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Melvin R. Hall

In 1983-1987, a Gardner color difference meter standardized to a pink tile (L=70.5, a=+23.9, b=+9.3) and equipped with an aperture of 3.8 cm (1983-1986), 1.9 cm (1987), or 1.0 cm (1988-1989) was used to measure lightness (L) and intensity (chroma) of `Georgia Red' sweetpotato [Ipomoea batatas (L.) Lam.] seed roots cut into longitudinal sections. Individual roots were selected with good color when L<68 and chroma≥39 and fair color when L≥72 and chroma <35 (1983-1985), L<65 and chroma≥42 for good color and L≥80 and chroma <25 for fair color (1986), L≤66 and chroma≥41 for good color and L≥85 and chroma≤20 for fair color (1987). In each year, roots falling between the defined selection values were discarded. In 1988, root sections from a common 1983-ancestor parent root were bulked for plant propagation if L and chroma values were similar. Subsequent measurements of these bulk populations were made in 1989. Measurements by a color difference meter were helpful in making objective judgements in selecting for internal color of sweetpotato. Also, these measurements were helpful in following changes in internal color through several generations of vegetative propagation.

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Gregg C. Munshaw, John M. Layton, Barry R. Stewart, H. Wayne Philley, Jeffrey S. Beasley and Rocky W. Lemus

As turfgrass quality of seeded bermudagrass (SB) [Cynodon dactylon (L.) Pers.] cultivars has increased over the past 20 years, so has their use. Improved SB cultivars offer ease of establishment and convenience of storage while providing an economic advantage over vegetative propagation. Currently, most improved seeded cultivars are marketed with a seedcoating unique to each seed company. However, germination of some of the new cultivars is not ideal. The objectives of this study were to determine commercial coating effects on germination, compare germination among cultivars, and evaluate the effect of temperature on germination of five bermudagrass cultivars. ‘Princess-77’, ‘Riviera’, ‘Transcontinental’, and ‘Yukon’ were selected for a series of 21-day germination studies with ‘Arizona Common’ included as a standard cultivar. The study compared two seed lots of coated and uncoated samples of the five cultivars for germination response to six temperature regimes. Cumulative count intervals occurred on Day 7, Day 14, and Day 21. Overall, commercial seedcoating did not significantly affect SB germination. However, both temperature regime and cultivar were significant factors. Germination percentage was greatest with either the 35/25 °C or the 30/20 °C temperature regimes. ‘Riviera’ exhibited the lowest overall germination, whereas ‘Transcontinental’ and ‘Arizona Common’ exhibited the highest.

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Choun-Sea Lin, Krishnan Kalpana, Wei-Chin Chang and Na-Sheng Lin

An in vitro method for obtaining bamboo mosaic virus (BaMV)-free plantlets of Bambusa oldhamii Munro was developed. BaMV-free meristems were incubated on MS basal medium supplemented with 0.45 μm thidiazuron (TDZ) to induce the development of multiple shoots. Multiple shoot proliferation was higher in stationary liquid culture than on semisolid medium. Cytokinin was the key component for inducing proliferation, and TDZ was the stable and effective cytokinin for proliferation in long-term subcultures. Multiple shoots rooted after 1 month in MS basal medium containing 10.74 to 26.85 μm α-naphthaleneacetic acid with a rooting efficiency of 83%. Healthy, well-developed plantlets were transferred to soil in pots and raised in a greenhouse. Those plants derived from tissue culture were more vigorous than the ones derived from the traditional in vivo vegetative propagation method, air layering. The tissue culture-derived plants could produce the culms after 15 months. Fifteen of 38 plants flowered 2 years after being transplanted to the field.

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Donita L. Bryan, Michael A. Arnold, R. Daniel Lineberger and W. Todd Watson

