EVALUATION OF DENDROBIUM CROSSES
INVOLVING FOUR NEW AMPHIDIPLOID PARENTS

Abstract

Four new amphidiploid dendrobium plants became available for breeding: K706-18 and D184-4N, having Dendrobium discolor in their background, and K916-57 and K927-27, having D. gouldii in their background. Twenty-four crosses were made utilizing the four amphidiploids to possibly identify cross combinations that might complement existing cultivars in reducing the peaks and valleys of seasonal flower yields.

Among the eight progenies involving K706-18 as a parent, K1299 (K706-18 x D. Jaquelyn Thomas D192) gave the best results and therefore will be released for trail by growers. K1323 (K706-18 x D. Jaquelyn Concert D239-1), which produced attractive red flowers, will be recommended for trial as potted plants. K1430 (D184-4N x K916-57), K1426 (K440-50 x K916-57), and K1427 (K927-27 x D168-12) produced the best results among their related crosses. These crosses will be offered to growers for trail to complement the commercial cultivars UH232, UH503, and UH507 in broadening seasonal yields.

Introduction

Evaluation of the dendrobium crosses to develop new cultivars for commercial cutflower production has been an ongoing activity of the dendrobium breeding program at the University of Hawaii. In 1989 the results of an experiment comparing 16 seed-propagated amphidiploid dendrobium progenies were summarized (Kamemoto et al., 1989). The cross UH800 (‘Uniwai Mist’) combined many desirable characteristics and therefore was released to dendrobium growers to complement the cultivars UH44 (‘Uniwai Blush’), UH232 (‘Uniwai Supreme’), UH306 (‘Uniwai Pearl’), UH503 (‘Uniwai Prince’), and UH507 (‘Uniwai Princess’) developed earlier (Kamemoto 1985, Kamemoto et al. 1976, Kamemoto and Bobisud 1979, Kamemoto and Kunisaki 1980, Kamemoto and McConnell 1982).

A few new amphidiploid plants have become available for breeding, namely K706-18 (D. Manoa Ruby), D184-4N (D. superbiens), K916-57 (D. Jaquelyn Thomas), and K927-27 (D. Jaquelyn Thomas). These amphidiploids were crossed to several other amphidiploid plants in hope of identifying desirable new cross combinations that might complement existing cultivars in reducing the peaks and valleys of seasonal yields.

Materials and Methods

New amphidiploid parent plants

The origin and genome characteristics of the four new amphidiploid breeding plants are as follows:

Crosses

The parent plants used in producing 24 crosses with the four new amphidiploid plants are listed in Table 1, along with their registered hybrid names and origins. Two University of Hawaii cultivars released earlier UH232 and UH503, served as controls. Pollinations with K706-18 were made between February and May 1988 while all other pollinations were made between January and April 1991. Seeds were germinated aseptically about three months after pollination, and seedlings were transflasked three months later. Seedlings were transplanted into community pots about six months after germination, and into 2-inch pots about six months later. About 9 to 10 months later, seedlings were moved into 6-inch black plastic pots containing no. 3 crushed blue rock as a medium.

The amphidiploid progenies were arranged on benches in a polypropylene shadehouse (30 percent shade). Twenty-two plants per cross were observed.

Raceme (spray) yield was recorded weekly for K706-18 progenies from July 1990 until December 1993, while progenies of the other three amphidiploids were observed from June 1993 to June 1996. Scape length was measured from the point of attachment to the pseudobulbs to the lowest flower, while raceme length was measured from the point of attachment to the pseudobulbs to the tip of the raceme. Other flower characteristics measured were flower width, pedicel length, number of flowers per raceme, and percentage bud drop. The vase life was expressed as the number of days until 50 percent of the flowers on the raceme wilted or dropped off. At the end of the experiment the height of the tallest pseudobulbs was recorded.

Data were analyzed using SAS software (SAS Institute, Cary NC). Analysis of variance was conducted for each characteristic using the general linear model procedure. Bud drop percentage was transformed with the arc sine transformation prior to analysis. Differences among treatment means at the 95% probability level were calculated using Duncan’s multiple range test.

Results and discussion

Crosses with K706-18

No differences were observed for raceme length, but statistically significant differences were observed for scape length. However, the magnitude of the differences were small, and they probably do not have any practical significance.

