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Zhanao Deng and Brent K. Harbaugh

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Baldwin D. Miranda and Brent K. Harbaugh

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Zhanao Deng, Fahrettin Goktepe and Brent K. Harbaugh

The ornamental value of caladium (Caladium ×hortulanum Birdsey) depends to a large extent on its foliar characteristics. Efficient genetic improvement of caladium foliar characteristics requires a good understanding of the inheritance of these traits, including leaf shape, color, and spots. This study was conducted to determine the inheritance of leaf spots in caladium and to understand their relationships with leaf shape and main vein color. Eighteen controlled crosses were made among eight commercial cultivars expressing red or no leaf spots, and progeny of these crosses were observed for segregation of leaf spots as well as leaf shape and vein color. A single locus with two alleles is shown to be responsible for the presence or absence of leaf spots in caladium, with the presence allele (S) dominant over the absence allele (s). The major spotted commercial cultivar Gingerland is heterozygous for this trait. Leaf spots are inherited independently from leaf shape, but they are closely linked with the color of the main leaf veins. The recombination frequencies between the leaf spot locus and the main vein color locus ranged from 0.0% to 8.9% with the crosses or the parental cultivars used, with an average of 4.4%. Leaf spots and vein colors represent the first linkage group of ornamental traits in caladium and possibly in other ornamental aroids. The knowledge gained in this study will be valuable when it comes to determine what crosses to make for development of new cultivars. It may be also useful to those interested in determining the inheritance of similar traits in other ornamental plants, including other ornamental aroids such as dieffenbachia (Dieffenbachia Schott).

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Richard O. Kelly and Brent K. Harbaugh

Annual bedding plants comprised 50% of the $4.6 billion wholesale value of United States floricultural crops in 2000. Florida is one of the top wholesale producers of bedding plants in this industry, and in 2000 was number one in the production of potted marigolds. Evaluation of marigold cultivars is vital for continued growth of the industry. We evaluated 84 cultivars of african marigold (Tagetes erecta) and french marigold (T. patula) in replicated class tests at the University of Florida's Gulf Coast Research and Education Center at Bradenton, Fla. (lat. 27°4' N, long. 82°5' W; AHS Heat Zone 10; USDA Cold Hardiness Zone 9b) in Fall 1999. In this report, we provide objective plant measurements of vegetative and floral characteristics as well as six weekly subjective ratings. Subjective ratings were on a 1 to 7 scale with the highest rating of 7 for excellent. In general, cultivars with vegetative and floral ratings ≥5 were considered outstanding, 4 to 4.9 as good performers, and ≤3.9 as fair to poor. These ratings permit readers to evaluate foliage and floral characteristics at different times during the season, and to evaluate performance over time. Cultivars were grouped into classes based on species, plant height, flower type, and flower color. Outstanding cultivars (those cultivars with an overall rating ≥5) and their class were: `Inca Gold' and `Royal Gold' [african marigold (African)—gold class]; `Mesa Orange' and `Royal Orange' (African— orange class); `Inca Yellow', `Mesa Yellow', and `Perfection Yellow' (African—yellow class); `Disco Granada' [french marigold (French) dwarf—single gold/red class], `Disco Flame' (French dwarf—single red/gold class); `Golden Boy' and `Hero Gold' (French dwarf—double gold class); `Bonanza Orange', `Orange Boy', `Girl Orange', `Jacket Orange' (French dwarf—double orange class); `Yellow Boy', `Girl Primrose', and `Jacket Yellow' (French dwarf—double yellow class); `Harmony Boy' (French dwarf— double orange/red class); `Hero Flame' (French dwarf—double red/orange class); `Bonanza Flame Improved' (French dwarf—double red/yellow class); `Legend Gold' (French double— gold class); `Legend Orange Improved' (French—double orange class); `Spry Boy' (French double—yellow/red class); `Durango Bee', `Durango Red', and `Hyper Red/Yellow' (French— double red/yellow class). We believe these cultivars would perform well in the southern U.S. or areas of the world with similar heat and cold hardiness zones.

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Brent K. Harbaugh and R. J. McGovern

Fusarium crown and stem rot, caused by Fusarium avenaceum (Fr.: Fr.) Sacc., is a serious disease of lisianthus [Eustoma grandiflorum Raf. (Shinn.)]. While more than 80 new cultivars of lisianthus have been released for sale in the United States in the last decade, there is a lack of information on their susceptibility to this pathogen. Forty-six cultivars of lisianthus were evaluated for their response to infection by F. avenaceum. Cultivars were grouped according to blue/purple, pink, or white flower colors and evaluated within their color class. Although some plants of all cultivars were susceptible to F. avenaceum, partial resistance was observed as indicated by differences in the length of time to symptom expression and in the frequency of diseased plants within each color group. In 21 of the 46 cultivars, 80 to 100% of the plants expressed symptoms within 55 days after inoculation. The lowest frequencies of diseased plants 55 days after inoculation were found in `Ventura Deep Blue' and `Hallelujah Purple' (25%), `Bridal Pink' (23%), and `Heidi Pure White' (53%) for the blue/purple, pink, and white flower color groups, respectively. Screening cultivars for resistance to F. avenaceum is the first step in breeding resistant cultivars. The methods we developed for these studies should be useful in screening for resistance. These results also may help growers select cultivars that are less susceptible to F. avenaceum, which should aid in the management of this disease.

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Brent K. Harbaugh and John W. Scott