ZYGOMYCETES
They have thick walled resting spores called zygospores formed by gametangial coupulation and do not have motile zoospores at any stage of life cycle . Therefore they are also called conjugating fungi .
One of the order under zygomycetes is mucorales . It includes Mucor , Rhizopus etc .
Rhizopus
Class - Zygomycetes
Order - Mucorales
Family - Mucoraceae
Genus - Rhizopus
Rhizopus has branched , filamentous and coenocytic mycelium . Hyphae are stolons , rhizoids and sporangiophores . Asexual reproduction takes place by non-motile sporangiospores ( aplanospores ) and chlamydospores . Sporangium is divided into peripheral cytoplasm and central sterile columella . Peripheral cytoplasm divide to form sporangiospores .
Most of the species of Rhizopus are heterothallic . Sexual reproduction takes place by isogametangial coupulation . Progametangia develops into club shaped isogametangia and suspensor . After gametangial coupulation zygospore is formed . Zygosore contains many diploid nuclei formed by fusion between nuclei of two opposite strains . Unfused nuclei degenerate . Zygospore enlarges , secretes several layers around themself and becomes thick walled . After a long resting period zygospore germinates to form a zygosporangium on sporangiophore . Dipoid nuclei in zygosporangium divide to form haploid meiospores . If coupulation does not take place zygospore develops into azygospore .
Mucor
Mucor has same classification as Rhizopus . Mucor are commonly called pin mould or black mould . They cause mucoromycosis ( a disease of lung and brain ) in domestic animals as well as in humans . In anaerobic liquid cultures especially in the presence of CO2 the hyphae break to form yeast like bodies . This condition is called torula stage . It is a reversible condition . If the O2 is made available it reverts to filamentous stage . A. F. Blakeslee studied the phenomenon of heterothallism in Mucor . Heterothallic species requires two different strains for sexual reproduction .
Differences between Rhizopus and Mucor
1. Mycelium is differentiated ( stolons , rhizoids and sporangiophores ) in Rhizopus but undifferentiated in Mucor .
2. Food material is absorbed by rhizoids in Rhizopus and by entire mycelial surface in Mucor .
3. Sporangiophores occurs in tuft in Rhizopus and singly in Mucor .
Study material for TGT , PGT , CSIR-NET , Assistant Professor , M Sc entrance , Medical entrance etc
OOMYCETES - Peronosporales
PERONOSPORALES
Order Peronosporales is more advanced than Saprolegniales . Some of the families of order Peronosporales are -
1. Pythiaceae - Phytophthora , Pythium
2. Albuginaceae - Albugo
Phytophthora
Class - Oomycetes
Order - Peronosporales
Family - Pythiaceae
Genus - Phytophthora
Phytophthora means plant that causes destruction . Many of the species of Phytophthora are pathogenic . P. infestans causes late blight of potato . Irish potato famine occurred in north europe during 1845 was due to late blight of potato . Symptoms of Phytophthora appear in the form of dark coloured irregular water soaked areas on tips and margins of old leaves . Tuber shows wet rot ( soft tuber ) in humid conditions and dry rot in dry conditions . Low temp. and humid conditions favour the rapid spread of Phytophthora . Mycelium is intercellular in most of the species . They have club shaped haustoria and branched conidiophores.
Pythium
They have similar classification like Phytophthora but mycelium is intracellular in most of the species . P. debaryanum causes dampimg off seedlings in tobaco , tomato , mustard and chillies . In pre-emergence phase of disease the young seedlings are killed before reaching the soil surface . In post-emergence phase stem becomes constricted at the base and finally the plant collapses .
Albugo
Class - Oomycetes
Order - Peronosporales
Family -Albuginaceae
Genus - Albugo
Albugo is also called Cystopus . They usually infect families like Cruciferae , Convolvulaceae , Compositae , Amaranthaceae etc . The most common species is Albugo candida which causes white rust of crucifers . Floral parts become fleshy and hypertrophied ( abnormal growth of infected part ) and the growth of entire plant is stunted . Bordeaux mixture is an inorganic copper fungicide which is effective in controlling white rust of crucifers . Mycelium is aseptate , coenocytic , intercellular and has knob like haustoria . Multinucleate Conidia are formed in Albugo . They develop in basipetal succession and intercalary mucilaginous disc called disjunctor joins successive conidia . Antheridia and oogonia develop side by side , this condition is called paragynous .
