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Eugenio Pérez-Molphe-Balch, Martha Evelia Pérez-Reyes, Carlos Antonio Dávila-Figueroa, and Enrique Villalobos-Amador

In vitro propagation systems were developed for Carnegiea gigantea (Engelm.) Britt & Rose, Pachycereus pringlei (Berger) Britt & Rose and Stenocereus thurberi (Engelm.) Buxb, three North American species of columnar cacti. In vitro germinated seedlings were used as a source of explants. Multiple shoot formation from areoles was achieved for three types of explants (apical, lateral, and transverse) cultured on Murashige and Skoog (MS) basal media supplemented with 3% sucrose, 10 g·L-1 agar and various treatments with growth regulators. The highest shoot production efficiency for C. gigantea was obtained on transverse explants cultured on a medium with 2 mg·μmL-1 (8.87 μm) BA, where 5.3 shoots per explant were obtained. In P. pringlei and S. thurberi the best response was obtained using transverse explants on medium with 1 mg·L-1 (4.44 μm) BA (3.8 and 4.3 shoots per explant, respectively). Rooting of the in vitro generated shoots was achieved most efficiently on MS basal media with 3% sucrose, 10 g·L-1 agar and 1 mg·L-1 (4.9 μm) indole-3-butyric acid. Rooting frequencies were 92%, 88%, and 96% for C. gigantea, P. pringlei and S. thurberi, respectively, and the frequency of survival of the plants once transferred to soil was 86% on average. Chemical name used: benzyladenine (BA).

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José M. Iriondo, Carmen Moreno, and César Pérez

Micropropagation methods for six rockrose species (Cistus albidus L., C. clusii Dunal, C. ladanifer L., C. laurifolius L., C. psilosepalus L., and C. salvifolius L.) were established. Cultures, initiated from nodal segments of seedlings, were grown on MS medium, alone, or supplemented with 0.88 μm BAP or 0.93 μm Kin. Multiple shoot formation was obtained after the first subculture (30 days) from which new nodal segments were taken and grown on the same culture medium to maintain proliferation. Shoots obtained at the third subculture were rooted alone or supplemented with different concentrations of IBA. The plantlets of the six species, thereby obtained, were successfully acclimatized to ex vitro conditions. Chemical names used: 6-benzylaminopurine (BAP), indole-3-butyric acid (IBA), 6-furfurylaminopurine (Kin).

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D. Michael Glenn and Stephen S. Miller

This study examines the effect of multiple spray applications of Apogee on shoot growth and whole-canopy photosynthesis (WCPn) rate in young, bearing apple trees. Apogee increased fruit numbers and reduced shoot growth and inconsistently reduced leaf area but the reduction in photosynthetic area did not result in reduced WCPn or a detrimental effect on the fruit number:fruit size relationship. Since WCPn was not affected when leaf area was reduced by Apogee treatment, it suggests a greater photosynthetic efficiency of leaves on Apogee treated trees due to reduced shading. The use of Apogee for canopy management may produce a side-effect of increasing fruit set, which may be managed through a crop thinning program.

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Yaseen Mohamed-Yaseen, Raymond J. Schnell, Robert J. Knight, and T.L. Davenport

A procedure was developed to regenerate plants via tissue culture from embryonic axes of mature avocado seeds. Explants were cultured in Murashige and Skoog (MS) medium supplemented with benzyladenine (BA) and naphthalene-acetic acid (NAA) or thidiazuron (TDZ) and NAA. Culture were kept in the dark for 7-10 days to reduce browning resulting from phenolic oxidation. Multiple shoots (5-8) were formed after transfer to light. Further multiplication were achieved using different combination of BA and NAA or TDZ and NAA. Shoots were cultured in MS supplemented with 2mg/l indolebutyric acid (IBA) for 2 weeks then transferred to MS supplemented with lg/l activated charcoal for root induction. Complete plants were obtained in vitro.

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G.E. Boyhan, J.D. Norton, and J.A. Pitts

The dwarfing characteristics of St. Julien and Pixy rootstocks, measured by shoot growth, were evident with `AU-Amber' and `AU-Producer' plum (Prunus salicina Lindl.) scions. Dwarfing did not occur with `AU-Rubrum'. Trunk cross-sectional area (TCA) was reduced with `AU-Amber', `AU-Producer', and `AU-Rubrum' scions on St. Julien and Pixy rootstocks. After 3 years, tree survival was 94% for Lovell; 89%, Halford; 57%, Nemaguard; 75%, Nemared; 83%, St. Julien; and 47%, Pixy. Tree survivability was significantly lower on Nemaguard and Pixy rootstocks than on Lovell and Halford. Multiple regression of total shoot growth, TCA, and survivability against foliar nutrient content resulted in the following significant equations: 0.460Mg - 0.210Mn, 0.236B - 0.487Mn, and 0.359N + 0.398Ca - 0.267P - 0.360Fe for each, respectively. Growth, survivability, and foliar nutrient content are significantly affected by rootstock in plum production.

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James McConnell

Numerous shooting and post-production techniques can be used to improve the quality of images used in horticultural publications. Certain lenses, lens attachments, and camera accessories are useful for enabling greater success in photographing plants. Small diffusers and reflectors allow the shooting of close-ups in the field, even when the sun is directly overhead. Shift lenses can be used to photograph trees at a closer distance without the extreme distortion of wide focal length lenses. Stitching of multiple images to produce panoramic shots can produce images with increased resolution, less distortion, and without the need for a wide-angle lens. Experiences with digital asset management management and post-production workflows are also presented.