Three spineless phenotypes of Acacia wrightii G. Bentham ex A. Gray were identified with aesthetic landscape potential. Experiments in seed, cutting, grafting, and tissue culture propagation were undertaken to perpetuate this desired spineless phenotype. Germination percentages for mechanically scarified seeds ranged from 33% to 94%, however yield of spineless seedlings was low (0% to 34%). Sulfuric acid scarification for 10, 20, 30, or 60 minutes hastened and unified germination compared to nontreated seeds by 7 to 8 days. Vegetative propagation was successful for softwood cuttings. Rooting measures increased with auxin (2:1 indole butyric acid to naphthalene acetic acid) concentrations from 0 to 15000 mg·L–1, with maximum rooting percentage (70%), root number (9.2), and root length (12.4 cm) per softwood cutting at 15000 mg·L–1 auxin 8 weeks after treatment. Rooting was not successful for semi-hardwood or hardwood cuttings. Whip-and-tongue or T-bud grafting was not successful. Tissue culture of shoots from in vitro germinated seedlings indicated that shoot proliferation was greatest in Murashige and Skoog (MS) medium with 15 μm zeatin. The number of shoots that rooted in vitro increased with increasing concentrations of indole-3-butyric acid from 0 to 25 μm.

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Juan Manuel González Gonzalez, Francisco Radillo Juarez, Marcelino Bazan Tene and Juan Carlos González Ramos

Soursop (Annonamuricata L.) is reproduced by seeds from `Criollo' cultivars in Mexico. The replication of desirable agronomic traits is difficult when selected plants are from sexual reproduction. The heterogeneity of plants is observed as taller trees, irregular fresh fruit yield, variable fruit quality, different insect pests, disease susceptibilities, and lower number of plants per hectare. There is an extended time period for recovering investments and commericialization problems due to fruit quality and price. Vegetative propagation is an alternative for reducing the heterogeneity of soursop trees. Three grafting methods were evaluated for propagating soursop in the dry tropic region of Colima, Mexico: 1) splice side graft; 2) wedge graft; and 3) bud graft. The experiment was carried out on the Tecoman Campus of the Universidad de Colima. Rootstocks were from 8-month-old healthy plants, 1-m tall and 1-cm diameter, obtained from `Criollo' seedlings, and the scions were obtained from a healthy 10-year-old `Sin Fibra' donor tree. This donor tree was selected for its excellent agronomic traits and fruit yield. Vigorous and terminal scions were used, disinfected with fungicide, and used the same day of excision. The experiment was distributed under a completely randomized design. Splice side grafting had 67% success after 60 days, while wedge grafting and bud grafting had 0% success.

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John M. Dole and Harold F. Wilkins

Poinsettia (Euphorbia pulcherrima Wind. ex. Klotzsch) cultivars were divided into free-branching and restricted-branching groups. Auto and reciprocal grafts were made among three free-branching cultivars, Annette Hegg Brilliant Diamond (BD), Annette Hegg Topwhite (TW), and Annette Hegg Hot Pink (HP), and two restricted-branching cultivars, Eckespoint C-1 Red (CR) and Eckespoint C-1 White (CW). when CR scions were grafted onto BD stocks, vegetative characteristics of branching pattern and leaf morphology of CR plants were altered when compared to the control graft combination CR/CR (scion/stock). Branching pattern was determined by pinching the scion above the 12th node and measuring axillary shoot length, diameter, and node number 30 days later. CR scions grafted onto BD stocks produced a plant very similar to BD plants when axillary shoot length and node number were compared. However, axillary shoot diameter and leaf morphology were intermediate between CR and BD plants. Changes were retained after two generations of serial vegetative propagation and are considered permanent. The reproductive characteristics of anthesis date, bract color, and cyathia cluster diameter were not influenced by the stock. CR/BD plants produced twice as many axillary inflorescences as BD/BD or BD/CR plants, while CR/CR plants did not produce any. All of the free-branching cultivars were able to alter the vegetative characteristics of all of the restricted-branching cultivars.

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Charles A. Walker Jr. and Dennis J. Werner

Two banding patterns were revealed by phosphoglucomutase (PGM) isozyme analysis of 24 accessions of Cherokee rose (Rosa laevigata Michx.) from eight southeastern states, based on the presence (in 5 accessions) or absence (in 19 accessions) of an additional slow-migrating band. RAPD analysis of these accessions showed a corresponding division into the same two groups determined by PGM analysis, except for two accessions with unique RAPD phenotypes. Field-grown accessions showed distinguishing morphological characters corresponding to the groupings from the isozyme and RAPD analyses. Those in the predominant isozyme and RAPD groups, as well as the two with unique RAPD phenotypes, exhibited smooth lateral stems, while those in both nonpredominant groups exhibited markedly bristly laterals. These results suggest that the 24 accessions are ramets of two major clones with one clone predominating and that, contrary to long-standing belief, the Cherokee rose has not naturalized by reseeding in the southeast. PGM and RAPD analyses of putative Cherokee rose hybrids `Anemone' and `Silver Moon' showed that `Anemone' is likely to be such a hybrid but that `Silver Moon' is not. Historical records revealed that widespread vegetative propagation of the Cherokee rose was initiated in 1820-21 and that L. Wiesener, not J.C. Schmidt, was the originator of `Anemone'.

