PAT 212 L 4-1.ppt pathology pests and diseases

Mode of reproduction of fungi

1. PAT 212
L 4. Mode of Nutrition and
Reproduction of Fungi

2. NUTRITION OF FUNGI
•Fungiarechemoorganotrophs.i.ederiveenergyby
organiccompounds.
•Unlikeanimalswhicharealsochemoorganotrophs,
fungalabsorptionisabsorptive.
•Ingestionisrareandrestrictedonlytotheslime
moulds.
•Fungineedabout17elements.
•Calcium,whichisanessentialmacroelementforgreen
plants,isneededintracesornotatallbyfungi.

3. •Amongmonosaccharides,xyloseglucoseand
fructosesupportgoodgrowthoflargestnumberof
fungi.
•Therearesomefungi,whichdonotutilizeglucose.
•Disaccharides,sucrose,maltose,cellobioseand
lactosearefirstbrokenbyextracellularhydrolytic
enzymesandthecomponentsugarsarethen
absorbed.
•Exceptlactose,otherdisaccharidesaregoodsources
ofcarbon.

4. •Amongpolyaccharides,cellulosedegradationbyfungiis
importantformaintnanceofthecarboncycle.
•Itisapolymerofbetaglucoseunitsjoinedbyb1-4glycosidic
linkages.
•Therearefivetypesofcellulolyticenzymesviz.endoglucanase,
exoglucanase,cellobiase,oxidativecellulases,andcellulose
phosphorylase.
•Thethreemainenzymesendoglucanase,exoglucanaseand
cellobiasebytheirsequential,synergisticandcooperativeaction
bringabouttotalbreakdownofcellulosetobetaglucose.

5. Pecticsubstancethemostcomplex
macromoleculesinnaturearemadeoffive
polyaccharides.
Theseare,
•Galacturonans
•Rhamnogalacturonans
•ArabinogalactanI
•Arabinan
•ArabinogalactanII
•Theyarecollectivelyformthepecticpolymer
structure.

6. •This is a pectic backbone comprising HG
(Homogalacturonans) and RG I (Rhamnogalacturonans)
regions.
•TheRGIbarsseveralsidechainviz.HG,RGII,arabinan,
AGI,AGII,XGAandiscalledhairyregion.
•TheHGiscalledsmoothregion.
•ThetypesofsidechainandtheirarrangementsontheRG
Iregionvarywithpectinsample.
•Pectolyticenzymesdegradethehomogalacturanani.ethe
“smoothregion”ofthepecticmacromolecule.

7. •Theenzymesarebroadlyclassifiedintotwobroad
categories,thechainmodifyingenzyme(PME)andchain
splittingordepolymerizingenzymes(glycosidasesand
lyases).
•PMEhydrolyticallyremovesthemethylgroup.
•Chainsplittingenzymesbreaktheα-1,4glycosidicbonds,
formingsmallerfragments,andultimatelyreleasing
galacturonicacidresidues.
•Theirnomenclatureisbasedonthepreferenceofthe
substance(pectinorpecticacid)andsiteofsplit.

8. •Starchisagoodcarbonsourceformajorityoffungiandis
oftenbetterthanglucosepossiblyduetothepresenceof
someglucosefactors,thatusuallyaccompanysomenative
starch.
•Itisacomplexpolymermadeofalphaglucoseunitsandcan
alsobesaidtobemadeofmaltoseunits.
•Itconsistsofunbranchedportion,amylose(20-25%)andrest
ofbranchedportionamylopectin.
•Therearetwotypesofextracellularenzymesthatdegrade
starch,αandβamylase.

9. •Thealphaamylaseattackstheglycosidiclinkage
randomlytoproduceshorterchains,arecalled
dextrins.
•Whilebetaamylaseactsterminallyreleasing
maltose.
•Maltoseisthenacteduponbymaltasereleasing
glucose.
•ChitinthepolysaccharideofN-acetylglucosamine
unitsisdegradedbyanextracellularchitinase.

