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Toktam Taghavi, Alireza Rahemi, Reza Rafie, and Maru K. Kering

rooting. Some investigators used a combination of BAP and NAA, benzyladenine (BA), and NAA ( Ghosh et al., 2013 ), while some used a combination of KT and BAP or KT and NAA ( Mohanty et al., 2010 ). The objectives of this study were to optimize the

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Milica Ćalović, Chunxian Chen, Qibin Yu, Vladimir Orbović, Frederick G. Gmitter Jr, and Jude W. Grosser

can be peeled, it is not considered “zipper skinned.” The goal of this project was to optimize the method of protoplast fusion to create tetraploid parents that could be used in breeding for production of the high-quality triploid cultivars with the

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Salvatore Campisi-Pinto, Yusheng Zheng, Philippe E. Rolshausen, David E. Crowley, Ben Faber, Gary Bender, Mary Bianchi, Toan Khuong, and Carol J. Lovatt

income and to sustain this commodity-based industry. Optimizing tree nutrient status is an essential and cost-effective strategy for improving yield ( Lovatt, 2013 ). Nutrient analysis of plant tissues is a popular tool used to assess the nutrient status

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Changhoo Chun and Cary A. Mitchell

`Waldmann's Green' leaf lettuce (Lactuca sativa L.) is being used as a model leafy vegetable crop to develop a protocol for variable control of photosynthetic photon flux (PPF) during crop production. Feedback from real-time photosynthetic gas exchange rates by lettuce canopies is used to modulate electronic dimming ballasts of lamp banks. Algorithms within process-control software are being fine tuned to maximize increments of photosynthetic output relative to increments of photon input. Dynamic optimization of PPF was 21% more efficient than constant high PPF saturating photosynthesis with respect to biomass accumulated per photons absorbed. Dynamic optimization also is being combined with principles of phasic control, in which environmental resources such as photosynthetically active radiation (PAR) and carbon dioxide (CO2) are deliberatively limited in input during specific phases of crop development when plants are less sensitive to inputs (e.g., lag, plateau, and senescence phases) but optimized for the responsive exponential phase. Preliminary results indicate that leaf lettuce growth benefits from optimizing environments for no more than 4 or 5 days during a 20-day production cycle. Dynamic optimization of CO2 level is achieved by controlling the injection of CO2 into the inlet air stream of Minitron II crop canopy cuvette/growth chambers. Algorithms are being modified to simultaneously vary PPF and CO2 for optimum photosynthesis.

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Zhanyuan Zhang, A. Mitra, and D.P. Coyne

Optimization of parameters influencing biolistic transformation is a crucial stage towards repeatable transformation of common beans. However, there has been no published study on such optimization of this crop species in a helium particle delivery system (BioRad). Using an intron-containing β-glucuronidase (GUS) gene as a reporter, we optimized several critical parameters of biolistic PDS-1000/He delivery system for common bean transformation. The target explant tissues included cotyledons, zygotic embryos, and meristemic shoot tips suitable for organogenesis. Thus, pretreatment of target tissues with osmotic medium containing 0.15–0.25 m mannitol and 0.15–0.25 m sorbitol, positioning of target tissues in 4 cm microcarrier flying distance, the use of 1.6-μm gold particle and high concentration of coating DNA, and bombardment of young immature tissues twice at 2000 psi, etc., significantly increased transformation rate and achieved the best coverage and penetration of the meristemic areas involved in direct shoot organogenesis.

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Jacob George, Harsh Pal Bais, G.A. Ravishankar, and P. Manilal

Response surface methodology was utilized in statistical optimization of three quality factors (the number of multiple shoots, shoot length, and number of leaves) pertaining to regeneration of plantlets from leaf calli of Decalepis hamiltonii Wight. & Arn. (swallow root). The variables evaluated were the levels of sucrose, BA, and NAA each at two different concentrations. Response surfaces for shoot length and multiple shoot number were useful in achieving optimal levels of media constituents and in understanding their interactions, but response surfaces for number of leaves were not. The data indicate that sucrose, BA, and NAA levels may be manipulated to increase or decrease quality factors chosen. This approach may be useful in developing a micropropagation protocol for D. hamiltonii. Chemical names used: benzyladenine (BA); napthaleneacetic acid (NAA).

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Bob Bors and J. Alan Sullivan

Previous research has optimized the colchicine dropper technique for chromosome doubling under greenhouse conditions. In recent years, in vitro germination of cut strawberry achenes has greatly increased germination rates. Combining the two techniques would be especially useful when chromosome doubling is desired for interspecific hybridization. Fragaria vesca was chosen for initial study. Treatments included colchicine levels of 0%, 1%, 2%, 3%, 4%, or 5% (w/v); exposure time to colchicine was from 6 to 16 to 26 hours; application was at the cotyledon stage or after the first true leaf formed; presence or absence of 3 g activated charcoal/liter; and presence or absence of DMSO. Media consisted of MS salts and vitamins, 30 g sucrose/liter, and 2.5 g phytogel/liter. Charcoal enhanced upward growth of seedlings, thus allowing better placement of colchicine droplets. Reduced exposure time and application at the first true-leaf stage allowed higher levels of colchicine to be used without greatly reducing the vigor of treated seedlings.

