$Self incompatibility

Self incompatibility

1. Assignment
Subject : Advanced Plant Breeding System (GPB903)
Presented by: Mr. Indranil Bhattacharjee
Student I.D. No.: 17PHGPB102
Presented to : Prof. (Dr.) S. Marker

Sam Higginbottom University of Agriculture, Technology &
Sciences
Allahabad-211007
Self Incompatibility

2. Introduction

•The term first coined by Stout in 1917
•Koelreuter in the middle of 18
th
century, first reported
self incompatibility in Verbascum phoeniceum plant.
•Later on many scientists reported self incompatibility
in flowering plant.
•This has been reviewed by several workers
Rowland 1964
Duvick 1966
Arasu 1968
Frankel 1977
Richard 1986
•If, a plant does not set seed when pollinated with its
own functional pollen, but exhibits normal seed setting
when cross pollinated, it indicates presence of self
incompatibility.

5. Self compatible
•Capable of self pollination or cross pollnation
 Self incompatible
•It refers to inability of a plant with functional pollen
to set seeds when self pollinated.
•It is the failure of pollen from a flower to fertilize
the same flower or other flowers of the same plant
It is a general name for genetic mechanisms which
prevent self- fertilization and encourage outcrossing.

6. Features

•It is an important outbreeding mechanism which
prevents autogamy and promotes allogamy.

•It do not produce seed on self pollination but lead to
normal seed set on cross pollination.

•It maintains high degree of heteroztgosity in a
species due to outbreeding and reduces homozygosity
due to elimination of inbreeding or selfing.

•It can operate at any stage b/w pollination and
fertilization.

7. Self incompatibility is a genetic mechanism controlled
by a single highly polymorphic locus called as S
locus.
A common feature of these S loci is that separate
pollen- and style-expressed genes (pollen S and style S,
respectively) determine S allele identity.
Style S gene has long been known to encode an
extracellular ribonuclease called the S-RNase.
Pollen S has more recently been identified and encodes
an F-box protein known as either SLF or SFB.

8. Type based on flower morphology involved
Heteromorphic: different flower morphology
Distyly
Tristyly
Homomorphic: similar flower morphology
Gametophytic
Sporophytic

Type based on no. of gene involved
Monoallelic: Governed by Single gene (SP11 (S locus protein 11 gene)
Diallelic: Two gene (S, M each with 2 allele, ex: Tristyly)
Polyallelic: Many gene (S locus with many allele ex: SSI)

Type based on site of expression involved
Stigmatic : expression site is stigma
Stylar: style
Ovarian: Ovary

Type based on Pollen cytology involved
Binucleate: Pollen with 2 nuclei (GSI)
Trinucleate: 3 nuclei (SSI)

9. Heteromorphic Self Incompatibility
In species with heteromorphic system, the anthers and
stigmas are found at different levels within the flower
In distyly, the allele for short style (S) is dominant
over the allele for long style (s)
Tristyly is determined by two genes (M and S) with
two alleles each
The incompatible reaction of pollen is determined by
the genotype of plant producing them

10. Distyly
(DSI)

2 floral morphs.

“Thrum” flower
long filaments with short styles

“Pin” flower
short filaments with long styles

Only pollinations between
different floral morphs are
successful.

E.g.: Primula

11. Tristyly
(TSI)

3 floral morphs

Style short, stamens
medium and long

 Style medium, stamens
short and long

 Style long, stamens short
and medium

12. Homomorphic Self Incompatibility
In homomorphic self incompatibility, all the flowers have
exactly the same structure.

