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  • Author or Editor: Brent K. Harbaugh x
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Cultivated caladiums (Caladium ×hortulanum Birdsey) are valued as important pot and landscape plants because of their bright, colorful leaves. Improving leaf characteristics or generating new combinations of these characteristics has been one of the most important breeding objectives in caladium. A major leaf characteristic in caladium is leaf blotching, the presence of numerous irregularly shaped color areas between major veins on leaf blades. This pattern of coloration in combination with bright colors has resulted in the popularity of a number of caladium cultivars. In this study, controlled crosses were made among three blotched and six nonblotched caladium cultivars. Their progeny were analyzed to understand the mode of inheritance of leaf blotching and its genetic relationship with the color of main leaf veins. Progeny of selfing nonblotched or crossing nonblotched cultivars were all nonblotched; selfing blotched cultivars (Carolyn Whorton, White Christmas, and Florida Blizzard) or crossing ‘Florida Blizzard’ and ‘Carolyn Whorton’ resulted in a 3:1 ratio (blotched:nonblotched); and progeny from crosses between blotched and nonblotched cultivars segregated in a 1:1 ratio (blotched:nonblotched). These results indicate that leaf blotching is controlled by a single nuclear locus with two alleles (B and b). χ2 analysis of the joint segregation between leaf blotching and vein color (V) in five crosses showed that the blotching allele B is linked to the green vein allele V g. ‘Carolyn Whorton’, ‘White Christmas’, and ‘Florida Blizzard’ are heterozygous for leaf blotching, and their genotype for leaf blotching and vein color (V r, V w, and V g for red, white, and green veins, respectively) are V r b//V g B, V g b//V g B, and V w b//V g B, respectively. This information will be valuable for planning crosses and breeding populations to develop new blotched caladium cultivars. The information gained in this study may be helpful for understanding the inheritance of similar traits in other aroids.

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Nonplanted Caladium × hortukmum Birdsey `Candidum' tubers were exposed to 26 (control), 38,43, or 48C for 1,2, or 3 days. Then tubers were planted and forced in a glasshouse for 4 weeks at 18 to 33C (air). Leaf emergence from tubers exposed to 48C for 1 or 2 days required 3-12 days longer than leaf emergence from control tubers. No leaves emerged from tubers treated at 48C for 3 days. Exposing tubers to 38C for 3 days or 43C for 1 day did not affect subsequent plant growth. Exposing tubers to 43C for 2 or 3 days or 48C for 1 or 2 days resulted in plants with reduced shoot fresh weights and fewer leaves ≥ 15 cm. In a second experiment, planted tubers were forced for 10 days at 26C so that roots had developed to the edge of the pot and shoots had emerged to the soil surface. These planted (sprouting) tubers were exposed to 43C for 0,4,8,12,16,20, or 24 hours/day for 1,3, or 5 days and then forced for 7 weeks in a glasshouse. With 3- or 5-day treatments, days to leaf emergence increased as the hours of exposure to 43C increased. Only 33% of planted tubers exposed to 43C for 24 hours/day for 5 days sprouted. Tubers exposed to 43C for≤ 12 hours/day for 3 days produced plants of similar or greater height, numbers of leaves □≥15 cm wide, and shoot fresh weights, but additional hours of daily exposure decreased these plant characteristics. At 5 days, plant height, number of ≥ 15-cm-wide leaves, and shoot fresh weight decreased linearly with increased hours of exposure of tubers to high temperature.

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Before being forced as potted plants, tubers of two Caladium ×hortulanum Birdsey cultivars were subjected to different methods of de-eyeing (terminal bud removal), either before or after 6 weeks of curing and storage. The cultivar Frieda Hemple (`FH'), a type with numerous buds that does not require de-eyeing, was less affected by deeyeing than `Fannie Munson' ('FM'), which has a single dominant bud and requires deeyeing. De-eyeing had little effect on `FH' development. For `FM', regardless of the time of de-eyeing, all treatments reduced height, increased the number of leaves, increased total leaf area, and reduced mean leaf area when compared to intact tubers. However, as the size of the tuber piece removed during de-eyeing increased, the variability within each treatment increased. Based on the results of this research, the best method of de-eyeing would be to destroy or remove the dominant terminal bud while removing as little of the surrounding tissue as possible. The time of de-eyeing can depend on producer preference, since the time of de-eyeing did not affect development significantly.

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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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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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The sporadic nature of inflorescence production and flower protogyny in caladium (Caladium ×hortulanum Birdsey) makes it desirable to store pollen and to rapidly assess its viability for cross-pollinations in breeding programs. This study was conducted to develop a procedure to determine caladium pollen viability and to use that procedure to evaluate the effect of short-term storage conditions on pollen viability. The sucrose level in the culture medium was found to have a significant impact on the in vitro germination of caladium pollen; a concentration of 6.8% was determined to be optimal for pollen germination. Caladium pollen lost viability within 1 day under room (24 °C) or freezing (-20 °C) temperatures, but could be stored at 4 °C for 2 to 4 days. Pollen stored at 4 °C produced successful pollinations. Data obtained from large-scale greenhouse pollinations supported use of this in vitro germination assay as a convenient way to evaluate caladium pollen viability (and fertility).

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