Azalea

Abstract

Belgian pot azaleas are presumed to have been created from a relatively narrow genetic basis of collector's material introduced into botanical gardens and private collections from Eastern Asia. Both Japanese and Chinese traditional varieties, some of them with a cultivation history of more than 400 years, were at the basis. The history of Belgian pot azalea started about 200 or more years ago; the first Belgium-bred and commercially released cultivar `Madame Van der Cruyssen' was introduced in 1867. Historical research supported by phylogenetic and molecular marker studies revealed a genetic continuum must be accepted which spans many species of the Tsutsusi subgenus. This continuum has been exploited in the past by both Asian and European breeders and still proves to be a good source for genetic variation and interesting forms. Until today, major improvements have been obtained by conventional crossbreeding and selection of spontaneous bud sports. Some of the historically major breakthroughs in breeding of pot azalea are (1) cultivars that could easily grow on their own roots, eliminating the need for grafting; (2) early (fall) flowering cultivars, particularly `Hellmut Vogel'; and (3) longer shelf life. Breeding goals have traditionally been driven by mass production aims and consumer wishes. From small to large double flowers and from colored to white flowers, the consumers are always in for something new, and their desires can change very quickly. Today, flower characteristics are still the most important criteria for selection. In addition, leaf shape and color, shininess of leaf surface, presence or absence of hairs, growth vigor, plant architecture, earliness of flowering, and postproduction quality (longevity of flowering, absence of brown bud scales) are other important traits for breeding. More recently, breeding for biotic resistance gained attention. Especially resistance against some fungal diseases has become a major selection criterion. Furthermore, candidate cultivars in an early stage are already being tested under commercial growing conditions to evaluate their reaction to specific culture practices as pinching, application of plant growth regulators, and reaction time during forcing.