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  • Author or Editor: G.M. Greene x
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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.

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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.

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In the 1992-93 experiments tufted apple bud moth (TABM) damage generally had little effect on at-harvest maturity/quality indices of `Golden Delicious', `Delicious' or `York Imperial' apples. However, at harvest starch scores of `Golden Delicious' and the soluble solids (SS) of `York Imperial' were higher in fruit with TABM damage. Following storage however, there were little or no effects of TABM damage on firmness or SS in any of the 3 cultivars. Percent decay was 0 and 18% in `Golden Delicious' and 2 and 6% in `Delicious' for control fruit and those with the most TABM damage (> 10 mm aggregate diameter), respectively. These were significant linear relationships - R2 = 0.41 and 0.12 for `Golden Delicious' and `Delicious', respectively. Weight loss increased by 2-3 fold in the apples in the highest damage category. These results show that the post-storage quality of apples with slight TABM damage did not differ from that of undamaged fruit. Good CA atmospheres for storage of undamaged fruit were also good for storage of damaged fruit. Additional studies done in 1993-94 included experiments attempting to mimic TABM damage artificially on fruit while still on the trees. Apples with natural TABM damage were inoculated with P. expansum before storage to insure decay potential.

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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.

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‘Nittany’ is a ‘York Imperial’-type apple possessing outstanding processing characteristics. Fruit from the original seedling tree has been essentially free of corking; mild corking has been observed in some large fruits from propagules on size-controlling rootstocks. The fruit can be held in refrigerated storage for at least 6 months without appreciable shrinkage or loss of quality. The flesh oxidizes very slowly when exposed to the air and imparts a highly desirable yellow color to processed products.

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Tufted apple bud moth (TABM) damage had little or no effect onthe soluble solids, starch, or firmness of stored apples. Decay increasedfrom 0% to 18% in `Golden Delicious' and from 2% to 6% in `Delicious' between control fruit and those with the most TABMdamage (> 10 mm aggregate diameter, significant linear relationships R 2 = 0.41 and 0.12, respectively). Weight loss increased 2- to 3-fold in apples in the highest damage category. These results show that the post-storage quality of apples with slight TABM damage (<5 mm aggregate diameter) does not decline more rapidly than undamaged fruit. The best controlled atmospheres for storing undamaged fruit were also the best for storing damaged fruit. Widely varying fungicide spray programs did not influence the quality or decay levels of apples following storage. However, even those fruit from blocks with few or no sprays had very little decay due either to low inoculum or unfavorable environmental conditions.

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Cultivar and planting site are two factors that often receive minimal attention, but can have a significant impact on the quality of apple (Malus ×domestica) produced. A regional project, NE-183 The Multidisciplinary Evaluation of New Apple Cultivars, was initiated in 1995 to systematically evaluate 20 newer apple cultivars on Malling.9 (M.9) rootstock across 19 sites in North America. This paper describes the effect of cultivar and site on fruit quality and sensory attributes at a number of the planting sites for the 1998 through 2000 growing seasons. Fruit quality attributes measured included fruit weight, length: diameter ratio, soluble solids concentration (SSC), titratable acidity (TA), flesh firmness, red overcolor, and russet. Fruit sensory characteristics rated included crispness, sweetness, and juiciness, based on a unipolar intensity scale (where 1 = least and 5 = most), and acidity, flavor, attractiveness, and desirability based on a bipolar hedonic scale (where 1 = dislike and 5 = like extremely). All fruit quality and sensory variables measured were affected by cultivar. The two-way interaction of cultivar and planting site was significant for all response variables except SSC, TA, russet, crispness, and sweetness ratings. The SSC: TA ratio was strongly correlated with sweetness and acidity sensory rating, but was weakly correlated with flavor rating. The results demonstrate that no one cultivar is ideally suited for all planting sites and no planting site is ideal for maximizing the quality of all apple cultivars.

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