Progress 09/15/01 to 09/30/04

Outputs
The project has accomplished as follows: (1) Established a regeneration method of pothos (Epipremnum aureum) cv. Jade. Adventitious shoots regenerated from leaf and petiole explants cultured on MS basal medium supplemented with TDZ, zeatin, or 2iP individually with NAA. Shoot regeneration from leaf and petiole explants occurred in 30 days on media containing TDZ with NAA. Regeneration frequencies were up to 20% and 50% for leaf and petiole explants, respectively. Shoot numbers per responding explant reached 30 for leaf and petiole explants on media containing TDZ but only one to four on media containing either 2iP or zeatin. (2) Established regeneration methods of E. aureum cv. Golden pothos, Jade, and Marble Queen through direct somatic embryogenesis. Somatic embryos directly formed from petiole and stem explants of pothos on MS medium supplemented with CPPU or TDZ with NAA. Somatic embryos were also produced on MS medium containing 2.0 mg/l kinetin and 0.5 mg/l 2,4-D from leaf and petiole explants, MS medium supplemented with 2.0 mg/l CPPU and 0.5 mg/l 2,4-D from petiole and stem explants, and 2.0 mg/l TDZ and 0.2 or 0.5 mg/l 2,4-D from stem explants. Somatic embryos matured and grew into multiple buds, shoots, or even plantlets after two to three months on the initial culture medium. Germination was optimal on MS medium containing either 2 mg/l BA and 0.2 mg/l NAA or 2 mg/l zeatin and 0.2 mg/l NAA. Shoots elongated better and roots developed well on MS medium with no growth regulators. Approximately 30 to 100 plantlets were regenerated from each explant. The regenerated plants grew vigorously after transplanting to a soilless container substrate in a shaded greenhouse. (3) Established methods of Aglaonema regeneration. Explants of Aglaonema cv. 277028 cultured on medium supplemented with either BA or zeatin with NAA. About 5 to 30 big buds were produced from the explants, and such buds developed into plantlets on the same medium. On medium containing CPPU or TDZ, nodule structures emerged from explants. Many small buds appeared from the surface of the nodule via somatic embryo like structures or organogenesis. The buds then developed into plantlets on medium with supplemented with either BA or Zeatin with NAA. (4) Selecting and characterizing somaclonal variants. Research on this phase has not been completed. In addition to selecting variants directly derived from regenerated populations, plantlets were treated by X-rays at various dosages, and treated materials are grown in greenhouses for screening mutants. Thus far, we isolated several off-type pothos, potentially somaclonal variants. These isolated plants differ significantly in the patterns of foliar variegation from the parental type. We have no conclusion yet if any off-type Aglaonema could be isolated from regenerated plantlets. The variants will be propagated via vegetative means and evaluated in shaded greenhouse for several generations to test their stability and ornamental value. If desired traits are stable and acceptable by the foliage plant industry, the variants will be released as new cultivars.

Impacts
In spite of their popularity and great market value as foliage plants, Aglaonema and pothos have not been regenerated through somatic embryogenesis. Currently, Aglaonema propagation is mainly by shoot cuttings. Large production areas designated for stock plants have to be established and maintained year round for producing cuttings. Our success in somatic embryogenesis of Aglaonema will offer an important method of producing disease-free propagalues, greatly reduce production cost in maintaining stock plants, and potentially generate somatic variants from the culture. Pothos is propagated through eye cuttings. Diseases have been extremely common as the result of using infected stock plants. Additionally, the pothos market has only three cultivars Golden Pothos, Marble Queen, and Jade because traditional breeding approaches have not been established for this plant. The established regeneration and somatic embryogenesis systems will produce liners that are free of diseases, and the systems can also be used for generate somaclonal variants for new cultivar development. Hopefully, new cultivars will be released from this project.

Publications

• Zhang, Q., J. Chen, and R.J. Henny. 2004. Somatic embryogenesis and plant regeneration from various explants of Golden Pothos. HortScience 39:847 (Abstract).
• Zhang, Q., J. Chen, and R.J. Henny. 2004. Somatic embryogenesis and plant regeneration of leaf, petiole, and stem explants of Golden Pothos. Plant Cell Reports (in press).

Progress 10/01/02 to 10/01/03

Outputs
The objectives of this project are to (1) establish efficient micropropagation and regeneration systems for producing disease-free Aglaonema and Epipremnum (pothos) liners, (2) alter culture media and/or induce culture materials for uncovering existing mutants and/or somaclonal variants, and (3) select and characterize identified mutants or variants to provide the ornamental industry with new Aglaonema and pothos cultivars. Research accomplishments in 2003 are as follows: (1) In addition to establishing a regeneration method of Epipremnum aureum Jade, we have established an effective procedure for producing somatic embryos from all three cultivars Golden pothos, Jade, and Marble Queen. Somatic embryos are structurally similar to zygotic embryos found in seeds and possess many of their useful features, including the ability to grow into complete plants without separated shoot development and rooting phases. Somatic embryos after encapsulation can be used as conventional seeds. (2) We are in the process of screening for somatic variants. Thousands of plantlets germinated from somatic embryos have been carefully separated, transplanted into medium-filled plug trays, and grown in a shaded greenhouse. Off-type plants will be identified and propagated. We hope some desired variant could be isolated from the screening process. (3) We have developed a method of generating somatic embryo from Aglaonema cultivars after extensive testing of leaves, petioles, spadices, and developing seeds of more than 10 cultivars under various culture media with different growth regulator combinations. Somatic embryo germination produces plantlets. As we stated before, Aglaonema cultivars, explant sources, and combinations of growth regulators are important factors determining the somatic embryogenesis.

