

9) PHYLUM DICTYOSTELIOMYCOTA

 

(DICTYOSTELID CELLULAR SLIME MOLDS)

 

 

Spore producing Bodies: Sorocarp (asexual; literal meaning = heap fruit)

 

Dictyostelium discoideum

Types of Spores: Macrocyst (sexual), Microcyst (asexual), and Spores produced from different types of sorocarps are also Asexual.

Host range: Dung, soil and decaying plant material

Examples:

• Dictyostelium discoideum is model organism to study cell differentiation.
• Polysphondylium pallidum is also a common Dictyostelid.

10) PHYLUM ACRASIOMYCOTA

 

(ACRASID CELLULAR SLIME MOLDS)

 

 

Acrasis rosea

Spore producing Bodies: Sorocarp (asexual); Studies about sexual life cycle are not complete.

Types of Spores: Microcyst (asexual), and Spores produced from different types of sorocarps are also Asexual.

Host range: dead plants, rotting mushrooms, moist chambers of culture soil

Examples: Acrasis rosea and Guttulina are common.

11) PHYLUM MYXOMYCOTA

 

(TRUE SLIME MOLDS)

 

 

Hemitricha clavata

[also know as; Plasmodial Slime Molds and Acellular Slime Molds]

 

Spore producing Bodies: Sporangia (asexual); Sexual reproduction through zygote formation is reported but detailed study has not been reported.

Types of Spores: Sclerotia (asexual), many kinds of asexual spores are present in different genera.

Host range: Well manicured flowerbeds and lawns especially with wood chips and bark; tropical forests, alpine regions, grasslands, the Arctic and Antarctic, and deserts.

Didymium iridis

Examples:

• Ceratiomyxa fruticulosa is most common slime mold of wooden habitat.
• Didymium iridis and Hemitricha clavata are beautiful slime molds.

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FOOT NOTE:

 

Anamorph: The sexual stage of the life cycle of fungi.

Telemorph: The asexual stage in the life cycle of fungi.

Holomorph: A fungus in all its form either latent or expressed

Pleomorphy: The ability of a fungus to exist in mora than one form producing more than one type of spores.

Heterkont: A condition in biflagellate zoospores where the two flagella are unequal in length, movement or form; espacially one is trailing whiplash and the other is anteriorly directed flagellum bearing flagellar hairs.

Peridium: The outer covering/ wall of any fructification.

Benthic: An ecological region at the lowest level in a water body like lake or ocean.

Estuary: A partially enclosed coastal water body with one or two rivers flowing into it; and with a free connection to open sea.