Over half of the flowering plants have flowers with similar
shape and this type of self-incompatibility

The incompatible reaction of pollen may be controlled by its
own genotype (gametophytic control) or by the genotype of
plant on which it is produced (sporophytic control)

13. SPOROPHYTIC
(SSI)

outcome of the interaction between the pollen tube
and the style is determined by the genotype of the
sporophyte (diploid tissue)

S-locus products are synthesized before completion
of meiosis

growth of the pollen tube arrests at the surface of
the stigma

Example: Brassicaceae, Polemoniaceae,
Caryophyllaceae, Betulaceae, Asteraceae, Sterculiaceae
and Convolvulaceae








GAMETOPHYTIC
(GSI)

outcome of the interaction between the pollen
tube and the style is determined by the genotype
of the pollen (gamete)

S-locus products are synthesized after completion
of meiosis

growth of the pollen tube arrests in the style

Example:Solanaceae, Scrophulariaceae, Poaceae,
Fabaceae, Campanulaceae, Onagraceae,
Papaveraceae and Rosaceae

14. Character GSI SSI
No. of Loci, No. of
alleles
One multiple One of more two alleles when one
or two genes distyly or tristyly.
Multiple alleles for a single locus
Homomorphic.
Reaction of SI
factor
Pollens itself determine
independent of other grains
function or 50% or more may not
function at all.
May show independent action or
dominance or complex interaction.
The reaction of pollen is determined
by both alleles present in the
saprophytic pollen grain produced
by plant either do not function at all
or function hundred percent
Reciprocal
differences
No Reciprocal differences do occur

15. Population structure Homozygoten are not normal
part of the system. The
parental genotypes do not
occur in the progeny.
Homozygoten are a normal
part of the system. The
parental genotypes occur in
the progeny
Pollen morphology Bi nucleate except grasses,
which have tri nucleate pollen
grain.
Generally tri nucleate except
Lythrum primula, which has bi
nucleate pollen grain
Site of action Pollen tube inhibited in style
and ovary.
Inhibition of pollen
germination or pollen tube
growth or stigma except
Linum kelianthus, where
incompatibility reaction takes
place in stylar tissue.
Effect of polyploidy May result in to SI No effect
Time of S. Gene action Post -meiotic Pre –meiotic or meiotic

16. Problems in exploiting Self-incompatibility


This may also lead to complete loss of inbred
lines.

Reduction of strength of incompatibility by
environmental factor may weaken or even break
down the incompatibility

17. USE OF SELF INCOMPATIBILITY

PRODUCTION OF LARGE SCALE OF F1 SEEDS

REDUCED COST OF HYBRID SEED PRODUCTION

SPEEDUP THE HYBRIDIZATION PROGRAMME

COMMERCIAL EXPLOITATION OF HYBRID VIGOUR
Most of cole vegetables like Broccolis, Cabbage, flowers like
Petunia, Marigold, Ageratum, Bellies etc are commercially
exploited crops developed through Self Incompatibility and
Natural Pollination
Some mandarin (Citrus fruit) varieties such as "W. Murcott Afourer" mandarin, "Page"
mandarin, "Minneola" tangelo and pummelo varieties such as "Chandler” and "Reinking“ are
self-incompatible will not result in fertilization or seed development and as a result seedless
fruits obtained.

18. The superior self incompatible lines for hybrid seed
production should posses the following characters

STABLE SELF INCOMPATABILITY

HIGH SEED SET OF SELF POLLINATION

FAVOURABLE AND UNIFORM ECONOMIC CHARACTERS

DESIRABLE COMBINATION ABILITY

19. CROP VARITIES
CAULIFLOWER IIVR-1, IIVR-50, Kataki Early-29, HAZIPUR-4
(BP), Pusi – 4, Agahani JBT -23/60, Late
Agahani, Aghani-8, Pusi Hazipur, Agahani
long leaf, Agahani small leaf, Kuwari-1,
Kataki-12 57
RADISH Pusa Chetaki, Pusa Desi, Half Red, Acc. No.
30205, Acc. No. 282, Chinese Pink, BDJ-689
USE OF SELF INCOMPATABILITY FOR HYBRID SEED PRODUCTION
Source: IIVR, Varanasi
IARI, New Delhi

20. USE OF SELF INCOMPATABILITY COMBINED WITH PARTHENOCARPY
FOR SEEDLESS FRUIT PRODUCTION
CROP VARITIES
Mandarins IDE 2 Shasta Gold, TDE 3 Tahoe Gold, TDE 4
Yosemite Gold
Grapefruit Rio Red, Marsh, Oroblanco
*Sweet Orange
Orlando, Osceola, Sunburst, Minneola, Page,
Nova
Ref: Tracy L. Kahn1 and C. Thomas Chao2
Department of Botany and Plant Sciences, University of California, Riverside
*Source: Dr. C. Jack Hearn, Retired Plant Breeder, USDA Horticultural Field Station,
Ft. Pierce, Florida.

