Scientia Horticulturae 125 (2010) 129–135 Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti Pollen biology of ornamental ginger (Hedychium spp. J. Koenig) Hamidou F. Sakhanokho a,∗ , Kanniah Rajasekaran b a USDA-ARS Southern Horticultural Laboratory, 810 Hwy 26 W, Poplarville, MS 39470, United States b USDA-ARS, Southern Regional Research Center, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, United States article info Article history: Received 31 July 2009 Received in revised form 25 September 2009 Accepted 22 December 2009 Keywords: Hedychium Pollen germination and tube growth Pollen viability Polyethylene glycol 4000 (PEG 4000) Pollen nuclear status Pollen:ovule ratio abstract An improved in vitro pollen germination assay was developed to assess the viability of stored Hedychium pollen. The effect of polyethylene glycol (PEG) (10, 15, and 20%, w/v) on pollen germination and tube growth was evaluated for Hedychium longicornutum and two commercial Hedychium cultivars, ‘Orange Brush’ and ‘Filigree’. Overall, the inclusion of PEG 4000 in the medium improved both pollen germination and tube growth for the three different genotypes tested and the results varied depending on genotype. In vitro germination was used to assess the viability of Hedychium pollen stored up to two months. Pollen nucleus status was determined for four Hedychium cultivars, ‘Orange Brush’, ‘Anne Bishop’, ‘Filigree’, and ‘Daniel Weeks’. Pollens of ‘Orange Brush’, ‘Anne Bishop’, and ‘Daniel Weeks’ were found to be bin- ucleate but ‘Filigree’ was shown to possess both binucleate and trinucleate pollens. High pollen:ovule ratio values were obtained in several Hedychium taxa. The results obtained on the nuclear pollen status and pollen:ovule ratios will further our understanding of the pollination biology and help clarify the taxonomy and phylogeny of Hedychium species. Published by Elsevier B.V. 1. Introduction The genus Hedychium consists of about 80 species characterized by beautiful foliage as well as diverse, showy, and fragrant flowers. Some species are grown for their edible flowers and others for their medicinal or industrial properties (He, 2000; Gopanraj et al., 2005; Gao et al., 2008). Most Hedychium species are native to central and southeastern Asia with high concentrations in southern China and the Himalayan regions (Hayes et al., 2009). They are increasingly becoming popular as ornamental plants worldwide because of their showy and scented flowers. For example, in Great Britain where no commercial sources for Hedychium existed in 1982 (Schilling, 1982), the 2009 Royal Horticultural Society (RHS) Plant Finder lists 116 taxa that are available to British gardeners. Many more taxa are found in Japan and the United States (Branney, 2005). Despite the potential ornamental, medicinal, and industrial values of the Hedychium genus, very little work has been done to understand the pollen biology such as germinability, storage, viability, nuclear status, and pollen/ovule ratio. In the United States, Hedychium plants are mostly grown in the southern part of the country where they generally flower in the summer and fall, but some species bloom in winter and spring ∗ Corresponding author. Tel.: +1 601 403 8767; fax: +1 601 795 4965. E-mail addresses: rsakhanokh@aol.com, Hamidou.Sakhanokho@ars.usda.gov (H.F. Sakhanokho). times. This asynchronous flowering could constitute an impedi- ment for breeders of that region to fully take advantage of the tremendous diversity that exists within Hedychium genus. There- fore, optimal storage conditions for Hedychium pollen to be used later on for pollination need to be investigated, but to assess the viability of the stored pollen, a convenient and reliable method of testing the pollen quality is required. Currently, there are no published reports available on Hedychium pollen storage and via- bility. Assessing pollen viability on the basis of its functions of delivering sperm cells to the embryo sac is not only tedious and time-consuming but also not always feasible (Heslop-Harrison et al., 1984), so other techniques including staining pollen with vital dyes and in vitro pollen germination and tube growth are often used to evaluate pollen viability. Furthermore, successful fertiliza- tion depends greatly not only on the ability of pollen to germinate but also on its elongation rate, assuring the successful delivery of the sperm cells to the ovules (Daher et al., 2009). In vitro pollen ger- mination and pollen tube growth are greatly influenced by different factors including the composition of the germination medium, genotype of the accession, temperature and humidity. For example, addition of polyethylene glycol (PEG) to the germination medium has been reported to improve in vitro pollen germination frequency and tube growth by preventing tube bursting (Read et al., 1993; Shivanna and Sawhney, 1995). Pollen of flowering plants is either binucleate or trinucleate. Compared to binucleate pollens, trinucleate pollens are known to have a rapid germination rate but short viability (Brewbaker, 1967). 0304-4238/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.scienta.2009.12.037