Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 328
7.9.3 Crossing with clonal selection
ОглавлениеThis procedure is applicable to species that are capable of producing seed in appreciable quantities. Because heterosis can be fixed in clonal populations, the breeder may conduct combining ability analysis to determine the best combiners to be used in crosses. The steps below are not applicable to trees in which much longer times are needed.
| Year 1 | Cross selected parents. Harvest F1 seed. |
| Year 2 | Plant and evaluate F1s. Select vigorous and healthy plants. |
| Year 3 | Space plant clonal progeny rows of selected plants. Select about 100 to 200 superior plant progenies. |
| Year 4 | Conduct preliminary yield trials. |
| Year 5–7 | Conduct advanced yield trials for cultivar release. |
Other techniques that are applicable include backcrossing to transfer specific traits and wide crossing. The challenges with backcrossing are several. As previously indicated, clonal species are very heterozygous and prone to inbreeding depression. Backcrossing to one parent (the recurrent parent) provides opportunity for homozygosity and consequently inbreeding depression. To prevent this, breeders may cross the backcross to another clone instead of the recurrent parent, followed by selection to identify superior plants. The process is repeated as needed.
