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Derek J. Plotkowski and John A. Cline

, Food, and Rural Affairs Guelph, ON Pate, J.S. 1980 Transport and partitioning of nitrogenous solutes Annu. Rev. Plant Physiol. 31 313 340 Plotkowski, D. Cline, J. 2021 Evaluation of selected cider apple ( Malus domestica Borkh

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Neal Mays, Curt Richard Rom, Kristofor R. Brye, Mary C. Savin, and M. Elena Garcia

soil erosion ( Carter, 2002 ; Karlen et al., 1992 ; Kemper and Rosenau, 1986 ). Surface crusting and erosion may be reduced or eliminated in orchards with application of non-living groundcover mulches. Mulches useful for organic apple ( Malus

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Cecil Stushnoff, Philip L. Forsline, Leigh Towill, and John Waddell

Cryopreservation of dormant buds has potential to provide back-up conservation of vegetatively propagated genetic resources for fruit crop species. This system may be useful where clonal integrity must be maintained and where it is desirable to rapidly recover plants with flowers for crossing purposes. In 1988, a pilot project involving the National Clonal Apple Repository at Geneva, NY and the National Seed Storage Laboratory, Fort Collins, CO, was initiated to test handling protocols as a prelude to establishing a cryopreservation backup system for apple genetic resources. Sufficient buds have been cryopreserved to permit viability evaluation after 1 month, 1, 2, 3, 4, 5, 10, 15, 20, and 25 years storage in liquid nitrogen vapor phase storage (-150 C]. Recovery of dormant buds collected 12/12/88 and 02/06/89 after one month in LN2 was 36% and 35%, respectively, for eight different taxa. After one year in LN2, recovery was 50% and 48% for the same taxa. The difference was attributed to improved handling during dehydration prior to patch budding for viability estimation. In 1990, recovery after 1 month in LN2 was 38% for six different cultivars. The response to controlled acclimation and desiccation for 15 taxa will be presented.

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Wenbin Zhang, Junru Zhang, and Xulan Hu

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Jacques J. Crabbe

The flushing behavior of shoot growth and its consequences on shoot differentiation are important features in fruit tree development, with regard to flowering ability. In this respect, two different approaches were applied to young `M26' apple trees. First, poorly branched 2-year-old trees were headed back, either in the second-year or in the first-year wood, at different times from right before to 6 weeks after budbreak. Early pruning resulted in rapid and prolonged regrowth, with a final very similar shaping of the tree to that of the intact controls. Late pruning, in contrast, leads to a two-step reaction (late spring and summer flushes), sometimes stronger on 2-year-old than on 1-year-old wood. In a second experiment, buds and young shoots were sampled on pruned trees in locations where they could be supposed to remain short shoots or grow long, with one or two flushes. They were weighed, their leaves and internodes measured, and the plastochron evaluated. During budbreak and the first month afterwards, shoot differentiation appears achieved. The primary difference between long and short shoot types does not consist in faster internode elongation but, rather, in faster production (reduced plastochron) of larger leaves.

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Manfredo J. Seufferheld, Cecil Stushnoff, and Philip Forsline

Cryopreservation of mature dormant vegetative buds is a useful method to preserve germplasm of a large number of cold hardy apple cultivars. However, cold tender cultivars have proven to be much more difficult to cryopreserve. Eight cultivars were harvested in September 1993 at Geneva, NY before developing cold hardiness naturally. The twigs were encapsulated with 5% alginate and treated with stepwise imbibition of 0.5 to 1.0 M sucrose. The samples were desiccated over glycerol at 0C. Half of the samples were plunged directly into liquid nitrogen (IN) and the other half were first cooled slowly to -30C. The twigs that had been exposed to prefreezing conditions showed the highest survival (20 to 100%). The samples that were plunged directly in LN survived poorly (0 to 20 %). Samples without encapsulation and no sucrose imbibition had 0% survival. We conclude that this protocol opens up the possibility to expand cryopreservation of cold tender apple cultivars, presently grown only in field gene banks, at great expense and inconvenience.