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John Clemens and R. Hugh Morton

Containerized plants of Heliconia psittacorum L.f. × H. spathocircinata Aristeguieta `Golden Torch' were grown in a greenhouse for 8 months from early summer to winter under selected combinations of N, P, and K. Fertilizer rates ranged from zero to rates that exceeded those reported in the literature by 50% to 100%. Biomass variables (vegetative and inflorescence dry weight, and leaf area) were predicted to be maximized at high N and high N to P, and N to K ratios corresponding to N-P-K application rates of 1.2, 0.5, and 0.6 kg·m-3, respectively (≈2:1:1). However, the number of shoots and flowers produced per rhizome were maximal at lower N to K ratios (1:1). Flower yield could therefore be optimized with appropriate fertilization, provided attention was paid to the N to K ratio so that the size of plants and their flowers was not compromised by efforts to increase shoot and flower number. The heavier the rhizome planted, the shorter the time for shoot emergence and flowering to occur, and the greater the number of flowers harvested. However, rhizome weight had no effect on number of shoots to emerge. The probability of shoots flowering declined markedly with order of shoot emergence, although this could be increased with appropriate mineral nutrition. The maximum number of leaves subtending the inflorescence (seven) was obtained at high N and P rates. Flower production was probably limited by declining solar radiation in autumn, and by within-plant competition for rooting space.

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Maritza I. Tapia, P.E. Read, H.F. Kaeppler, and P.L. Herman

Direct DNA delivery via microprojectile bombardment has been successfully used to transform a wide range of species. Transformation using this system is dependent on the optimization of several parameters. These parameters involve the explant, the gene construct, and parameters in the bombardment system. DNA was delivered into bisected axillary buds of grape hybrids `Chancellor' and `Valiant'. Target tissues were bombarded with gold microprojectiles coated with GUS::NPTII fusion gene construct(pBI426). Several experiments with varying parameters were conducted in order to increase the frequency of DNA delivery. Data were analyzed as a completely random design with 6 single petri dish as a replication and 50-60 bisected axillary buds per replication in each treatment. The treatment design was the single-factor method. Higher frequencies of transient transformation were obtained using microprojectiles of 1.6 μm diameter, adding 0.15 m mannitol and 0.15 m sorbitol, under a pressure of 68.6 cm Hg and a target distance of 6 cm. After 40 days on the selection medium containing 50 mg kanamycin/L regenerated plantlets were obtained and 40% of them expressed the GUS gene. The biolistic approach using bisected axillary buds as target tissue could be a method to achieve stable transformation and transgenic grape plants.

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John C. Beaulieu, Allison K. Rausch, and Elaine T. Champagne

Fresh-cut melons in many consumer-ready packages are notorious for “wetting” and accumulation of standing juices. These conditions likely create undesirable flavor and aroma changes. We initiated a study to investigate flavor changes in stored fresh-cut cantaloupe. One objective was to optimize solid phase microextraction (SPME) to evaluate organoleptic compounds. Static head-space SPME analyses were performed on fresh-cut cantaloupe cubes (≈2.5 mm, 5 mm, or 2.5 cm), expressed juice, and homogenized slurries. SPME fiber (100 μm PDMS vs. 75 μm Carboxen/PDMS) exposure time (5, 7.5, 10, 12.5, 15, 17.5, 20 min) was evaluated at 40 °C with various head-space: product ratios, plus or minus NaCl to produce typical chromatograms. Fibers were desorbed in an HP5890 GC with a DB-624 or DB-5 column for 45-min runs and an HP6890 GC (DB-5) equipped with a 5973 MS detector for 35-min runs. Albeit qualitative, the best chromatograms were obtained with 7-ml slurries, stirred with NaCl, exposed to a 10 0μm PDMS SPME fiber for 12.5 min. The 100 μm PDMS fiber produced better chromatograms considering the fact that many important flavor volatiles are low-molecular-weight polar esters and alcohols. These conditions were subsequently used to analyze numerous fresh-cut cantaloupe samples stored various times (0 to 9 days). Over 100 peaks were identified, many of which changed through storage and some are suspected as probable agents responsible for undesirable flavor changes. Our analyses are progressing in an attempt to authenticate compounds associated with flavor-related changes in numerous fresh-cut cantaloupe varieties from various growing regions.