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 self-compatibility 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 produced viable seed after self-pollination in a glasshouse (personal observation; unpublished data).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 self- or cross-pollination 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.
Dirr, M.A. 2009 Manual of woody landscape plants: Their identification, ornamental characteristics, culture, propagation and uses. 6th Ed. Stipes, Champaign, IL
Harden, G.J. (ed.). 1992 Flora of New South Wales. Vol. 3. New South Wales University Press, Kensington, New South Wales, Australia
Roche, D., Chen, Z., Hanna, W.W. & Ozias-Akins, P. 2001 Non-Mendelian transmission of an apospory-specific genomic region in a reciprocal cross between sexual pearl millet (Pennisetum glaucum) and an apomictic F1 (P. glaucum × P. squamulatum) Sex. Plant Reprod. 13 217 223
Tsukaya, H., Fukuda, T. & Yokoyama, J. 2003 Hybridization and introgression between Callicarpa japonica and C. mollis (Verbenaceae) in central Japan, as inferred from nuclear and chloroplast DNA sequences Mol. Ecol. 12 3003 3011
USDA, NRCS 2012 The PLANTS database. National Plant Data Center, Baton Rouge, LA. 27 Jan. 2014. <http://plants.usda.gov>