Developing Triploid Maples

Ryan Contreras,Tyler Hoskins

doi:10.3390/horticulturae6040070

Abstract

Maples are common street and shade trees throughout the temperate zone. They are widely used for their wide range of ornamental traits and adaptability, particularly to urban settings. Unfortunately, some species such as Acer tataricum ssp. ginnala (Amur maple) and A. platanoides (Norway maple) have escaped cultivation to become pests or in some cases threaten native flora. However, these species remain economically important and are still asked for by name. To ameliorate potential future ecological damage from additional escapes, we have been breeding for sterile forms using ploidy manipulation and backcrossing to develop triploids. We began with a series of experiments to develop tetraploids of Amur, Norway, and trident (A. buergerianum) maples. Treatment of seedlings at the cotyledon or first true leaf stage was successful in inducing tetraploids of each species. Mortality, cytochimeras, and tetraploids varied among species. After identifying tetraploids, they were field planted alongside diploid cultivars and seedlings, which served as pollinizers in open-pollination. Seedlings derived from open-pollinated tetraploids were generally found to be a high percentage triploids. Thus far, no Norway or trident maple triploids have flowered but after three years we observed five, 22, and 22 Amur maple triploids flowering over three respective years with no seedlings recovered to date. Further evaluation is required but our findings are encouraging that the triploids we have developed thus far will be sterile and provide new cultivars for nursery growers and land managers.

Highlights

Maples (Acer sp.) are popular landscape trees often identified by commonly having palmately lobed leaves and characteristic schizocarps
For Row 71, all tetraploids were derived from Jefferson St. seed and A. tataricum (AT) atsource theexcept
Treating germinated seedlings of Amur, Norway, and trident maples with oryzalin was effective in developing tetraploids

Summary

Introduction

Maples (Acer sp.) are popular landscape trees often identified by commonly having palmately lobed leaves and characteristic schizocarps (joined samaras). Many species differ from the archetype palmately lobed leaves and most species are not desired for their flowers or fruit, though few exceptions exist (e.g., ‘Flame’ amur maple grown for its red schizocarps). In 2014, overall U.S sales of maples exceeded $173 million, which accounted for 31% of the nearly $562 million of deciduous shade trees sold nationally [1]. Oregon, the leading shade tree production state in the U.S, ships approximately 80% of its nursery plant material out of state and historically has relied on regions in the eastern part of the U.S as principle markets.

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