Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 256

The concept of multiple alleles can be studied only in a population. Any individual diploid organism can, as previously stated, have at most two homologous gene loci that can be occupied by different alleles of the same gene. However, in a population, members of a species can have many alternative forms of the same gene. A diploid by definition can have only two alleles at each locus (e.g. C¹C¹, C⁷C¹⁰, C⁴C⁶). However, mutations may cause additional alleles to be created in a population. Multiple alleles of allozymes are known to occur. The mode of inheritance by which individuals have access to three or more alleles in the population is called multiple allelism (the set of alleles is called an allelic series). A more common example of multiple allelism that may help the reader better understand the concept is the ABO blood group system in humans. An allelic series of importance in plant breeding is the S alleles that condition self‐incompatibility (inability of a flower to be fertilized by its own pollen). Self‐incompatibility is a constraint to sexual biology and can be used as a tool in plant breeding as previously discussed in detail in this chapter.