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H. Brent Pemberton* and Ursula K. Schuch

Rose (Rosa sp.) cultivars Blue Girl and Mister Lincoln were harvested bare-root on 1 Nov. 2001 and 22 Nov. 2002 from a commercial nursery in Arizona. Grade 1 plants were then potted and forced to flowering in either Tucson, Ariz., or Tyler, Texas. Total chilling hours were calculated as the number of hours that the plants were exposed to a temperature below 7 °C in the field and during shipping and cold storage. Data were recorded when the petals on the first flower beg an to reflex. Overall, the number of flowering shoots and plant performance was positively correlated to digging date, weeks of cold and total chilling hours received. Days from potting to flower were negatively correlated to weeks of cold storage and chilling hours. However, when the data were separated by location, the number of flowering shoots, the percentage flowering shoots, and plant performance was positively correlated to weeks of cold and chilling hours in Arizona, but was positively correlated to digging date in Texas. Days from potting to first leaf unfolding were recorded in Arizona only and were negatively correlated to weeks of cold storage and chilling hours. Days from potting to flower were negatively correlated to chilling hours at both locations and also to weeks of cold storage in Texas. The increase in chilling from two or four weeks of cold storage increased the number of flowering shoots and performance rating of plants forced in Arizona during both seasons, but only for the 2001 season in Texas. During the 2002 season in Texas, these responses were not influenced by cold storage, but were greater than those seen during the 2001 season. In Arizona, days from potting to flower were greater in 2001 than 2002, and decreased in response to cold storage in 2001, but not in 2002.

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H. Brent Pemberton and William E. Roberson

The East Texas Bedding Plant Pack and Garden Performance Trials began several years ago at the Texas A&M University Agricultural Research and Extension Center at Overton (Overton Center) with the goal of providing information on greenhouse and field performance of bedding plant varieties to the local bedding plant industry and consumers of these products. The program began with local trials that have now expanded in scope with the Smith County Master Gardeners Association playing an integral role in performing the trials. Entries are received from most of the major ornamental seed companies doing business in the United States giving the regional industry access to the only comprehensive greenhouse performance trials in this part of the country. Performance evaluation data is important to this industry since it has a wholesale value of over $500 million in the northeast Texas region, of which over $100 million is bedding plant production. The field performance trials are now replicated at the Overton Center, the Dallas Arboretum and Botanical Garden (Dallas Arboretum) and the Texas A&M University Agricultural Research and Extension Center at Dallas (Dallas Center), giving over 5 million consumers in the northeast Texas region the opportunity to see how promising new plants from all over the world perform in the local climate. Plants that grow well in this climate have the potential to reduce inputs needed for production and use in the home or commercial landscape. Many of the top performing varieties from the bedding plant trials are also chosen to be part of the Coordinated Education and Marketing Assistance Program (CEMAP), a statewide testing program headquartered at the Dallas Center in which entries vie for designation as Texas Superstar plants. The comprehensive benefit of the East Texas Bedding Plant Pack and Garden Performance Trials is the link between the rural bedding plant producers and the urban consumers which serves as a basis for improving the quality of life for the citizens of Texas.

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Titus M. Kyalo and H. Brent Pemberton

Rooted liners of Rosa cvs. Meijikatar and Meirutral were potted into 11 cm pots and placed into growth chambers. One chamber provided 14 hours of light with 30C/21C (day/night) air temperature (HTLD) and another chamber provided 8 hours of light with 21C/17C (day/night) air temperature (LTSD). PPF was 725 μmoles m-2 s-1 in both chambers. When plants were established, they were pinched and forced to flower. Simulated shipping for 4 days at 16C in darkness resulted in a shorter shelf-life when placed in an interior environment at 21C with a continuous PPF of 30 μmoles m-2 s-1 and compared to non-shipped plants. In addition, LTSD grown plants exhibited a shorter shelf-life than HTLD grown plants. When Meirutral plants were sprayed to runoff 24 hours prior to shipping, 2 mmolar (aminooxy)acetic acid (AOA) increased the shelf-life to the same length as the non-shipped plants and 2 mmolar silver thiosulphate (STS) increased the shelf-life to longer than the non-shipped plants. However, AOA did not increase shelf-life over that of shipped plants for Meijikatar whereas STS increased the shelf-life to that of the non-shipped plants.

