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A-M. Boland, P.D. Mitchell, I. Goodwin, and P.H. Jerie

An experiment designed to study the effects of different root volumes was installed in Fall 1991. `Golden Queen' peach trees [Prunus persica (L.) Batsch.] were planted into different isolated soil volumes (0.025, 0.06, 0.15, 0.4, and 1.0 m3), which were essentially individual drainage lysimeters. Trunk cross-sectional area (TCA) increased from 5.76 to 14.23 cm2 for the smallest and largest volumes, respectively, while leaf area was 4.56 and 21.32 m2 for the respective treatments. Leaf size was not affected by soil volume. Soil volume was positively related to the number of lateral shoots produced, lateral shoot density, and internode length. Total flower bud number and flower bud density were inversely related to soil volume. Fruit set was similar among treatments despite an almost 4-fold difference in tree size. Tree water use (liters·mm-1 pan evaporation) increased with soil volume; however, when adjusted for tree size (tree water use per TCA), there were no consistent differences between treatments for tree water use over the season. These results suggest that trees planted in the smaller soil volumes were more efficient reproductively per unit of tree size and would be easier to manage in an ultra-high-density planting.

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L.J. Grauke, Bruce W. Wood, and Marvin K. Harris

populations of nutmeg hickory has been observed following limited examination ( Grauke and Mendoza-Herrera, 2012 ) and should be systematically evaluated. Carya floridana has the smallest mature tree size among the hickories. Collections from across the

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Gregory M. Peck, Ian A. Merwin, Michael G. Brown, and Arthur M. Agnello

. 1 ). Over the 4 years, tree size (TCSA) remained similar between production systems ( Table 1 ). In the IFP system, there were greater crop densities in 2007 and greater yield efficiencies in 2006 and 2007. Average weight (a measure of fruit size) of

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Richard H. Zimmerman and George L. Steffens

Tissue-culture (TC)-propagated `Gala' and Triple Red `Delicious' apple trees grown at three planting densities were not treated (CON) or treated with plant growth regulators (PGRs) starting the third or fourth season to control tree size and maximize fruiting. `Gala' and `Delicious' trees budded on M.7a rootstock (BUD) were also included as controls. `Gala' trees were larger than `Delicious' after the first three growing seasons but `Delicious' were larger than `Gala' at the end of 9 years. BUD trees were larger than CON trees the first few seasons hut final trunk cross-sectional area (TCSA) of CON trees averaged 43% greater than BUD trees. Paclobutrazol and uniconazole treatments more readily controlled the growth of `Gala' than `Delicious' and uniconazole was more effective than paclobutrazol in controlling tree size. Daminozide + ethephon sprays (D+E-S) did not influence tree size. Tree size of both cultivars was inversely related to planting density and both triazole PGRs were more effective in controlling tree size as planting density increased. The trees had fewer flowers as planting density increased and BUD trees generally had more Bowers than CON. Triazole PGRs had little effect on the flowering pattern of `Gala' trees but tended to stimulate flowering of young `Delicious' TC trees, although the increases were not sustained. The D+E-S treatment increased flowering of `Gala' trees the last 3 years of the experiment and consistently increased flowering of `Delicious' TC trees. Fruit yields were higher for young `Gala' compared to `Delicious' trees and the final cumulative yield per tree for `Gala' was also greater. Yield per tree decreased as tree density increased and was the same for BUD and CON trees. D+E-S increased cumulative per tree yield of `Delicious' but not of `Gala'. Cumulative yields per tree for triazole-treated TC trees were the same as, or significantly lower than, CON trees. Increasing tree density did not increase yield/ha. Yield efficiency of `Gala' trees was increased by three, and of `Delicious' trees by one, of the triazole treatments, because they reduced TCSA proportionally more than they reduced per tree yield. There was less bienniality with `Gala' than `Delicious' and no difference between BUD and CON trees. Bienniality indices were higher for paclobutrazol-treated `Gala' trees compared with CON `Gala' but only uniconazole applied as a trunk paint increased the bienniality index of `Delicious' trees. Chemical names used: succinic acid-2,2-dimethyl hydrazide (daminozide), (2-chloroethyl) phosphonic acid (ethephon), (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-01 (paclobutrazol), (E)-(l-chlorophenyl)-4,4-dimethyl-2-(I,2,4-triazol-l-yl)-1-penten-3-ol (uniconazole).

