Interspecific Hybridization and Introgression

Abstract

Some of the economically important horticultural crops have two common features. First, they are of interspecific hybrid origin and, second, they are mostly polyploids. The histories of the origin of such ornamentals as Rosa, Narcissus, Iris, Crocus and Chrysanthemum, among others, have been well documented (Stern, 1946; Wylie, 1952; Darlington, 1976; Brighton et al., 1980; Brandham, 1987) and they can be traced back to 18^th and 19^th centuries or even earlier. Initially, most of these crops were diploids, the polyploid forms originated spontaneously from interspecific hybrids in the breeders’ nurseries. In those early days, the knowledge regarding the status of the species, the genomes and polyploidy was nonexistent; nevertheless the horticultural breeders were successful in creating considerable genetic variation. These efforts were subsequently responsible for the selection of thousands of horticultural varieties in some of those crops. For example, in Narcissus, more than 25,000 cultivars have been recorded (Throckmarton, 1980). In Lilium, which has probably followed a similar path of origin as other horticultural crops, more than 7000 cultivars have been registered since 1960 alone (Leslie, 1982). The existence of thousands of cultivars in Tulipa is well documented.