Wei-Chin Chang

Plant regeneration from callus culture of Cymbidium ensifolium var. misericors

Abstract Totipotent calli of Cymbidium ensifolium var. misericors, a locally grown orchid of high commercial value, were induced from sections of pseudobulbs, rhizomes and roots of seed-derived plantlets on 1/2-strength Murashige and Skoog medium plus 10 mg/l 2,4-dichlorophenoxyacetic acid and 0.1 mg/l thiadiazuron. The calli could be maintained by subculturing in the same medium. The calli could be induced to develop further along one of three distinct morphogeneic routes: (1) production of rhizomes, (2) production of shoot buds, or (3) development of granular embryoids. Efficient mass propagation was possible via rhizome proliferation and embryoid formation.

Direct somatic embryogenesis and plant regeneration from leaf explants of Phalaenopsis amabilis

Leaf explants of Phalaenopsis amabilis var. formosa formed clusters of somatic embryos directly from epidermal cells without an intervening callus within 20 – 30 d when cultured on 1/2-strength modified Murashige and Skoog medium supplemented with 0.1, 1 and 3 mg dm−3 TDZ. Repetitive production of embryos involved secondary embryogenesis could be obtained by culturing segments of embryogenic masses on TDZ-containing media. Plantlet conversion from embryos was successfully achieved on regulator-free growth medium.

Effect of thidiazuron on vegetative tissue-derived somatic embryogenesis and flowering of bamboo Bambusa edulis

Current research on somatic embryogenesis of bamboo uses reproductive tissue as explants. However, it was hard to obtain the explant. Shoots of a local accession (3–4 m high) were used for multiple shoot production. In order to obtain embryogenic callus, nodal and internodal tissues from in vitro plantlets were placed on Murashige and Skoog (MS) medium supplemented with 9.2 μM kinetin (KN), 13.6 μM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.1% (v/v) coconut milk, and 6% (w/v) sucrose. We studied the effects of sucrose and thidiazuron (TDZ) on callus proliferation. Optimal additives to the MS medium for embryogenic callus proliferation were 0.046 μM TDZ, 13.6 μM 2,4-D and 3% (w/v) sucrose. TDZ also promoted the germination of bamboo somatic embryos. The germination rate of the somatic embryos exceeded 80% on MS-based medium supplemented with 0.455μM TDZ. Naphthaleneacetic acid (NAA) reduced germination. Well-developed plantlets were successfully transferred to soil. There was no albino mutant in subsequent culture. In vitro regenerants and potted plants flowered, but no seeds were produced.

A reliable protocol for plant regeneration from callus culture of Phalaenopsis

SummaryCallus of Phalaenopsis Nebula was induced from seed-derived protocorms on 1/2 Murashige and Skoog (MS) basal medium plus 0–1.0 mg l−1 (0–4.52 μM) N-phenyl-N′-1,2,3,-thiadiazol-5-yl urea (TDZ) and/or 0–10 mg l−1 (0–45.24 μ M) 2,4-dichlorophenoxyacetic acid (2,4-D). Protocorms 2 mo. old performed better than 1-mo.-old protocorms for callus induction. More calluses formed on 1/2 MS basal medium supplemented with 0.1–1.0 mg l−1 (0.45–4.52 μM) TDZ. These calluses could be maintained by subculturing every month with basal medium supplemented with 0.5 mg l−1 (2.27 μM) TDZ and 0.5 mg l−1 (2.26 μM) 2,4-D. Protocorm-like bodies were formed, and plants regenerated from these calluses on 1/2 MS basal medium alone or supplemented with 0.1–1.0 mg l−1 (0.45–4.52 μM) TDZ. Plantlets were then potted on sphagnum moss in the greenhouse and grew well. No chromosomal abnormalities were found among the root-tip samples of 21 of the regenerated plantlets that were successfully acclimatized.

Plant regeneration through direct shoot bud formation from leaf cultures of Paphiopedilum orchids

Leaf explants of Paphiopedilum phiIippinense hybrids (hybrid PH59 and PH60) directly formed adventitious shoots from wound regions within 1 month, when cultured on modified Murashige and Skoog medium (1/2-strength macro- and full-strength micro-elements) free of plant growth regulator in darkness. The combinations of 2,4-dichlorophenoxyacetic acid ((2,4-D) acid (0, 4.52 and 45.25 μM) and 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea (TDZ) (0, 0.45, 4.54 and 22.71 μM) were used to test their effects on direct shoot bud formation from two types of explants (1.5-cm long intact leaf explants and 0.5-cm long leaf segment explants). In hybrid PH59, 4.54 μM TDZ increased mean numbers of shoots per explant with leaf segment explants. In hybrid PH60, 4.52 μM 2,4-D plus 0.45 μM TDZ promoted direct shoot bud formation from leaf segment explants. In addition, three treatments (4.52 μM 2,4-D, 22.71 μM TDZ, 4.52 μM 2,4-D plus 4.54 μM TDZ) gave a higher response than control on mean numbers of shoots per explant with intact leaf explants. Healthy plantlets each with one to three roots were obtained from leaf-derived shoots after transfer onto a hormone-free medium for 22 months. These plantlets were acclimatized in a greenhouse and grew well with 100% survival rate.

