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Richard K. Volz, F. Roger Harker, and Sandy Lang

Puncture force was measured in `Gala'apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit from 16 to 175 days after full bloom over 2 years using a range of circular flat-tipped probes (1 to 11 mm diameter) to test the firmness of each fruit. The area-dependent (Ka) and perimeter-dependent (Kp) coefficients of puncture force were determined and were used to calculate the indicative puncture force approximating a standard 11.1-mm-diameter Effegi/Magness-Taylor probe for even the smallest fruit. Ka declined exponentially throughout fruit development with much greater changes occurring closer to bloom. In contrast, maximum Kp occurred at 107 to 119 days after full bloom before declining progressively. Estimated firmness (using a 11.1-mm-diameter probe) declined constantly from 16 days after full bloom. Ka was associated with developmental changes in cortical tissue intercellular air space, cell volume and cell packing density although relationships changed throughout fruit growth. However seasonal change in Kp was not associated with any obvious anatomical change in the cortex.

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Christopher B. Watkins and Jacqueline F. Nock

The effects of temperature during 1-MCP treatment, and the effects of delays of up to 8 d after harvest before treatment, have been investigated using `Cortland', `Delicious', `Jonagold', and `Empire' (normal and late harvest) apple [(Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] cultivars stored in air for 2 and 4 months and in controlled atmosphere (CA) storage for 4 and 8 months. Fruit were treated with 1 μL·L–1 1-MCP for 24 hours on the day of harvest (warm) or after 1, 2, 3, 4, 6, or 8 days at cold storage temperatures. CA storage was established by day 10. Little effect of temperature during treatment (warm fruit on the day of harvest compared with cold fruit after 24 hours of cooling) was detected. Major interactions among cultivars, handling protocols before 1-MCP treatment, storage type and length of storage were observed. Delays of up to 8 days before 1-MCP treatment either did not affect efficacy of treatment, or markedly reduced it, depending on cultivar, storage type and length of storage. The results indicate that, depending on cultivar, the importance of minimizing the treatment delay increases as storage periods increase.

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Jun Song, Lihua Fan, Charles F. Forney, and Michael A. Jordan

Volatile emissions and chlorophyll fluorescence were investigated as potential signals of heat injury for apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] fruit. `McIntosh', `Cortland', `Jonagold', and `Northern Spy' apples were exposed to 46 °C for 0, 4, 8, or 12 hours (heat treatments). Following treatments, fruit were kept at 20 °C and evaluated after 1, 2, 4, or 7 days. Heat treatments induced volatile production including ethanol and ethyl acetate. The 8 and 12 hours heat treatments increased ethanol and ethyl acetate production in all four cultivars by as much as 170- and 11-fold, respectively, 1 day after treatments. Heat treatments also reduced ethylene production and chlorophyll fluorescence. Heat for 12 hours caused serious flesh browning. Among the cultivars investigated, `Northern Spy' and `McIntosh' were most susceptible to heat stress based on the degree of flesh browning. Correlation coefficients of heat stress induced ethanol emission and chlorophyll fluorescence with flesh browning were 0.82 and -0.66, respectively. The nondestructive measurements of ethanol emission and chlorophyll fluorescence have potential to identify stressed fruit with reduced quality or compromised storage life.

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Wesley Autio*, LaMar Anderson, Bruce Barritt, Robert Crass-weller, David Ferree, George Greene, Scott Johnson, Joseph Masabni, Michael Parker, and Gregory Reighard

`Fuji' apple trees [Malus ×sylvestris (L.) Mill. Var domestica (Borkh.)] on nine dwarfing rootstocks (CG.4013, CG.5179, G.16N, G.16T, M.9 NAKBT337, M.26 EMLA, Supporter 1, Supporter 2, and Supporter 3) were planted at 10 locations (CA, KY MO NC OH 2 in PA SC UT and WA) under the direction of the NC-140 Multistate Research Project. After four growing seasons (through 2002), largest trees were on CG.4013. Smallest trees were on M.9 NAKBT337, Supporter 1, Supporter 2, and Supporter 3. Trees on CG.5179, G.16 N, G.16T, and M.26 EMLA were intermediate. Cumulative root suckering was greatest from trees on CG.4013 and similar from the other rootstocks. CG.4013, CG.5179, and G.16T resulted in the greatest yields per tree in 2002, and M.26 EMLA, M.9 NAKBT337, Supporter 2, and Supporter 1 resulted in the lowest. Cumulatively, CG.4013 resulted in the greatest yields per tree, and M.26 EMLA resulted in the lowest. Rootstock did not affect yield efficiency in 2002, but cumulatively, Supporter 1, Supporter 2, and Supporter 3 resulted in the most efficient trees, and M.26 EMLA the least. Fruit weight in 2002 or on average was not affected by rootstock. Limited data will be presented on CG.3041, CG.5202, and CG.5935, which are planted only at some locations. Data for the fifth season (2003) will be presented.

