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Horticulture Digest

Date Last Edited:  08/24/2001

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Hawaii Cooperative Extension Service


Horticulture Digest #107
OBSERVATION AND EVALUATION OF DENDROBIUM ACCESSIONS

Background

The appearance of several new dendrobium cut flower cultivars during the 1980s contributed greatly to the rapid expansion of Thailand's dendrobium industry. Around that time the Government of Okinawa began to encourage the cultivation of dendrobiums for export to Mainland Japan. With generous government subsidies along with the strong Japanese currency, Okinawan growers procured large quantities of relatively inexpensive mericloned cultivars from Thailand.

In Okinawa, dendrobiums are cultivated in glasshouses. The growers there were particularly interested in producing large whites, and large two-tone lavenders (pinks). The Okinawan demand for mericloned cultivars, in turn, spurred the development of new cultivars in Thailand.

The University of Hawaii-bred dendrobium cut flower cultivars have been essentially seed-propagated Jaquelyn Thomas-type amphidiploids not generally favored in Thailand or Okinawa. In order to keep abreast of the current status of cultivar development in Southeast Asia, the senior author made a trip to Thailand, Singapore and Okinawa in 1989 to observe and introduce cultivars for evaluation. At that time, Sonia was the predominant cultivar, while Ekapol, which was popular earlier, was already on the decline. Both of these two-tone lavender (pink) cultivars exhibited exceptional keeping quality. Only a few plants each of the new, desirable cultivars were obtained due to the limitation of greenhouse space at the University of Hawaii. Some desired cultivars were not available for purchase because the propagators had exclusive contracts with buyers from Okinawa.

Procedure
The introduced plants were potted with shredded tree fern fiber in appropriate size clay pots and grown in the glasshouse at the Mauka Manoa Campus. Plants were hand-watered three times per week and fertilized biweekly with soluble Gaviota Orchid Fertilizer. Data were assembled over a period of four years and were summarized. Because only a few plants of any given cultivar were grown, statistical analysis was not meaningful, and therefore only the means are presented in the tables. However, the means of some characters such as width (natural spread) of flowers and percent bud drop may be representative of the accessions despite the limited observations. The introduced cultivars were grouped into lavender, purple, and red-purple, or white.

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Lavender, Purple, and Red-Purple

The summarized characteristics are presented in Table 1.

Sonia, the most popular cultivar of Thailand, is represented by several clones as well as mutants that arose in mericlone culture. The Sonias are characterized by:

  • long sprays
  • attractive large two-toned lavender (pink) flowers measuring 3 to 4 inches in width
  • relatively few flowers per spray (7-10) compared to Jaquelyn Thomas-types that bear about 20 flowers per spray
  • excellent vase life (half-life) of two to three weeks
  • bud drop percent seems to vary among clones
  • yield is relatively low, and
  • height of pseudobulbs reaches 39 inches.

Like Sonia, Ekapol is represented by several clones, the best known of which are Small Panda and Big Panda. Although the Ekapol clones make attractive potted plants, they do not appear to be suitable for cut sprays because of low yields, short sprays and relatively high bud drop.

Sabin and Queen Southeast produce attractive two-tone, red-purple flowers with contrasting white throat. The yields are low and sprays are short. They make attractive potted plants, but probably are not suitable for cut flower production in Hawaii.

Three clones with lavender (pink) flowers--Poh Kiew, Terri Ann Hasabe (Walter Oumae x Doreen) and Waipahu Pink--were evaluated. Both Poh Kiew and Waipahu Pink performed well, except the pseudobulbs of Waipahu Pink were excessively tall (60 inches). Terr i Ann Hasabe performed poorly with low yield, short sprays, poor vase life and high bud drop.

 
Table 1.  Average characteristics of lavender, purple and 
red-purple dendrobium accessions.

                    Accession  Raceme/ Raceme  No.Flowers  Half-  Flower  Bud   Pseudobulb
                      Number   Plant/  Length  Per Raceme  Life   Width   Drop    Height
                                year    (in.)             (days)  (in.)   (%)     (in.)

