Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 227

Infertility of any kind hinders plant breeding. However, this handicap may be used as a tool to facilitate breeding by certain methods. Self‐incompatibility may be temporarily overcome by techniques or strategies such as the removal of the stigma surface (Figure 5.7) (or application of electric shock), early pollination (before inhibitory proteins form), or lowering the temperature (to slow down the development of the inhibitory substance). Self‐incompatibility promotes heterozygosity. Consequently, selfing self‐incompatible plants can create significant variability from which a breeder can select superior recombinants. Self‐incompatibility may be used in plant breeding (for F₁ hybrids, synthetics, triploids), but first homozygous lines must be developed.

Figure 5.7 Cut‐style and embryo rescue in lily. Overcoming reproductive barriers. (a) Pollination barriers; (b) post‐fertilization reproductive barriers. Courtesy of JM van Tuyl/P Ariens Wageningen UR ‐ Plant Breeding.

Self‐incompatibility systems for hybrid seed production have been established for certain crops (e.g. cabbage, kale) that exhibit sporophytic incompatibility (Figure 5.8). Inbred lines (compatible inbreds) are used as parents. These systems generally are used to manage pollinations for commercial production of hybrid seed. Gametophytic incompatibility occurs in vegetatively propagated species. The clones to be hybridized are planted in adjacent rows.

Figure 5.8 Application of self‐incompatibility in practical plant breeding. Sporophytic incompatibility is widely used in breeding of cabbage and other Brassica species. The single cross hybrids are more uniforms and easier to produce. The top cross is commonly used. A single self‐incompatible parent is used as female, and is open‐pollinated by a desirable cultivar as pollen source.