Flower, Fruit, and Petiole Color of American Beautyberry (Callicarpa americana L.) Are Controlled by a Single Gene with Three Alleles

American beautyberry (Callicarpa americana) is a deciduous shrub native to the southeast United States and is grown primarily for its metallic-purple fruit that develop in the fall. There are also pinkand white-fruiting and variegated forms but these traits are rare in nature and there is no information available regarding their inheritance. Also, there is confusion regarding self-compatibility and the presence of apomixis in Callicarpa L. Crosses were performed to investigate the genetics of fruit color, self-compatibility, and apomixis in american beautyberry. Test crosses between C. americana (CA) and C. americana ‘Lactea’ (CAL) suggested that white fruit is recessive to purple. White fruit appears to be controlled by a single recessive gene for which we propose the name white fruit and the gene symbol wft. Although there were only a limited number of progeny grown, crosses between CA and ‘Welch’s Pink’ suggest that purple is dominant to pink. Test crosses between CAL and ‘Welch’s Pink’ are needed to draw conclusions; however, we propose that purple, pink, and white fruit are controlled by an allelic series for which we suggest the gene symbols Wft > wft p > wft. Segregation ratios suggested that all progeny in the study developed through sexual hybridization. All genotypes used in the current study were self-compatible. Callicarpa L. is a genus of 150 species of shrubs and trees distributed throughout the world including warm-temperate and tropical America, southeast Asia, the Pacific Islands, and Australia (Harden, 1992) with the greatest concentration of species found in southeast Asia, specifically the Philippine Islands (Atkins, 1999). There are 28 New World species, of which 16 are endemic to Cuba (Moldenke, 1936). The native distribution of american beautyberry (C. americana L.) in the United States ranges from Maryland in the north, west to Missouri, and south along the Gulf Coast from south Texas to Florida (USDA, 2012). American beautyberry produces a berry-like drupe in axillary cymes that encircle the stem and ripen in the fall. The wild-type color is metallic-purple to magenta but there are cultivars with white (‘Lactea’ and ‘Bok Tower’) and pink (‘Welch’s Pink’) fruit, both of which are rare in nature. There are also leaf-variegated forms of American beautyberry such as ‘Berries and Cream’, which exhibit a mottled and unstable variegation pattern. To our knowledge, there is no information in the literature on the inheritance of either trait for any species of Callicarpa, including C. americana. There is confusion about the selfcompatibility and presence of apomixis in Callicarpa. Dirr (2009) reported that C. dichotoma (Lour.) K. Koch produces fruit consistently every year even when isolated from other seedlings or species, suggesting self-compatibility, but C. japonica Thunb. produces fruit only when planted in a group, possibly indicating self-incompatibility. Three species of beautyberry (C. glabra Koidz., C. nishimurae Koidz., C. subpubescens Hook et Arn.) endemic to the Bonin Islands of Japan have been reported to be functionally dioecious (Kawakubo, 1990). However, C. longissima (Hemsl.) Merr. and C. pedunculata R. Br. produced viable seed after selfpollination in a glasshouse (personal observation; unpublished data). Populations resulting from open-pollination of C. dichotoma ‘Issai’ or C. americana ‘Welch’s Pink’ were very uniform, appearing almost clonal (M. Dirr, personal communication). This anecdotal lack of diversity in seedling populations suggests apomixis or homozygous parent plants because either selfor crosspollination of heterozygous parents should result in variation from the parental type (Ozias-Akins, 2006). Tsukaya et al. (2003) confirmed that C. ·shirasawana Makino is a natural hybrid resulting from the cross C. japonica · C. mollis Sieb. et Zucc. and its fertility was confirmed by pollen staining and seed germination of the F1 as well as successful back-crossing to C. japonica (Tsukaya et al., 2003). These results indicate that sexual reproduction exists in the genus and at least some level of outcrossing is observed. The goal of the current research was to use controlled crosses to investigate the genetics of fruit color in C. americana. Results of crosses and segregation ratios of progeny were also used for inference about apomixis and self-incompatibility in american beautyberry. Materials and Methods Plants of Callicarpa americana (Accession no. GEN08-0036), C. americana ‘Lactea’, and C. americana ‘Welch’s Pink’ were maintained at the University of Georgia Tifton Campus in 11.4-L containers filled with substrate containing 8 pine bark:1 sand amended with 0.91 kg·m dolomitic lime and 0.45 kg·m Micromax (The Scotts Co., Marysville, OH) and top-dressed with 45 g of Osmocote Plus 15-4.0-9.1 (The Scotts Co.). The wild-type (GEN08-0036) was from a north Georgia provenance collected near Athens, GA. Controlled crosses were conducted in a glasshouse with day/night set temperatures of 27/20 C. For cross-pollination and emasculation only (EO) treatments, emasculation was performed at least 1 d before anthesis. For selfpollination, emasculation was not performed and pollen was applied to the stigma by direct contact with an anther of the same flower. For cross-pollination, pollen was collected by tapping inflorescences over a petri dish and was then applied to receptive stigmas of emasculated flowers using brushes. After ripening, fruit were scored as purple, pink, or white (Fig. 1), collected and counted, and then seed were cleaned by hand and counted. Seed were then subjected to cold, moist stratification at 4 C for 60 d and sown in the same pine bark substrate as described previously. Controlled crosses performed to investigate fruit color may be found in Table 1. In addition to these crosses, 113 flowers of CA were subjected to EO to determine if pollination was necessary for fruit development. Chi square analysis was conducted to test for goodness of fit to theoretical ratios (PROC FREQ; SAS Version 9.1; SAS Institute Inc., Cary, NC). Received for publication 20 Dec. 2013. Accepted for publication 31 Jan. 2014. We thank Nancy Hand and Bruce Tucker for technical assistance. Assistant Professor. Professor. Emeritus Professor. To whom reprint requests should be addressed; e-mail [email protected]. 422 HORTSCIENCE VOL. 49(4) APRIL 2014