10. •Fattyacidsaregenerallyutilizable,butaretoxictosome
fungi.
•However,LeptomituslacteusandApodachlyasp.which
failtogrowonsugars,includingglucose,utilizesfatty
acidsavidly.
•Cutinthemaincomponentofcuticleofplants,isa
polymerofC16andC18hydroxyfattyacidsjoinedby
esterbondsandsomeperoxidebridgesandether
linkages.
•Thesearedegradedbycutinesteraseandcarboxincutin
esterease

11. •Theformerhydrolysestheesterbondsreleasing
monomersC16andC18hydroxyfattyacids,whilethe
latterhydrolysestheperoxidegroup.
•Fungiderivetheirnitrogenrequirementsfrominorganic,
aswellas,organicsources.
•Fungiusuallyderivetheirsulphurrequirmentsfrom
sulphateions.
•Phosphorous,potassiumandmagnesiumaretakenin
organicform.
•Calciumisrequiredintracesornotatall.

12. •Vitaminrequirementsoffungiareonlyforwater
solublevitamins.
•Eg:vitaminsofBgroup(vitaminB1orthiamine,B2
orriboflavinandB6orpyridoxine)andvitaminH
(biotin).
•Mostcommondeficiencyisforthiaminefollowed
bybiotin.
•Thedeficiencyismorecommoninyeasts.
•Fungirarelyneedsexternalriboflavin,ascorbic
acidandfolicacid.

13. •Fungiareusedastestorganismsforbioassayof
vitamins.
•Phycomycesblakesleeanus,andPhytoiphthora
(allspecies)areusedasbioassayofthiamine
pyridoxineandpantothenicacidassayemploys
Saccharomycescarlsbergensis.S.cerevisiaeis
usedfortheassayofbiotin.

14. TYPES OF PARASITISM
•Therelationshipbetweentheparasiteandthe
hostiscalledasParasistism.
•Basedonthesourceofnutrition,thefungimay
beclassifiedas
•Parasites
•Saprophytes

15. PARASITES
•Parasites may be classified as
1.Obligateparasites
2.Facultativeparasites
3.Facultativesaprophytes
1)Obligateparasites
•Theseareparasiteswhichcannotbegrpwnon
deadorartificialfoodandneedlivinghostto
completetheirentirelifecycle.
–It is also called biotrophs. Eg. Rusts, Mildews, Viruses.

16. Hemibiotrophs.
Thesepathogensattacklivingtissuesandgrowsinoron
theminthesamewayasthatofbiotrophsthetissueisdead
butcontinuetogrowandreproduceafterthetissueisdead.
Eg.Leafspottingfungi.
1)Ectoparasite.
Theparasitemaybeliveontheexternalsurfaceofthe
host.Eg.Erysiphepolygoni.
2) Endoparasite
Theparasitesmaygrowinsidethehostcell(intracellular)
orinbetweenthecells(intercellular)ofthehostplantand
drawnutrition.Eg.Leveilullataurica

17. 3) Destructive parasite
Thosewhichdrawnutritionfromthehostand
oftendestroyorkillthehostarecalleddestructive
parasite.
•Eg.Rootrot,wiltcausingpathogens
4)Balancedparasites:
Thosewhichdrawnutritionwithout
killingthehostaretermedasbalancedparasite.

18. Saprophytes
Anyorganismslivingondeadorganic
matter.
Facultativeparasites.
Thesearetheorganismswhichareusually
saprophyticintheirmodeoflifebutundercertain
conditionstheybecameparasites.
Eg:Pythium,Fusariumetc.

19. Facultative saprophytes:
Thesearetheorganismswhichareusually
parasitesintheirmodeoflifebutundercertain
conditionstheybecamesaprophytes.
Eg:Smuts,Phytophthora,Venturiainaequalis,
Sphacelothecasp.
Necrotrophs:
Aparasiteiscallednectrotrophwhenitkills
thetissueinadvanceofpenetrationandthen
livesaprophytically.Alsocalledperthotrophs.

20. •Theyaresocalledlessspecializedparasitewhichcan
causeimmediateandseveredamagetotheirhost
tisssue.
•Eg:Sclerotiumrolfsii,Venturia,Claviceps,
Phytophthora.
SYMBIOSIS
•Therelationshipoftwodissimilarorganismslivingtogether
incloseassociationformutualbenefitsalsocalled
mutualism.
•Eg: lichens –close association of fungus and algae.

