The document discusses sexual incompatibility (s.i) in plants, detailing its definitions, mechanisms, and the physiological and genetic underpinnings that prevent fertilization within or between species. It explores various forms of s.i, methods to overcome it through different pollination techniques, and highlights the significance of s.i in promoting cross-pollination for the development of new plant varieties. Furthermore, it addresses specific examples and mechanisms that contribute to incompatibility, such as genetic interactions and environmental factors affecting pollen tube growth.

1. SEXUAL ………………….
....INCOMPATiBILITY S.I

2. • Definition
• interspecific
• intraspecific
Pollen grain is fail to bring out
fertilization in the ovule of the same plant
Occurs between individual of different species…
Same species

3. dichogamy basis of s.i
Maturation of male and female at different time.
E.g. Saxifraga aizoides anther dehisce before stigma
attain receptivity
E.g. Aristolochia stigma loss receptivity by the time
of
anther dehisce

4. herkogamy basis of s.i
. Structure of male and female sex organ itself forms a barrier to self pollination
E.g. Caryophyllaceae flower have stigma projecting beyond the stamens

5. physiology & biochemistry basis of s.i
1. Recognition reaction
Pollen contact  stigma  REC reaction .
2. Rejection reaction
Occur  stigma . Preventing entry of pollen tube  stigma

6. genetic & molecular basis of s.i
East & Mangelsdorf 1925
Single gene with several alleles
Avoiding

7. Crosses
When the cross between S1S2 (pollen) x S1S2 (egg) = 0 %
When the cross between S1S3 (pollen) x S1S2 (egg) = 50%
When the cross between S3S4 (pollen) x S1S2 (egg) = 100%

8.  Incompatible pollen tube growth is stops in stylar region due to synthesis of sRNA with in the style
 Which is enter in pollen tube and degrade the rRNA because it is responsiple for elongation of pollen
tube
E.g. Armeria maritime

9. S-locus
 Which is 3 loci.
SCR (S-locus Cysteine Rich Protein)
SRK (S-Receptor Kinase)
SLG (S-Locus Glycoprotein)
S1 & S2 pollen produces the SCR1 & SCR2 react with pistil
Stigma activates the kinase enzyme , that makes stigma function for pollen tube germination
Another protein MLPK of Serine –Threonine kinasae is attached to the plasmamembrane then inhibit the pollen

10. Other mechanisms of s.i
1. Heteromorphic S.I ;
 2 or more morphologically distinct matting types within a species.
 Distinguised without the breeding test
 S.I is controlled by one gene with two alleles. E.g Primula
 S.I is controlled by two gene with four alleles. E.g Lathyrum

11. Heterostyly
Two or more lengths of the style and stamen
filaments
E.g. Primula vulgaris

12. 2.homomorphic
Within species , morphologically indistinguishable . Want a breeding test.
Gametophytic S.I
genotype of male gametophyte itself. E.g. Liliaceae. Reject reaction in style.
Sporophytic S.I
Genotype of the sporophytic tissue of the plant, where the pollen is derived. E.g. Asteraceae.
Reject reaction in stigma.

13. 3. Late acting S.I ;
S.incompatible pollen reaches the ovule buy fail to set fruit . It’s called Ovarian S.I.
occur 2 ways. A. Pre zygotic L.S.I
Embryo sac deteriorates before the entry of pollen tube. E.g. Narcissus triandrus
B. Post zygotic L.S.I
The zygote is not able to develop. E.g. Spathodea campanulata

14. significance of s.i
 Selfing of plant produce , less surveying value.
 S.I is way to prevent.
 S.I favour to cross –pollination so new varieties and desired qualities are developed
 Interspecific S.I , emerges new races and species through open hybridization & mutation
 Etc…..,

15. methods to overcome s.i
 Bud pollination
Pollination is done in early stage of bud , in Intraspecific S.I
E.g. Petunia axillaris , at bud stage the stigma lacks the exudates. So the stigma is
pollinated by pollen in bud stage. Its proved.
 Stub pollination
The S.I reaction is occur in the Stigma or the style. So remove that. Its proved.
E.g. Ipomoea trichocarpa
 Intra –Ovarian pollination
S.I occur in both regions so the pollen is directly enter into the ovule . Its done by
following steps ; ovary sterilization , two punctures are made , one for introduce the
pollen by hypodermic syringe , another for aeration. After intro both punctures are
closed with petroleum jelly.
E.g. Argemome Mexicana

16.  Heat treatment
Provide upto 50 degree Celsius to style , it is used to reduce the S.I
E.g. Lilium longifolium , above mentioned temperature for 6 mints. slightly
increase the temperature is leads to injurious to pistil.
 Modification of stigmatic surface
The pollen surface proteins and stima surface pellicle is essential for identify
compatible or incompatible .
Pre-treatment of triton-X 100 & some organic solvents like hexane modifies
the pellicle and favours the fertilization.

17. Thank you for your co-operation