Crossability Relations

Abstract

The term hybridization is used to describe a wide range of processes involving cross-fertilization. In wide crosses it usually refers to events which may lead to gene flow between populations which are reproductively isolated from one another to various extents. Successful hybridization depends on: (1) the inter-crossing potential or crossability of the parties involved, this refers to all the events that occur from the time of germination of pollen grains on the alien stigma to the formation of the zygote; and (2) the development of the hybrid embryos and the F₁ plants, and the fertility of the F₁ hybrids and their derivatives. The terms hybridization and crossability are often confused and are sometimes used interchangeably in the literature. Obviously crossability is a component of the hybridization process. However, some authors use the term hybridization when really referring only to inter-cross potential; others use the term crossability to describe hybrid behavior as well. In practice, crossability is usually expressed by the number of seeds obtained per pollination, or the number of hybrid embryos which can be rescued by in vitro techniques. Accordingly, in this chapter, crossability is defined as the potential of individuals belonging to different taxonomic categories for intercrossing and for production of sufficiently mature seeds or embryos which can give rise to F₁ plants.