21. TYPES OF SELF INCOMPATIBILITY
Self Incompatibility Self Incompatibility
Flower
Morphology
Flower
Morphology
Heteromorphic Heteromorphic
Distyly Distyly Tristyly Tristyly
Homomorphic Homomorphic
Gametophytic Gametophytic Sporophytic Sporophytic
Genes
Involved
Genes
Involved
Monoallelic Monoallelic Diallelic Diallelic Poly
allelic
Poly
allelic
Site of
expression
Site of
expression
Stigmatic Stigmatic
Stylar Stylar
Ovarian Ovarian
Pollen cytology Pollen cytology
Binucleate Binucleate Trinucleate Trinucleate

22. Physiological Hindrance of Self incompatibility

•Failure of the pollen to germinate on the stigma

•If some pollen grains do germinate, pollen tube
fails to enter the stigma e.g Rye, Radish, Cabbage

•If the pollen tube enters the style but they grow
too slowly to effect fertilization before the flower
drops

•Sometimes fertilization is effected but the embryo
degenerate at very early stage e.g Sugarbeet

•It appears to be a biochemical reaction but the
precise nature of the reaction is not clearly
understood.The genetic control of incompatibility
reaction is relatively simple and governed by
multiple alleles of single gene.

23. Importance of Self incompatibility in plant
breeding

•It effectively prevents self pollination, as a result
it has a profound effect on plant breeding
approaches and objectives.

•In self incompatible fruit trees, it is necessary to
plant two cross compatible varieties to ensure
fruitfulness.

•It may be used in hybrid seed production where
two self incompatible but cross compatible lines
are to be interpolated. Seeds obtained from both
the lines would be hybrid seed.

•It has limited use due to problems associated
with the maintenance of inbred lines through
hand pollination as it is tedious & costly.

24. Classification of S.I

1.Based on Flower Morphology
2.Based on genes involved
3.Based on site of expression
4.Based on pollen cytology

25. 1. Based on Flower morphology

a) Heteromorphic : S.I is associated with
differences in flower morphology.
Example:
1.Distyly:Style & Stamens are of two types(Pin
& thrum flowers)
2.Tristyly: Style& Stamens have three
positions i.e short, medium and long.

b) Homomorphic
The flowers do not differ in their morphology
1.Sporophytic: SI is govern by pollen
producing plant.

2.Gametophytic: SI is govern by genetic
constitution of gametes.

30. 2. Based on Genes involved
•Monoalleleic –S.I is controlled by
single gene.
•Dialleleic – S.I is govern by two genes.
•Polyallelic – S.I is govern by several
genes.

31. 3. Based on site of expression
•Stigmatic – S.I genes express on the
stigma.
•Stylar – S.I genes express in the style.
•Ovarian – S.I genes express on the
ovary.

32. 4. Based on pollen cytology
•Binucleate- The pollen grains have
two nuclei.
•Trinucleate-The pollen have three
nuclei.

33. Heteromorphic Self Incompatibility

In species with heteromorphic system, the anthers
and stigmas are found at different levels within the
flower
In distyly, the allele for short style (S) is dominant
over the allele for long style (s)
Tristyly is determined by two genes (M and S)
with two alleles each
The incompatible reaction of pollen is determined
by the genotype of plant producing them

34. Distyly

2 floral morphs.
“Thrum” flower
long filaments with short styles
“Pin” flower
short filaments with long styles
Only pollinations between different floral morphs are
successful.
E.g.: Primula

36.  3 floral morphs
 Style short, stamens medium and long
 Style medium, stamens short and long
 Style long, stamens short and medium

