Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 363

Haploids contain half the chromosome number of somatic cells. Anthers contain immature microspores or pollen grains with the haploid (n) chromosome number. If successfully cultured (anther culture), the resulting plantlets will have a haploid genotype. Haploid plantlets may arise directly from embryos or indirectly via callus. To have maximum genetic variability in the plantlets, breeders usually use anthers from F₁ or F₂ plants. Usually, the haploid plant is not the goal of anther culture. Rather, the plantlets are diploidized (to produce diploid plants) by using colchicine for chromosome doubling. This strategy yields a highly inbred line that is homozygous at all loci, after just one generation.

Methods used for breeding self‐pollinated species generally aim to maintain their characteristic narrow genetic base through repeated selfing over several generations for homozygosity. The idea of using haploids to produce instant homozygotes by artificial doubling has received attention. Haploids may be produced by one of several methods:

 Anther culture to induce androgenesis;

 Ovary culture to induce gynogenesis;

 Embryo rescue from wide crosses.