21. Three typs of mycorrhizas.
Ectomycorrhiza–eg.Amanitasp,Boletussp,
Psiolithustinctorius,Marasmiusscorodonius
Endomycorrhiza–VAM(vesiculararbuscular
mycorrhiza)
Ectendomycorrhiza –Endogonesp,
Gigasporasp,Glomussp,Acaulosporasp,
Gigasporamargarita,Glomusmosseae,Glomus
fasciculatus.

22. •Inallthethreetypes,thehyphaeofthe
fungalsymbiontspermeatethesoiland
obtainscarceandrelativelyimmobile
nutrientsespesciallyPhosphorousbutalso
Nitrogen,Potassium,Cu,Znandsupply
moreeffectivelytotheplantsthentheroot
hairsoftheconcernedplant

23. Synergism
Theabilityoftwokindsoforganismstogrowbetteror
producegreatereffectconjointlythaneitheronecouldalone.
Eg.DiplodianatalensisandColletotrichumgloeosporioides
togetherproducemuchgreatereffectoncitrusbarkthaneither
oneofthepairalonecanproduce.
Commensalism
Incommensalismoneofthepartnerprofitsliving
togetherwithasecondspecies,butthelatterreceivesneither
goodnorharmfromtheorganismitfavors.
Eg:Penicillimdigitatumisresponsibleforthestimulation
ofthefungusDiplodianatalensisincitrus

24. •Amensalism
Amicrobialcommunitysupportshighdensityof
dissimilarpopulationsthatarecharacterizedby
interactionsdetrimentaltomanyoftheinhabitant.
ThisprocessiscalledAmensalism.
Eg:Whenureafertilizerappliedtothesoil;the
soilinhabitantfungiconvertitintoammoniawhich
resultsinanincreasedpH.Ammoniaisfurther
oxidizedintonitritewhichinturnchecks
populationofFusariumoxysporum

25. Reproduction of Fungi

26. Fungi
Thallus: Vegetative body of the fungus. It
consists of elongated continuous tubular or
hallow filamentous structure. This individual
filament is called Hypha
Mycelium: Collection of hyphal bodies are
called mycelium
Septate mycelium
Aseptate or Coenocytic mycelium

27. Types of mycelia
•Intracellular Intercellular
Phytophthora
Pythium

28. Reproduction
•Vegetative –modification of hyphal cell or
mycelium
•Asexual-No union of male and female
gametes
•Sexual-Union of male and female
gametes

29. Sexual reproduction in fungi
Union of two nuclei consists of three phase
Plasmogamy:Fusionoftwoprotoplastwhich
bringstwohaploidnucleiclosetogetherinthe
samecell
Karyogamy: Fusion of two nuclei
It follows plasmogamy immediately
In many fungi, this pahse is delayed which results
in the formation of dikaryon
Meiosis and follows nuclear fusion

30. Sexual spores
•Fusion of male and female gametes of opposite
sex
•functions as resting spores
•Pass through dormant period before germination
•Oospores, Zygospores, Ascospores, Basidispors

31. Monoecious Vs Dioecious
•Monoecious: Both sexes occur in same thallus
•Dioecious: Sexes occur in different thalli

32. Homothallic Vs Heterothallic
•Homothallic :Every thallus is self fertile and
can be reproduced by itself
•No dioecious fungi can be homothallic
•Eg: Volvariella volvaceae
•Heterothallic: They are self sterile and Two
separate thalli are required for sex reproduction
•Eg: Mucor, Rhizopus

33. Gametes vs Gametangia
•Sex cells are called gametes and mother cell is
called gametangia
•Isogametes (when the male & female gametes
look alike)or isogametangia
•Heterogametes or heterogametangia (when the
male & female sex organs look distinctly
different)
•Heterogametes: Male : Sperm ; female: Egg or
oosphere
•Heterogametangia: Male : Antheridium
Female : Oogonium

34. Methods of sexual reproduction
1.Planogametic conjugation
2.Gametangial contact
3.Gametangial copulation
4.Spermatization

35. 1. Planogametic conjugation
•Male and female gametes are motile
•Common in aquatic fungi
•Iso planogametic conjugation:
morphologically similar gametes fused together
•Eg: Synchitrum endobioticum