46. self-incompatibility
very important in the evolution of flowering plants
~70% of plants are hermaphroditic
SI appears to have
evolved
independently at
least 21 times
SI has also been independently lost in
numerous lineages, due to human or
environmental selection pressures

47. the S-locus
in dicots, self-incompatibility maps to a
single genetic locus
(grasses have 2 unlinked loci!)

molecular dissection of the S-locus in
several plant species has shown that:

the S-locus consists of multiple,
tightly-linked genes, encoding
male and female compatibility
determinants

divergent mechanisms of self-
incompatibility are encoded by
the S-loci of different plant
species

48. GAMETOPHYTIC
(GSI)

outcome of the interaction between the
pollen tube and the style is determined
by the genotype of the pollen (gamete)

S-locus products are synthesized after
completion of meiosis

growth of the pollen tube arrests in the
style






SPOROPHYTIC
(SSI)

outcome of the interaction between
the pollen tube and the style is
determined by the genotype of the
sporophyte (diploid tissue)

S-locus products are synthesized before
completion of meiosis

growth of the pollen tube arrests at the
surface of the stigma

49. Papaveraceae
ASTERIDS
ROSIDS
Fagaceae
Betulaceae
Begoniaceae
Rosaceae
Fabaceae
Sasifragaceae
Geraniaceae
Brassicaceae
Malvaceae
Apocynaceae
Rubiaceae
Convolvulaceae
Solanaceae
Scrophularaceae
Bignoniaceae
Oleaceae
Campanulaceae
Asteraceae
Ericaceae
GAMETOPHYTIC
SPOROPHYTIC
MIXED

50. papaveraceae: GSI; ♀-
determinant induces a
calcium-dependent
signaling network;
♂-determinant is not yet
identified
solanaceae: GSI; ♀-
determinant is a
ribonuclease,
♂-determinant is an F-
box protein
brassicaceae: SSI,
♂-determinant is a pollen
ligand; ♀-determinant is a
receptor kinase
www.ogrod.uj.edu.pl

51. brassicaceae: SSI,
♂-determinant is a pollen
ligand; ♀-determinant is a
receptor kinase
www.ogrod.uj.edu.pl
•SLG (S-locus glycoproteins): identified
immunologically as an S-haplotype-specific antigen;
SLG is not sufficient (or necessary) for SI response,
but enhances the activity of SRK
•SRK (S-locus receptor kinase): identified by
sequencing S-locus; high similarity to SLG
•SP11/SCR (S-locus protein 11/S-locus cysteine-rich):
identified though cloning and sequencing of the S-
locus region and polymorphic gene identification
using differential display; induces incompatible
reactions in stigma papilla cells (SP11/SCR of
matching S-locus haplotype induced
autophosphorylation of SRK in stigma plasma
membrane)
•ARC1 (Armadillo repeat-containing 1): identified
through protein interaction with SRK, proposed to
promote the degradation of stigmatic proteins
promoting pollen germination/growth
•MLPK (M-locus protein kinase): positive mediator of
SI signaling, loss of function leads to self-
compatibility

53. these signaling
reactions lead to
changes within the
pistil that prevent
growth of “cross”
pollen
treatment of stigma
with “self” SP11/SCR
protein induces
signaling reactions in
the pistil
SP11/SCR induces
incompatible reactions in
stigma papilla cells
Kachroo et al. 2001 Science 293:1824-1826
S6S6 stigmas (A) and S2S2 stigmas (B) were
treated with purified recombinant SCR6 and
pollinated with S13 pollen

54. solanaceae: GSI; ♀-
determinant is a
ribonuclease,
♂-determinant is an F-
box protein
“solanaceae-TYPE”
Scrophulariaceae Rosaceae
the ribonuclease selectively degrades rRNA from pollen of
the matching S-haplotype

55. a single origin of S-
RNase mediated
gametophytic self-
incompatibility in
eudicots?
Steinbachs & Holsinger 2002 Mol. Biol. Evol 19: 825-829