Impacts
In spite of their popularity and great market value as foliage plants, Aglaonema and pothos have not been regenerated, somatic embryogenesis has never been established. Currently, Aglaonema propagation is mainly by shoot cuttings. Large production areas designated for stock plants have to be established and maintained year round for producing cuttings. Our success in somatic embryogenesis of Aglaonema will offer an important method of producing disease-free propagalues, greatly reduce production cost in maintaining stock plants, and potentially generate somatic variants from the culture. Pothos is propagated through eye cuttings. Diseases have been extremely common as the result of using infected stock plants. Additionally, the pothos market has only three cultivars Golden Pothos, Marble Queen, and Jade because traditional breeding approaches have not been established for this plant. The established regeneration and somatic embryogenesis systems will produce liners that are free of diseases, and the systems can also be used for generate somaclonal variants for new cultivar development.

Publications

• Chen, J., R.J. Henny, and T.C. Chao. 2003. Somaclonal variation as a source for cultivar development of ornamental aroids. In S.G. Pandalai (ed.) Recent Research Developments in Plant Science. Research Signpost. Kerala, India (in press).
• Zhang, Q., J. Chen, and R.J. Henny. 2003. Direct embryogenesis and plant regeneration from various explants of golden pothos. HortScience (abstract submitted).

Progress 10/01/01 to 10/01/02

Outputs
The objectives of this project are to (1) establish efficient micropropagation and regeneration systems for producing disease-free Aglaonema and Epipremnum (pothos) liners, (2) alter culture media and/or induce culture materials for uncovering existing mutants and/or somaclonal variants, and (3) select and characterize identified mutants or variants to provide the ornamental industry with new Aglaonema and pothos cultivars. Research accomplishments in 2002 are as follows: (1) Adventitious shoots of Epipremnum aureum `Jade' were regenerated using leaf and petiole explants. Explants were cultured on Murashige and Skoog (MS) basal medium supplemented with thidiazuron (TDZ), 6-(4-hydroxy-3-methy-trans-2-butenyl-amino) purine (zeatin), or N-isopentenylaminopurine (2iP) individually with alpha naphthaleneacetic acid (NAA) in 18 combinations. Callus was initiated from cut surfaces and along the midrib or major vein of leaf sections. Shoot regeneration from leaf and petiole explants occurred in 30 days on media containing TDZ with NAA. More time (50 days) was needed for shoot regeneration when explants were cultured on media containing either 2iP or zeatin with NAA. Regeneration frequencies were up to 20% and 50% for leaf and petiole explants, respectively. Shoot numbers per responding explant reached 30 for leaf and petiole explants on media containing TDZ but only one to four on media containing either 2iP or zeatin. These results indicate that TDZ is a more effective cytokinin for in vitro regeneration of pothos than either zeatin or 2iP. The next step is to test and refine these regeneration systems for cultivars `Golden Pothos' and `Marble Queen'. (2) The progress on developing regeneration systems for Aglaonema has been slow due to the recalcitrance of this plant genus. Explants from leaves, petioles, spadix, and developing seeds of 10 cultivars have been cultured in media with growth regulators in more than 50 combinations. Callus formed from explants cultured in selected media. Based on the results of callus formation, Aglaonema cultivars, explants, and combinations of growth regulators are important factors determining the callus formation. The next steps are to test if adventitious shoots could be produced and root systems could be developed in shooting and rooting media, respectively, and to specialize which media are the best suitable for which type of explants of a cultivar. We would therefore establish effective regeneration systems for Aglaonema.

Impacts
In spite of their popularity and great market value as foliage plants, Aglaonema and pothos have not been micropropagated and regenerated. Currently, Aglaonema propagation is mainly by shoot cuttings. Large areas designated for stock plants have to be established and maintained year round for the production of cuttings. Success in micropropagation of Aglaonema will greatly reduce production cost in maintaining stock plants. Pothos is propagated through eye cuttings. Diseases have been extremely common as the result of using infected stock plants. Additionally, the pothos market is lacking new cultivars because traditional breeding approaches have not been established for this plant. There are only three cultivars 'Golden Pothos', 'Marble Queen', and 'Jade' in the market. Established regeneration systems will produce liners that are free of diseases, and the systems can also be used for generate somaclonal variants for new cultivar development.

Publications

• Qu, L., J. Chen, R. J. Henny, Y. Huang, R. D. Russell, and C. A. Robinson. 2002. Adventitious shoot regeneration of pothos (Epipremnum aureum) using leaf explants. In Vitro Cellular and Development Biology-Plant 38:268-271.
• Chen, J., R. J. Henny, and D. B. McConnell. 2002. Development of new foliage plant cultivars. p. 466-472. In J. Janick and A. Whipkey (Eds.). Trends in New Crops and New Uses. ASHS Press, Alexandria, VA.
• Chen, J. and R. J. Henny. 2002. The role of micropropagation in foliage plant production: Review and forecast. p. 124A. Final Program and Abstracts of the 10th International Association for Plant Tissue Culture and Biotechnology Congress: Plant Biotechnology 2002 and Beyond. June 23-28, 2002. Disney's Coronado Spring Resort, FL. (Abstract).