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

developed for phenotyping high temperature susceptibility in garden roses. At the Texas A&M Rose Breeding Program, landscape performance was quantified on a 1–5 scale. Landscape performance was influenced by the ability of the rose to maintain healthy

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Yan Ma, David H. Byrne, and Katrina G. Porter

Several colchicine-induced amphidiploids of blackspot-resistant, wild diploid rose species were produced for interbreeding with tetraploid garden roses. Shoot-tip chromosome counts confirmed that 86-7 (Rosa wichuraiana Crep. × R. rugosa rubra Hort.) and 86-3 (R. laevigata Michx. × R. banksiae Aiton) are amphidiploids (2n = 4x = 28), and that 84-1000 (R. roxburghii Tratt. × R. laevigata Michx.) is a mixoploid with diploid (2n = 2x = 14) and hypotetraploid (2n = 4x-1 = 27) sectors. The measured volume of pollen grains and guard cells was higher in the tetraploids. Pollen stainability was higher in amphidiploids 86-3 and 86-7 than in mixoploid 84-1000. The amphidiploid 86-7 has greater pollen fertility as determined by crossing with a range of commercial tetraploid roses than 86-3 and 84-1000, but is less fertile than its parental diploid species. Leaflets of the amphidiploids are larger and more crinkled along the midrib than in their diploid parents. These three amphidiploids provide new additions to tetraploid rose germplasm.

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Xianqin Qiu, Hao Zhang, Hongying Jian, Qigang Wang, Ningning Zhou, Huijun Yan, Ting Zhang, and Kaixue Tang

1) to analyze genetic relationships and distances among the three Rosa classes; and 2) to detect the role of wild roses in the history of rose breeding. The results of this study will clarify our understanding of which accessions were used in the

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Tina M. Waliczek, Dave Byrne, and Don Holeman

. The purpose of this study was to investigate growers’ and consumers’ opinions of roses available on the market and preferences for future roses coming into the market. The hope of the study was to determine future rose breeding endeavors to develop

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Ian S. Ogilvie, Neville P. Arnold, and Daniel C. Cloutier

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Ian S. Ogilvie, Neville P. Arnold, and Daniel C. Cloutier

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Ian S. Ogilvie and Neville P. Arnold

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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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Ian S. Ogilvie, Neville P. Arnold, and Daniel C. Cloutier