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H. Brent Pemberton and William E. Roberson

Field grown `Mr. Lincoln' rose plants were dug and wrapped in plastic to reduce moisture loss during transport to the lab. Plants were then pruned, weighed, and returned to the plastic cover. After recording initial weights, plants were allowed to dry for 0, 1, 4, 7, or 24 hours at 16°C. Plants were then oven dried, potted, or soaked in water for 20 hours before potting for each drying time treatment. The potted plants were forced to first flower in a glasshouse at which time growth measurements were made. Undried plants had a moisture content of 48%. Seven hours drying reduced moisture content to 41%, but had no effect on growth or flowering. The 24 hour drying time resulted in a plant moisture content of 33%, a plant loss of 44%, and delayed growth initiation and flowering by up to 15 days compared to undried controls. Soaking after 24 hours drying increased plant survival from 38 to 75%. Plants that survived the excessive drying produced flowering growth comparable to plants with a moisture content of > 40%. A critical moisture level for rose plant survival was found to be between 33 and 41%.

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Garry V. McDonald and H. Brent Pemberton

Cut flower production in a low-input greenhouse for winter and spring holiday sales was evaluated. Low-input structure was a plastic covered Quonset greenhouse modified with sides that could be manually raised or lowered. Sides were raised on mild days for ventilation and remained closed for minimum heating for the few brief periods of sub-freezing temperatures characteristic of the local winter climate. Bulbs of tulip (Tulipa sp L.) cultivars `Maureen', `Negrita', and `Oxford' were dry cooled for 12 weeks and planted in December for Valentine's Day forcing. 30% shading did not significantly increase stem length in `Maureen' and `Oxford' but did increase stem length in `Negrita'. `Oxford' was at a harvestable stage for the. Valentine's Day market, but not `Maureen' or `Negrita'. All cultivars were of an acceptable quality. Plugs of snapdragon (Antirrhinum majus) cultivars `Appleblossom', `Potomac white', and `Rocket Rose' were planted in late winter at 4 and 6 inch spacing and were either pinched or not pinched. For all cultivars, pinching resulted in higher yield but lower grade. Four inch spacing had a slightly larger number of higher grade stems possibly due to stretching. `Appleblossom' and `Potomac White' were florist grade, whereas `Rocket Rose' was more appropriate for mass marker For both tulip and snapdragon, cultivar evaluation is necessary to determine suitable market strategy.

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H. Brent Pemberton and William R. Roberson

Long days are known to hasten flowering of Petunia hybrida. However, breeding of modern standard-type petunia cultivars has reduced this response. With the introduction of new genetics involved in the creation of trailing-type petunias, many cultivars have been observed to have a strong photoperiodic response to the point that it is an issue for late winter or early spring flowering cropping cycles. In order to characterize this photoperiodic response in modern seed-grown trailing-type petunia cultivars, seed of 51 cultivars of trailing petunias (Petunia hybrida) were sown in November in 288 plug trays. When established about 4 weeks later, uniform plants were selected and transplanted individually to 15-cm pots. Plants were exposed to either natural days or a 4-hour night interruption using incandescent light from 2200 to 0200 HR each day until flowering. A minimum night temperature of 17 °C was maintained. Days to first flower from sowing ranged from 72 to 117 days. Generally, the night interruption treatment hastened flowering. However, the degree of hastening ranged from 4 and 5 days for `Ramblin' Burgundy Chrome' and `Ramblin' Lilac Glo', respectively, to 27 and 32 days for `Tidal Wave Cherry' and `Tidal Wave Hot Pink', respectively. Effects of night interruption treatment on plant architecture will also be presented.

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H. Brent Pemberton and William E. Roberson

The East Texas Bedding Plant Pack and Garden Performance Trials are performed as an interaction between the plant material source companies, the plant producer companies, volunteers, and retail consumers. The Overton Trial Site is located near a concentration of bedding plant growers ($80 million annual wholesale value) which is part of the close to $500 million in ornamental plant production in northeast and north central Texas, about half of the state industry value. The spring and fall trials consist of two phases. The greenhouse phase consists of assessing production performance for use by the crop production industry. Crops are usually finished in packs (36 cells per flat), but larger size containers are used as needed according to species. Height control is a major issue and specific issues have been addressed. This is one way that publishable data can be generated by these trials. The garden phase consists of assessing garden performance in a replicated field setting at the Overton site. Garden performance is also assessed for many of the entries at sites at the Dallas Arboretum and Botanical Garden and the Texas A&M Univ. Agricultural Research and Extension Center at Dallas. An integral part of the trials are the volunteers who, as members of the Smith County Master Gardener Association, donate hundreds of hours of labor to the seeding, transplanting, and garden establishment phases of the trials. In addition, a web site has been initiated as the only practical way to share the data and hundreds of images that are generated each trial season.

