Return to METRIA 12

Development of New Woody Plants by the Texas Coordinated Education
and Marketing Assistance Program

Michael A. Arnold1, Wayne A. Mackay2, Jerry M. Parsons1, Larry Stein3, Greg Grant4,
Steven W. George2, Tim D. Davis2, R. Daniel Lineberger1, H.B. Pemberton5, and C.B. McKenney2

1Texas A&M University, Dept. of Horticultural Sciences, M.S. 2133, College Station, TX 77843-2133, ma-arnold@tamu.edu
2Texas A&M University Research and Extension Center at Dallas, 17360 Coit Road, Dallas, TX 75252-6599
3Texas Agricultural Extension Service, TAMUS Research and Extension Center, Uvalde, TX 78802-1849
4Mercer Arboretum and Botanical Garden, 22306 Aldine Westfield Road, Humble, Texas 77338-1071
5Texas A&M University Research and Extension Center at Overton, P.O. Box 200, Overton, TX 75684

A paper from the Proceedings of the 12th Metropolitan Tree Improvement Alliance Conference (METRIA 12), Landscape Plant Symposium: Plant Development And Utilization, held in Asheville, NC, May 23-25, 2002, co-sponsored by the North Carolina State University, North Carolina Division of Forest Resources, USDA Forest Service Southern Region, North Carolina Landscape Association, North Carolina Association of Nurserymen, The Landscape Plant Development Center, The North American Branch of The Maple Society, and The International Ornamental Crabapple Society.


Abstract

The CEMAP (Coordinated Education and Marketing Assistance Program) program is one of the oldest state-wide cooperative university-industry sponsored landscape plant trialing programs in the country. Promoted plants are marketed under the Texas SuperstarTM name. During the initial evolution of the program, trials and promotions focused predominantly on the evaluation of existing cultivars and species already in the trade. Recently a greater proportion of the university participants' efforts have been directed toward the development of new genotypes for the Texas landscape industry, rather than simply trialing of existing taxa. Several members have spear-headed efforts in breeding new taxa or introducing taxa of previously unavailable plants from exotic locations. Current breeding efforts with woody plants include the development of more cold tolerant and novel growth forms of the common oleander, Nerium oleander L. (Nerium odorum W. Aiton), from irradiated seeds. Another effort involves selection of improved forms of Chastetree, Vitex agnus-castus L. for enhanced flowering characterstics. The bush morning glory, Ipomoea carnea N. von Jacquin subsp. fistulosa (K. von Martius ex J. Choisy) D. Austin, is the subject of a breeding program for a more compact dwarf habit, increased flowering, a broader range of flower colors, rust resistance, and sterility. Introduction of previously unavailable or under-utilized cultivars is also being pursued with the introduction in this country of new Satsuma, Citrus reticulata F.M. Blanco var. unshiu (Marcow) H.H. Hu cultivars (Citrus unshiu), and selection of disease resistant EarthKindTM roses, Rosa L. While this presentation will highlight developments in the CEMAP woody plant development program, herbaceous plant breeding is also in progress by various members of the group with Calylophus E. Spach, Helenium amarum (C.Rafinesque-Schmaltz) H. Rock, Lupinus texensis W. Hooker, Lupinus havardii S. Watson, Melempodium L., Oenothera L., Petunia x hybrida P.L. de Vilmorin, and Verbena L.

Introduction

CEMAP is one of the oldest state-wide cooperative university-industry sponsored landscape plant trialing programs in the country (Arnold et al., 2001; Mackay et al., 2001). Promoted plants are marketed under the Texas SuperstarTM name (Mackay et al., 2001). During the initial evolution of the program, trials and promotions focused predominantly on the evaluation of existing cultivars and species already in the trade. Recently a greater proportion of the university participants' efforts have been directed toward the development of new genotypes for the Texas landscape industry, rather than simply trialing of existing taxa. Involvement in breeding and selection efforts have been expanded to include more faculty, as well as graduate and undergraduate student involvement (Arnold et al., 2001; Harvey et al., 2002). Initial breeding efforts involved mostly herbaceous annuals and perennials, such as Lupinus L., Petunia Juss., and Verbena L. species (Arnold et al., 1998; Davis et al., 1994; Mackay et al., 2001). Recently, efforts have been expanded to more woody perennial species. Efforts have also been directed to solving limiting production or establishment problems for both species in the breeding programs and promising taxa in landscape trials that have production limitations (Arnold and McDonald, 2001; Arnold et al., 2002). Costs are defrayed by combining the breeding program activities and shared resources with existing research, extension, and teaching programs (Arnold et al., 2001). Some regular flow of funds is generated for the program via the sale of Texas SuperstarTM tags (Mackay et al., 2001).

Our regional conditions present some unique challenges relative to the use of landscape plants in other regions of the country (Arnold, 2002; Simpson, 1988). In order to be useful throughout Texas alone, plants need to be tolerant of blazing hot summers where temperatures may exceed 100°F for a month or more at a time, while night temperatures may not drop below 80°F for several months. Winter temperatures may be nearly subtropical (borderline USDA zones 9 and 10) to very cold (USDA zone 6). If these extremes of temperature were not challenging enough, the sequence of temperatures from fall through spring may vary by as much as 80°F within a day's time, leading to serious acclimation and deacclimation problems for plants. Natural precipitation varies from nearly 60 in./yr. in Beaumont to less than 8 in. / yr. in El Paso. Compounding these challenges are a predominance of heavy alkaline clays and caliche soils in much of the central and western portions of the state to acidic sugar sands in portions of east Texas. Irrigation water quality can be excellent, but is more often then not very poor with high levels of bicarbonates and sodium. As an example, the irrigation water (municipal source) at our College Station test site has a pH of 8.3 to 8.9, about 500 ppm of bicarbonates and 250 ppm of sodium, an electrical conductivity of about 1.1 dS/m, and a sodium adsorption ration of 33. This is typical of many south, central, and west Texas locations. In many cases, plants that would normally thrive in USDA hardiness zones 6 through 10 cannot survive under these conditions, resulting in the need to breed adapted genotypes of suitable landscape plants for the region. The objective of this paper is to highlight some of these efforts.

