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- Author or Editor: Brent K. Harbaugh x
Caladium × hortulanum Birdsey `Candidum' tubers were forced in pots until at least one-half the visible sprouts were 2 cm above the soil surface. These prefinished plants were subjected to simulated transit durations of 2, 4, or 6 days in the dark at 12.5, 15.5, 18.5, 21.0 or 24C. Plants were then grown for 4 weeks in a greenhouse and were either fertilized weekly with 100 ml of a solution containing 500 N-218P-415K (mg·liter-1) or were not fertilized. Interactive effects between transit duration and temperature were significant for all measured growth responses. Transit temperature maintained for 2 days had little effect on subsequent growth and only moderate effects after 4 days. With transit duration of 6 days, an increase in temperature resulted in increased plant height, fresh weight, number of leaves, white coloration of leaves, and percent of plants judged marketable (finished) in 4 weeks. Holding at ≈ 18.5C was most favorable for transit durations of 4 or 6 days. Use of fertilizer during finishing improved plant growth regardless of transit conditions, but did not totally negate deleterious effects from transit conditions.
Symptoms of foliar chlorosis or bleaching, interveinal chlorosis of lower leaves, leaf edge and tip necrosis, stunted growth and delayed flowering of Eustoma increased as pH decreased below 6.5 in various peat-vermiculite based media for all cultivars tested. Symptoms were evident with or without microelement amendments in the media or fertilizer. A 5×5 factorial with pH of media and fertilizer solutions ranging from 5.1 to 7.5 indicated fertilizer pH did not negate plant response to low media pH. Leaf tissue levels of Zn were elevated at low media pH and negatively correlated to plant growth and flowering characteristics, while imbalances in tissue levels of N, P, K, Ca, Mg, Fe, Mn, Cu and B appeared to be less important. Symptomatic plants grown in media with a pH from 5.0 to 5.8 had tissue levels of Zn ranging from 200 to 1200 ppm, and plants without symptoms in media with a higher pH had leaf tissue levels from 40 to 100 ppm Zn.
Rosetting response was determined for four lisianthus [Eustoma grandiflorum (Raf.) Shinn.] cultivars exposed to photoperiod and temperature treatments during stage 1(14 to 43 days after sowing) and stage 2 (43 to 79 days after sowing) seedling development. Stage 1 seedlings were exposed to short days (12 h photoperiod) or long days (18 h photoperiod) in combination with high (26C) or low temperatures (12C). After stage 1 treatments, stage 2 seedlings were divided and exposed to the same treatment combinations resulting in 16 treatments. Seedlings were then grown at 22C for 120 days to determine rosetting response. Cultivars responded differently to temperature and photoperiod. Short day-high temperature exposure during either stage 1 or stage 2 resulted in the greatest number of rosetted plants (50 to 100%) for `Yodel White', `HeidiPink', and `BlueLisa'. `GCREC-Blue' did not rosette with short day-high temperature. Low temperature during stage 1 did not prevent rosetting when stage 2 seedlings were subsequently exposed to high temperature, but low temperature during stage 2 decreased rosetting of seedlings exposed to high temperature in stage 1. Less rosetting occurred with long day-high temperature than with short day-low temperature, especially for `Blue Lisa'.
Interveinal chlorosis of lower (oldest) leaves followed by development of interveinal necrotic spots, marginal necrosis, downward cupping of leaves, and leaf abscission were symptoms of a disorder commonly observed during production of potted pentas. The disorder was determined to be an Fe toxicity problem associated with accumulation of extremely high levels of foliar Fe (649 to 1124 ppm). Cultivars varied in their response to soil-applied Fe-DTPA chelate solutions: `Starburst', `Mauve' and `Ruby Red' were very susceptible, `Pink Profusion' was intermediate, and `White', `Lavender Delight', and `Pink Rose' were resistant. Potted plant production in a root medium with an initial pH of 6.7 ± 0.1 and a end pH of 6.4 ± 0.2 reduced the accumulation of foliar Fe to levels ranging from 59 to 196 ppm and prevented development of significant visual symptoms for all Cultivars.
Seedling growth and flowering responses were examined for four Eustoma cultivars exposed to photoperiod × temperature treatments during two seedling ages. Seedlings were grown under short days (SD, 12-hour photoperiod) or long days (LD, 18-hour photoperiod) in soil at 12 or 28C from 14 to 43 days after sowing. Seedlings from each treatment were then subdivided into four lots and subjected to the same photoperiod × temperature treatments from 43 to 79 days after sowing, for a total of 16 treatments. To determine flowering response, seedlings were grown subsequently for 120 days at 22C under the same photoperiod that they received from day 43 to 79. For all cultivars and both seedling ages, seedlings were larger and had more leaves when grown at 28C rather than at 12C, but the tallest plants at flowering were from seedlings exposed to 12C. Seedlings from some treatments bolted but did not initiate visible flower buds, and some seedlings developed visible buds that later aborted, resulting in plants that did not flower by the termination of the experiment (199 days). Cultivar and interactive effects of photoperiod and temperature influenced the percentage of flowering plants. Vegetative growth and flowering responses were similar for `Yodel White', `Heidi Pink', and `Blue Lisa'. They flowered as LD plants when seedlings were grown at 12C from day 14 to 43 or day 43 to 79. Seedlings of these cultivars that were grown under SD at 28C from day 43 to 79 did not flower, regardless of photoperiod or temperature treatments from day 14 to 43. However, SD photoperiod or 28C did not decrease flowering for `GCREC-Blue'.
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.
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.
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.
The ornamental value of caladium (Caladium ×hortulanum Birdsey) depends primarily on leaf characteristics, including leaf shape and main vein color. Caladium leaf shapes are closely associated with plant growth habit, stress tolerance, and tuber yield; leaf main vein colors are often used for cultivar identification. Thirty-eight crosses were made among 10 cultivars and two breeding lines; their progeny were analyzed to understand the inheritance of leaf shape and main vein color and to determine if there is a genetic linkage between these two traits. Results showed that a single locus with three alleles determined the main vein color in caladium. The locus was designated as V, with alleles V r, V w, and V g for red, white, and green main veins, respectively. The white vein allele was dominant over the green vein allele, but it was recessive to the red vein allele, which was dominant over both white and green vein alleles; thus the dominance order of the alleles is V r > V w > V g. Segregation data indicated that four major red-veined cultivars were heterozygous with the genotype Vr V g, and that one white-veined cultivar was homozygous and one other white-veined cultivar and one breeding line were heterozygous. The observed segregation data confirmed that the three leaf shapes in caladium were controlled by two co-dominant alleles at one locus, designated as F and f, for fancy and strap leaves, respectively. The skewedness of leaf shape segregation in some of the crosses implied the existence of other factors that might contribute to the formation of leaf shape. Contingency chi-square tests for independence revealed that caladium leaf shape and main vein color were inherited independently. The chi-square tests for goodness-of-fit indicated that the five observed segregation patterns for leaf shape and main vein color fit well to the expected ratio assuming that two co-dominant and three dominant/recessive alleles control leaf shape and main vein color and they are inherited independently.