56. Papaveraceae
ASTERIDS
ROSIDS
Fagaceae
Betulaceae
Begoniaceae
Rosaceae
Fabaceae
Sasifragaceae
Geraniaceae
Brassicaceae
Malvaceae
Apocynaceae
Rubiaceae
Convolvulaceae
Solanaceae
Scrophularaceae
Bignoniaceae
Oleaceae
Campanulaceae
Asteraceae
Ericaceae
GAMETOPHYTIC
SPOROPHYTIC
MIXED
SI system
S-RNase
mediated

57. ♂-determinant: receptor or inhibitor?
receptor model: whether or not a
pollen tube is degraded depends on
selective uptake of S-RNases by the
pollen tube
inhibitor model: all S-RNases are
taken up by the pollen tube, but S-
RNases of non-matching S-
haplotypes are inhibited/degraded
Golz et al .1999

59. additional factors:
•HT-B (small, asparagine-rich protein expressed
late in stylar development)
•4936-factor (not yet cloned, mutations result
in self-compatibility)
•120kDa glycoprotein (abundant in style, taken
up by growing pollen tubes, interacts with S-
RNase in vitro)
in the absence of HT-B or 4936-factor, S-RNase remains compartmentalized
in pollen tubes and does not cause pollen rejection

60. Goldraij et al. 2006 Nature 439: 805-810

61. papaveraceae: GSI; ♀-
determinant induces a
calcium-dependent
signaling network;
♂-determinant is not yet
identified
•stigmatic S-proteins isolated through in
vitro assays of pollen tube inhibition
•the male determinant is believed to be a
receptor located at the pollen plasma
membrane
•SBP (S protein binding protein) specifically
binds S-proteins, but without haplotype
specificity
•interaction of self-pollen with the stigma
induces a calcium-dependent signaling
cascade leading to programmed cell death in
the pollen (Thomas & Franklin-Tong 2004)

63. Summary
●SI is an important mechanism for preventing
inbreeding in plants
●3 different mechanisms of SI have been described at
the molecular level
●Sporophytic SI dependent on a kinase-mediated signaling
cascade
●Gametophytic SI based on selective degradation of pollen
rRNA by S-RNases
●Gametophytic SI based on a calcium-dependent (MAPK)
signaling cascade leading to cell death in pollen

64. brassicaceae


solanaceae



papaveraceae
G or S?
S
G
G
signaling?
kinase-mediated
calcium-dependent
NO
direction
♂ to ♀
♀ to ♂
location
of action
♀
♂
♂
Summary

77. 1

78. 2

80. 3

84. Incongruity

Pollen pistil interactions
• Pollination
– pollen germinates at a correct condition in stigma
– Pollen tube grows through pistil tissue interacting with the
pistil tissues
– Reaches the ovule release its content and fuses
• Pistil : complex of barriers and promoters
• Pollen: with genetic information to overcome barriers and
react to promoters on its way from pollination to fertilization
• So for fertilization : pollen should contain the suitable
counterparts to the genes for barriers and promoters of pistil
and should be active in the right moment

86. Mechanisms of non functioning
• Incompatibility : prevents or disturbs the functioning of the
relationship ( though the potential of functioning is complete,
control from outside the matching genic system for normal
fertilization)
• Incongruity : the incompleteness of relationships (matching
genetic systems is not complete)

87. Incompatibility and incongruity
• Incompatibility : out breeding mechanism mostly based on
multiple alleles of one or two loci
– If products of s gene action in pistil and pollen have same
specificity, an inhibiting principle results which stop the pollen tube
growth.
• Incongruity : lack of genetic information in one partner about
some relevant character of other
– Pollen lacking the penetration or reaction gene
– Pistil lacking promoter genes

89. Incongruity
• Passive reproductive barrier which is caused by isolation between
the taxa
• Term coined by Hogenboom (1973)
• Describes pollen pistil dysfunction in wide crosses
• Evolutionary divergence : consequence of adaptation to different
environment or different ways of adaptation of populations in the
same habitat
• Acts as an isolating mechanism between original and sub
populations
• Incongruity occurs between pistil of one and pollen of other
population
• Incongruity between these populations will be slight at first but
then increase as the divergence proceeds