The number of flowers per spray was about equal for most crosses, except for K1304 and K1306, which had fewer flowers. Flower size expressed as flower width (natural spread of flowers) was largest for K1290, K1299, and K1302, which had K159-21, D192, and K159-19, respectively as the second parent. The pedicel was longest in K1299, undoubtedly an influence of the D192 parent.

With the exception of K1323, with a vase life of 14.5 days, the vase lives of 16.9 to 19.6 days for all other crosses did not differ statistically. Bud drop percentage was less than 1.5 for all crosses. The pseudobulb height showed variation, from 106.4 cm for K1299 to 72.1 cm for K1308.

Slight variation in flower size and color was observed among individuals within progenies. Both K1299, with red-purple (RHSCC 72B) flowers, and K1323, with dark red-purple (RHSCC 71A) flowers, showed slight variation among offspring.

Based on all characters enumerated above, two crosses appear worthy of trial by growers. K1299, a cross between K706-18 and Jaquelyn Thomas D192, produced long racemes, numerous flowers per raceme, relatively large flowers, fairly uniform flower color, good vase life, and a low bud drop. A weakness might be the tall pseudobulbs. The performance of K1299 was equal to that of the control, K1281 (UH232). The seasonality is shown in Figure 1. K1299 might well complement the cultivar UH503 (‘Uniwai Prince’), which is now under commercial production.

The major attribute of K1323 is the attractive, reddish-purple flower resulting from the combination of dark purple (K706-18) and bright reddish-purple (Jaquelyn Concert, D239-1). Unfortunately, the vase life of K1323 is shorter than the other crosses. Because of attractive “red” flowers, K1323 was released earlier for trial. As shown in Figure 1, flowering is spread throughout the year, without the pronounced peaks of other PPCC-type cultivars. Perhaps K1323 is better suited as a potted plant cultivar than as a cutflower cultivar.

Crosses with D184-4N

Some variation in size and color of flowers was observed within progenies. K1431, having NH-4N as a parent, showed greater variation among offspring than other crosses. K1442, having K706-18 as a parent, produced several distorted racemes.

K1444, having K44-50 as a parent, and K1430, having K916-57 as a parent, outperformed all crosses including the control, K1440 (Uh503). Raceme yield, number of flowers per raceme, and seasonality were similar (Fig. 2). Because the flower color of K1430 was slightly darker purple than that of K1444, and similar to that of UH503, K1430 will be recommended for trial by interested growers.

Crosses with K916-57

The results of crosses with K916-57 (D. Jaquelyn Thomas K916-57) are presented in Tables 6 and 7. K1426, having K44-50 as a parent, along with the reciprocal cross (K1441) outperformed UH232 (K1439) in raceme yield, raceme length, and number of flowers. The crosses having 0580-4N as a parent (K1412, K1432, K1438) had fewer flowers and flowers with shorter pedicels than the crosses involving K44-50. The size of the flowers, vase lives, and bud drop percentage of all crosses did not differ.

Flower colors of K1426 and K1441 were similar to that of K1439 (UH232), for all of these crosses have K44-50 as a common parent. On the other hand, those crosses with 0580-4N as a parent had slightly darker, two-tone lavender flowers.

Because K1426 and the reciprocal cross, K1441, produced similar flowers, but with slightly better yield and length of racemes and number of flower per raceme, K1426 will be released to growers for trial as UH1426. The seasonal yields of K1426 and K1439 (UH232) showed a slight variation (Fig. 3).

Crosses with K927-27

The characteristics of crosses with D. Jaquelyn Thomas K927-27 are shown in Tables 8 and 9. K1433, having O580-4N as a parent, produced the highest raceme yield and scape length. However, compared to K1427, having D168-12 as a parent, it produced shorter racemes, fewer flowers per raceme, and shorter vase life. K1427 and the reciprocal cross (K1435) produced flowers that were similar in color (purple RHSCC 78A), shape, and size to those of K1440 (UH503). However, their yields were higher, racemes were longer with more flowers per raceme, and the vase lives were longer. K1436, having K44-50 as a parent, also showed good characteristics but with slightly lighter purple flowers (purple-violet, RHSCC 81C).

