Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 316

As previously discussed, plants may be naturally sexually or asexually propagated. Further, sexually propagated species may be self‐fertilized or cross‐fertilized. These natural modes of reproduction have implications in the genetic structure and constitution of plants and breeding implications as already discussed. Plant breeders are able to manipulate the natural reproductive systems of species to develop plants that have atypical genetic constitution. The terms pure line, inbred line, and clone are applied to materials developed by plant breeders to connote sameness of genetic constitution in some fashion. However, there are some significant distinctions among them.

 Pure linesThese genotypes are developed as cultivars of self‐pollinated crops for direct use by farmers. As products of repeated selfing of single plants, pure lines are homogeneous and homozygous and can be naturally maintained by selfing.

 Inbred linesThese are genotypes that are developed to be used as parents in the production of hybrid cultivars and synthetic cultivars in the breeding of cross‐pollinated species. They are not meant for direct release for use by farmers. They are homogenous and homozygous, just like pure lines. However, unlike pure lines, they need to be artificially maintained because they are produced by forced selfing (not natural selfing) of naturally cross‐pollinated species.

 ClonesClones are identical copies of a genotype. Together, they are phenotypically homogeneous. However, individually, they are highly heterozygous. Asexually or clonally propagated plants produce genetically identical progeny.