90. Genetic basis of incongruity
• Grun and Aubertin (1966) : an interspecific pollen growth
inhibition based on one or more independent dominant genes
• Hogenboom (1972) : Lycopersicon – unilateral incongruity was
complex of separate processes in the style and ovary : pollen
tube growth inhibition due to independent dominant genes
• Complexity of incongruity depends on relatedness of the
population
• Genetically more complex than incompatibility

91. Letter model for matching genic systems and
incongruity
• The total of pistil characters relevant to pollen tube growth and
fertilization : barrier capacity (b) – mainly base on dominant genes
• Total information in the pollen grain for the normal function of pistil
: penetration capacity (p) – dominant or recessive genes
• Gene complexes : A to Z and A to Z
• A -barrier gene or gene complex, A -corresponding penetration
gene or gene complex
• Eg, A: gene governing cutin production
A: governing cutinase production in pollen tube
• Congruity :
– Pistil : [b: AA, p:AA]
– Pollen : [b: AA, p:AA]
• Incongruity :
– Pistil : [b: AA, p:AA]
– Pollen : [b: BB, p:BB]

92. Incongruity mechanisms
• Pollen may lack genetic information on pistil’s
– Osmotic pressure
– Cutin or waxy layers of the epidermis
– Length
• Physiological characters
• Biochemical characters
• Structural characters
• The lack of accurate coordination of genomes in the fused nuclei

93. Pre-zygotic dysfunction
• dysfunction : prevent fertilization
– Cross sterility and reduced fertility
e.g. Carica, Papaver, Pennisetum
– Failure of pollen germination
– Slow growth of pollen tube
– Inability of pollen tube to reach the ovary

94. Overcome pre-zygotic barriers
• Mechanical removal of style :
pollination of exposed stylar end
• Mentor pollination :
– The mentor pollen may be defined as the compatible pollen
which has been treated in many ways to inhibit its fertilization
ability and retain its power to stimulate incompatible pollen to
accomplish fertilization
• Pollen mixture
• Bud pollination
• Growth hormones like GA3, IAA, NAA
• Invitro fertilization
• Protoplast fusion
• Chromosome doubling before hybridization
• Adopting bridging species

95. Post-zygotic dysfunction
• Affects the F1 generation
– Embryo death
– Endosperm dysfunction
– Slow seedling growth
– Seedling mortality
– Unusual susceptibility to diseases
– Abnormal organ development
– Chlorophyll abnormalities-Hybrid albinism
– Tumor development
– Lack of flowering
– Sterility without cause
– Seed abortion
– Hybrid lethality
– Hybrid sterility

96. Overcome post-zygotic barriers
• Embryo rescue
• Chromosome doubling
• Backcrossing
• Tissue culture

98. Exploitation
• New means of preventing self-fertilization for hybrid seed
production
– An extra barrier gene may be transferred from a related
population to the female line, the corresponding penetration
gene(s) to the male.
• Use incongruity for eradication of species – In host parasite
relationships one may transfer a barrier to the host which cannot
be overcome by the parasite.

99. REFERENCES
•Allard,R.W. (1960). Principles of Plant Breeding .
John Wiley and Sons, Inc.,New york.
•Arasu,N.T. (1968). Self incompatibility in
Angiosperms; a review. Genetica 39: 1-24.
•Frankel,R. and Galun, E. (1977). Pollination
Mechanisms, Reproduction and Plant Breeding.
Springer, Berlin, Heidelberg, New York.
•Gustafsson,A.(1968).Reproduction mode and crop
improvement. Theoretical application in
genetics.38:109-117.
•Talkayama,S. and Isogai,A.(2005). Self
incompatibility in plants. Annual Revelation Plant
Biology.56:467-489.
•Singh B.D (2009).Principles of Plant
Breeding.Kalyani Publishers, Ludhiana 5: 65-84.