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Winfred P. Cowgill Jr., M.H. Maletta, W.H. Tietjen, J. Compton, D. Polk, and J.F. Goffreda

Six scab-resistant apple cultivars, Enterprise (CO-OP 30), CO-OP 36, Liberty, Freedom, Nova-Ez-Grow, and NY-754 were propagated on M.26 EMLA. Trees were planted in 1990 in a randomized complete-block design with six replications, five trees per replication. `Empire'/M.26 EMLA was the control cultivar. Tree spacing was 3 m apart in the row and 6 m between rows. Trees were individually staked and trained to a modified spindle bush. Precocity, bloom counts, tree height and width, TCA, cumulative yield efficiency, and fruit quality have been determined annually. `CO-OP 36', `Enterprise', and `Liberty' had significantly higher cumulative yields in 1993–94 than the other cultivars. The same three also had significantly superior fruit quality characteristics. `Liberty' was the most precocious of the scab-resistant cultivars, very similar to `Empire'. `Liberty' was also the weakest-growing cultivar, followed by `Empire'.

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Richard Marini*

Six-year-old York/M.9 trees were used to evaluate combinations of chemicals for fruit thinning. In one experiment a factorial combination of 2 levels of carbaryl (0 or 600 mg·L-1) and 5 levels of 6-BA (0, 40, 80, 120, and 160 mg·L-1) were sprayed when fruit diam. averaged 10.5 mm. Carbaryl significantly reduced fruit set, number of fruit/tree, yield efficiency, and crop density, and increased fruit weight. The main effect of 6-BA did not significantly influence any response variable. Two variables were significantly influenced by the carbaryl × 6-BA interaction. In the absence of carbaryl, fruit set was reduced and fruit weight was increased by 6-BA at concentrations less than 160 mg·L-1, but the addition of 6-BA to carbaryl was no more effective than carbaryl alone. In a second experiment, a factorial combination of 2 levels of carbaryl (0 vs. 600 mg·L-1), 2 levels of NAA (0 vs. 5 mg·L-1), and 2 levels of ethephon (0 vs. 450 mg·L-1) were sprayed when fruit when fruit diam. averaged 10.5 mm. Carbaryl and NAA reduced fruit set by about 30%, but ethephon overthinned and reduced set by 65%. When the other materials were combined with ethephon, thinning was similar to ethephon alone. The combination of carbaryl and NAA was no more effective than either material alone. The lowest values for yield, yield efficiency, and numbers of fruit per tree were associated with the combination of ethephon plus NAA. Ethephon was the only material that increased fruit weight.

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Kirk W. Pomper*, Joseph G. Masabni, Desmond R. Layne, Sheri B. Crabtree, R. Neal Peterson, and Dwight Wolfe

The pawpaw [Asimina triloba (L.) Dunal] has great potential as a new fruit crop. A pawpaw variety trial was established in Fall 1995 in Princeton, Ky. as a joint Kentucky State Univ.-Univ. of Kentucky research effort with the objective to identify superior varieties for Kentucky. A randomized block experimental design was used with 8 replicates of 28 grafted scion selections on seedling rootstock. Cultivars being tested included Middletown, Mitchell, NC-1, Overleese, PA-Golden, Rappahannock, Shenandoah, Sunflower, Susquehanna, Taylor, Tay-two, Wells, and Wilson. The other 15 clones were selections from the PawPaw Foundation. In 2002 and 2003, the following parameters were examined: tree survival, trunk cross-sectional area (TCSA), average fruit weight, total fruit harvested per tree, average fruit per cluster, total yield per tree, and yield efficiency. In 2003, 54% of the trees had survived, with `Susquehanna' (13%) showing the poorest survival. Based on TCSA, most selections displayed excellent vigor, with the exception of the selections: 5-5 and `Overleese'. Average fruit weight was greatest in 1-7-2 (194 g), 1-68 (167g), 4-2 (321 g), 5-5 (225 g), 7-90 (166g), 9-58 (176 g), 10-35 (167 g), NC-1 (180 g), `Sunflower' (204 g), and `Shenandoah' (168g), with the smallest fruit in `Middletown' (70 g), `Wells' (78 g), and `Wilson' (88 g). The selections `Wilson' (81), `Middletown' (75), and `Wells' (70) had the greatest average number of fruit per tree, whereas 4-2 (9), 5-5 (17) and 8-20 (15) the fewest. Yield efficiency and average fruit per cluster also varied greatly among selections. Several pawpaw selections in the trial show promise for production in Kentucky.