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Juan Manuel González-González, Salvador Guzmán-González and Sergio Chavez-Luna

Starfruit (Averrhoa carambola L.) is reproduced by seeds from `Criollo' cultivars. The replication of desirable agronomic traits is difficult when selected plants are from sexual reproduction. The heterogeneity of plants is observed as higher trees, irregular fresh fruit yield, variable fruit quality, differential insect pest and disease susceptibilities, and extended period for recovering the inversion. Vegetative propagation is an alternative for reducing the heterogeneity of starfruit trees. Four grafting methods for propagating starfruit in the coast of Colima, Mexico: splice-side graft, wedge graft, whip graft, and bud graft were evaluated. The experiment was carried out on the Tecoman campus of the Universidad de Colima. The ambient conditions were dry tropic (BS1). Seven-month-old rootstocks were obtained from Criollo seedlings, and the scion was obtained from a healthy 15-year-old `Miss' donor tree. The experiment was distributed under a completely randomized design. The splice-side graft had 70% success and was the best, bud graft had 40% success, wedge graft, had 5% success and whip graft 0% success, and was the least successful.

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Wahiba Boutebtoub, Michel Chevalier, Jean-Claude Mauget, Monique Sigogne, Philippe Morel and Gilles Galopin

Mandevilla sanderi is a plant of tropical origin of great horticultural interest because of its abundant flowering and its persistent foliage. Vegetative propagation requires the removal of leafy branches on the mother plant to produce cuttings. This loss of biomass must be compensated for by the growth of new branches thanks to the mobilization of reserves within the plant. Lack of knowledge about the physiology of this species therefore makes it necessary to characterize its different organs both at the level of their anatomic organization as well as at the level of their ability to store starch. After histological characterization of the different organs (leaves, stems, and roots), starch reserves were localized by histochemical analysis and quantified by biochemical analysis. Starch grains are mainly found in the parenchymatous cortex, the parenchymatous pith and xylem parenchyma cells, in tuberous roots and stems, and in the palisade and spongy mesophyll of leaves. In 22-week-old plants, the greatest quantity of starch is found in the leaves, whereas the tuberous roots have the highest concentration. The histological description of the different organs of Mandevilla sanderi and the localization of starch reserves allow us to assess the potential role of the different organs in plant growth and development. In the particular case of mother plant management, it is hoped that this knowledge will make it possible to optimize conditions for removing leafy branches.

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Daniel Warnock* and Charles Voigt

Greenhouse production of rosemary, Rosemarinus officinalis, as small potted Christmas tree topiaries for holiday sales have become necessary for many companies marketing to large retail outlets. Topiaries must be sheared multiple times to obtain an acceptable Christmas tree shape. Cultivars vary in physical attributes suggesting that they may respond differentially to mechanical shearing during production. This study assessed 16 rosemary cultivars for their potential as potted Christmas tree shaped topiaries. Beginning July 2001, rosemary plants derived from vegetative propagation of shoot tips were grown in a greenhouse with temperatures set at 73/65 °F day/night. Plants were pinched immediately after transplant and provided high fertility and maximum light. From August to October, plants were pruned monthly for a total of three shearing events. The crop was considered mature on the targeted market date of 5 Dec. Final plant quality was visually assessed using a 1 to 5 scale that accounted for plant-to-pot ratio, canopy density, foliage quality, taper, and overall appeal with one point being removed for each factor not meeting industry expectations. The cultivars varied in their performance as Christmas tree shaped topiaries with most being unacceptable. Many of these cultivars had minimal basal branching, perhaps due to selection for use as standard ball shaped topiary performance. Six of the cultivars, `Athens Blue Spire', `Taylor's Blue', `Herb Cottage', `Golden Rain', `Shady Acres', `Rex', and `302100', were suitable for commercial use having visual ratings ranging from 3.8 to 4.5. We suggest that these cultivars be examined for additional attributes that may enhance their performance as Christmas tree shaped topiaries.