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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETICS, GENETIC RESOURCE EVALUATION, AND GENETIC IMPROVEMENT OF LANDSCAPE TREES AND SHRUBS

Location: Floral and Nursery Plants Research Unit

2012 Annual Report


1a.Objectives (from AD-416):
The overall objective of this project is to breed, evaluate, select, and release improved landscape trees and shrubs that are disease and pest resistant, tolerant of environmental stresses, are not invasive, and have superior ornamental value. This objective is achieved by genetically characterizing and evaluating the horticultural merit and stress resistance contained in germplasm and advanced selections of Cercis, Lagerstroemia, and Prunus (primary genera), as well as historical or exploratory genera such as Corylopsis, Deutzia, Ilex, Gaylussacia, Syringa, and Viburnum (secondary genera); developing new or improved genetic marker systems for assessing genetic diversity and accelerating genetic improvement of these genera; incorporating improved disease and stress resistance and ornamental traits into this germplasm using traditional and new breeding methodologies; and transferring superior landscape plant cultivars and germplasm to end users. This research will result in new cultivars of landscape trees and shrubs that have value to the nursery and landscape industries; germplasm that has been evaluated or enhanced for various traits; and technology on molecular markers, gene manipulation, and wide hybridization.


1b.Approach (from AD-416):
Conduct comprehensive breeding programs by genetically characterizing and evaluating the horticultural merit and stress resistance contained in germplasm and advanced selections of Cercis, Lagerstroemia, and Prunus (primary genera), as well as historical or exploratory genera such as Corylopsis, Deutzia, Ilex, Gaylussacia, Syringa, and Viburnum (secondary genera); developing new or improved genetic marker systems for assessing genetic diversity and accelerating genetic improvement of these genera; incorporating improved disease and stress resistance and ornamental traits into this germplasm using traditional and new breeding methodologies; and transferring superior landscape plant cultivars and germplasm to end users.


3.Progress Report:
During FY12, progress was made on all three objectives, which fall under NP301.

Selections were made from mature flowering cherry hybrids that had been growing in the field for 7-15 years. Plants were propagated for replicated trials in our nurseries and to send to cooperators. A study to verify interspecific hybrids among flowering cherry taxa was begun.

Selections of mature crapemyrtles were also made based on flower color, habit, and flowering time. Crapemyrtle selections were propagated for replicated field evaluation, and to initiate a study to determine the inheritance of early flowering. Crosses were made among early-flowering hybrids in order to develop early flowering cultivars.

A propagation study in box huckleberry was concluded and data is being analyzed to determine the best time of the year to take cuttings of this species. Seeds from open-pollinated crosses were harvested, and seedlings grown from previously collected seeds were evaluated for variability. Despite the fact that these seedlings represent a somewhat rare (for this species) instance of recombination, little phenotypic variability is evident.

Controlled interspecific hybridizations in Corylopsis were repeated in order to create novel or sterile interploid hybrids. Hybridizations among early-flowering crapemyrtle selections continued.

Selections of crapemyrtle and flowering cherry were maintained in tissue culture and treated with oryzalin to create tetraploid plants. Tetraploids were confirmed by flow cytometry, and will be multiplied and hardened off for use in breeding.


4.Accomplishments
1. Release of Prunus ‘Helen Taft’. The introduction of new woody ornamental plants is one of the driving forces behind the sustained growth of the ornamental horticulture industry. Researchers in Washington, D.C. released a new cherry tree variety named for former First Lady Helen Taft to commemorate the 100th anniversary of the Japanese gift of cherry trees that now are a celebrated landmark of the nation’s capital. The new variety was created by crossing a Yoshino cherry tree with a Taiwan cherry tree. The Yoshino parent is a clone of a tree originally planted 100 years ago by the Japanese Ambassador’s wife, Iwa Chinda. The new variety can grow to 35 feet in height and width over 30 years and is characterized by large single pale pink flowers. This variety will help to broaden the genetic base of cultivated flowering cherries in the U.S.


Review Publications
Pooler, M.R., Ma, H., Kidwell Slak, D.L. 2012. Interploid hybridizations in ornamental cherries using Prunus maackii. Journal of Environmental Horticulture. 30:89-92.

Wadl, P.A., Trigiano, R.N., Werner, D.J., Pooler, M.R., Rinehart, T.A. 2012. Simple sequence repeat markers from Cercis canadensis show wide cross-species transfer and use in genetic studies. Journal of the American Society for Horticultural Science. 137:189-201.

Last Modified: 7/28/2014
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