Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 226

Mutagens (agents of mutation) such as X‐rays, radioactive sources such as P³², and certain chemicals have been used to make a self‐infertile genotype self‐fertile. Such a change is easier to achieve in gametophytic systems than sporophytic systems. Furthermore, doubling the chromosome number of species with the sporophytic system of incompatibility does not significantly alter the incompatibility reaction. This is because two different alleles already exist in a diploid that may interact to produce the incompatibility effect. Polyploidy only makes more of such alleles available. On the other hand, doubling the chromosome in a gametophytic system would allow the pollen grain to carry two different alleles (instead of one). The allelic interaction could cancel any incompatibility effect to allow selfing to be possible. For example, diploid pear is self‐incompatible whereas autotetraploid pear is self‐fruitful.