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Ockert Greyvenstein, Brent Pemberton, Terri Starman, Genhua Niu and David Byrne

The decline in sales of garden roses can, in part, be attributed to the lack of well-adapted cultivars. Successful selection for any trait requires an accurate phenotyping protocol. Apart from field screening, a protocol for phenotyping high-temperature tolerance in garden roses is yet to be established. An experiment was conducted to determine the stage of development when flowers were most sensitive to high-temperature stress. Liners of Rosa L. ‘Belinda’s Dream (BD) and the Knock Out® rose ‘RADrazz’ (KO) were planted in a soilless medium and grown in a greenhouse. Established plants were pruned retaining several nodes with leaves on two main shoots and treatments started. The experiment was conducted in growth chambers held at either 24/17 °C (control) or 36/28 °C (stress) day/night temperatures. Six time and duration temperature treatments included 8 weeks of continuous control conditions, 8 weeks of continuous stress conditions, and four sequential 2-week high-temperature shock treatments. Continuously stressed plants flowered in the least amount of days but did not differ from the continuous control-treated plants based on nonlinear thermal unit accumulation until flowering. Both cultivars had a 70% reduction in flower dry weight under continuous stress conditions. Flowers were most sensitive to high-temperature stress at the visible bud stage, which corresponds to Weeks 5 to 6 and Weeks 7 to 8 for BD and Weeks 3 to 4 and Weeks 5 to 6 for KO, respectively. KO was more resistant to flower abscission than BD when treated at the visible bud stage, but no difference in flower dry weight reduction between BD and KO was found. The number of vegetative nodes to the flower was unaffected by treatment and differed between the cultivars.

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Ockert Greyvenstein, Terri Starman, Brent Pemberton, Genhua Niu and David Byrne

The decline of garden rose sales over the past 20 years can be partially attributed to the lack of material adapted to a wide range of landscapes, which includes adaptation to high temperature stress. Current methods for evaluating high temperature susceptibility in garden roses are based on field observations, which are time consuming and subjected to ever-changing environmental conditions. A series of experiments were conducted to optimize protocols and compare the use of chlorophyll fluorescence (CFL) and cell membrane thermostability (MTS) by way of electrolyte leakage as methods to screen for high temperature susceptibility. Immature leaves proved better than mature leaves for both CFL and MTS measurements, using either detached leaf or whole plant stress assays. MTS measured on immature leaves stressed in a water bath at 50 °C for 45 minutes proved most consistent in separating rose clones based on high temperature susceptibility. Stressing actively growing plants with flower buds of 2 mm in diameter in a heat chamber at 44 °C for 3 hours resulted in increased flower abscission and leaf necrotic lesions on more susceptible clones when compared with those that were heat tolerant. Combining MTS measurements from immature leaves stressed in a water bath with the flower abscission and leaf necrosis responses 10 days after stress in a heat chamber could be the first step to screen and select against the more susceptible clones in a garden rose breeding program. Power analyses suggest that the proposed MTS protocol would be efficient in detecting differences between clones when the difference in electrolyte leakage is greater than 10%.

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Ursula K. Schuch, H. Brent Pemberton and Jack J. Kelly

Five cultivars of bare-root rose plants were exposed to increasing periods of drying and after rehydration were grown in containers until flowering in a plastic-covered greenhouse. At the start of the experiment, moisture content of well-hydrated roses was between 51% and 56%. Five or 7 h of drying resulted in moisture contents below 43% for four of the cultivars and caused up to 80% mortality, increased time to flower, and decreased the number of flowering shoots. ‘First Prize’ was most tolerant of drying conditions and all plants survived, whereas ‘Mister Lincoln’ plants were most susceptible and had poor regrowth performance. Whole-plant moisture of ‘Mister Lincoln’ was similar to that in the stem or shank, which means that aboveground components instead of the entire plant can be used for moisture determination.