Self-sterility in Nicotiana

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Self-sterility in Nicotiana In plants, multiple alleles have been reported in association with self-sterility or self incompatibility. 

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 S₁S₁ or S₂S₂, but all plants were heterozygous as S₁S₂, S₃S₄, S₅,S₆. 

When crosses were made between different S₁S₂ plants, the pollen tube did not develop normally. 

But effective pollen tube development was observed when crossing was made with other than S₁S₂ for example S₃S₄. 


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 S₁S₂XS₃S₄, all the pollens were effective and four kinds of progeny resulted: S₁S₃, S₁S₄, S₂S₃ and S₂S₄.

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