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Xiang Shen*, Zhenlin Wei, and Ling Guo

`Pingyitiancha' has good agricultural traits and is an important rootstock for apples. It was studied for Kam, Cef and Carb concentrations, precultural times, active medium of A.tum, Ca++ concentration, mixed inoculation times of AgNO3, and PVP delay selection times for getting transgenic `Pingyitiancha' stock with more resistance to drought and salt. It was demonstrated that the highest transformation frequency was obtained with 200 mg·L-1 Cef as an A.tum restraining antibiotic, 8 mg·L-1 Kam as a selection antibiotic, GCJ8 active medium, a precultural of 2 days, 5 Ca++ concentrations in preculture and coculture medium compared with standard MS medium, immersed in A. tum as OD600 for 0.5 to 1 min., 4 mg·L-1 AgNO3 and 0.7% PVP as an anti-oxidation compound to reduce hydroxybenzene oxidation and delay selection for 5 days by using `Pingyitiancha' apex shoots as explants. Using mediate of A. tum strain LBA4404 under conditions mentioned above and same explants, the HVA1 gene were transformed into `Pingyitiancha' under the control of CaMV35S promoter and obtained Kam resistance regeneration plants. Six transgenic plants were confirmed by PCR and subsequent dot blot methods.

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Xuetong Fan, J.P. Mattheis, M.E. Patterson, and J.K. Fellman

Several strains of Fuji apples were harvested weekly from September through October in 1990 and 1991, and evaluated for maturation and quality after 1 and 7 days at 20 °C following harvest and storage in atmospheres of 0.5%, 1.0%, 2.0% O2 and air. Results showed that Fuji apples have very low ethylene production rates and little firmness loss during maturation. A change in the postharvest respiration pattern preceded the increase ethylene synthesis. Oxygen concentration during storage directly affected apple respiration rate after removal from storage. Ethylene production rates and internal ethylene concentrations indicated that the apples were still in the preclimacteric stage after 7 to 9 months storage at 0.5%, 1.0%, or 2% O2. Fuji apples develop watercore and tend to have a particular type of corebrowing during maturation on the tree, or during and after storage. The cause is unknown.

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Giorgio Bargioni, Giorgio Baroni, Pietro Tonutti, Andrea Pitacco, and Angelo Ramina

Effects of scion inclination on root growth and distribution were studied on INRA GF 677 (Prunus persica × Prunus amygdalus) and apple/M.9 trees. At planting, central leaders were positioned vertically (0°) or inclined 45° or 60° to the north and south. Three years after planting, root total dry weight of inclined trees was lower than that of the control (0°, vertical central leader). Five years after planting, the isotropic distribution of the normal root systems was distorted by inclination in both species. Roots were more numerous and more elongated in the direction of inclination. Statistical analysis of root density data, using a polar coordinate system, confirmed that the trunk inclination reduced root development and redirected root distribution. The major effect was induced on GF 677 by 60° inclinations. Tree orientation did not seem to influence root distribution.

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Patrick J. Conner, Susan K. Brown, and Norman F. Weeden

Two half-sib populations (cross 1 = `Wijcik McIntosh' (WM) × NY 75441-67, and cross 2 = WM × NY 75441-58) were used to create maps for the parents and to find RAPD or isozyme markers for qualitative and quantitative traits. WM is a sport of `McIntosh' and is heterozygous for the dominant columnar (Co) gene for reduced branching. WM is of great interest in breeding because of the tremendous effect of the Co gene on many aspects of plant form. NY 75441-67 and NY 75441-58 are advanced selections with commercial fruit quality and resistance to scab (Vf resistance from M. floribunda). Traits examined included both tree (plant height, stem diameter, suckering, branching habit, leaf break, burr knot production) and fruit (size, shape, color, stem length, seed number) characters and fruit quality traits (pH, acid content, Brix). The conservation of RAPD markers in these closely related crosses will be examined and the usefulness of molecular markers to preselect for components of plant form and fruit quality will be discussed. Molecular markers will increase the efficiency of the apple breeding program by aiding the understanding and manipulation of complex genetic traits.