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Adam Dale, Stoyan Prigozliev, George Chu*, and Selim Kermasha

`Seascape' strawberries were harvested and treated with various concentrations of riboflavin and placed on a lab bench for 0, 1, 2, 3, or 4 days, respectively, in a cold room at 4 °C. After each day, samples were taken and stored in a freezer at -20 °C until they were evaluated for anthocyanins content. Both exogenously applied riboflavin and storage time increased cyaniding 3-glucoside and pelargonidin 3-glucoside in the strawberry fruits. This result indicates that riboflavin could be used to increase red color in strawberries destined for processing as well as be included as a vitamin supplement in the processed products.

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Lisa J. Skog*, Theo Blom, Wayne Brown, Dennis Murr, and George Chu

Ozone treatment has many advantages for control of fungal diseases. There are no residue concerns, no registration is required, and it is non-specific, therefore potentially effective against a broad spectrum of pathogens. However, ozone is known to cause plant damage. There is little information available on either the ozone tolerance of floriculture crops or the levels required to kill plant pathogens under commercial conditions. Nine floriculture crops (begonia, petunia, Impatiens, Kalanchoe, pot roses, pot chrysanthemums, lilies, snapdragons and Alstroemeria) were subjected to increasing levels of ozone. Trials were conducted at 5 and 20 °C (90% to 95% RH) and ozone exposure was for 4 days for either 10 hours per day (simulating night treatment) or for 10 minutes every hour. Damage was assessed immediately after treatment and after an additional 3 days at room temperature in ozone-free air. Trials were terminated for the crop when an unacceptable level of damage was observed. Trials to determine the lethal dose for actively growing pathogens (Alternaria alternata, Alternaria zinniae and Botrytis cinerea) and fungal spores were conducted under identical conditions. Ozone tolerance varied with plant type and ranged between <0.2 and 3ppm. Generally, the crops surveyed were more susceptible to ozone damage at the low temperature. As a group, the bedding plants were the least tolerant. Fungal spores were killed at treatment levels between 0.8 and 2 ppm ozone. The actively growing fungal mycelium was still viable at 3 ppm ozone when the trial had to be terminated due to ozone-induced structural damage in the treatment chambers. Under the trial conditions, only the Kalanchoe would be able to tolerate the high levels of ozone required to kill the fungal spores.

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Wayne Brown, Theo J. Blom, George C.L. Chu, Wei Tang Liu, and Lisa Skog

The sensitivity of easter lilies (Lilium longiflorum) to either ethylene or methane (products of incomplete burning in gas-fired unit heaters) was tested during rooting [3 weeks at 18 °C (65 °F)], vernalization [6 weeks at 6 °C (43 °F)] and subsequent greenhouse forcing (15 weeks at 18 °C). Starting at planting, easter lilies were exposed for one of seven consecutive 3-week periods (short-term), or for 0, 3, 6, 9, 12, 15, 18, or 21 weeks starting at planting (long-term) to either ethylene or methane at an average concentration of 2.4 and 2.5 μL·L-1(ppm), respectively. Short- or long-term exposure to ethylene during rooting and vernalization had no effect on the number of buds, leaves, or plant height but increased the number of days to flower. Short-term exposure within 6 weeks after vernalization reduced the number of buds by 1 bud/plant compared to the control (no ethylene exposure). However, extensive bud abortion occurred when plants were exposed to ethylene during the flower development phase. Long-term exposure to ethylene from planting until after the flower initiation period resulted in only two to three buds being initiated, while continued long-term exposure until flowering caused all flower buds to abort. Short-term exposure to methane at any time had no effect on leaf yellowing, bud number, bud abortion, or height and had only a marginal effect on production time. Long-term exposure to methane from planting until the end of vernalization increased both the number of buds, leaves and height without affecting forcing time, leaf yellowing or bud abortion.

Open access

Derald Harp, Gaye Hammond, David C. Zlesak, Greg Church, Mark Chamblee, and Steve George

Landscaping today involves the struggle to balance aesthetically pleasing plants while minimizing the impact on the environment, reducing water usage, decreasing fertilizer use, and eliminating or significantly reducing pesticide usage. Roses (Rosa sp.), although seen as challenging plants, remain the most popular flowering shrub in the United States. The identification of new cultivars that combine beauty, pest and disease resistance, and drought tolerance are important to Texas landscapes. Sixty roses were assessed over a 3-year period to determine flowering, drought tolerance, disease resistance, and overall landscape performance in minimal-input gardens in north central Texas. Atypical weather during the study had a significant impact on performance. A 2-year drought (2010–11) was accompanied by the hottest summer on record (2011), which included a record number of days of at least 100 °F or higher. As a result, supplemental irrigation was provided three times both summers. Roses generally fared well under these conditions and survived the drought. Flowering was most abundant during the spring and fall, and it was least abundant in the summer. Powdery mildew [PM (Sphaerotheca pannosa var. rosae)] was a minor problem. Nine of 60 cultivars developed no visible symptoms of PM during the study. Most PM occurred in Spring 2010, with very little found after June; none was found in 2011. Black spot [BS (Diplocarpon rosae)] was serious for some cultivars, but most were BS-free; RADrazz (Knock Out®) and Lady Banks White had no observed BS during the study. BS occurred mostly in May, June, and November. Overall landscape performance ratings were high, with 23 cultivars having a mean landscape performance rating equal to or better than the Belinda’s Dream standard. The best-performing cultivars were RADrazz (Knock Out), RADcon (Pink Knock Out®), RADyod (Blushing Knock Out®), WEKcisbaco (Home Run®), and Alister Stella Gray. This study was able to identify many other highly performing roses in north central Texas.

Open access

Derald Harp, Gaye Hammond, David C. Zlesak, Greg Church, Mark Chamblee, and Steve George

Griffith Buck (Iowa State University) bred roses (Rosa sp.) to survive long, cold winters and hot, humid summers yet still retain their foliage without fungicides. Unfortunately, there is little known about the performance of Buck roses in the southern United States. Thirty-eight Buck rose cultivars were evaluated for flowering, disease resistance, drought tolerance, and overall landscape performance in alkaline soils with no fertilizer, no pesticides, and only limited irrigation. Flowering occurred on a bimodal basis, with the highest per plant mean bloom number (16.3 blooms) and bloom coverage (9.7%) in April, and a second flowering in the fall, with 13.7 blooms per plant and 6.9% bloom coverage in October. Drought stress symptoms were most evident in October, with a wide range of symptom severity across cultivars. Black spot (Diplocarpon rosae) and powdery mildew (Podosphaera pannosa) incidence were rare across all roses and years. Landscape performance scores, rated using a 0 to 10 scale with 10 representing a perfect plant and 0 a dead plant, were highest in April (6.5) and lowest in June (4.6) and July (4.6). Landscape performance was not correlated with bloom number or coverage. While unable to recommend many of the Buck roses for north-central Texas, the cultivars April Moon and Freckles, and possibly a few other roses, can join Carefree Beauty™ (BUCbi) as recommended roses for the area.