Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 136

Some form of evaluation precedes selection. A breeding material is selected after evaluating the variability available. Similarly, advancing plants from one generation to the next is preceded by an evaluation to determine individuals to select. In self‐pollinated species, individuals are homozygous and when used in a cross their genotype is precisely reproduced in their progeny. A progeny test is hence adequate for evaluating an individual's performance. However, open‐pollinated species are heterozygous plants and are further pollinated by other heterozygous plants growing with them in the field. Progeny testing is hence not adequately evaluative of the performance of individual plants of such species. A more accurate evaluation of performance may be achieved by using pollen (preferably from a homozygous source – inbred line) to pollinate the plants. As previously described, the method of evaluating the performance of different mother plants in a comparative way using a common pollen source (tester line) is called a test cross. The objective of such a test is to evaluate the performance of a parent in a cross, a concept called combining ability.

The methods used by plant breeders in population improvement may be categorized into two groups, based on the process for evaluating performance. One group of methods is based solely on phenotypic selection and the other on progeny testing (genotypic selection). The specific methods include mass selection, half‐sib, full‐sib, recurrent selection, and synthetics.