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P. Allan-Wojtas, K.A. Sanford, K.B. McRae, and S. Carbyn

The apple industry worldwide would benefit from an improved and standardized description of fresh-apple textural quality. The description proposed here is unique in that it integrates structural, sensory, and consumer information. To demonstrate its benefits, 24 apple cultivars [Malus ×sylvestris (L.) Mill. var. domestica (Borkh..) Mansf.] were sampled over two harvest seasons and analyzed using microstructural and sensory techniques. Cultivars were selected to cover a range of known sensory textures, and microstructural profiles were compiled in parallel with sensory and instrumental studies. Each cultivar was pre pared for conventional scanning electron microscopy (SEM) observation using standard methods. Representative fruit from each cultivar were photographed at three magnifications to visualize fruit architecture, tissue relationships, and size, shape, and arrangement of cells within layers to compile the microstructural profile. A trained sensory panel evaluated the cultivars for crispness, surface coarseness, sponginess, hardness, juiciness, degree of melting, mealiness, and skin toughness while a consumer panel rated liking. This information was compiled into a texture profile. The microstructural and texture profiles were then combined into a cultivar profile for each sample. Cultivar profiles were collected to form a database; subtle similarities and differences among the 28 market-quality samples were interpreted and noted. With this technique, those structures with similar sensory properties can be identified with some form of microscopy. Clarifying and predicting the parameters that are related to textural quality in new cultivars will streamline the introduction process.

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Luisa Monte-Corvo, Luis Goulão, and Cristina Oliveira

Inter-simple sequence repeat (ISSR) markers were used for cultivar identification and for determination of the phenetic relationships among 24 pear cultivars (Pyrus communis L.). The ability of several molecular marker systems including randomly amplified polymorphic DNA (RAPD), amplified fragment length polymorphisms (AFLP), inter-simple sequence repeats (ISSR), simple sequence repeats (SSR), and selective amplification of microsatellite polymorphic loci (SAMPL) to detect variation among clones of the most significant Portuguese cultivar, Rocha, was also investigated. Each of the eight ISSR primers tested was able to distinguish the 24 pear cultivars. The ISSR primers generated 337 markers, 79.5% of which were polymorphic. The cultivar dendrogram obtained with the ISSR marker data was very similar to that obtained with previous RAPD+AFLP analysis, confirming the genetic divergence of `Pérola', `Carvalhal' and `Lawson' from the other cultivars. Eight out of 15 apple [Malus sylvestris (L.) Mill. var domestica (Borkh.) Mansf.] SSR primers tested also amplified microsatellites in pear. None of the five molecular marker systems analyzed (with a total of 1082 markers) detected reproducible polymorphisms among the nine `Rocha' clones, in spite of the presence of clear phenotypic differences.

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I. Lara and M. Vendrell

Endogenous ABA, free and conjugated ACC concentrations, ethylene-forming capacity (EFC), and presence of ACC oxidase (ACO) and ACC synthase (ACS) proteins were monitored during the preharvest maturation period of `Granny Smith' apple fruit (Malus sylvestris L. Mill. var. domestica (Borkh.) Mansf. `Granny Smith'). Total proteins from peel and pulp tissues were also extracted at different maturity stages and separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis, providing evidence of differential protein accumulation during fruit development. Endogenous ABA concentration in the peel tissue was higher than in pulp, the highest level occurring ≈2 months before commercial harvest. In the pulp tissue, concomitant increases in ACC and ABA concentrations were observed, preceded by a peak in EFC. However, no ACO or ripening-related ACS proteins were detectable throughout the period considered, suggesting that very low levels of both enzymes are present during the preclimacteric stage of `Granny Smith' apples. A hypothesis on the possible interaction between ABA and ethylene during maturation of `Granny Smith' apples is proposed. Chemical names used: abscisic acid (ABA); 1-aminocyclopropane-1-carboxylic acid (ACC).