Sonia, Bom 17          D411      4.0    20.9       7.1     24.5    3.0     7.8     37.0
Sonia, Bom 28          D425      7.3    19.9       8.6     19.8    3.5     4.6     32.5
Sonia, Bom 16 mutant   D453      1.0    26.6       7.5     12.3    3.2    66.7     27.0
Sonia, Bom 28 mutant   D454      2.5    24.4      10.6     19.0    3.5    17.7     39.0
Sonia, Chao Praya      D444      3.0    26.7       7.3     19.0    3.2     2.2     25.0
Sonia, Red             D438      3.0    20.3      10.6     21.3    4.0    17.5     30.0

Ekapol, Small Panda    D409      7.5    22.6       7.1     13.7    2.8    13.7      --
Ekapol, Big Panda      D420      3.0     --        6.0      --     2.2     5.2      --
Ekapol, Red No. 1      D439      7.0    19.4       9.7     17.2    3.0     3.3     42.0
Ekapol, Genting        D450      1.5    25.1      10.3     19.0    3.0     0       42.5

Queen Southeast        D458      4.5    21.0       9.0     11.0    2.2     4.1     24.0
Sabin                  D424      2.0    15.0       5.7     21.0    3.0     5.9     18.5
Sabin                  D430      1.5    21.6       5.0     32.0    3.5     0       22.5
Poh Kiew               D419      4.6    20.9      14.1     19.2    2.8     4.3     30.0
Terri Ann Hasabe       D434      2.0     6.9      12.1      7.0    2.8     9.3     31.0
Waipahu Pink           D441      5.5    20.6      12.7     11.8    2.8     4.5     60.5
Uniwai Pearl*          UH 306   12.0    26.0      20.2     12.7    2.5     1.7     41.1

* Data from Kamemoto, H. and C.A. Bobisud that appeared in the Horticulture Digest
  September, 1979, prsented here for comparative purposes.
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White

The characteristics of several white clones are presented in Table 2. Every accession showed at least one defect.

  • Pattaya Beauty (D437) showed some pink pigmentation in the throat of the flower and the pedicel.
  • Jonnie Osterholt (D446), Pattaya Beauty (D437), Waipahu (D426), and Terri Ann Hasabe (D435, D442) produced at times excessively long, droopy sprays.
  • Bud drop percentages were high for all accessions except Waipahu (D426) and Terri Ann Hasabe (D435, D442).
  • Because the accessions were grown in the glasshouse rather than the saranhouse, excessively long pseudobulbs measuring as much as 61 inches for D451 (Walter Oumae x Waipahu) and 49 inches for Terri Ann Hasabe (D435) were obtained.
  • Another undesirable character was the fusion of leaf blades. Clones that showed fused blades were Jonnie Osterholt (D431-2, D446-2), and Pattaya Beauty (D437-1). 
Table 2.  Average characteristics of white dendrobium accessions.

                    Accession  Raceme/ Raceme  No.Flowers  Half-  Flower  Bud   Pseudobulb
                      Number   Plant/  Length  Per Raceme  Life   Width   Drop    Height
                                year    (in.)             (days)  (in.)   (%)     (in.)

Waipahu                D426      4.0    27.2      12.0     19.0    2.8     3.9     31.0
Jonnie Osterholt       D431      5.0    24.2      10.5     12.0    2.5    12.1     37.0
Jonnie Osterholt       D446      5.0    24.8      11.0     12.8    2.5     6.4     28.0
Terri Ann Hasabe       D435      4.7    29.2      14.7     15.7    3.0     2.0     49.0
Terri Ann Hasabe       D442      9.0    29.4      15.2     18.4    2.5     0.9     38.5
Walter Oumae X Waipahu D451      7.0    25.0      12.7     13.6    2.5    14.4     61.5
BM White               D436      4.0    21.5      11.6     15.7    2.8    13.2     28.5
Pattaya Beauty         D437      4.5    25.0      13.3     13.3    3.0     8.0     41.0
Pattaya Beauty,
  T Orchids            D440      4.0    22.6      13.1     12.0    2.8     7.0     32.0

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Chromosome Numbers

Chromosome numbers were determined for the accessions (Table 3). Most of the accessions were tetraploid (2n=76). Several were hypertetraploid (the tetraploid number, 2n=76, plus a few additional chromosomes, e.g., 2n=80), hypertriplo id (triploid, 2n=57, plus a few additional chromosomes, e.g., 2n=59) and a large number of mixoploids (accessions having cells with differing chromosome numbers).

Among the Sonias, two were tetraploid, two were hypertetraploid and two were mixoploid. The parents of Sonia were Caesar (probably an amphidiploid) and tetraploid Tomie Drake, and therefore the resulting offspring were expected to be tetraploid. The hyp ertetraploid and mixoploid Sonias, as well as mixoploid Waipahu (D426), Jonnie Osterholt (D446) and Terri Ann Hasabe (D435), probably resulted from mutations in tissue culture.

Because the accessions are advanced generation hybrids with mixed genomes, they are probably not suitable for the production of seed-propagated cultivars. However, for seedling selection and subsequent clonal propagation through tissue culture, tetraploi ds and hypertetraploids might be useful for further breeding.

