Albugo

ALBUGO - PLANT DISEASE - FUNGI- MYCOLOGY

1. (CYSTOPUS)
Classification:
Kingdom :Mycota/Fungi
Division:Eumycotina
Subdivision:Mastigomycotina
Class :Oomycetes
Order :Peranosporales
Family :Albuginaceae
Genus :Albugo
By:
DrPBMALLIKHARJUNA
GFGCYELAHANKABANGALORE-64
Infected mustard leaf with white pustules
GFGC Yelahanka 13/11/2022
Ploidy state is controversial : Diploid / Haploid

2. Introduction:Albugoisanobligateparasiticfungalgenus.Itconsists
ofabout45species.Allthesewillinfecthigherplantsandcauseleafspot
/blisterdiseases.Someoftheseare;
Albugocandida:infectsthecrucifers/mustardfamilyandcausewhite
rustdisease(misnomer),aleafspotdiseaseinmorethan300species.
Albugoipomae-panduranae:infectstheplantsbelongingtothefamily
Convolvulaceae
Albugobliti:infectstheAmarantheceaemembers.
Albugooccidentale:infectsspinach-(Spinaceaoleracea,phalak)
Albugoportulacea:infectsPortulacaoleracea
Albugooleracea:infectstheAsteraceaemembers
GFGC Yelahanka 23/11/2022

3. Albugospeciescanbeidentifiedbasedonthehostspecificity,oospore
ornamentationandconidialcharacteristics.
Albugocandidaisthecommonandwidelydistributedfungus,which
infectsthecrucifermembers suchasmustard,cabbage,radish,
horseradishandCapsellabursa-pastoris(Shepardpurse).
Itcauseswhiterust/blisterdiseaseespeciallyontheleaves.
Thisfunguscausestwotypesofsymptoms.Theprimarysymptomswill
occurontheleafsurfaceinthehostplants,indicatingthepredominant
phase/stageofthefunguscalledtheasexualstage.
Whereas,thesystemic(infection)symptomsmayappearatlaterstageas
thehypertrophiedandhyperplasiastructures,appearsastumoursonthe
entireaerialpartsoftheplants(suchasstem,leaves,petiolesandveins)
indicatingthesexualstageofAlbugo.
GFGC Yelahanka 33/11/2022

4. Habit and Habitat:
•Albugocandidais an obligate parasitic plant pathogenthat infects primarily
the leaves and finally spreads into the different aerial parts, especially, the
cortical tissues of the petiole , stem andfloral parts.
Itisanaseptatemycelialformandhighlybranched,siphonlikemycelial
fungus.
Itwillgrowintercellularinthehosttissuesandabsorbsthenutrientsfromthe
hostbyproducingthecharacteristicknoborbuttonshapedhaustoria.
Further,themyceliumiscoenocytic(multinucleate)duetothenocross
septaformationinthehypha.Thecytoplasmwithallcellorganellesmainly
confinedtotheperipheralregion.Itswallismadeofcellulose.
Albugowillundergoboththeasexualandsexualreproductionsoonafter
establishinginthehostvegetatively.
GFGC Yelahanka 43/11/2022

5. The ultrastructure of haustorium
Nuclei
GFGC Yelahanka 53/11/2022

6. Asexualreproduction:isthemostpredominanttypeof
reproductionofAlbugo,thatoccursduringfavourable
conditions.
Itoccursduetotheformationofsporangiospores
Someofthemycelialhyphaeterminaltipsaregoingto
accumulateasapalisadelikestructuresjustbelowthe
lowerepidermisofleaf.
Thesehyphaetipswillprotrudeverticallyastheclub
shapedconidiophores/sporangiophores duetothe
accumulationofmorenutrientsandnuclei.Further,theyare
withthicklateralwallsandthinapex.
Theterminaltipofeachsporangiophoreproducesabulged
structure,whichmetamorphosesintoasporangium.
The developmental
stages of sporangia
GFGC Yelahanka 63/11/2022

7. VS of mustard leaf showing the asexual reproduction of Albugo
In the permanent slide under microscope
micrograph
GFGC Yelahanka 73/11/2022

