First report of triploidy in Ailanthus altissima, an invasive tree species

Abstract

Ailanthus altissima is a woody plant that has become invasively naturalized in many countries. Using nuclear SSR markers, we studied specimens of this species collected throughout Japan and found an individual (labeled Aa-1) that was not diploid. We examined pollen morphology and ploidy level of Aa-1 by optical microscopy and flow cytometry (FCM), respectively. Some pollen grains were morphologically abnormal and much larger than normal. FCM analysis demonstrated that Aa-1 was triploid. Formation of abnormal pollen indicates that Aa-1 may well have reduced fertility compared to normal diploids. If this were the case, vegetative progeny Aa-1 could be used as ornamentals without attendant risks of future naturalization.

Keywords:

• Ailanthus altissima
• FCM analysis
• Invasive tree species
• Nuclear SSR marker
• Triploid

Acknowledgments

We thank the Civil Engineering Center at Toyama City for allowing us to sample our target Ailanthus altissima tree (Aa-1). We also thank the University of Tokyo's Tanashi Forest Center for allowing us to use their optical microscope.