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Gabino Reginato, Terence Robinson, and Victor Garcia de Cortazar

Several field experiments to assess the effect of tree size and crop load on fruit size and yield were conducted in a `Ross' cling peach orchard and in three nectarine orchards of different harvest seasons in Chile. Trees were randomly selected in each orchard and then hand-thinned at the beginning of pit hardening to a wide range of crop loads. The fraction of above-canopy photosynthetically active radiation intercepted by the canopy (PARi) was determined at harvest and all fruits were counted, weighted, and average fruit weight calculated. Cropload and yield were expressed in terms of fraction of PARi. Data on farm gate prices for export fruit of different sizes and export dates were obtained from a Chilean export company. For each orchard, the relationship between cropload and fruit size or cropload and yield efficiency was assessed by regression analysis. Fruit size distribution was calculated from adjusted fruit size assuming a normal fruit size distribution and valued according to shipment date and price. Using crop load as a covariate, fruit size adjusted for cropload was calculated for each nectarine orchard. Differences in adjusted fruit size and yield efficiency were detected among cultivars. Predicted crop value, normalized in terms of PARi intercepted, was calculated for all the cultivars. Large differences in predicted crop value were found for early, mid-season, and late-ripening nectarines. The early and late ripening cultivars showed the highest predicted crop value, especially at lower crop loads and larger fruit sizes. On the other hand, `Ross' cling peach showed its highest crop value at a medium crop load with high yield and relatively small fruit size. (Funded by FONDECYT grant 1930695.)

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Wesley R. Autio

In 1990, trials were established at 13 sites including `Golden Delicious', `Jonagold', `Empire', and `Rome' apple cultivars in all combinations on M.9 EMLA, B.9, Mark, O.3, and M.26 EMLA rootstocks. After 10 growing seasons, rootstock and cultivar interacted significantly to affect trunk cross-sectional area and yield efficiency but not yield per tree or survival. Generally, trunk cross-sectional area was greatest for M.26 EMLA, followed by O.3, M.9 EMLA, B.9, and Mark. However, differences between B.9 and Mark and between M.9 EMLA and O.3 varied with cultivar. B.9 was 34% to 46% larger than Mark with `Golden Delicious' and `Empire,' but they were similar for `Jonagold' and `Rome.' O.3 was 27% larger than M.9 EMLA with `Golden Delicious' and `Empire,' they were similar for `Rome', and O.3 was 12% smaller than M.9 EMLA with `Jonagold'. M.26 EMLA resulted in the greatest cumulative yield per tree, followed by O.3, M.9 EMLA, B.9, and Mark. Generally, cumulative yield efficiency (1992–99) was greatest B.9 and Mark and least for M.26 EMLA. M.9 EMLA and O.3 were similar and intermediately efficient. However, differences between B.9 and Mark and between M.9 EMLA and O.3 varied with cultivar. M.9 EMLA and O.3 were similarly efficient with `Golden Delicious', `Jonagold', and `Rome,' but M.9 EMLA was 11% more efficient than O.3 with `Empire'. B.9 and Mark were similarly efficient with `Golden Delicious' and `Jonagold', but Mark was 15% more efficient and 25% less efficient than B.9 trees with `Empire' and `Rome', respectively. Site played an important role, but survival was best for B.9 and poorest for O.3. Cooperators included: J.L. Anderson, W. Autio, J. Barden, G. Brown, R. Crassweller, P. Domoto, A. Erb, D. Ferree, A. Gaus, R. Hayden, P. Hirst, F. Morrison, C. Mullins, J. Schupp, and L. Tukey.

