Heterothalism in fungi

Heterothallic species have sexes that reside in different individuals. . The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism.

1. Dr. Rachana Choudhary
Department of Microbiology
Shri Shankaracharya MahavidyalayaJunwani, Bhilai

2. Synopsis
1.Introduction
2.Brief History
3.Types of heterothallism
A. Morphological Heterothallism
B. Physiological heterothallism
a. Two-allele heterothallism
b. Multiple-allele heterothallism
i. Bipolar multiple-allele heterothallism
ii. Tetrapolar multiple-allele heterothallism
iii. Octapolarmultiple-allele heterothallism
4.Heterothallism in Lower Fungi
5.Heterothallism in Higher Fungi
6.References

3. Introduction
•Inafungalspeciespresenceofhyphaeoftwodifferent
matingtypesi.e.(+)&(-)strainisknownas
heterothallic&thephenomenonisknownas
heterothallism.
•ItderivedfromtheGreekwords-heteromeansotheror
different&thallusmeansshootorthallus.
•Thehyphaearemorphologicallysimilarbut
physiologicallydifferent.
•Therearenodifferencebetweenthemyceliumofmale&
female.Theyperformdifferenceonlyintheirsexual
behavior.

4. Hyphae(+)
Hyphae(-)
Zygospores
(Zygosporangium)

5. Brief History
•Thetermheterothallismisfirstproposedbythefamous
scientistBlakeslee(1904).Onthebasisofhisexperiments,
hesuggestedthatsomemembersoffungiaremonoecious
(homothallic)&whileothersaredioecious(heterothallic).
•Inheterothallicspeciesfusiontakesplacebetweenhyphae
oftwooppositestrainswhichismorphologicallysimilarbut
physiologicallydifferent,suchtypearecalled(+)&(-)
strainsofhyphae.
•Dodge(1920)inAscomycetesanystraincanmale&female
branches.Craigie&Buller(1941)speciesof
Hymenomycetes&Gastromycetesareofbothtypesi.e.
homothallic&heterothallc.WhiteHouse(1951)two
strainsarealsofoundinSmutswhichrepresents
heterothallism.

6. Types of heterothallism
Morphological Heterothallism Physiological Heterothallism
Two-allele Heterothallism Multiple-allele Heterothallism
Bipolar TetrapolarOctapolar

7. Types of heterothallism
1.MorphologicalHeterothallism
Itmaybedefinedastheconditionwhen
morphologicallydifferentmale&femalesexorgansare
producedintwocloselyassociatedmycelia.
Thetwosexorgansorgametesaresomorphologically
differentthatitiseasiertotermoneofthemasmale&
theotherasfemale.
Example-Achlya ambisexualis, Blastocladeia
variabilis,Phytophthoraparasiticaetc.

8. •Inthis,theinteractingthallidifferinmatingtypeor
incompatibility,irrespectiveofthepresenceorabsence
ofthesexorgansorgametes.
•Thismeansthatsexualreproductiontakesplacebytwo
morphologicallysimilarbutphysiologicallydifferent
hyphae.
A.Two-alleleHeterothallism
•Whenthenucleiofboththematingtypesaredifferent
ingeneticcharacters,isknownasTwo-allele
heterothallism.
•Inthesetypecompatibilityisgovernedbyapairof
allelesrepresentedby(A)&(a)locatedatsinglesame
locusofchromosome.
•Duetothedominanceof(A)over(a),(A)is
representedby(+)&(a)by(-).
2. Physiological Heterothallism

9. Mucormucedo
Pucciniagraminis

10. •In this type, one or more than two alleles determine the
sexual compatibility.
•This may be located at one or two loci, because of the
larger number of alleles involved inthistype of
heterothallism.
I.Bipolar Multiple-allele heterothallism
•This type of heterothallism is controlled by multiple
alleles at a single locus, instead of a pair of alleles.
•For example, if the locus is named as (L), the multiple
alleles will be designed as (L1,L2,L3,L4,….Ln) & these
are present on the single locus (L).
b. Multiple allele Heterothallism

11. N
N
N
N
C C C
C C C
C C C
C C C
L1 L2
L
L3 L4
L1
L2
L3
L4
Fig.-Bipolar Multiple-allele Heterothallism

12. •This type of heterothallism is characteristic of
Basidiomycetesexcept rusts.
•Multiple-allele-the compatible factor is present on two
loci (L1) & (L2) of two chromatids of chromosome.
•It can be represented as (A1B1) & (A2B2).
ii) Tetrapolar Multiple-allele Heterothallism

13. N
N
N
N
NFC NFC
NFC NFC
NFC NFC
NFC NFC
C
C
C
C
A1B1
A1B1
A2B2
A2B1
A2B2A2B1
A1B2
A1B2
Fig.-Tetrapolar Multiple-allele Heterothallism

14. iii) Octapolar Multiple-allele Heterothallism
•In this type of heterothallism,thereis only
one report of the occurrence of octapolar
heterothallism in Basediomycetousfungus.
•In these fungal incompatibility is controlled
by three factors (A,B,&C)

15. Heterothallism in Lower Fungi
•In this, the zygospores (zygosporangium) germinates
after a rest period & form a germ sporangium.
•In mucoralesgenerally the heterothallism is occurs in
the member of the family Mucoraceaelike-Mucor
mucedo, Rhizopus stolonifers.

16. Mucor
Systematic Position
Kingdom –Fungi
Group –Eumycota
Division –Zygomycota
Sub division –Zygomycotina
Class –Zygomycetes
Order –Mucorales
Family –Mucoraceae
Genus –Mucor
Occurrence –They occurs in bread& sugary substance
like-jam , jelly. It is saprophytic which is occurs on rotten
fruit, vegetable & organic food material & also on bread &
syrup.

17. Fig. Vegetative structure of Mucor
•Vegetative structure

18. Reproduction
•Vegetative reproduction –It takes place by
the mean of fragmentation.
•Asexual reproduction
a)By Oidia
b)By Chlamydomonas
c)By spores
•Sexual reproduction

19. Asexual reproduction
By Chlamydomonas By Oidia

22. Heterothallism in Higher Fungi
•In higher fungi the heterothallism occurs in the
members of the family Ascomycetes.
•In ascomycetes the mating systems are regulated
with much greater precision than lower fungi.

23. Puccinia
Systematic position
Division-Eumycota
Sub division-Basidiomycotina
Class-Basidiomycetes
Sub class-Heterobasidiomycetes
Order-Uredinales
Family-Pucciniaceae
Genus-Puccinia
species-graminis
Occurrence –The members of this family are autoecious &
heteroecious & are mostly polymorphic, which causes black
rust disease in wheat crop.Theymainly occurs in wheat &
cereals crops.

27. References
•Botany-Fungi -VashistaB.R. & Sinha A.K.
•Textbook of Microbiology by R.P.Singh.
•Textbook of Microbiology by R.C. Dubey &
Maheshwari.
•Textbook of Botany by Dr. Y.D.Tyagi.
•www. Google.com

28. THANK YOU