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Glenn R. Thayer and Preston K. Andrews

Dwarfing rootstocks are essential for developing high-density pear orchards with increased precocity. The graft compatibility of Amelanchier alnifolia, A. x grandiflora, A. canadensis, and A. alnifolia `Thiessen' as a rootstock for `Anjou' pear or as an interstock on `Bartlett' seedling, `Old Home × Farmingdale' and Crataegus rootstocks are being tested. Twenty rootstock and rootstock/interstock combinations were top grafted 27 Jan. 1994. Ten replicates will be planted in pots for each graft combination in March after callusing. Growth of successful graft combinations will be measured every two weeks. Shoot length and diameter and trunk diameter at a designated reference point will be measured. Leaf color will be evaluated periodically using a Minolta colorimeter. At natural leaffall, leaf areas will be measured. Graft compatibility will be evaluated. All data will be analyzed by analysis of variance.

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G.H. Neilsen, D. Neilsen and F. Peryea

Traditionally, broadcast or foliar fertilizer applications sufficed to improve the nutrition of many irrigated, deciduous fruit orchards in western North America. Recent developments, including adoption of low-pressure, micro-irrigation systems and planting at higher densities (especially for apples), have increased interest in controlled application of fertilizers directly with irrigation waters (fertigation). The possibility of using fertigation to synchronize fertilizer application and plant nutrient uptake seems attractive as environmental concerns to minimize leaching of nutrients (especially N) to groundwater increase. Recent fertigation research in western North America will be reviewed and compared to traditional fertilizer application methods to assess the potential of fertigation to overcome inadequate nutrition. Emphasis will be placed on the use of soil solution monitoring to assess changes in soil NPK status. Tree response will be illustrated by studies in high-density orchards where N, P, K, Ca, B, or Zn have been fertigated.

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Eric Hanson, Brent Crain and Joshua Moses

Red raspberry cultivars that produce fruit on current season canes (primocanes) can produce additional fruit the following year on floricanes. The primocane-fruiting raspberries ‘Himbo Top’, ‘Joan J’, and ‘Polka’ were grown organically in high tunnels and pruned to different floricane densities to determine the effects on fruit yield (primocane, floricane, total) and harvest times. Floricane densities were 0, 2.4, or 4.8 canes per meter of row length in 2015, and 0, 4.9, or 9.8 canes per meter in 2016 and 2017. Total yield (floricane plus primocane) was significantly greater with low floricane density (17 t·ha−1) or high density (19 t·ha−1) compared with no floricanes (12 t·ha−1). Floricane density did not affect primocane yield or harvest times. Primocanes of ‘Polka’ were taller when floricanes were present, but primocanes of other cultivars were unaffected. Results indicate that producing fruit on both primocanes and floricanes (double cropping) can improve sustainable overall yields.

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Chano H. Kim, Jonq H. Park, In S. Chung, Sung R. Kim and Seung W. Lee

Secondary metabolite production by plant cell culture has been become of interest because of its commercial value in use. However, cultured plant cells usually yield lower levels of secondary metabolites than those of intact plants. In order to improve the anthocyanin productivity in hairy root culture of Daucus carota, fungal elicitors from 8 species of Fungi were examined. Through the studies of fungal elicitors in this work, it was turned out that fungal elicitors were very effective to improve the yield of anthocyanin. Despite of its low yield of anthocyanin, high density culture of hairy roots is achieved in fluidized-bed bioreactor, Anthocyanin production in fluidized-bed bioreactor with fungal elicitor treatment was increased greatly. We are currently researching more detailed aeration effects and scale-up in air-lift bioreactors. And these studies could provide important data to establish mass production system for secondary metabolites.

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In the Southeast spring frosts often kill all or part of the flowers on peach trees. Increased flower bud density is one mechanism that increases the likelihood of enough flowers surviving to produce a crop. Mean buds per node in-North Carolina varied in 1986 from 1.6 for `Harko' to 0.4 for `Topaz'. The effect of environment on bud density was unknown. Therefore, for 3 years we compared the bud density of 25 peach and nectarine cultivars grown in completely randomized designs (4 reps per location, 10 twigs per tree) in Georgia and North Carolina. Genotypie variability was greater than that due to location or year effects. Cultivars selected for high bud density in one location can be expected to have high densities at other locations.

