Self incompatibility

self-incompatibility for hybrid seed production

1. SELF-INCOMPATIBILITY Sanjay Kumar Bishnoi Ph. D. Research Scholar SKRAU, Bikaner

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. T erm first coined by Stout in 1917 .

3. CAUSES OF SELF-INCOMPATIBILITY Pollen grain fails to germinate on stigma P ollen tube fails to enter the stigma S low growth of tube E mbryo degenerate at early stage

4. FEATURES OF SELF-INCOMPATIBILITY It is an important outbreeding mechanism which prevents autogamy and promotes allogamy . D o not produce seed on self pollination but lead to normal seed set on cross pollination. M aintains high degree of heterozygosity in a species due to outbreeding and reduces homozygosity due to elimination of inbreeding or selfing .

5. Given by Lewis, 1954

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 . T wo types:- 1. Gametophytic self incompatibility Sporophytic self incompatibility 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 s porophytic 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 Production of hybrids Multiplication of inbred lines 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