Self incompatability in plants,pseudoalleles and isoalleles

Inability of a plant with functional pollen to set seed when self-pollinated.
Hindrance to self-fertilization.
Prevents inbreeding and promotes outcrossing.
Reported in about 70 families of angiosperms including crop species.

1. Self-incompatibility in Plants;
Pseudoalleles, Isoalleles
STUDENT COURSE TEACHER
Miss. RUPIKA S Dr. M. KANIMOLI MATHIVATHANA
ID. No. 2017021055 Assistant Professor
Plant Breeding and Genetics
COLLEGE OF AGRICULTURAL TECHNOLOGY
(Affiliated to Tamil Nadu Agricultural University, Coimbatore)
(Accredited to Indian Council of Agricultural Research, New Delhi)
Kullapuram, Via Vaigai dam, Theni-625562

2. What is Self-incompatibility?
Inabilityofaplantwith
functionalpollentoset
seedwhenself-pollinated.
Hindrancetoself-
fertilization.
Preventsinbreedingand
promotesoutcrossing.
Reportedinabout70
familiesofangiosperms
includingcropspecies.

3. HISTORY OF S.I
FirstdiscussiononSIby
Darwin(1877).
SIwascoinedbyStout
(1917).
FirstreportedSIby
Kolreuterinthemiddleof
18
th
centuryinVerbascum
phoenicieumplants.
ReportedSIinflowering
plantsbyEast(1940).
Kolreuter

4. General features of S.I
Preventsselfingandpromotesout-crossing.
Increasesheterozygosityandreduceshomozygosity.
Causesmaybemorphological,physiological,genetical
orbiochemical.
SIcanoperateatanystagebetweenpollinationand
fertilization.
Normalseedsetoncrosspollination.
Inplants,SIisgovernedisofteninheritedbyasingle
gene(S)withmultiplealleles(S1,S2,S3etc,)inthe
speciespollination.

5. CLASSIFICATION OF S.I:

7. Heteromorphic system
Distyly:
Twotypesofstyles(long
andshort)andstamens
(lowandhigh).
SeeninPrimulaceae
family.
InPrimula,thereare2
typesofflowers:
Thrumtype-Hasshort
styleandhighanthers.
Pintype-Haslongstyle
andlowanthers.

8. Thrum and Pin type

9. Heterostyly in Primula

11. Thrum type Pin type

12. Tristyly:
Styleandantherhave3
positions,viz.short,
mediumandlong.
Commoninthefamily
Lythraceae(Lythrum
salicaria).
Controlledbytwo
genes(SsandMm).
S–shortstyle,
sandM–mediumstyle,
Sandm–longstyle.

13. Tristyly

14. Distyly and Tristyly

15. HOMOMORPHIC SYSTEM
Self-fertilizationinhibitiondependsongeneticor
biochemicalorphysiologicalmechanisms.
Mostly seen in crop plants.
Itoccursinvariousways,
•Pollengrainsdonotgerminateonthestigmaofsame
flower.
•Eveniftheygerminate,thepollentubefailsto
penetratethestigma.Eg:Rye,Cabbage,Radish.
•Ifpenetrates,pollentubegrowthretardsorveryslow
rateofpollentubegrowthoccurs.
•Noreleaseofmalegametesfromthepollentube
havingnormalgrowth.

16. Homomorphic S.I

18. Gametophytic S.I
•Governedbygenotypeofpollen.
•Stimaissmoothandwet.
•Pollentubeinhibitioninstyle.
•Pollen-Pistilinteractionisgovernedby
haploidgenomeofeachmalegametes
anddiploidgenomeofpistiltissue
(Haplo-Diplo).
•1
st
discoveredbyEastandMangelsdorfin
Nicotianasanderae.
•Reportedinrye,redclover,whiteclover,
potato,tomatoetc,.

19. Sporophytic S.I
Governedbygenotypeofpollen
producingplant.
Stigmaispapilateanddry.
Pollengermination,tubeentryinhibited
onthestigmaticsurface.
Pollen-Pistilinteractiongovernbygenome
oftheplantonwhichthemaleandfemale
gameteproduced(Diplo-Diplo).
1
st
discoveredbyHughesandBabcock
(1950)inCrepisfoetidaandGerstel
(1950)inPartheniumargentatum.
Reportedinradish,cabbage,cauliflower,
sunflower,cosmosetc,.