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Wesley Autio*, LaMar Anderson, Bruce Barritt, Robert Crass-weller, David Ferree, George Greene, Scott Johnson, Joseph Masabni, Michael Parker, and Gregory Reighard

`Fuji' apple trees [Malus ×sylvestris (L.) Mill. Var domestica. (Borkh.)] on five semidwarfing rootstocks (CG.4814, CG.7707, G.30N, M.26 EMLA, and M.7 EMLA) were planted at nine locations (CA, KY MO NC OH PA SC UT and WA) under the direction of the NC-140 Multistate Research Project. After four growing seasons (through 2002), trees on CG.7707 and M.7 EMLA were the largest, and those on M.26 EMLA were the smallest. M.7 EMLA resulted in more cumulative root suckering per tree than did any other rootstock. Yield per tree in 2002 and cumulatively was greatest from trees on CG.4814, CG.7707, and G.30N and least from trees on M.26 EMLA and M.7 EMLA. The most yield efficient trees in 2002 and cumulatively were on CG.4814, and the least efficient trees were on M.26 EMLA and M.7 EMLA. Rootstock did not affect fruit weight in 2002; however, on average, CG.7707 resulted in the largest fruit, and CG.4814 resulted in the smallest. Limited data will be presented on CG.6210, G.30T, and Supporter 4, which are planted only at some locations. Data for the fifth season (2003) will be presented.

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Wesley Autio*, John Cline, Robert Crassweller, Charles Embree, Elena Garcia, Emily Hoover, Kevin Kosola, Ronald Perry, and Terence Robinson

`McIntosh' apple trees [Malus ×sylvestris (L.) Mill. Var domestica (Borkh.)] on 10 dwarfing rootstocks (CG.3041, CG.4013, CG.5179, CG.5202, G.16N, G.16T, M.9 NAKBT337, Supporter 1, Supporter 2, and Supporter 3) were planted at 10 locations (MA, MI MN NS 2 in NY ON PA VT and WI) under the direction of the NC-140 Multistate Research Project. After four growing seasons (through 2002), trees on CG.5202 and CG.4013 were significantly larger than those on all other rootstocks. Smallest trees were on M.9 NAKBT337. Trees on other rootstocks were intermediate. Rootstock did not influence cumulative root suckering. Yield per tree in 2002 was greatest from trees on CG.4013 and lowest from trees on M.9 NAKBT337; however, cumulatively, trees on M.9 NAKBT337 and CG.4013 yielded the most. Yield efficiency in 2002 was not affected by rootstock. Cumulatively, rootstock had very little effect, but trees on CG.5202 were the least efficient. In 2002, M.9 NAKBT337, CG.3041, and Supporter 2 resulted in the largest fruit, and CG.5179 resulted in the smallest. On average, M.9 NAKBT337 resulted in the largest fruit, and G.16T resulted in the smallest. Limited data will be presented on CG.5935 and M.26 EMLA, which are planted only at some locations. Data for the fifth season (2003) will be presented.

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Rongcai Yuan and Duane W. Greene

Experiments were conducted to evaluate the effects of BA, removal of bourse shoot tips including only folded leaves and growing point, and different numbers of leaves per fruit on fruit retention and fruit development in `More-Spur McIntosh'/Malling 7 (M.7) apple trees [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.]. Removal of the bourse shoot tip increased fruit retention, whereas BA thinned fruit regardless of whether shoot tips were removed or not. There was no interaction between BA application and shoot tipping. BA thinned fruit only when one leaf per fruit was on a girdled small fruiting branch, but not when leaf number per fruit was two or greater. Fruit weight and soluble solids concentration increased dramatically with increasing leaf number per fruit. BA reduced fruit growth rate when <16 leaves per fruit were present on the girdled branches between 3 and 7 days after treatment, but it did not affect fruit growth rate when 32 leaves per fruit were on the girdled branches. Increasing leaf number also increased viable seed number per fruit while decreasing the number of aborted seeds, but it had no effect on the number of total seeds per fruit. BA reduced the number of viable seeds per fruit only when the number of leaves per fruit was less than four. Results suggest that BA thins apple fruit mainly by reducing carbohydrates available to developing fruitlets. Chemical name used: N-(phenylmethyl)-1H-purine-6-amine [benzyladenine (BA)].