Ruellia L. is the second largest genus in the Acanthaceae and consists of ≈300 species of perennial herbs, shrubs, small trees, and lianas with tropical, subtropical, or temperate distribution (Tripp, 2007). Ruellia simplex Wright (commonly known as mexican petunia, mexican bluebell, or britton’s petunia) has low maintenance requirements and prolific flowering, and has become a very popular landscape plant in the southern United States (Gilman, 1999) since its introduction to Florida sometime before 1940 (Hupp et al., 2009).
Ruellia simplex has naturalized in disturbed uplands and wetlands of seven southern U.S. states (from Florida and South Carolina, west to Texas), plus the U.S. Virgin Islands, Puerto Rico, and Hawaii (USDA, 2012). Since 2001, the Florida Exotic Pest Plant Council has considered mexican petunia as a Category I invasive plant, described as “plants that are altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives” (FLEPPC, 2015). The University of Florida Institute for Food and Agricultural Science (UF/IFAS) Assessment of the Status of Non-Native Plants in Florida’s Natural Areas also considers R. simplex as an invasive species, and does not recommend its use in Florida (IFAS, 2015).
A survey conducted in 2002 including 946 active nurseries in Florida indicated that 15.9% of them grew or sold R. simplex, and the total annual sales for this plant was estimated at about $12 million (Wirth et al., 2004). Until recently, the only R. simplex cultivars available were tall (‘Purple Showers’, ‘Chi Chi’, and ‘Snow White’) and dwarf (‘Katie’ and ‘Southern Star’ series) in purple, pink, and white flower colors. These cultivars are clonally propagated, except for the ‘Southern Star’ series which is propagated by seed (PanAmerican Seed Co., Chicago, IL). With the exception of ‘Purple Showers’, which does not set fruit by open pollination (Wilson and Mecca, 2003), all known cultivars set fruit and are potentially invasive.
In 2007, a Ruellia breeding program was initiated at UF/IFAS in Gainesville, FL, directed specifically toward creating new highly infertile cultivars for the landscape plant industry. To reduce the spread of R. simplex by seed, cultivars with low female fertility (fruitlessness or lack of seed viability) and reduced or lack of male fertility are developed (Freyre et al., 2012a). Ruellia Mayan Purple (R10-102, PP24422) and Mayan White (R10-108, PP25156) were released in 2012 (Freyre et al., 2012b), and Mayan Pink in 2013 (R10-105-Q54, PP26063) (Freyre and Wilson, 2014). These three cultivars were evaluated by the IFAS Invasive Plants Assessment and their landscape use was approved. Ruellia R12-2-1 described below was obtained by a combination of hybridization and polyploidization using oryzalin. It was selected in multilocation trials in Florida in 2015 from a group of 13 different clones and commercial cultivars due to excellent landscape performance, medium plant height, and no fruiting.
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