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The influence of rootstocks on the growth and productivity of `Starkspur Supreme Pagnelli Delicious' was determined in an NC-140 experiment started in 1984. The planting was supplemental to the main experiment and it contained Ottawa (Ott) 3, M.20, and Arnold Lynd (AL) 800, but did not contain Budagovsky (Bud) 490, Bud 9, Antonovka 313, or C6. Trees that apparently would not stand were given support. Data on tree size and yield were collected every year. As expected, many characteristics were strongly influenced by rootstock. Yield efficiency calculated as the total fruit weight per square cm of trunk cross-sectional area was used as a measure of production efficiency. In 1989, efficient producers of fruit (all in decreasing order) were Poland (P) 2, EMLA.26, P 16, and Michigan Apple Clone (MAC) 39. Intermediate in productivity were M.20, Cornell-Geneva (CG) 10, Pl, and AL 800. A lower efficiency group of rootstocks were EMLA.7, Ott 3, MAC 1, Seedling, M.4, P 18, and CG 24. `Golden Delicious' and `McIntosh' on EMLA.26, used as pollinizers, were ranked second and third in yield efficiency.
Water stress in mature `Redhaven' / Lovell peach [Prunus persica (L.) Batsch] trees was imposed, during the 1988 growing season. Trickle irrigation was reduced from 100% to 25% of a calculated weekly evaporation amount on 22 June, 11 July, and 8 and 27 Aug. Trees were isolated from rainfall by tents under the canopy and from horizontal water movement between root systems on 4 sides to a depth of 0.5 m by a water-proof barrier. Canopy to air temperature differentials monitored throughout the growing season were developed into 3 stress indexes: crop water stress index (CWSI); cumulative crop water stress index (CCWSI); and postharvest cumulative crop water stress index (PCCWSI). CWSI values varied from 0 to 0.6, while both CCWSI and PCCWSI increased through late Sept. Mean PCCWSI of the 22 June 25% treatment increased at a greater rate than the other treatments. Significant linear regressions were found with some of the indexes and net photosynthesis or stomatal conductance; however, the r-square values were low. In general, no linear relationships were found between either CCWSI of PCCWSI and the Index of Injury for cold hardiness.
Reduction of heat stress disorders of `Golden Delicious' apples, such as sunburn, has been accomplished with cellulose fibers that modify reflective fruit surface properties. Incidence of sunburn on apples, directly exposed to sunlight, was decreased from 38% for untreated fruit to 12.5% for apples treated with cellulose fibers and binding agent and to 25.1% for apples treated with the binding agent only. Field stability of the binding agent (1% colloidal suspension of corn starch) was improved over the formulation used during the previous growing season. It was found that heating the starch suspension to 121C for 15 minutes increased its stability as a binding agent. A cumulative total of 3 cm (over three events) removed enough fibers to necessitate reapplication of the reflectant. The cellulose fiber/binder residue remaining at harvest was readily removed from fruit surface with water and a brush. Specialized sprayer was developed to deliver long fiber cellulose formulations that conventional sprayers are not capable of dispensing.
A grant from the Pa. Dept. of Agriculture has allowed Penn State University to increase postharvest physiology research of fruit, vegetables, and mushrooms. One part of this program is a CA storage research facility described herein. An insulated pole barn (26m × 18m with 5m ceilings) houses the facility. Three coolers (6m × 7m with 10cm insulation) provide environmental control for the CA systems (-2 to 10C ±0.5C). A laboratory within the building (6m × 7m × 3m) provides space for product evaluation and for CA control equipment. A total of 239 steel drums (208-liter), fitted with 28 cm round plexiglass windows, are the CA chambers. Gas pumps provide flow to: each chamber, the gas analysis system, and the CO2 scrubbing system. A David Bishop Instruments Oxystat 2, analyzes O2 and CO2 and provides control signals. High CO2 can be removed either by lime scrubbing or by flushing with gases containing N2 and the desired O2 level. Several large experiments involving 7.8 MT of apples were started and preliminary results will be presented.