Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 291

The first choice of parents for use in a breeding program is cultivars and experimental materials with desirable traits of interest. Most of the time, plant breeders make elite × elite crosses (they use adapted and improved materials). Even though genetic gains from such crosses may not always be dramatic, they are nonetheless significant enough to warrant the practice. After exhausting the variability in the elite germplasm as well as in the cultivated species, the breeder may look elsewhere, following the recommendation by Harlan and de Wet. These researchers proposed that the search for desired genes should start from among materials in the primary gene pool (related species), then proceed to the secondary gene pool, and if necessary, the tertiary gene pool. Crossing involving materials outside the cultivated species is collectively described as wide crosses. When the wide cross involves another species, it is called an interspecific cross (e.g., kale). When it involves a plant from another genus, it is called an intergeneric cross (e.g. wheat) (see Box 6.1). Crosses between crops with their wild progenitor species should not be considered wide crosses, despite the sometimes‐used different scientific names (barley, Hordeum vulgare, was derived from H. spontaneum; lettuce, Lactuca sativa, was derived from L. serriola). Genetically such “species” are fully compatible and behave genetically as an intraspecific cross (i.e. cross within the same species).