8. Both these structures create pressure over the leaf lower epidermis, and
hence ruptures, so as the tuft of club shaped sporangiophoresalong with
the sporangial chains is being exposed.
Thetipofsporangiophoreiscontinuouslyproducesporangia,andhence
thesearearrangedintheformofachaininanbasipetalmanneri.e,the
earliest(older)sporeatthetipandyoungoneatthebase.
Allthespores/conidiaarecolourlessandmultinucleate.Further,theyoung
sporesarespheroidalwhilethematuredsporesarehexagonalinshape.
In-betweentheseconidia,therewillbehygroscopicintercalarydiscs
calleddisjunctors,whichhelpinthesporedispersal.
Thematuredsporangia/conidiaaregetdetachedfromtheconidialchain
andtherebygerminateonthesameleafordifferenthostplant.
GFGC Yelahanka 83/11/2022

9. Thegerminationofthesesporangiaisoftwo
typesbasedonavailabilityofwater/moisture
content.
Usuallyunderfavourableconditions(sufficient
water)eachsporangium willproduce8
zoosporesduetocytokinesis.
Eachzoosporeissmall,motile,biflagellate
(heterokont),nakedanduni-nucleatestructure.
Whereas,underunfavourableconditionsrarely
thesporangia directlygerminates and
establishesthedaughtermycelia.
Theentireasexualreproductioniscompleted
within10days. The germination of Sporangium
Zoospore
GFGC Yelahanka 93/11/2022

10. Sexualreproduction:inAlbugooccursduringunfavourableconditions
liketheendofhostseason.
Thisprocessoccursinthehostplantdeepertissueslikethepetiolaror
thestemcortex,whichisindicatedbythehypertrophied(tumour)
structure.
SexualreproductioninAlbugoistheOogamous andgametangial
contact.Further,itisaeucarpic,andthehomothalial or
heterothalialfungus.
Antheridium ismalesexorgan,whichisatubularorclubshaped
structure.Further,itisalongslenderandmultinucleate(6-8)structure,
richwithnutrients.
Oogonium isthefemalereproductivestructure.Itisalargeand
conspicuousglobularstructurewithdistinctPeriplasmandOoplasm.
GFGC Yelahanka 103/11/2022

11. TheOoplasmispresentatthecentrewithdensecytoplasmandeggnucleusand
othernuclei.
Whereas,theperiplasmisavacuolatedcytoplasmthatsurroundstheooplasm.
Theantheridiumandoogoniumusuallyproducedbythetwodifferentindividual
myceliaandlayside-by-side(Perigynous)ortheantheridiumsurroundsthe
oogonium.
Thefertilizationtakesplaceduetothegametangial contact.Bothsexorgans
undergomeiosisandproducehaploidnuclei.
Theantheridiummakesacontactwiththeoogoniumatreceptivepapilla.
Further,theantheridiumpenetratesintotheoogoniumbyproducingthe
fertilizationtube.
Meanwhile,somevisiblecytologicalchangesoccursintheOogonium.Twodistinct
regionsdevelopsnamelythevacuolatedperiplasmandthemultinucleateddense
cytoplasminthecentrecalledOoplasm.GFGC Yelahanka 113/11/2022

12. Thecentreoftheooplasmisdenser
and multinucleated structure
generally referred as the
coenocentrum.
Thetipofthefertilizationtube
rupturesandthefunctionalmale
nucleusandsomeamount of
cytoplasm dischargedintothe
oogonium.
Themalenucleusfuseswiththe
oneeggnucleuscalledOogamy
andproducesadiploidoospore
(zygote). The sequential events occurring in the sexual reproduction
of Albugo
Gametangial
contact GFGC Yelahanka 123/11/2022

13. Theoosporeisadiploid,restingspore
withtrilayerthickwall,darkbrownin
colour,spheroidalandhighlyresistant
structure,usuallyfoundinthesoilor
infectedplantdebris.
Duringfavourableconditionseach
oosporewillundergomitoticdivisionsin
ordertoproduce32to64zoospores
(reniformandbiflagellate).
Thesesporesgerminateonthesuitable
hostplantanddevelopsintoindividual
Albugo.
Resting
Oospore
GFGC Yelahanka 133/11/2022

14. The life cycle of
Albugo
Asexual
Sexual
Diplobionticlife cycle
GFGC Yelahanka 143/11/2022