BREEDING AND GENETIC STUDIES OF RUELLIA SIMPLEX (MEXICAN PETUNIA)

Wild Ruellia simplex (Mexican petunia) is a popular landscape plant in the southern USA. This introduced plant is highly fertile, has escaped from cultivation and become invasive in natural areas. For several years ‘Purple Showers’ was the only existing sterile cultivar. Our breeding objective has been to develop sterile Ruellia cultivars with different flower colors and growth habits. Breeding approaches are ploidy manipulation and hybridization. Selected hybrids are evaluated in replicated trials in Florida. Female and male fertilities are determined by collection of fruits produced by open pollination, by manual hybridizations in the greenhouse, and by evaluation of pollen staining. From 2011 to 2013 the first three sterile hybrids named ‘Mayan Purple’, ‘Mayan White’ and ‘Mayan Pink’ were released, and are commercially available now. The ‘Mayan’ series was evaluated in several research and commercial trials in the USA demonstrating very good to excellent performance in terms of growth habit and flowering. In another research topic, genetics and anthocyanins responsible for flower color were studied in R. simplex. An F₁ population was obtained from crossing a maternal individual with white corolla with purple throat (WP), and a paternal individual with pink corolla and dark pink throat (PK). All plants in the F₁ generation had purple flowers (P). The F₂ generation segregated 94P:30PK:24WP:5WPK (WPK is white corolla and pink throat). These data were separated into two groups: the corolla color fit a 9:3:4 recessive epistasis interaction (P=0.22) whereas the throat color fit a 3:1 ratio (P=0.54). HPLC analyses indicated that delphinidin derivatives conferred purple corolla color, while pelargonidin derivatives were responsible for the pink corolla color. Purple throat color resulted from delphinidin derivatives whereas the pink color was caused by peonidin derivatives.