The plant produces tens of thousands of seeds that are transported by rainwater and birds to other sites, especially open woodlands, where they create dense thickets that displace native vegetation. The plant’s root system forms a tight mat below the soil surface and its broad profile (it averages 6 to 9 feet in height and is capable of reaching 15 feet) creates heavy shade that threatens the survival of plants living beneath it.

Native to eastern Asia, the deciduous Euonymus alatus was introduced in the United States around 1860. The shrub’s natural ornamental features have been genetically improved over time, giving rise to its widespread popularity. It can be found in the eastern United States from New England to Florida, and as far west as Illinois.

Recognizing the plant’s popularity among consumers and its economic importance to the ornamental plant and landscape industries, Li obtained a grant from the U.S. Department of Agriculture in 2003 to work on the development of a non-invasive variety of burning bush. The New England Invasive Plant Center has provided additional funding for the research since 2006. The invasive plant center was made possible through the support of Connecticut Rep. Rosa DeLauro (D-3rd District). DeLauro helped secure federal funding to launch the center, which aims to develop strategies and methods to address invasive plant problems.

The new lines of sterile non-invasive burning bush plant—which were derived from a popular dwarf variety known as (E. alatus) ‘Compactus’—took years to develop. Members of Li’s research team, Chandra Thammina, Mingyang He, Litang Lu, and others, painstakingly removed thousands of immature and mature endosperm from deep inside the plant’s seeds under sterile conditions and then treated them with special plant growth regulators. The team carefully maintained endosperm tissue explants in Petri dishes so that a callus, bud, seedling, and ultimately a new triploid seedless variety were grown.

“Finding the right combination of plant growth regulators and repeatedly testing and re-testing the process to validate its success was a lengthy, yet ultimately rewarding, process,” Li says.

The process to produce triploid plants from endosperm tissues is so difficult that since endosperm regeneration of plants was first reported in the early 1950s, it has been successful in only 32 plant species. Li praises his research team’s persistence, dedication, and passion, which, he says, carried his staff through the long hours necessary for separating thousands of mature and immature endosperms once the plants went to seed in the fall.

The research report appears in the August 2011 issue of HortScience, an international journal serving horticulture scientists and the horticulture industry.

The research team reports that it successfully produced 12 independently regenerated triploid plants of burning bush. Triploid plants are sterile due to uneven chromosome division as cells multiply. Li is working with UConn’s Office of Technology Commercialization to patent the process used to regenerate the burning bush triploid and ultimately bring the new plant variety to the commercial horticulture industry.