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Bipul K. Biswas*, Nirmal Joshee, and Anand K. Yadav

Guava (Psidium guajava L.), also called `apple of tropics,' is immensely nutraceutical and horticulturally important. Being a tropical plant, it cannot stand temperatures below 25° F and needs frost protection to grow in temperate regions. To adapt in cold climate, cold hardy guava cultivars are needed. Conventional ways are uneconomic in time and efforts. Still, transgenic plants developed using biotechnological approaches of tissue culture and rDNA technology, appear to have great potential. Thus, protocols for in vitro propagation of guava were developed via organogenesis and somatic embryogenesis using nodal explants from mature trees and young zygotic embryos, respectively. Nodal explants induced multiple shoots when cultured on MS medium fortified with KIN, BAP and Ad.S. Adding a (NO3)2 to medium was useful to prevent in vitro shoot tip browning of adventitious shoots. Rocker liquid culture greatly increased growth of multiple shoots compared to the agar-based medium. It appears to be a good tool for woody plant tissue culture. Induction of somatic embryos in guava was also achieved on MS medium supplemented with IAA auxin. About 80% to 90% somatic embryos germinated normally. To achieve Agro-bacterium-mediated gene transfer in guava, on-going co-cultivation of organogenic tissues of guava is to optimize protocols for freeze tolerance gene (CBF1, CBF2, CBF3) transfer. Plasmid vectors containing selectable markers (nptII gene for antibiotic selection and GUS reporter gene as scorable gene mediated selection), with CaMV 35S promoter gene has been introduced into guava tissues and the resultant plants showed antibiotic resistance. Details of the experimental procedures and up-to-date results will be discussed.

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Michael A. Arnold

Bare-root 17.5-inch-tall (44.45-cm) `Sarah's Favorite' crapemyrtle (Lagerstroemia indica L.) liners were grown in #3 [2.75-gal (10.4-L)] black plastic containers and trained to one, three, or five trunks by one of two methods. Half of the plants were established from multiple liners with each trained to form one of the trunks. The others were established by planting a single liner in each container, pruning them back to within 2 inches (5.1 cm) from the substrate surface, and then training elongating buds or adventitious shoots to the desired number of trunks. Once plants reached a marketable size they were transplanted to a landscape for two growing seasons to determine the effects of the treatments on trunk survival or growth uniformity in the landscape. The study was replicated in time with containerized `Basham's Party Pink' crapemyrtle liners, but only grown in the field for 1 year. Growth and quality differences were minimal at the end of nursery production for either clone, thus favoring recommendation of whichever treatment would be most economical to produce the desired growth form. However, in the landscape phase, survival of `Sarah's Favorite' crapemyrtle and growth and uniformity of `Basham's Party Pink' crapemyrtle were greater for several growth measures when multiple trunks were produced by training stems of the same plant as opposed to planting multiple liners. Trunk survival was generally good for three or fewer trunks, but significant losses often occurred when the planting units had five trunks, especially when grown from multiple liners. Growth and survival differences among treatments were more pronounced with increasing trunk number and the longer the planting units were in the field (landscape).

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Michael E. Compton, Brenda L. Fuchs, and Jack E. Staub

Cucumis hystrix Chakr. is a rare cucurbit species native to Asia. The species is valued by breeders because of its multiple branching habit and has been used in interspecific crosses with Cucumis sativus. However, individual C. hystrix plants have not been identified in the wild since 1990. Therefore, it was our objective to develop a micropropagation protocol that would allow us to clonally propagate plants in cultivation. Shoots tips (2 cm) were excised from a single C. hystrix plant grown in the greenhouse. All tendrils and leaves were removed before surface-sterilization in 1.25% NaOCl for 5 or 10 min and rinsed six times with sterile distilled water. Shoot tips were trimmed to 1 cm (meristem with two to three young leaf primordia) and placed into 25 × 125-mm test tubes containing 25 ml of initiation medium [MS plus (per liter) 100 mg inositol, 30 g sucrose and 5 g Agargel; pH 5.7-5.8]. PGR combinations tested were initiation medium with 1 μM BA, and initiation medium with 1.7 μM IBA, 0.5 μM kinetin and 0.3 μM GA3 (IKG). Explant survival was greater when shoot tips were surface-sterilized for 5 min (75%) compared to 10 min (33%). More axillary shoots formed when shoot tips were cultured in IKG medium (10.8) than in medium with BA (5.5). Shoots were considerably longer (10 mm) when cultured in medium with IKG compared to BA (1.5 mm). About 64% of shoots place in medium containing 8 μM NAA formed roots and were acclimatized to greenhouse conditions.

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María Luisa Osorio-Rosales and Martín Mata-Rosas

Experiments were conducted to establish an efficient protocol of micropropagation of Beaucarnea gracilis and B. recurvata two endemic and endangered Mexican species. Multiple shoots were induced by direct organogenesis from in vitro seedlings and longitudinal sections of seedlings in both species. The highest formation of shoots per explant, both B. gracilis and B. recurvata, was obtained from longitudinal sections of seedlings on Murashige and Skoog (MS) medium supplemented with 22.2 μm 6-benzylaminopurine, induced 8.2 and 11.1 shoots per explant respectively. In vitro rooting was readily achieved on MS medium with 1 g/l activated charcoal without growth regulators. According to initial treatment and depending on where the shoots come from, the rooting rates were 61% to 100% for B. gracilis, and 83% to 100% for B. recurvata. Survival rates in greenhouse conditions for both species were 80% to 100% after 3 months. These results indicate that the micropropagation of these species of Beaucarnea is technically feasible, and that in vitro culture is a useful option for the conservation and propagation of these important endangered species.