Order Peronosporales is more advanced than Saprolegniales . Some of the families of order Peronosporales are -
1. Pythiaceae - Phytophthora , Pythium
2. Albuginaceae - Albugo
Phytophthora
Class - Oomycetes
Order - Peronosporales
Family - Pythiaceae
Genus - Phytophthora
Phytophthora means plant that causes destruction . Many of the species of Phytophthora are pathogenic . P. infestans causes late blight of potato . Irish potato famine occurred in north europe during 1845 was due to late blight of potato . Symptoms of Phytophthora appear in the form of dark coloured irregular water soaked areas on tips and margins of old leaves . Tuber shows wet rot ( soft tuber ) in humid conditions and dry rot in dry conditions . Low temp. and humid conditions favour the rapid spread of Phytophthora . Mycelium is intercellular in most of the species . They have club shaped haustoria and branched conidiophores.
Pythium
They have similar classification like Phytophthora but mycelium is intracellular in most of the species . P. debaryanum causes dampimg off seedlings in tobaco , tomato , mustard and chillies . In pre-emergence phase of disease the young seedlings are killed before reaching the soil surface . In post-emergence phase stem becomes constricted at the base and finally the plant collapses .
Albugo
Class - Oomycetes
Order - Peronosporales
Family -Albuginaceae
Genus - Albugo
Albugo is also called Cystopus . They usually infect families like Cruciferae , Convolvulaceae , Compositae , Amaranthaceae etc . The most common species is Albugo candida which causes white rust of crucifers . Floral parts become fleshy and hypertrophied ( abnormal growth of infected part ) and the growth of entire plant is stunted . Bordeaux mixture is an inorganic copper fungicide which is effective in controlling white rust of crucifers . Mycelium is aseptate , coenocytic , intercellular and has knob like haustoria . Multinucleate Conidia are formed in Albugo . They develop in basipetal succession and intercalary mucilaginous disc called disjunctor joins successive conidia . Antheridia and oogonia develop side by side , this condition is called paragynous .
OOMYCETES - Saprolegniales
OOMYCETES
Oomycetes are characterised by oogamous type of sexual reproduction and the presence of biflagellate zoospores .
Some of the orders of oomycetes are -
1. Saprolegniales - Achlya , Saprolegnia
2. Peronosporales - Phytophthora , Pythium , Albugo
Order Saprolegniales
Saprolegniales are commonly known as water moulds . Moulds mean fungus made up of hyphae ( multicellular filaments ) . They are found in water . Saprolegnia and Achlya grow as parasites on fishes and their eggs . Plasmogamy takes place by gametangial contact ( by fertilization tube ) .
Saprolegnia
Class - Oomycetes
Order - Saprolegniales
Family - Saprolegniaceae
Genus - Saprolegnia
S. parasitica causes salmon disease in fishes . Myceliun is profusely branched and coenocytic . Septa are formed only at the base of sex organs . Hyphae may be rhizoidal and external . Asexual reproduction takes place by biflagellate zoospores .One of the flagellum is of whiplash type and second one is of tinsel type . Zoosores are released through apical pore of zoosporangium . Zoospores are of two types - primary zoospores ( pear shaped ) and secondary zoospores ( kidney shaped ) .Secondary zoospores have lateral flagella . Production of two types of spores is called diplanetism . Primary zoospore encysts and then germinates in to secondary zoospore . Secondary zoospore deflagellates and germinates in to hyphae .
One of the characteristic feature of Saprolegnia is proliferation of zoosporangium . New zoosporangium is formed inside the old zoosporangium (from the septum of first one ) . In some species of Saprolegnia this process is repeated several times .
