Petunia is considered to be the first cultivated bedding plant. It is the product of complex breeding begun in the 19th century that used two South American species with white (Petunia axillaris) and purple flowers (Petunia integrifolia) (Liberty Bailey Hortorium, 1976). Subsequent petunia breeding resulted in five petunia class divisions: grandiflora, floribunda, milliflora, multiflora, and spreading. In the 1930s, the first consistently double flowers became available from Japan, whereas more flower colors were introduced in Germany from open-pollinated plants. After World War II, breeders began working on larger flowers, better growth habit, and disease and weather resistance. In the 1950s, breeders produced award-winning F1 hybrids, designated as floribundas, by crossing the larger flowered, but heat-sensitive grandifloras with the adverse weather-resistant multifloras (smaller, but more numerous flowers than grandiflora). The hybridization resulted in costly seed, but plants were superior to open-pollinated cultivars. New flower colors, such as true red and the first yellow, and plants with spreading and miniature growth habits (millifloras) expanded the available choices in color and form (Lewis, 1997; Trinklein, 2001). The range of colors, color patterns, and availability of double-flower cultivars is greatest in the grandifloras, floribundas, and multiflora classes. Use of the petunia as a model for plant physiology research resulted in important changes in plant breeding through the understanding of pollen sterility, resulting in economical production of F1 seed. These changes resulted in significant contributions to the further development of the bedding plant industry in the last half of the 20th century (Craig, 2003).
In 2005, the wholesale value of petunias was $94 million, and ranked third in value behind pansy (Viola ×wittrockiana)/viola (V. cornuta) and impatiens (Impatiens walleriana). Florida is one of the top wholesale producers of bedding plants, and in 2005 was ranked fourth in the United States in annual bedding plant production. The wholesale value of petunia flats in Florida in 2005 was $2.0 million, whereas potted petunia sales in Florida ($4.5 million) ranked second in the United States. (U.S. Department of Agriculture, 2006).
Major seed companies from Europe, Asia, and North America produce new petunia cultivars and submit them for testing in Florida. These plants may not have been bred to survive in our climate (Nordlie, 2002). Plant breeders and seed companies use Florida trial information and apply it to similar climatic regions, such as Australia, Japan, China, and southern France (T.K. Howe, pers. comm., Dec. 2001). Therefore, evaluation of petunia cultivars in Florida is vital for continued growth of the industry.
Standards have not been fully developed for petunias that identify the great diversity of color and form found in the bedding plant industry today, nor do they recognize a cultivar as a standard for each unique class that can be used for comparison. New cultivars are often compared with a random number of cultivars, and often many of these cultivars that failed to outperform a new entry in a recent trial are used repeatedly in future trials. We estimated there are more than 360 petunia cultivars currently available in the United States from a survey of eight major companies (R.O. Kelly, unpublished data). The establishment of plant and color classes, a system of class standards for each class used for comparison with new cultivars in future trials, and the effective elimination of previously evaluated cultivars was accomplished for marigolds (Tagetes erecta and T. patula), pansies, and violas in our initial evaluations. Detailed information for each cultivar about growth, flowering, performance, and pest damage was collected in seasonal replicated trials that could be used by the scientific community as well as growers, landscapers, consumers, and seed companies (Kelly and Harbaugh, 2002, Kelly et al., 2005, 2006). This petunia study was conducted to establish classes and class standards specific to this crop (such as plant and flower forms/types, and flower colors, and color patterns) and to evaluate petunia cultivar performance.
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