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Patrick E. McCullough, Haibo Liu and Lambert B. McCarty

Trinexapac-ethyl (TE) is an effective plant growth retardant for hybrid bermudagrass; however, growth responses of various dwarf-type bermudagrass cultivars to TE have not been reported. Two 60-day greenhouse experiments were conducted at the Clemson Greenhouse Research Complex, Clemson, S.C., to evaluate the response of `Champion', `FloraDwarf', `MiniVerde', `MS Supreme', `Tifdwarf', and `TifEagle' bermudagrass with and without TE at 0.0125 kg·ha-1 a.i. per 10 days. From 20 to 60 days after initial treatments, TE enhanced visual quality 9% to 13% for all cultivars. From four samples, TE reduced clippings 63%, 63%, 69%, 62%, 64%, and 46% for `Champion', `FloraDwarf', `MiniVerde', `Tifdwarf', and `TifEagle', respectively. Trinexapac-ethyl enhanced root mass 23% and 27% for `MiniVerde' and `FloraDwarf' bermudagrass, respectively. `Champion', `MS Supreme', `Tifdwarf', and `TifEagle' bermudagrass treated with TE had similar root mass to the untreated respective cultivars. Among untreated cultivars, `FloraDwarf', `MiniVerde', `MS Supreme', and `Tifdwarf' had similar root masses; however compared to these cultivars, `Champion' and `TifEagle' had 33% and 81% less root mass, respectively. Root length was unaffected by TE; however, `Champion' and `TifEagle' averaged 20% and 36% less root length compared to `Tifdwarf' bermudagrass, respectively, while `FloraDwarf', `MiniVerde', and `MS Supreme' had similar root length to `Tifdwarf'. Trinexapac-ethyl safely enhanced turf quality and reduced clipping yield at 0.0125 kg·ha-1 per 10 days without inhibiting root growth of six dwarf-type bermudagrasses. Chemical name used: [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (trinexapac-ethyl).

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A.S. Devyatov

An orchard trial was established by planting an orchard with between-row intervals of 4 m. The French Axe was trained for trees with intervals in the row of 1 and 1.5 m. The hedgerow was used for treatments of 2–2.5 and 3 m between trees in the row. Semi-dwarf rootstock of Bud54-118 and dwarf one Bud62-396 were used. The growth of of these rootstocks was analogous to MM106 and M26, respectively. The trunk cross-sectional area of 7-year trees on 54-118 rootstock was 2.3 times more than on 62-396 for cv. Antey and 1.5 times more for cv. Tellisaare. The height of tree with French Axe crown at 7 years after planting on 54-118 rootstock reached 3.5–4 m. The height of tree was 0.5 m smaller on 62-396. The crown habit of tree on 62-396 rootstock was more comfortable for high -density orchard than trees on 54-118. The sum length of twigs that were cut out during 1993–96 to attain of normal density of crown was 2-4 times more than on 62-396 rootstock. Commercial fruiting of cv. Antey started at the 3rd leaf, but it was on 4th leaf for the more-dwarf rootstock 62-396. Average yield of fruit at 3–6 years after planting of cv. Antey for treatment of distance between trees in the row of 2 or 1.5 m was 6.8 kg/tree per year-1 for 54-118 rootstock, 3.4 and 3.5, respectively, for 62-396 rootstock. Yield at the 7th year after planting reached 24 and 32 kg on 54-118 rootstock, 16 and 15 kg on 62-396, respectively. Analogous date obtained for cv. Tellisa are. cv. Spartan on both rootstocks started to fruiting at 5-6 years after planting. The fruit quality was very high in all treatments of the trial.

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E.N. Estabrooks, C.G. Embree and H.Y. Ju

Apple trees of the tender cultivar Gravenstein were grown on four promising, dwarfing, stembuilders and two known hardy rootstocks to evaluate hardiness. After eight growing seasons and a “test winter” from 1992 to 1993, trees were subjected to a destructive harvest to assess the amount of blackheart. The extent of blackheart was used as an indicator of sublethal winter injury. The amount of blackheart in the stembuilder trunk was significantly different among stembuilders but not between rootstocks. The stembuilder Bud 9 had more blackheart than Dudley, Lobo, KSC 28, and Ungrafted (Dudley). Similarly, the percentage of blackheart in the scion part of the tree showed differences due to cultivars and stembuilders but no difference due to rootstocks.

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B.H. McCown, E.T. Jordan, C.H. Chen, D.D. Ellis and R.D. Vierstra

Although the size of pot mums can be controlled with retardants, the use of such chemicals may become limited. Genetically dwarfing current cultivars may be an alternative. Using a construct including a chimeric oat phytochrome structural gene, tobacco phenotypes have been produced that strongly resemble retardant-treated plants. We wished to insert this construct in mum by using particle bombardment and determine the effects on plant size and flowering dynamics. A target system was developed using `Iridon' mum leaf sections regenerated on an IAA/BA medium. Shoots developed from surface cells principally at the cut edges. Regenerates were grown-on through flowering and no visual aberrations were apparent. Levels of 50 to 100 mg/l kanamycin were inhibitory to bud development. Sections were exposed to gene transfer and shoots recovered that appear resistant to kanamycin. Some appear chimeric while others appear to be escapes stimulated by a `feeder' effect from nearby transformed cells. Further analyses will determine whether some plants are stably transformed. (Supported by a Duffett Research Grant from Yoder Brothers, Inc.)

