Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 269

As previously indicated, crossing is a major procedure employed in the transfer of genes from one parent to another in the breeding of sexual species. A critical aspect of crossing is pollination control to ensure that only the desired pollen is involved in the cross. In hybrid seed production, success depends on the presence of an efficient, reliable, practical, and economic pollination control system for large‐scale pollination. Pollination control may be accomplished in three general ways:

1 Mechanical controlThis approach entails manually removing anthers from bisexual flowers to prevent pollination, a technique called emasculation, removing one sexual part (e.g. detasseling in corn), or excluding unwanted pollen by covering the female part. These methods are time consuming, expensive, and tedious, limiting the number of plants that can be crossed. It should be mentioned that in crops such as corn, mechanical detasseling is widely used in the industry to produce hybrid seed.

2 Chemical controlA variety of chemicals called chemical hybridizing agents (or by other names, e.g. male gametocides, male sterilants, pollenocides, androcides) are used to temporally induce male sterility in some species. Examples of such chemicals include Dalapon®, Estrone®, Ethephon®, Hybrex®, and Generis®. The application of these agents induces male sterility in plants, thereby enforcing cross pollination. The effectiveness is variable among products.

3 Genetical controlCertain genes are known to impose constraints on sexual biology by incapacitating the sexual organ (as in male sterility), or inhibiting the union of normal gametes (as in self‐incompatibility). These genetic mechanisms are discussed further in Chapter 5.