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Thomas M. Gradziel and Dale E. Kester

Breeding lines have been developed incorporating introgressed genes from three native almond species Prunus fenzliana, Prunus webbii and Prunus argentea. Selected traits include self-fertility and autogamy, late bloom, smaller tree size, early nut maturity, improved cropping potential, and a well-sealed shell (endocarp) with high kernel/shell crack-out percentages. Fertility barriers, while present were easily overcome though linkage to introgressed genes with undesirable phenotypes remains an important obstacle to commercial use. Current breeding results, however, support a general conclusion that the wide diversity present within the range of species related to the cultivated almond (Prunus dulcis) provides an valuable gene pool for variety improvement.

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Bryan Blackburn and Curt R. Rom

The effects of six freestanding training systems (Open Center, Untrained, 2-Scaffold V, 4-Scaffold V, Leaning V, and Central Leader at tree densities of 161, 161, 245, 375, 375, and 300 trees/acre, respectively) on yield and tree growth of `Redhaven' on Lovell rootstock were evaluated. Open-center and untrained trees were largest and had greatest yields per tree. The 2-scaffold V had the greatest production in kilograms per acre. Early productivity was related to tree density and pruning severity, not tree size. Training systems had no effect on fruit size.

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T.M. Gradziel and W. Beres

A single seedling exhibiting a semidwarf growth habit was found in an open-pollinated clingstone peach [Prunus persica (L.) Batsch] population. The growth habit was upright and open, with short, spur-like lateral branching. Tree size was about half that of its siblings as a result of shorter internodes. The total number of nodes on first-order branches was not significantly different from that on standard-sized trees. The semidwarf growth habit remained stable after vegetative propagation. Segregation in sexual progeny showed the trait to be highly heritable.

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D.M. Lauderdale, C.H. Gilliam, D.J. Eakes, and G.J. Keever

Two tree species, Acer rubrum `October Glory' (October Glory red maple) and Quercus phellos (willow oak) were planted in Columbus, GA and Mobile, AL. Variables evaluated were location (park vs residential) and tree size (1.5 vs 3.0 inch caliper). Greater shoot elongation occurred with 1.5 inch red maples and willow oaks than with 3.0 inch caliper trees. First year growth differences were not related to photosynthesis, night respiration, leaf water potential, or foliar nitrogen levels. Little height or caliper change occurred with either species. Red maple shoot elongation was greater in Mobile than into Columbus. Growth was not affected by location within either city.

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Jonathan Crane, Carlos Balerdi, Richard Campbell, Carl Campbell, and Seymour Goldweber

Hurricanes occur periodically in southern Florida, resulting in severely damaged or destroyed orchards due to high winds, fresh-water flooding, and salt damage accompanying these storms. Commercial fruit production is often markedly reduced following hurricane damage. Orchard establishment and management practices that increase tree rooting depth and reduce tree size decrease tree losses due to high-velocity winds that accompany these storms. Cultural practices, such as post-hurricane pruning, whitewashing, resetting, and irrigation of trees, can rehabilitate a damaged orchard. Planning for a hurricane will increase the ability of orchards to withstand a storm and resume fruit production as soon as possible following a storm.

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Dale E. Kester and Thomas M. Gradziel

Approximately twenty native almond species have been described. Representative germplasm from seven of these are present in UC collections and have been used in crossing. Three specific breeding lines utilizing these species are described. One (1980 series) involved increasing yield potential through selection of high blossom density following gene introgression from Prunus fenzliana. A second involved incorporation of self-fertility, late bloom, smaller tree size, early maturity, high blossom density, and desirable nut characters from Prunus webbii into commercial breeding lines. A self-fertile selection resembling `Nonpareil' has been obtained from this material. The third line involves transmission of a unique thin, netted-surfaced, hard-shell phenotype from Prunus argentea.