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- Author or Editor: T. C. Clark x
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More than 60 new poinsettia cultivars have been introduced in the past 3 years, and many of these have nontraditional bract color or plant form. About 75% of all poinsettias sold are red and `Freedom' represents more than 50% of the red poinsettia market in the United States In Fall 1999, 212 individuals were surveyed and asked to indicate their favorite 10 cultivars out of the 89 in a cultivar trial. The top choices were `Plum Pudding', `Winter Rose Dark Red', `Cranberry Punch', and `Monet Twilight', which were selected by 48%; 38%; 32%, and 31% of the participants, respectively. These cultivars are all nontraditional in appearance. The top red cultivars were `Freedom', `Orion', and `Red Velvet', which were selected by 27%, 26%, and 23%, respectively. The participants were then asked to rate on a 1 to 10 (most favorable) scale 15 plants that represented different poinsettia forms and colors. Five of these plants were cultivars with different shades of red that the industry easily separates. However, the participants' ratings of these were not significantly different, which indicates the shade of red in bract color may be more important to the industry than it is to the public. These results also indicate that there are strong differences in individual preferences for poinsettias. Each of the 15 plants received both high and low ratings. Also, of the participants that included `Freedom Red' in their top 10 selection, only 13% of those selected `Plum Pudding', which has purple bracts, and only 11% selected `Winter Rose Dark Red', which has a nontraditional plant form.
Salvia (Salvia splendens F.), vinca (Catharanthus roseus L.), and pansy (Viola × wittrockiana Gams.) were examined to determine efficacy of growth retardants for inhibiting stem elongation of seedlings in the plug stage and after transplanting to 10-cm pots. Studies on salvia showed plugs sprayed with single applications of ancymidol at 10 or 20 ppm, paclobutrazol at 30 or 60 ppm, or daminozide/chlormequat tank mix at 2500/1500 ppm inhibited plug elongation by 17% to 22%. Pansy plugs were sprayed either once or twice with ancymidol at 5, 10, or 15 ppm. Number of applications was statistically significant with two applications reducing elongation by an average of 35%, whereas a single application resulted in a 23% average reduction. Ancymidol concentration was significant in reducing stem elongation with increasing rates in pansy; however, the concentration and application time interaction was not significant. In both pansy and salvia, plant size at flowering was similar to controls after transplanting. Vinca plugs were sprayed with ancymidol at 5, 10, or 15 ppm either the 3rd week, 4th week, or both weeks after sowing. As ancymidol concentrations increased, plug height decreased, and the concentration effect was greater week 3 than at week 4. Two applications of ancymidol was most effective in retarding stem elongation (36%) followed by one spray the 3rd week (29%) and one spray during week 4 (20%).
Uniconazole was applied as a spray to the surface of container media prior to planting bedding plant plugs. This medium spray was compared to a standard whole-plant spray applied 2 weeks after planting. For petunia (Petunia ×hybrida Vilm.) and coleus (Solenostemon scutellarioides L.) the efficacy of the medium spray was similar to the whole-plant spray. However, for impatiens (Impatiens wallerana Hook. f.) and vinca [Catharanthus roseus (L.) G. Don.] the medium spray had greater efficacy than the whole-plant spray. Increased concentrations of uniconazole in the medium spray decreased plant height; however, the effect of higher concentrations was greater in a medium with out pine bark compared to a medium with pine bark as a component. In the above experiments, uniconazole was applied in a volume of 200 mL·m-2. In a test where spray volume varied, there was a negative linear relationship between plant height and spray volume. Chemical name used: (E)-(+)-(S)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pent-1-ane-3-ol (uniconazole).
In some species of bedding plants, rapid hypocotyl elongation during germination makes size control in plug production difficult. Commercial growers often start applying growth regulators as cotyledons are expanding or after the first true-leaves are expanding. Using `Bonanza Spry' marigolds, we evaluated applying paclobutrazol at sowing and after 3 and 6 days. Sprays at 30 mg·L–1 in a volume of 0.2 L·m–2 or 3 mg·L–1 in 0.6 mg·L–1 applied at sowing reduced hypocotyl elongation by 25% and produced more compact plugs. In a second study, plugs of `Double Madness Rose' petunia, `Showstopper Orange' impatiens, `Wizard Rose' coleus, and `Cooler Rose' vinca were grown in 10-cm pots with a growing medium that did not contain pine bark. Uniconazole was sprayed in a volume of 0.2 L·m–2 onto the surface of the medium before planting at concentrations of 25%, 50%, and 100% of the label's recommended concentration for each crop. An additional treatment was uniconazol applied 2 weeks after planting at the label concentration. All early applications reduced final plant size compared to the nonsprayed plants. For impatiens, the early application at 25% of the label concentration produced plants similar to the spray at 2 weeks after planting. For the other crops, the 50% treatment prodcued plants similar to the spray after planting. The early applicaiton of growth regulators offers the industry an additional stradagy to use for controlling the growth of vigorous bedding plant crops.
In this study, the temporal and spatial regulation of putative ethylene receptor genes was examined during ethylene and pollination-induced flower petal abscission of zonal geranium (Pelargonium × hortorum L.H. Bailey). We used the Arabidopsis thaliana ETR1 gene as a heterologous probe to isolate two full-length cDNA clones, GER1 and GER2, from an ethylene-treated geranium pistil cDNA library. Both cDNAs share a high degree of DNA sequence similarity to ETR1, and examinations of deduced amino acid sequences indicate that the proteins encoded by each gene have the conserved ethylene binding and response regulator domains found in ETR1. Experiments focused on determining the temporal regulation of these genes revealed that both genes are expressed in geranium florets much earlier than when the florets become responsive to ethylene treatment, which is sufficient to cause petal abscission in 1 hr. Both genes are expressed in pistils throughout floret development. Experiments focused on determining the spatial regulation of these genes revealed that both genes are expressed at moderate levels in leaves, pistils, anthers, and petals, and are expressed at very low levels in roots. Preliminary evidence suggests that GER2 is transcriptionally regulated by ethylene in pistils after exogenous ethylene treatment. Currently, the transcriptional regulation of these genes in pistils after pollination is unknown.
Chemical rates for commercial apple orchards are derived from replicated single-tree spray studies based upon dilute (>3740 l/ha) amounts of carrier to standard trees and are not adjusted to tree size. The purpose of this study was to evaluate a season long pest management program where rates had been reduced to 60% of standard recommended rates on trellised apple trees. The experimental unit consisted of 4 trellised rows of apples planted in 1976. The cultivars in the study were `McInstosh', Golden Delicious, and spur and nonspur `Delicious'. Treatments were full rate (100), 60% of the full rate (60) and a control (0). Disease and insects damage was monitored periodically throughout the season and damage was assessed at harvest on the spur `Delicious' and `Golden Delicious' fruit. During the experiment it was discovered that the orchard used had developed resistance to benomyl resulting in some apple scab present even in the 100 treatment. There was a reduction in the level of scab however in the 60 and the 100 trt compared to the 0 trt. At harvest the major diseases observed in the 0 trt blocks was sooty blotch and flyspeck. Insect damage was minimal. Results from the study suggest that pesticide rates may be reduced by 40% with little impact upon fruit quality.