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ORCHID HYBRIDIZATION

In the wild, orchid species rarely form natural hybrids in zones of overlap. The integrity of species is maintained by differences in flowering times, floral morphology, visual and olfactory cues, as well as by genetic incompatibility or inability of the hybrid to establish and reproduce. Once one or more of these barriers or isolating mechanisms are removed, though, for example when orchids are pollinated by hand in the greenhouse, two different species will often produce viable hybrids quite readily. Artificial hybrids are common between species in the same genus, between species of different genera in the same subtribe, more rarely between species in different subtribes (but within the same tribe). In fact, the genes from as many as six different genera are present in some hybrids, leading to the perception of orchids as most promiscuous plants indeed!

The first orchid hybrid to flower (1856) was Calanthe Dominyi (furcata x masuca), a cross made by John Dominy, head grower for the English firm of Veitch & Sons. Shortly thereafter, a showier hybrid, Cattleya Hybrida (guttata  x loddigesii) flowered, and a new era in orchid cultivation had dawned. Relatively few hybrids were produced in the last half of the nineteenth century, however, because growers were still unaware of the specific relationships between orchids and mycorrhizal fungi that governed the germination of seeds and establishment of seedlings. At the turn of the century, Frenchman Noel Bernard effectively demonstrated that the presence of such fungi was necessary for germination. A practical application of this startling phenomenon was suggested by German Hans Burgeff, who argued that orchid seeds could be germinated on laboratory agar with the addition of the appropriate fungal strain. Finally, in 1922 an American plant physiologist named Lewis Knudson published his discovery: orchids could be germinated on agar not with the fungi themselves but with the sugars normally provided by the fungi along with some mineral nutrients. Hybrids could now be mass-produced in the laboratory simply using nutrient agar in flasks. A veritable explosion of new hybrids ensued, which continues today. The earliest hybrids were intrageneric, that is, they were crosses between species in the same genus. The generic name of the hybrid remained the same, and a fancy name, not italicized, was given to the cross itself, e.g. Calanthe Dominyi. Subsequent more adventurous crosses were made between species of different but related genera, requiring the creation of a new generic name by combining the two.

For example, Cattleya mossiae x Laelia purpurata became Laeliocattleya (abbreviated as Lc.)  Canhamiana.  When a Laeliocattleya was then crossed with a species (or hybrid) of Brassavola the hybrid genus name became Brassolaeliocattleya (abbreviated as Blc.). It was not long before the genes of yet a fourth genus were added, and the former method of simply combining generic names had become unwieldy. Accordingly, the practice of creating generic names ending in -ara was adopted for hybrids with genes from multiple genera.

Examples are Vuylstekeara (Cochlioda x Miltonia x Odontoglossum) and Potinara (Brassavola x Laelia x Cattleya x Sophronitis). One way of distinguishing a natural genus from a hybrid genus is to insert a multiplication symbol before the hybrid name, such as X Potinara. Today, the Royal Horticultural Society registers all new orchid hybrids and publishes them regularly in major orchid periodicals and every five years in Sander's Complete List of Orchid Hybrids.

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