 
Table 3.  Chromosome numbers of accessions.

Accession                                                               Chromosome
Number             Cultivar                 Parents of cultivar           Number

D411       Sonia, Bom 17             Caesar x Tomie Drake                   81
D421-1     Sonia, Bom 28             Caesar x Tomie Drake                   89
D425-3     Sonia, Bom 28             Caesar x Tomie Drake                   76
D453       Sonia, Bom 16 mutant      Caesar x Tomie Drake                   81
D454       Sonia, Bom 28 mutant      Caesar x Tomie Drake               71, 76
D444       Sonia, Chao Praya         Caesar x Tomie Drake                   76
D438       Sonia, Red                Caesar x Tomie Drake                   76

D409       Ekapol, Small Panda       Lim Hepa x Tomie Drake                 76
D420       Ekapol, Big Panda         Lim Hepa x Tomie Drake                 76
D439       Ekapol, Red No. 1         Lim Hepa x Tomie Drake                 76
D450       Ekapol, Genting           Lim Hepa x Tomie Drake                 80

D458       Queen Southeast           Hawaiian Beauty x Tomie Drake          76
D424       Sabin                     (not known)                            80
D430       Sabin                     (not known)                            80
D419       Poh Kiew                  Doreen x Bodhi Ngern                   80
D441       Waipahu Pink              Walter Oumae x Waipahu Beauty          76
D426       Waipahu                   Valley King x D. stratiotes    60, 70, 76
D446       Jonnie Osterholt          D. phalaenopsis x Walter Qumae     76, 78
D435       Terri Ann Hasabe          Walter Oumae x Doreen              58, 59
D442       Terri Ann Hasabe          Walter Oumae x Doreen                  59
D451       Walter Oumae x Waipahu    Walter Oumae x Waipahu                 76
D436       BM White                  (not known)                            76
D437       Pattaya Beauty            Margaret Joan Fell x Ng Eng Cheow      76
D440       Pattaya Beauty, T Orchids Margaret Joan Fell x Ng Eng Cheow      76
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Conclusions

  1. Because the accessions are clones and require the relatively expensive process of mericloning for propagation as contrasted to seed propagation for UH cultivars, they must exhibit exceptional qualities to warrant commercial cropping in Hawaii. Alth ough individual flower quality is excellent for such cultivars as Sonia, Ekapol and Sabin, one or more shortcomings such as relatively low yields, high bud drop and excessive pseudobulb length in most accessions might negate their suitability for commerci al cultivation in Hawaii.

  2. If economics warrant the cultivation of the Thailand accessions for cut flowers in Hawaii, then Sonia Bom 28 and Bom 17 among the two-tone lavenders, Poh Kiew among the lavender (pinks) and Waipahu among the whites might be recommended.

  3. Mutant clones of Ekapol, Sabin and Queen Southeast might be suitable for cropping as potted plants because of their attractive two-tone red-purple flowers.

  4. Due to differences in weather conditions between Southeast Asia and Hawaii, plant responses between the two locations differ. Pseudobulb height tends to be much taller in Hawaii. Another difference is the expression of floral necrosis due to cymbid ium mosaic virus. In Thailand where temperatures are high, floral necrosis may not be a problem, while the same clone grown in Hawaii may develop necrosis during the cooler months. Both Poh Kiew (D419) and Terri Ann Hasabe (D442) exhibited floral necrosi s.

  5. Fusion of leaf blades was common among some accessions. Jonnie Osterholt (Walter Oumae x phalaenopsis) showed excessive fusion. Every plantlet from a flask of a clone of Terri Ann Hasabe (Walter Oumae x Doreen) developed fused blades. The genetic background of clones undoubtedly affect fusion of leaf blades, but excessive mericloning from a single explant probably accentuates the development of this undesirable character.

  6. Chromosome numbers of accessions varied from tetraploid (2n=76), hypertetraploid (2n=76, plus a few chromosomes), hypertriploid (2n=57, plus a few chromosomes) and mixoploid (cells with differing chromosome numbers). Because accessions have varied s pecies chromosomes in their background, they are probably unsuitable as parents for the production of seed-propagated cultivars. However the tetraploids and' hypertetraploids might be useful in producing improved seedlings that can be propagated clonally .

    .

H. Kamemoto, haruyuki@hawaii.edu
T. D. Amore,
A. R. Kuehnle, heidi@hawaii.edu
and N. C. Sugii

Department of Horticulture, CTAHR
University of Hawaii at Manoa

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