Selected Breeding Programs

Oleanders

Cold hardiness and new growth forms head the list of improvements to Nerium oleander in a breeding program headed by Wayne Mackay (Fig. 1A) and Jerry Parsons. Half-sib seeds of 'Franklin D. Roosevelt', 'Hardy Red', and 'Professor Parlatorre' were treated in 1991 with 3 levels of irradiation (30, 45, 60 rads) plus a non-treated control. The highest level resulted in death of all seeds of the three cultivars. The next level resulted in the death of F.D. R. seedlings. but not those from the other cultivars. The resultant seedlings were grown for ten years in El Paso, with annual rouging of cold damaged plants (Fig. 1B, 10°F in 1993). The nine most promising selections have been grown for five years in Dallas (Fig. 1C) and Overton. Several promising seedlings include a dwarf selection just a few feet tall after ten years (Fig. 1D) with salmon flowers (Fig. 1E), a dark velvet red flower (Fig. 1F), dark pink flower (Fig. 1G), and lighter pink flower (Fig. 1H) forms with cold hardiness equal to or exceeding that of the industry standard 'Hardy Red'.

A B C D
Wayne Mackay field five year old selections growing in Dallas dwarf selection with salmon flowers
Wayne Mackay El Paso field Selections in Dallas A dwarf selection
E F G H
salmon flowers dark velvet red flower dark pink flower light pink flower
Salmon flowers on
dwarf selection
dark velvet red
flower
Dark pink flower Lighter pink flower

Figure 1. Nerium oleander breeding, field shots and flowers

Chastetree

CEMAP member Greg Grant is working on several breeding projects, but one of the most exciting is the selection of a blue flowering Vitex agnus-castus with flower panicles twice to three times the size of most cultivars. Greg indicates that this selection is "an open pollinated seedling from a fine specimen at an old homeplace in central Louisiana." It has been dubbed 'Saphire' (Fig. 2). Greg is also working to breed a deeper pink, perhaps even a red flowering form.

Vitex agnus-castus 'Saphire'

Figure 2. Vitex agnus-castus 'Saphire' at TAMU Horticulture Garden

Bush Morning Glory

The CEMAP group under the leadership of Dr. Jerry Parsons has been breeding Ipomoea carnea subsp. fistulosa for a more compact growth habit, greater range of flower colors, rust resistance, reduced cold sensitivity, and sterility (Fig. 3). Several promising genotypes are being tested at San Antonio, Dallas, and College Station (Harvey et al., 2002). This is one of the most asked about plants in our test gardens, providing flowers from spring to late autumn. Growth habit on the species ranges from a large woody shrub or small tree in the Rio Grande Valley to an herbaceous perennial or summer annual in portions of the region with cold winters.

bush morning glory blossoms white blossom
bush morning glory in field planting bush morning glory selection

Figure 3. Ipomoea carnea subsp. fistulosa selections from the breeding

'Miho' and 'Seto' Satsuma Cultivars

Early-maturing, high-quality, cold-tolerant varieties of satsumas, Citrus reticulata var. unshiu (syn. Citrus unshiu), were obtained from Japan for evaluation in Texas. 'Miho' and 'Seto' are two such varieties (Fig. 4) developed from seed produced by controlled pollination of 'Miyagawa' satsuma (similar to 'Okitsu', which was introduced to Spain in 1983, starting its commercial spread in 1987. 'Miho' and 'Seto' were obtained as seed from the Fruit Tree Research Station - Okitsu Branch, Obitsu, Shimizu, Shizuoka 424-02 Japan in November 1984, and subsequently planted in containers in the greenhouse in December. Trees were grown on their own roots for 2 years before budding additional trees on sour orange (Citrus aurantium L.). 'Miho' and 'Seto' were first fruited in 1990. They were then propagated and tested in San Antonio and at the TAMU Research and Extension Center in Uvalde. These small trees are also suitable for landscape use. Release information is available in Stein and Parsons (2002).

satsuma cultivar 'Seto' Fruit of satsuma cultivar 'Miho'

Figure 4. Fruit of satsuma cultivars 'Seto' and 'Miho'

EarthKindTM Roses

Three years of research have been conducted to identify cultivars of landscape roses which are attractive, heat tolerant, tolerant of poorly aerated, highly alkaline clay soils, and so tolerant/resistant to disease and insect problems that pesticide applications are seldom required. The following ten cultivars have demonstrated these characteristics and have been designated as EarthKindTM by the Texas Cooperative Extension Service: 'Sea Foam', 'Marie Daly', 'Caldwell Pink', 'Knock Out' (Fig. 5), 'Perle d'Or', 'Belinda's Dream' (Fig. 5), 'Else Poulsen', 'Katy Road Pink', 'Mutabilis' (Fig. 5), and 'Climbing Pinkie'.

'Belinda's Dream EarthKind rose
'Knock Out' Earthkind rose
'Mutabilis' EarthKind rose
'Belinda's Dream' 'Knock Out' 'Mutabilis'

Figure 5. A few EarthKindTM roses

Literature Cited

Format updated July 24, 2009