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Raymond L. Granger, Shahrokh Khanizadeh, and Yvon Groleau

In experimental plots established in 1989, `Spencer', `Empire', `MacSpur', and `Lobo' trees grafted on the in vitro-propagated Ottawa 3 (0.3) rootstock were trained in the triple axis and in the slender spindle systems. They were planted at 5 (between rows) × 2.04 m and laid out in a split plot array with four replicates. There were five trees per subplot unit. All trees were trickle-irrigated every year. Fruit thinning was chemically done for the first time in 1993. Trees from this experiment came into bearing in 1991, and their total cumulative yield was significantly superior in the case of trees of the Spindlebush system. Since no interactions were found, we cannot conclude that any given combination is better than the others. `Lobo', which has averaged nearly 21 tonnes/ha per tree, was best in terms of total cumulative yield and also in terms of yield efficiency. `MacSpur' and `Empire' were the second best ones in yield efficiency, and `Spencer' was significantly lower. Fruit size was very good for all combinations in 1993. At their fifth-leaf stage in 1993, the yield of `Empire' trees from this experiment was higher by an average of more than 1 kg per tree than that of comparable trees of conventionally propagated O.3 trees planted in adjacent test plots. The tree vigor of the micropopagated O.3 trees was better than that of the conventionally propagated ones as revealed by the trees' trunk and canopy development. However, a few trees exhibited slight burr-knot growth on their trunk. This has never been observed on the conventionally propagated O.3 rootstock.

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Zlatko Cmelik* and Stanislav Tojnko

The trial was conducted in a `Elstar'/M9 orchard (2500 trees/ha) and the experiment was designed as a split-block comprising five treatments (fertigation with 45 kg·ha-1 N, 60 kg·ha-1 N, 120 kg·ha-1 N, irrigation without fertilizers, and control—without irrigation and without fertilizers), and two timing variants (treatments during vegetation period from 1 May to 20 June—variant A, and treatments from 1 May to 1 Aug.—variant B). The treatments were imposed beginning in the second year after planting and lasted five years. Fertigation with different amounts of nitrogen had no consistent effect on tree growth, cumulative yield and yield efficiency, however, treatments had a significant influence on regularity of bearing. The index of alternate bearing varied with treatment, but in both variant was significantly higher in control and in treatment with irrigation without application of fertilizer. These results demonstrated that the natural tendency of `Elstar' to alternate bearing could be broken by the different rates of nitrogen applied by fertigation.

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Michelangelo Policarpo and Riccardo Lo Bianco*

Five different types/combinations of foliar fertilizers were tested on eight-year-old trees of `Nocellara del Belice' olive grown in central Sicily. Trees were sprayed four times during Summer and Fall 2002 with Floral 20-20-20 (mineral N, P, K, and microelements; FLO) in combination with Alga Cifo (extract of brown algae; ALG), Floral 20-20-20 alone, Alga Cifo alone, Azomin (organic N, amino acids and peptides; AZO), Supernat93 (organic N and K, distillation residue; SUP), and water (control). Yield and trunk circumference were measured during Fall 2002, whereas other vegetative and reproductive parameters were measured during Spring-Fall 2003. AZO and SUP trees produced more than control and ALG trees, whereas only AZO trees showed higher yield efficiency than control. The number of inflorescences per shoot was greatest in FLO and ALG trees and smallest in control trees. Percentage of ovary abortion and June drop were lowest in AZO trees and highest in FLO+ALG and ALG trees, whereas ALG was the only fertilizer that caused a greater fruit drop at harvest. Shoot growth was significantly reduced in ALG and FLO trees, and AZO trees presented leaves with reduced specific weight. Organic foliar fertilization with AZO and SUP generally improved yield and growth of `Nocellara del Belice' olive trees by reducing ovary abortion and June drop and increasing shoot growth.

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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 five semidwarfing rootstocks (CG.4814, CG.7707, G.30N, M.7 EMLA, and Supporter 4) 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.7707, G.30N, Supporter 4, and M.7 EMLA were significantly larger than those on CG.4814. Cumulative root suckering was most from trees on M.7 EMLA, and least from trees on CG.7707, G.30N, and Supporter 4. Yield per tree in 2002 and cumulatively was greatest from trees on G.30N and least from trees on CG.7707 and M.7 EMLA. In 2002 and cumulatively, CG.4814 resulted in the greatest yield efficiency, and M.7 EMLA resulted in the lowest. In 2002, fruit from trees on M.7 EMLA were largest, and those from trees on CG.4814 were smallest. On average, M.7 EMLA resulted in the largest fruit, and G.30N resulted in the smallest. Limited data will be presented on CG.6210, CG.8, G.30T, and M.26 EMLA, which are planted only at some locations. Data for the fifth season (2003) will be presented.

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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.