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United States Department of Agriculture

Agricultural Research Service


Location: Floral and Nursery Plants Research

2009 Annual Report

1a. Objectives (from AD-416)
The primary objective of this work is to develop seedless cultivars of invasive or potentially invasive nursery crops. Secondary objectives are to develop new technologies and methods to facilitate theses efforts and to further enhance pest resistance, adaptability, and commercial potential of these crops.

1b. Approach (from AD-416)
These efforts will focus on traditional breeding methods to develop seedless cultivars. Tetraploid clones will be identified or developed and then hybridized with diploids to create triploids. Additional approaches will include mutation breeding, wide hybridization and breeding for double flowers lacking pistils. Resulting progeny will be assessed for fertility and commercial merit. Target crops will include: amur maple (Acer ginnala), barberry (Berberis spp.), catalpa (Catalpa spp.), elaeagnus (Elaeagnus spp.), flowering crabapple (Malus spp.), flowering pear (Pyrus spp.), lace-bark elm (Ulmus parvifolia), miscanthus (Miscanthus spp.), mimosa (Albizia julibrissin), Norway maple (Acer platanoides), privet (Ligustrum spp.), spirea (Spiraea spp.), St. Johnswort (Hypericum spp.), and winged euonymus (Euonymus alatus).

3. Progress Report
The objective of this agreement is to develop seedless cultivars of invasive, but commercially important, nursery crops. Ongoing efforts have been successful in building germplasm collections and developing tetraploid clones of the principal taxa of interest. As these tetraploids reach maturity, interploid crosses have been initiated resulting in triploid hybrids which are being evaluated for fertility and commercial characteristics. Non-invasive cultivars of these species provide environmentally friendly and commercially desirable alternatives to older, invasive forms of these plants. Additional benefits from these seedless plants include elimination of nuisance fruits, reduced pollen-induced allergies, and improved flowering and re-blooming characteristics. These new products will be made available to the nursery industry and will ultimately benefit the environment and the general public. Progress has been made in the development of triploid plants in diverse genera of woody and herbaceous taxa. New tetraploid poplulations of Amur maple (Acer tartaricum subsp. ginnala) were created. Three purple-leaved cultivars of Norway maple were established in tissue culture for in-vitro polyploidy induction. Three additional tetraploid clones of mimosa (Albizia julibrissin) were developed, including ones with purple foliage. Initial results indicate that triploid clones of trumpet creeper (Campsis x tagliabuana) do not produce viable seeds. Tetraploids were developed in Scotch broom (Cytissus scoparius), but have not yet bloomed. Two hundred interspecific triploid hybrids of Elaeagnus were developed from controlled crosses between induced tetraploids and diploid cultivars, and are currently being evaluating for commercial merit. A new triploid winged euonymus was developed. An extensive study to evaluate fertility of new triploid hybrids of St. John’s-wort (Hypericum androsaemum) was completed using controlled pollinations. None of the hybrids produced viable seedlings and three hybrids have been selected for commercial release. Tetraploid trees of golden rain tree (Koelreuteria paniculata) were established in the field and will be crossed with diploids when they are old enough to flower. New tetraploid hybrids of privet (Ligustrum sinense) were developed and additional interploid crosses among L. japonicum and L. lucidum were completed. Over 300 triploids of maiden-grass (Miscanthus) were developed; initial evaluations indicate that triploids have greatly reduced fertility and the few seedlings that are produced have low vigor and fertility. Over 300 triploid hybrids of flowering pear (Pyrus) with a range of foliage colors were created and are being evaluated for commercial merit and fertility. Populations of triploid spirea with golden-colored foliage were developed and are being tested for fertility. Tetraploids of Chinese elm (Ulmus parvifolia) were developed, but have not bloomed so cannot be used yet for hybridizations. Research activities conducted under this agreement were monitored by regular email communication, submission of reports by the cooperator, and by in-person communication at scientific and stakeholder meetings.

4. Accomplishments

Last Modified: 06/28/2017
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