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Jyotsna Joshi, Geng Zhang, Shanqi Shen, Kanyaratt Supaibulwatana, Chihiro K.A. Watanabe and Wataru Yamori

“Plant factory with artificial lighting” (PFAL) refers to a plant production facility that can achieve mass production of vegetables year round in a controlled environment. However, the high-density planting pattern in PFALs causes low light conditions in the lower canopy, leading to leaf senescence in the outer leaves and thus to reductions in plant yields. In the present study, the effect of supplemental upward lighting underneath the plants on photosynthetic characteristics and plant yield was examined in lettuce, in comparison with supplemental downward lighting from above the plants at the same light intensity. Supplemental upward lighting increased the curvature factor of the photosynthetic response to light from above the plants. Moreover, supplemental upward lighting significantly enhanced the lettuce yield by retarding the senescence of the outer leaves. Here, we propose a novel cultivation system with a combination of downward lighting and supplemental upward lighting that can effectively increase plant growth and yield in PFALs.

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D. Michael Glenn, Donald L. Peterson, Daniela Giovannini and Miklos Faust

Hand-thinning (Prunus persica L. Batsch) “Y”-trained peach trees at bloom and 51 days after full bloom (DAFB) was compared to mechanical fruit thinning 51 DAFB using a spiked-drum and an impact shaker. The spiked-drum shaker removed more fruit from horizontal branches than from vertical branches, yet did not selectively remove either large or small fruit. Bloom thinning by hand increased fruit size compared to postbloom thinning 51 DAFB, and both postbloom mechanical thinning techniques were as effective as postbloom hand thinning. The spiked-drum shaker may be a better thinning technique than the impact shaker because it transfers less shaking energy to the fruit, can be used in high-density plantings, and does not contact the trunk, lessening the potential for tree damage.

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J.K. Collins, B.D. Bruton and P. Perkins-Veazie

Organoleptic evaluations of shrink film-wrapped and nonwrapped musk-melon (Cucumis melo L. var. reticulates cv.. TAM Uvalde) fruit were conducted to determine changes in flavor and taste during refrigerated storage. Ripe green and yellow `TAM Uvalde' muskmelons, shrink film-wrapped in 12.7-μm high-density polyethylene film, were compared to nonwrapped melons during 21 days of storage at 4C and 90% to 95% RH. After 21 days of storage, both yellow and green shrink-wrapped melons had better appearance, less surface mold, and less vein tract browning than nonwrapped melons. However, the flavor and taste of shrink-wrapped fruit were significantly inferior to those of nonwrapped melons. Green-wrapped melons were rated poorer in taste and flavor than yellow-wrapped and nonwrapped melons after 14 days of storage. These results indicate that shrink-wrapping may enhance undesirable flavor changes in muskmelon during storage.

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Du-Hyun Kim, Jung-Myung Lee and Jin-Ju Bae

Cucumber green mottle mosaic virus (CGMMV) is a noxious disease in cucurbits, especially in Asia where grafting is commonly practiced. CGMMV can be easily transmitted by seed, hands, soil, or grafting. Seed companies are rigorously looking for effective and efficient means of CGMMV inactivation in infected seeds. Among the various treatments applied to the seeds, dry heat treatment (35° C 1 day + 50 °C 1 day + 75 °C 3 days) was found to be most suitable for complete inactivation. Various identification methods including high-density latex agglutination test (HDLPAT), ELISA, RT-PCR, and bioassay (Chenopodium amaranticolor) were compared for accurate diagnosis of the presence of virus in seeds. The results from HDLPAT showed the highest correlation with the bioassay results, suggesting that HDLPAT can be safely used for accurate means of virus detection. Details of dry heat treatment, various seed treatment, and other detection methods will be presented.

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Milton E. McGiffen Jr. and Edmund J. Ogbuchiekwe

Poor root color is a recurring problem in carrot (Daucus carota L.) production. Consumers prefer dark orange carrots that are high in carotene. However, unfavorable environmental conditions and certain production practices can lead to light orange roots with low carotene content. Growers sometimes refer to this as “white root.” No one has clearly established the causes or cures for this disorder. Several environmental factors are known to affect the color of carrots, but to date there is no practical treatment. High-density planting often reduces carotene content. Field studies were conducted in the 1995-96 and 1996-97 winter growing seasons to determine if foliar applications of ethephon would improve carrot color, carotene content, and yield. Carotene content and root color increased as the number of applications or the amount of ethephon applied with each application increased. Root weight was not significantly affected.