K1427 and its reciprocal, K1435, produced flowers similar to those of UH503. Seasonality of yield was also similar (Fig. 4). Because of the good performance for most of the characteristics, K1427, will be released for trail as UH1427 to complement UH503.

Cross No.

Cross

Raceme yield

(per plant)

Scape length

(cm)

Raceme length (cm)

No. flowers per raceme

K1427

D168-12 X K927-27

13.6 b^z

15.3 b

53.1 bc

17.5 a

K1433

K927-27 X O580-4N

16.1 a

17.5 a

51.6 c

14.2 b

K1438

K927-27 X K44-50

13.3 bc

15.4 b

58.0 a

17.0 a

K1435

K927-27 X D168-12

12.8 bc

14.2 b

57.2 ab

16.8 a

K1440

UH503

11.5 c

15.4 b

45.8 d

14.1 b

Cross No.

Cross

Flower width (cm)

Pedicel length (cm)

Vase life (days)

Bud drop (%)

Mean plant height (cm)

K1427

D168-12 X K927-27

5.7 b^z

4.8 a

26.4 a

2.03 a

67.9 b

K1433

K927-27 X O580-4N

6.2 a

4.6 ab

21.4 b

2.10 a

69.2 ab

K1438

K927-27 X K44-50

6.1 a

4.2 c

19.0 b

1.53 a

75.4 a

K1435

K927-27 X D168-12

5.6 b

4.6 ab

26.0 a

1.72 a

63.6 b

K1440

UH503

5.6 b

4.5 b

20.1 b

1.14 a

66.5 b

Conclusions

Based on the evaluation of progenies involving four new amphidiploid plants, K706-18 and D184-4N having D. discolor in their background and K916-57 and K927-27 having D. gouldii in their background, the following conclusions were drawn:

1.      Among progenies of K706-18 as one parent, K1299 (K706-18 x D. Jaquelyn Thomas D192) produced long racemes, numerous flowers per raceme, large flowers, good vase life, and low bud drop, and therefore will be released as UH1299 for trial by growers. K1323 (K706-18 x D. Jaquelyn Concert, D239) with attractive reddish flowers (released earlier) might be better suited as a potted plant cultivar because of its shorter vase life.

2.      K1430 (D. superbiens, D184 x D. Jaquelyn Thomas K916-57) produced the best results among progenies of D184-4N. The flowers of K1430 are similar to those of UH503. It will be recommended for trial by growers.

3.      K916-57 with two-tone lavender flowers, produced offspring that were similar to UH232. K1426 (K44-50 x K916057) had the best results and therefore will be released for trial to complement UH232.

4.      Among the progenies of K927-27, K1427, having D168-12 as the other parent, produced long racemes and many flowers per raceme, and had good vase life. This cross will be recommended for trial by growers to complement the UH503.

5.      The seasonal yields of the crosses recommended for trial along with the established cultivars UH232 and UH503 are shown in Figure 5. It can be seen that by growing several cultivars the peaks and valleys of seasonal yields can be reduced.

Literature cited

Kamemoto, H. 1985. Seed-propagated amphidiploid dendrobium cultivars. HortScience 20:1-2, 163.

Kamemoto, H. and C.A. Bobisud. 1979. ‘UH306’ Dendrobium Jaq-Hawaii. Univ. of Hawaii, Dept. of Horticulture, Horticultural Digest 51:2-3.

Kamemoto, H., and J.T. Kunisaki. 1980. New names for university released seed-propagated dendrobium cultivars. Univ. of Hawaii, Dept. of Horticulture, Horticultural Digest 56:2.

Kamemoto, H., R.S. Kobayashi, and T.D. Amore. 1989. Evaluation of 16 seed-propagated amphidiploid Dendrobium progenies. Univ. of Hawaii, HITAHR Research and Extension Series 105. 8p.

Kamemoto, H. and J. McConnell. 1982. ‘Uniwai Prince’ and ‘Uniwai Princess’, two new dendrobium cut flower cultivars. Univ. of Hawaii, Dept. of Horticulture, Horticultural Digest 65:6-7

Kobayashi, R. and H. Kamemoto. 1989. Inheritance of floral necrosis in Dendrobium induced by cymbidium mosaic virus. HortScience 24:499-500.