Antheridia and oogonia develop terminally on the lateral branches of the mycelium . Fertilization takes place by gametangial contact ( by fertilization tube ) . Fertilized egg called oospore germinates to form zoosporangium .
Achlya
Achlya shows similarities with Saprolegnia in classification and in most of the characters . Some of the species of Achlya show polyplanetism . Raper studied the effect of hormones on development of sex organs in Achlya .
CHYTRIDIOMYCETES
CHYTRIDIOMYCETES
Chytridiomycetes mean little pot like fungus . They are most primitive fungi . Some anaerobic chytrids are found in stomuch of cow . Reproductive bodies may be on host surface ( epibiotic ) , within the host cells ( endobiotic ) , single ( monocentric ) or more than one ( polycentric ) . Zoospores are uniflagellate ( whiplash type ) .
Some of the 4 orders are -
1. Chytridiales - synchytrium
2. Blastocladiales - allomyces
Synchytrium
Class - Chytrdiomycetes
Order - Chytridiales
Family - Synchytriaceae
Genus - Synchytrium
Synchytrium endobioticum causes black wart disease of potato . In this disease dark brown , warty cauliflower like excrescences are formed on tuber . Synchytrium is unicellular , holocarpic monocentric fungus .
MYXOMYCETES
MYXOMYCETES
Myxomycetes means fungus with mucus or fungus with slimy nature . They are also known as slime molds . Molds mean fungus made up of hyphae . So slime molds mean fungus made up of hyphae and slimy in nature . They share characters of both animals and fungi . They have holozoic nutrition like animals and bear fruiting stage like fungus . Myxomycetes are called true slime molds . The plant body is a free-living true plasmodium . Plasmodium is multinucleated , irregularly shaped slimy mass of protoplasm . Plasmodium may be of three types -
Myxomycetes means fungus with mucus or fungus with slimy nature . They are also known as slime molds . Molds mean fungus made up of hyphae . So slime molds mean fungus made up of hyphae and slimy in nature . They share characters of both animals and fungi . They have holozoic nutrition like animals and bear fruiting stage like fungus . Myxomycetes are called true slime molds . The plant body is a free-living true plasmodium . Plasmodium is multinucleated , irregularly shaped slimy mass of protoplasm . Plasmodium may be of three types -
1. Protoplasmodium-It is simple and primitive type . At fruiting time it gets converted into a single sporangium .
2. Aphanoplasmodium- It shows network of protoplasmic strings .
3. Phaneroplasmodium- It is fan shaped and shows vein like structures .
Slime molds are found on moist decaying wood , dung , soil etc . Physarales is one of the order under myxomycetes .
Physarum
Class - Myxomycetes
Order - Physarales
Family - Physaraceae
Genus - Physarum
They are found all over the world . P. polycephalum is regarded as good study material for genetic , physiological and biochemical studies . Plant body is phanerolasmodium type ( fan shaped ) . Under unfavourable conditions plasmodia are cleaved into spherules which are then packed as thick walled sclerotia . Under favourable conditions fruiting bodies called sporangia are produced . Sporangia are covered by non-cellular slimy layer called peridium . Capillitium are sterile threads in sporangia for dispersal of spores . Spores germinate to form myxamoebae or swarm cells . These motile cells function as gametes and fuse to form zygote which ultimately form plasmodium .
Physarum
Class - Myxomycetes
Order - Physarales
Family - Physaraceae
Genus - Physarum
They are found all over the world . P. polycephalum is regarded as good study material for genetic , physiological and biochemical studies . Plant body is phanerolasmodium type ( fan shaped ) . Under unfavourable conditions plasmodia are cleaved into spherules which are then packed as thick walled sclerotia . Under favourable conditions fruiting bodies called sporangia are produced . Sporangia are covered by non-cellular slimy layer called peridium . Capillitium are sterile threads in sporangia for dispersal of spores . Spores germinate to form myxamoebae or swarm cells . These motile cells function as gametes and fuse to form zygote which ultimately form plasmodium .
Subscribe to:
Posts (Atom)