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J. Frick and C.A. Mitchell

Due to its short time to flower (14-18 days) and rapid maturation cycle (50-55 days), dwarf rapid-cycling brassica (Brassica napus) is under consideration as a candidate oilseed crop for NASA's Controlled Ecological Life Support Systems program. Recent work has focused on defining a set of optimum environmental conditions which permit increased crop yield in terms of g·m-2d-1 of edible biomass. A wide range of environmental variables have been considered including lamp type, CO2 level, nutrient solution pH, and planting density. In addition, nitrogen nutrition regimes have been manipulated with respect to nitrogen concentration (2 to 30 mM), source (NH4 + and/or NO3 -), and time of stepwise changes in nitrogen level (day 14 to 28). The highest seed oil content (42% DW basis) has been found under limiting nitrogen levels (2 mM). However, the low nitrogen inhibits overall seed production potential. Different cultural techniques also have been compared, including solid-substrate, passive wicking hydroponics versus liquid culture systems. Trials are underway to assess crop growth and development under the “best set” scenario of environmental conditions. At present, the highest seed yield (10.6 g·m-2d-1) has been obtained using solid-substrate hydroponic systems under a combination of metal halide and high-pressure sodium lamps. Constant CO2 enrichment to 1000 μmol·mol-1 did not increase crop yield rate.

Research supported in part by NASA grant NAGW - 2329.

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Kyung-Ku Shim, Yoo-Mi Ha and Jae-Ho Ha

This cultivar originated from a grafting mutant in grafted plants of a selected 100-year-old seedling of Hibiscus syriacus L. for 5 years. In 1999, the plant is named H. syriacus `Andong'. Hibiscus syriacus `Andong' is a deciduous, erect-growing, multiple-stemmed, dwarf type that, in 7 years, has grown 120 cm high and 65 cm wide, with dense branching to the base. It has more than 200 flowers in a 7-year-old tree. The alternate, leathery, waxy, dark green leaves are 5.3 cm long, 3.8 cm wide. But it is 0.48 mm thick and 34.42 mg/cm2 of fresh weight and then is thickier and heavier than that of other cultivars. Therefore, the plant is rarely damaged by aphids and is reliably hardy to -20 °C. The flowers are white with a prominent dark red eye spot that radiates along the veins to midpetal, 5-7 cm in diameter, and blooms profusely from July to October. Total flowering time of `Andong' was 36 h in both 1998 and 1999. It sets very little fruit. AIt does not only germinate by pollen, but also by seeds. This cultivar can be readily propagated by softwood (on 24 July with 7000 ppm IBA in the mist) or hardwood cutting (1000 ppm IBA) and by grafting on seedling H. syriacus understock.

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Tao Wu and Jiashu Cao

peroxidase in numerous plants including several species of dwarf plants ( Evans and Alldridge, 1965 ; Kamerbeek, 1956 ; Loy, 1967 ; McCune, 1961 ). Several species of genetically dwarf plants have been reported to have a higher peroxidase activity than

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Hamidou F. Sakhanokho, Anthony L. Witcher, Cecil T. Pounders and James M. Spiers

’s Nursery of Nashville, NC. Developing new dwarf compact cultivars with novel foliar characteristics is a major objective of the Hedychium breeding program at the USDA-ARS Thad Cochran Southern Horticultural Laboratory (TCSHL) in Poplarville, MS. Reported

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Dean E. Knavel and Robert L. Houtz

Plants of Main Dwarf, a short-internode mutant of the normal-internode `Mainstream' muskmelon (Cucumis melo L.), have shorter internodes, fewer nodes, less total vine length, less total dry weight, smaller leaves, increased chlorophyll concentrations, increased specific leaf dry weight, and increased ribulose-1, 5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39, rubisco) activity per unit leaf area than `Mainstream' plants. Main Dwarf plants produce an equal number of fruit as `Mainstream' plants but are only half their size. Many of the plant and fruit characteristics for F1(Main Dwarf × `Mainstream') are similar to those of `Mainstream', except for greater leaf chlorophyll and rubisco activity per unit leaf area. The F1 (`Mainstream' × Main Dwarf) produced fewer and lower weight fruit than its reciprocal, F1 (Main Dwarf × `Mainstream').

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Zhanao Deng and Brent K. Harbaugh

glasshouse in Wimauma, FL, 2007. z Recommendation UF 44-4 is a new lance-leaved cultivar with a novel combination of leaf color and shape (dwarf red with slightly undulated and rounded leaves). Plants of UF 44-4 produce a superb number of bright red leaves in