Kalmia L. is a small but diverse genus containing nine to 11 species (Ebinger, 1974; Southall, 1973; Weakley, 2012) native to North America and Cuba (Jaynes, 1997). Deciduous or evergreen woody shrubs, Kalmia spp. have a varied morphology and are each distinct. Some of their diverse characteristics include plants that are “… erect, or ascending, branching shrubs or rarely trees. The leaves are simple, alternate, opposite or whorled, coriaceous, dark green above, light green beneath, entire and often revolute (Southall, 1973).” Kalmia latifolia, and to a lesser degree, K. angustifolia L. and K. polifolia Wangenh. are valuable nursery crops and have been cultivated in North America and Europe since the early 1700s (Jaynes, 1997).
Cytology was performed on Kalmia species by Dr. Richard Jaynes of the Connecticut Agricultural Experiment Station in the late 1960s (Jaynes, 1969). His examinations found most species of Kalmia to be diploid (2n = 2x = 24), with the exception of K. polifolia that was tetraploid (2n = 4x = 48). However, that study only examined material from one or two plants per species to determine ploidy, and in the case of K. angustifolia, only samples from North Carolina were obtained as representatives of that species (Jaynes, 1969). Kalmia angustifolia and K. carolina Small [K. angustifolia var. carolina (Small) Fernald] are closely related with North Carolina provenances now generally classified as K. carolina (Gillespie and Kron, 2010; Southall and Hardin, 1974; Weakley, 2012). Cytology on Ericaceous plants, including Kalmia, is notoriously difficult, due in part to the small chromosomes (Jaynes, 1997). Flow cytometry provides a more efficient approach to broaden sampling within and among species and can provide accurate estimates of ploidy, particularly for Ericaceous plants (Jones et al., 2007).
The objective of this study was to survey genome sizes and ploidy levels of a broad range of species, hybrids, and cultivars of Kalmia from throughout North America.
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