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Griesbach, R.J., F. Meyer, and H. Koopowitz. 1993. New hybrid Ornithogalums and orchids. p. 602-603. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.

New Hybrid Ornithogalums and Orchids

R.J. Griesbach, F. Meyer, and H. Koopowitz

  1. NEW HYBRID ORNITHOGALUMS
  2. BREEDING METHODS
  3. BREEDING RESULTS
  4. PROSPECTS
  5. CURRENT TRENDS IN POT PLANT ORCHIDS
  6. REFERENCES

NEW HYBRID ORNITHOGALUMS

A joint breeding program to improve Ornithogalum was started in the Spring of 1988 by the United States Department of Agriculture's Florist and Nursery Crops Laboratory of Beltsville, Maryland (USDA) and the University of California at Irvine Arboretum (UCI). The selection of the genus Ornithogalum, Liliaceae, for a breeding program was based on several factors such as the need for improving the existing cut-flower crop, the need to develop new pot-plant types, and the existence of a large collection of species at UCI. We wanted to extend the color spectrum of the commercial cut flower types, presently only white, to include yellows, oranges, and pastels of these colors. We also wanted to expand the range of growth habits, flowering times, and the arrangement of the flowers on the stem in order to develop both pot-plant cultivars and novel cut-flower types.

Ornithogalum thyrsoides Jacq., the most commonly grown species, is characterized by a tall 20 to 100 cm raceme containing between 10 and 20, 3 to 5 cm flowers. The petals and sepals are nearly white [Royal Horticultural Society (RHS) Color Chart 4D] sometimes with a dark green or brown center which fades with age (Obermeyer 1978). Ornithogalum thyrsoides produces a very tight cluster of upright terminal flowers with short pedicels on a strong stem with short internodes between the flowers. Another species, O. dubium Houtt. is noted for its bright yellow (RHS 7A) to deep orange (RHS 28A) colored flowers. Ornithogalum dubium produces a short 10 to 20 cm raceme, containing between 10 and 20, 2 to 3 cm flowers (Obermeyer 1978). Ornithogalum dubium produces an inflorescence with long weak pedicels and long internodes between the flowers.

Our goal was to create interspecific hybrids between O. dubium and O. thyrsoides. Preliminary experiments suggested that mature seed could not be produced through classical sexual hybridization. In vitro, ovule-rescue was used to obtain seedlings (Meyer et al. 1991).

BREEDING METHODS

Ovaries were harvested 3 to 21 days after pollination (DAP). Between 10 and 14 DAP was optimal for ovule rescue. The seed capsules were surface sterilized in 1.5% NaOCl (30% laundry bleach) for 30 min and the ovules were aseptically removed. The excised ovules were then cultured in vitro. We were able to retrieve plants from ovaries harvested prior to the optimal 10 to 14 DAP, but the percentage of viable plants retrieved was extremely low. The medium consisted of 1/2 strength Murashige & Skoog salt and vitamins (MS) and 30 g/liter of sucrose and 6.5 g/liter of agar adjusted to 5.8 pH prior to autoclaving (Griesbach et al. 1992). After two to three months on this medium, the developing plants were large enough to be removed from culture and acclimated in the greenhouse. Flowering occurred after 6 to 9 months.

Specific clones were propagated via tissue culture (Griesbach et al. 1992). Mature but non-senescent leaves were harvested from plants before flowering and disinfected in 20% bleach for 20 min, rinsed twice in sterile water and cut into 2 x 1 cm sections. The leaf pieces were placed on a medium containing full strength MS salts, vitamins, and sugar supplemented with 1 mg/liter benzylaminopurine (BA). Within 3 weeks, 5 to 20 bulbous-plantlets developed at the cut surfaces. These plantlets continued to proliferate through off-shoots and were rooted on a hormone-free MS medium.

BREEDING RESULTS

Several hundred seedlings from 40 different crosses flowered (Meyer et al. 1991). Thirty-one of these crosses involved interspecific hybrids. Thirteen of these were F1 hybrids; 11 were F1-backcross hybrids; and 7 were F2 hybrids. Nine intraspecific crosses were produced. Five of these were F1 hybrids; 3 were F1-backcross hybrids; and 1 was an F2 hybrid.

Ornithogalum dubium produced flowers which ranged in color from dark yellow (RHS 7A) to dark orange (RHS 28B). Intraspecific F1 hybrids were yellow-flowered and F2 hybrids segregated for yellow and orange colors. No clear segregation patterns could be discerned.

Primary hybrids between O. thyrsoides and O. dubium produced flowers which were either light yellow (RHS 11C) or light orange (RHS 14D) depending upon the clones used. The gross morphology of the primary hybrids was intermediate between both parents, although the height of the flower stem and flower size tended to approach that of the larger parent. All of the primary hybrids had varying degrees of fertility, which provided the opportunity to generate successive generations.

The F1 primary hybrids were either sibling crossed to produce an F2 or back crossed with the highly colored species and hybrids. This effort was aimed at the continued introgression of deep, saturated colors into tall, cut-flower type species. We expected recombination and segregation to introgress both the saturated colors into the tall types and pastel colors into the dwarf types.

Of the over 200 F2 segregates, no plants were found to have darkly colored or pure white flowers. In fact, the color range of the F2 generation was very similar to that found in the F1. However, in backcross hybrids of O. dubium to the F1 primary hybrid, a wide range of colors from nearly white (RHS 4D) to dark orange (RHS 28A) or butter yellow (RHS 24B) were also found. A wide range of inflorescence types were obtained in the backcross hybrids. Tall, intermediate, and short inflorescences were found with either short, intermediate, or long internodes.

PROSPECTS

Several hybrids are now being multiplied in vitro in order to obtain a large quantity of plants for trials as cut flowers or pot plants. Some of these crosses produced 12 flower spikes from 4 to 5 bulbs in a single 10 cm pot. Such studies will also determine whether Ornithogalum can be commercially produced as a tissue-culture plug. We anticipate that pot plant Ornithogalum will be very successful as new crop and that the orange-colored cut flowered types will greatly expand the currently limited market for this crop.

CURRENT TRENDS IN POT PLANT ORCHIDS

Phalaenopsis hybrids are currently the most popular, pot-plant orchids. Sales at the Dutch Auctions has increased several hundred percent each year over the last few years. Plants are being produced in Europe, the United States, and Southeast Asia. The popularity of these hybrids is due to their short generation time of approximately two years, their ease of growth and flowering and the wide diversity of flowers colors. A new trend in Phalaenopsis breeding is in the development of dwarf, multiple flowering types.

Instead of producing a dozen or so 10 cm flowers on a 100 cm inflorescence, these new hybrids produce over 50, smaller 5 cm flowers on 50 cm long, laterally branched inflorescences.

REFERENCES

Last update May 2, 1997 aw