Genome size, ploidy estimates, and leaf morphology of temperate Lindera (Lauraceae) cultivated in North America

The genus Lindera Thunb. (Lauraceae Juss., nom. cons.) consists of ca. 100 species of shrubs and trees with economic value for medicinal drugs as well as oils used in aromatics, soaps, and biodiesel. Only a few Lindera species have received attention as ornamental plants, but considerable interspecific diversity in habit, foliage, and fruit offer significant potential to plant breeders and horticulture. We used flow cytometry to determine genome sizes of 100 accessions representing 23 temperate Lindera taxa and estimated ploidy level for each sample. In addition, we assessed stomatal size, density, and specific leaf area among accessions. We found a nearly 12-fold difference in 2C DNA context among accessions. We confirmed previous reports of diploid and tetraploid Lindera taxa, and present evidence of triploid (L. glauca (Seibold & Succ.) Blume and L. neesiana (Wall. ex Nees) Kurz), hexaploid (L. angustifolia W.C. Cheng and L. umbellata Thunb.), and octoploid (L. angustifolia, L. angustifolia var. glabra (Nakai) J.M.H.Shaw, and L. salicifolia (Blume) Boerl.) taxa for the first time. Although most taxa sampled were diploid, our findings indicate multiple cytotypes exist for L. angustifolia (6× and 8×) and L. umbellata (2× and 6×). Ploidy level had a significant positive relationship with stomatal size, but not stomatal density nor specific leaf area. Overall, these findings provide insight for plant evolutionary biologists, taxonomists, and breeders interested in Lindera, which remains to be resolved phylogenetically and has not been utilized in ornamental breeding programs. In addition, these data are relevant to plant ecologists and conservationists, particularly in North America where the Laurel wilt pathogen is threatening Lauraceae taxa, including the endangered species Lindera melissifolia and L. subcoriacea.