In vitro flowering of Bambusa edulis and subsequent plantlet survival

Bamboo shoots could be induced to flower in vitro, but there is very little information on the effect of growth components on flowering. In this study, multiple shoots grown from in vitro, spikelet-derived, somatic embryos of Bambusa edulis were used for in vitro flowering. Multiple shoots flowered on Murashige and Skoog medium (MS) with 0.5 mM thidiazuron (TDZ) and 30 g l sucrose. Different

Efficient plant regeneration through direct somatic embryogenesis from leaf explants of Phalaenopsis ‘Little Steve’

SummaryLeaf segments of the orchid sp. Phalaenopsis ‘Little Steve’ were used as explants testing the effects of 2,4-dichlorophenoxyacetic acid (2,4-D; 0.45, 2.26, 4.52 μM), 6-furfurylaminopurine (kinetin; 2.32, 4.65, 13.95 μM), N6-benzyladenine (BA; 2.22, 4.44, 13.32 μM), and 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea (TDZ; 2.27, 4.54, 13.62μM) on the induction of direct somatic embryogenesis. After 20–30 d of culture in darkness, clusters of somatic embryos formed from leaf surfaces and wounded regions of explants on half-strength Murashige and Skoog medium supplemented with BA and TDZ. However, kinetin had no response on direct embryo induction. In addition, 2,4-D highly retarded the frequency of embryogenesis that was induced by TDZ. Generally, adaxial surfaces near wounded regions had the highest embryogenic competency compared to other regions of explants. Histological sections revealed that somatic embryos mostly arose from epidermal cell layers of the explants. Secondary embryogenesis occurred at basal parts of embryos, and originated from outer cell layers. Following transfer of regenerated embryos onto growth regulator-free medium for 3.5–4 mo., plantlets with three to four leaves and several roots were obtained. This protocol provides a simple way to regenerate plants through direct somatic embryogenesis, and is suitable for further studies on embryo development and genetic transformation of Phalaenopsis.

Micropropagation of Bambusa edulis through nodal explants of field-grown culms and flowering of regenerated plantlets

Abstract Nodal explants obtained from 10-year-old field-grown culms of Bambusa edulis produced multiple shoots on a Murashige-and-Skoog-based medium supplemented with 0.1 mg/l of thidiazuron (TDZ). Hundreds of regenerated shoots rooted well on a medium supplemented with 0.01 mg/l TDZ and 0.5 mg/l 2,4-dichlorophenoxyacetic acid and were successfully transferred to soil for field trials. Albinism occurred at the rate of about 30% among the regenerated shoots, and isolated albino shoots also proliferated on the medium containing TDZ. Some of the green and albino shoots also flowered on the medium containing TDZ. A potted plant also flowered and survived after flowering.

INDUCTION OF REPETITIVE EMBRYOGENESIS FROM SEED-DERIVED PROTOCORMS OF PHALAENOPSIS AMABILIS VAR. FORMOSA SHIMADZU

SummaryAn in vitro culture procedure was established for repetitive embryogenesis and plant regeneration from seed-derived protocorms of Phalaenopsis amabilis var. formosa Shimadzu (Orchidaceae). Seed-derived protocorms were cultured on modified half-strength Murashige and Skoog (1962) basal medium (1/2MS) devoid of plant growth regulators. After 45 d, 28.1% of protocorms formed embryos from their posterior regions. 1-Phenyl-3-(1,2,3-thiadiazol-5-yl)-urea (TDZ; 0.45, 4.54, and 13.62 μM) promoted direct embryo formation. The best response was at 13.62 μM TDZ, and 100% of the protocorms formed a mean number of 13.5 embryos after 45d of culture. By contrast, naphthaleneacetic acid (NAA) at 0.54 and 5.37 μM inhibited direct embryo formation. On basal medium devoid of plant growth regulators, 18.8% of primary proliferating embryos could form more embryos. TDZ (0.45, 4.54, and 13.62 μM) also promoted this process. Proliferating embryos/protocorms were transferred to basal medium devoid of plant growth regulators for plantlet formation. Plantlets were successfully obtained from the embryos after 4–6 wk. Following subculture every 6 wk for three passages, the plantlets were transferred to sphagnum moss in a container for acclimatization in the greenhouse. The survival rate was 100%.

Plant regeneration from callus culture of a Paphiopedilum hybrid

Totipotent calli of a Paphiopedilum hybrid (Paphiopedilum callosum ‘Oakhi’ × Paph. lawrenceanum ‘Tradition’) were induced from seed-derived protocorms on a 1/2 strength Murashige–Skoog medium plus 1–10 mg l−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.1–1 mg l−1 1-phenyl-3-(1.2.3-thiadiazol-5-yl)urea (TDZ). These calli grew well when subcultured on the same medium, but proliferated more on 1/2 MS medium plus 5 mg l−1 2,4-D and 1 mg l−1 TDZ. Calli developed further along a route of production of protocorm-like bodies and eventually formed plantlets that could be transplanted to pots and grew well.