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प्रश्न
How is Nicotiana exhibit self-incompatibility? Explain its mechanism.
उत्तर
Self-sterility means that the pollen from a plant is unable to germinate on its own stigma and will not be able to bring about fertilization in the ovules of the same plant. East (1925) observed multiple alleles in Nicotiana which are responsible for self-incompatibility or self-sterility. The gene for self-incompatibility can be designated as S, which has allelic series S1 S2, S3, S4, and S5. The cross-fertilizing tobacco plants were not always homozygous as S1 S1 or S2 S2, but all plants were heterozygous as S1 S2, S3 S4, and S5 S6. When crosses were made between different S1 S2 plants, the pollen tube did not develop normally. But effective pollen tube development was observed when the crossing was made with other than S1S2 for example S3S4.
The self-incompatibility in relation to its genotype in tobacco
Different combinations of progeny in self-incompatibility
When crosses were made between seed parents with S1S2 and pollen parents with S2S3, two kinds of pollen tubes were distinguished. Pollen grains carrying S2 were not effective, but the pollen grains carrying S3 were capable of fertilization. Thus, from the cross S1 S2 X S3 S4, all the pollens were effective and four kinds of progeny resulted: S1S3, S1 S4, S2 S3, and S2 S4.
संबंधित प्रश्न
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| S. no | Gamete types | Number of progenies |
| 1. | ABC | 349 |
| 2. | Abc | 114 |
| 3. | abC | 124 |
| 4. | AbC | 5 |
| 5. | aBc | 4 |
| 6. | aBC | 116 |
| 7. | ABc | 128 |
| 8. | abc | 360 |
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