36. 1a. Isoplanogametic conjugation

37. 1b. Anisoplanogametic conjugation
•morphologically dissimilar gametes fused
together
•One is small and
another is big
Eg: Allomyces

38. 1c. Heterogamous planogametic
conjugation
•Female : Non-motile gametangium
•Male : Motile gametes which migrates and
conjugate
•Eg: Monoblepharella

39. Planogametic conjugation

40. 2. Gametangial contact
•Gametes reduced to undifferentiated protoplast and
they are not released outside
•Two gametangia of opposite sex come in contact
•One or more gamete nuclei from male gametangium
migrate into female gamatangium through
fertilization tube or pores
Eg: Pythium aphanidermatum, Erysiphe polygoni

41. Gametangial contact

42. Gametangial contact-Pythium

43. Gametangial contact-Erysiphe

44. 3. Gametangial copulation
•Two gametangia completely fuse with one
another
•Entire content is fused
•Mucor, Rhizopus

45. 4. Spermatization
•Spermatia carried by wind or insect or water
fused with receptive hyphae of female
gametangium
•Spermatia: minute, uninucleate, non motile spore
like male structures
•Puccinia graminis var tritici -Wheat rust

47. 5. Somatogamy
•No sex organs are produced
•Somatic cells function as gametes
•Ascomycotina ; Basidiomycotina fungi

48. Fructifications and fruiting bodies
Asexual fruiting bodies
1.Acervulus/ Acervuli
Saucershapedasexual
fruitingbodycontainsshort
conidiophoreswhichbear
singlecelled,hyalinesickleor
cylindricalshapedconidiaand
conidiophoresareintermingled
withblacklonghairlike
structurescalledsetae
Eg.Colletotrichum
Produced by mitosporic
fungi of the form order
Melonconiales
(Deutromycota
Coelomycetes)

49. 2. Pycnidium
Asexualfruiting body
produced by mitosporic
fungiin the form order
Sphaeropsidales
(Deuteromycota,
Coelomycetes). It is
often sphericalor
inversely pearshaped
(obpyriform) and its
internal cavity is lined
with conidiophores.
Macrophomina
Phoma
Phomopsis
Botryodiplodia
Diplodia

50. 3. Sporodochium/ Sporodochia
A small, compact
cushion like structure
produced by mitosporic
fungibelongs to
Tuberculariales
(Deuteromycota,
Hyphomycetes). This
stromabears the
conidiophoreson
which conidiaare
formed
Eg: Fusarium

51. 4. Synnemata or coremium
•Compact or fused,
generally upright
conidiophores, with
branches and spores
forming a headlike
structure
•Eg: Arthrobotryum

52. Sorus
•Spores or sporophores
are grouped into large
masses or clusters which
may be naked or covered
by host epidermis
•Eg: Puccinia , Uromyces
Hemileia

53. Sexual fruiting bodies
Sexual fruiting bodies produced by
Ascomycotina and Basidiomycotina fungi
Ascomycotina: Ascocarp
Basidiomycotina: Basidiocarp

54. Types of Ascocarp
1. Perithecium
•Asci are enclosed in a flask shaped fruiting
bodies with ostiole
eg. Claviceps,
Ceratocystis

55. 2. Cleistothecium
•Completely closed ascocarp
•No ostiole
•Asci are scattered ( Penicillium) or arranged
basally ( Erysiphe)

56. 3. Apothecium
•Open disc like ascocarp with concave or convex
structure
•Sclerotinia sclerotiarum

57. Ascostroma
An ascocarpresembling a
peritheciumbut whose
asciare not regularly
organised into a
hymeniumand are
bitunicate, having a
double wall which
expands when it takes up
water and shoots the
enclosed sporesout
suddenly to disperse
them
Venturia inaequalis

58. Basidiocarp
Large fruiting body of
the basidiomycotina
fungi in which
basidiospores are
produced on a club
shaped basidium.
Mostly epigeous and
rarely hypogeous
Epigeous: Mushroom
and bracket
Hypogeous: Truffles

59. Epigeous
Bracket Mushroom

60. Hypogeous-Truffles