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Timothy Spann, Robert H. Beede, Steven A. Weinbaum, and Theodore M. DeJong

Rootstock significantly alters the pattern of shoot growth of pistachio (Pistacia vera) cv. Kerman. Trees grown on P. atlantica typically produce a single flush of spring growth, whereas trees on P. integerrima selection PGI and P. atlantica × P. integerrima selection UCB-1 can produce multiple flushes during the season. We have shown that the spring flush is entirely preformed in the dormant bud for all three rootstocks, but later flushes are neoformed, that is, nodes are initiated and extended during the same season. Shoots producing both preformed and neoformed growth have lower yield efficiency than those producing only preformed growth. Additionally, yield components of the crop from shoots with both preformed and neoformed growth was different than for shoots producing only preformed growth. However, these differences do not appear to be significant at the whole tree level. These data suggest that neoformed growth can both compete with fruit growth for available resources (lower yield efficiency) and act as an additional source (altered yield components), depending on the factor being measured. Controlling neoformed growth may potentially increase pistachio yield through a shift to the more efficient preformed shoots while at the same time lowering orchard maintenance costs by reducing required pruning. We have data to indicate that regulated deficit irrigation and new pruning techniques may be viable methods for controlling neoformed growth in pistachio without affecting yield.

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Don Waneck, H. Mathews, J. Stamp, and R. Bestwick

Zygotic embryo explants of grape cultivar AXR#1 were isolated from maw-e seeds and cultured on medium supplemented with naphthoxy acetic acid beta-(NOA) and benzylaminopurine (BA). Embryo explants dedifferentiated to form embryogenic callus. Globular stage embryos were visible in 9-10 months. On transfer 10 a growth regulator free medium supplemented with charcoal these globular embryos underwent further stages of embryo development. In a period of 30-40 days embryogenic tissues turned into clumps of somatic embryos displaying different stages of development Cotyledonary stage embryos were separated and transferred to basal medium. These embryos developed into complete plants. Cold and desiccation treatment of somatic embryos significantly enhanced the rate of plant conversion. Hypocotyl segments of elongated somatic embryos were good source explant for induction of shoot organogenesis. The hypocotyl-length and the proximity to-shoot-apex were found to influence the rate of shoot induction from hypotyl segments. Multiple shoot complexes which formed on hypocotyl segments were separated and individual shoots were grown on a root induction medium resulting in complete plant development. The possibility of both embryogenic and organogenic modes of plant regeneration make somatic embryos a highly versatile explant source for experiments on genetic manipulation.

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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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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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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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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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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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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).