20. Mechanism of S.I
Complementary hypothesis:
ProposedbyBatemanin
1952.
S.Iisduetoabsenceof
stimulationbythepistilor
polleninthelike
genotypes(S1S2xS1S2)
whichareessentialfor
pollentubepenetration.
Oppositional hypothesis:
Interactionbetweenlike
alleles,(S1S2xS1S2)leads
toproductionofinhibitor
inpollenandpistilwhich
inhibitsenzymeorauxin,
block pollen tube
membrane,inhibitenzyme
necessaryforpollentube
penetration.

21. Site of Gene Expression
•S.I may express only at three different locations in the
flower;
Stigmatic inhibition:
Inhibition of pollen germination or pollen tube growth
in the stigmatic surface in S.I plant species with
trinucleatepollen (except Oenotherasp.)
Stylarinhibition:
Inhibition of pollen tube growth in the stylarregion
in S.I plant species with binucleatepollen.
Ovarian inhibition: In some species, S.I reaction
occurs only when the pollen tube reaches the ovary.
Reported in Theobromacacao.

22. How to overcome S.I?
Bud pollination
Delayed pollination
Late season pollination
Irradiation
High temperature
Mutilation of style
In vitro fertilization.

23. Utilization in Plant Breeding
1.ProductionofHybrids:S.Ihelpsinhybridseed
productionwithoutemasculationandwithoutresortingto
geneticorCMS.Eg:CommercialhybridsinBrassica
(cabbageandBrusselssprouts)andSunflower.
2.CombiningDesirableGenes:S.Ipermitscombining
desirablegenesinasinglegenotypefromtwodifferent
sourcesthroughnaturalcrosspollination.Ithelpsfruit
growerstoincreaseyieldbyprovidingsuitablepollinators.

25. LIMITATIONS IN S.I
•Verydifficulttoproducehomozygousinbred
linesinaS.Ispecies.
•Affectedbyenvironmentalfactorssuchas
temperatureandhumidity.
•Sometimes,beesvisitonlyoneparentalline
intheseedproductionplotresultinginsib-
mating.Eg:Brusselssprouts.

26. Pseudoalleles
Twogeneswithsimilar
functionslocatedsoclose
tooneanotherona
chromosomethattheyare
geneticallylinked.
Affect the same
character.
GivenbyMorgan(1928)
andLewis(1948).
Pseudoallelicseriesor
complexseries.
Eg:Affectpigmentationin
Drosophila.
Drosophila melanogaster

27. Isoalleles
Analleleconsideredasanormalbutcanbe
distinguishedfromanotherallelebyitsdiffering
phenotypicexpressionwhenincombinationwith
dominantgene.
2types:
Ifthephenotypeiswild,thesearenormalorwild
alleles.
Ifthephenotypeismutant,thesearecalledmutant
alleles.

28. References
PhundanSingh,2015,EssentialsofPlantBreeding,SixthRevisedEdition,
KalyaniPublishers,NewDelhi,Pp:76-87.
SeijiTakayama,HiroshiShiba,MegumiIwano,2000,Proceedingsofthe
NationalAcademyofSciences97(4).
EmmaEGoldberg,JoshuaRKohn,RussellLande,KellyARobertson,
StephenASmith,2010,Science330(6003),Pp:493-495.
SilvaNF,etal.CellMolLifeSci.2001Dec;58(14):1988-2007,Mechanisms
ofself-incompatibilityinfloweringplants,YorkUniversity,Canada.
https://www.sciencedirect.com

29. https://www.biology-pages.info
https://www.merriam-webster.com
Lewis. E. B, PSEUDOALLELISM AND GENE EVOLUTION, 1951, Cold
Spring HarborSymposia on Quantitative Biology, Pp:159-174.
https://hal.archives-ouvertes.fr
https://www.nature.com
https://doi.org/10.1017/S0016672300011459
https://biocyclopedia.com >genetics
www.notesonzoology.com>genetics