2. INTRODUCTION
• Self-incompatibility- Prevention of fusion of fertile male and female gametes after self-
pollination (Growers,1998)
• Koelreuter in the middle of 18th century, first reported self incompatibility in Verbascum phoeniceum
plant.
• Term first coined by Stout in 1917.
3. CAUSES OF SELF-INCOMPATIBILITY
• Pollen grain fails to germinate on stigma
• Pollen tube fails to enter the stigma
• Slow growth of tube
• Embryo degenerate at early stage
4. FEATURES OF SELF-INCOMPATIBILITY
• It is an important outbreeding mechanism which prevents autogamy and
promotes allogamy.
• Do not produce seed on self pollination but lead to normal seed set on cross
pollination.
• Maintains high degree of heterozygosity in a species due to outbreeding and
reduces homozygosity due to elimination of inbreeding or selfing.
6. HETEROMORPHIC SYSTEM
Flowers of different in morphology is called heteromorphic
system.
1. DISTYLY- e.g. Primula
• 2 types of flowers
• Pin flower- long styles and short stamens
• Thrum flower- short styles and long stamens.
• Compatible mating is only between pin and thrum flowers
• This system is of little importance in crop plants ; it occurs in
sweet potato and buckwheat.
7. Results of four types of crosses in Primula
Crosses between Genotypes Results
Pin * Pin ss * ss Incompatible
Thrum * Thrum Ss * Ss Incompatible
Thrum * Pin Ss * ss 1 Thrum : 1 Pin
Pin * Thrum ss * Ss 1 Thrum : 1 Pin
8. 2. TRISTYLY- e.g. Lythrum salicaria
• Styles are of 3 different length- short , medium and
long
• It is controlled by 2 dominant genes – S and M. (S-
short style , M- medium style)
• The compatible matings are- long * medium, long *
short, medium * short
9. HOMOMORPHIC SYSTEM
• Incompatibility is not associated with morphological differences among flowers.
• Two types:-
1. Gametophytic self incompatibility
2. Sporophytic self incompatibility
1. Gametophytic self incompatibility
• The incompatibility reaction of pollen is controlled by its own genotype.
• Pollen tube growth is usually inhibited in the style or ovary.
• First described by East and Mangelsdorf in 1925 in Nicotiana sanderae.
• Most widely distributed and ancestral.
• e.g.-potato, tomato, rye, beet, pine apple etc.
10. • Three types of mating-
• i) Fully incompatible = S1S2 x S1S2
• ii) Partially compatible = S1S2 x S2S3
• Iii) Fully compatible = S1S2 x S3S4
11. 2. Sporophytic self-incompatibility
(SSI)
• The incompatibility reaction of pollen is
controlled by the genotype of the plant on
which the pollen is produced called
sporophytic self-incompatibility.
• First reported by Hughes and Babcock in
1950 in Crepis foetida, and by Gerstel in
Parthenium (in the same year).
• e.g.- radish (R. sativus), diploid Brassica
crops, cabbage, cauliflower, sunflower etc.
12. APPLICATIONS OF SELF - INCOMPATIBILITY
1. Production of hybrids
2. Multiplication of inbred lines
3. Creation of variability
ACHIEVEMENTS OF S.I.
Crop Variety
Cauliflower Pusa Hybrid-2, Snow Queen, Snow King, White Contessa
Cabbage BRH-5, H-44,H-43, Pusa Synthetic, Meenakshi