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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.
`Summerland Red McIntosh' apple trees propagated on M.9/A.2,O.3, M.7 EMLA, M.26 EMLA, M.7A. OAR1, or Mark rootstocks were planted in 1985 in a randomized complete block design with seven replications. Fruit ripening and quality were assessed in 1988-93. Internal ethylene concentrations were measured weekly throughout each harvest season. Once each season, fruit weight, starch-index value, soluble solids concentration, flesh firmness, and surface ted color were assessed on a sample of fruit from each tree. Size was smallest for fruit from trees on OAR1 or Mark, after accounting for the effects of crop load with analysis of covariance. Surface ted color was greatest for fruit from trees on Mark and least for fruit from trees on M.7 EMLA. Ripening was variable, but generally, fruit from trees on 0.3 ripened first, and fruit from trees on M.7 EMLA or M.7A ripened last. Crop load impacted ripening, but its effects were removed with analysis of covariance.
The effects of rootstock on `Delicious' apple maturity, quality, size, mineral composition, and storability were studied over a 4-year period. Removing the effects of crop load and crop load within year by analysis of covariance produced results suggesting that M.27 EMLA and Ott.3 advanced fruit maturity and that M.7 EMLA delayed fruit maturity. M.9, MAC 9, OAR 1, M.9 EMLA, and M.26 EMLA either were inconsistent in their effect on maturity or consistently resulted in an intermediate maturity. Size, after adjusting for the effects of crop load and crop load within year, was consistently high for fruit from trees on M.9 EMLA, and lowest for fruit from trees on OAR 1. After adjusting for fruit size, fruit from trees on MAC 9 generally had high Ca contents, and fruit from trees on OAR 1 had low Ca contents. The effect of rootstock on storability appeared to be secondary and related to maturity and Ca level.
The effects of rootstock on `Delicious' (Malus domestics Borkh.) apple ripening, quality, size, mineral composition, and storability were studied over 4 years. Removal of the effects of crop load by analysis of covariance suggested that M.27 EMLA advanced fruit ripening and that M.7 EMLA delayed fruit ripening. Ott.3, M.9, MAC 9, OAR 1, M.9 EMLA, and M.26 EMLA either were inconsistent in their effects on ripening or consistently-resulted in an intermediate time of ripening. Fruit size consistently was largest from trees on M.9 EMLA and smallest from trees on OAR 1. Fruit from trees on MAC 9 generally had relatively high Ca contents, and fruit from trees on OAR 1 had relatively low Ca concentrations. The effects of rootstock on storability appeared to be related to their effects on maturity arid Ca levels.
Studies were conducted in 1989 to determine the effects of crop load and percent harvested on apple ripening. Twenty-seven `Golden Delicious' trees were selected and partitioned into 9 blocks. The crop load on one tree in each block was adjusted to 3.4, 6.9, or 15.0 fruit cm-1 trunk circumference in late June. Internal ethylene was measured in 6-fruit samples taken from each tree on 25 Sept., 2, 9, and 16 Oct. Increasing crop load had a significant linear effect on delaying ripening. Approximately 11 days separated the ripening of fruit from the 3.4 fruit cm-1 and the 15.0 fruit cm-1 treatments. In a second experiment, 18 `McIntosh' trees with similar crop load were partitioned into 6 blocks. Forty percent of the crop was harvested from 1 tree and 80% from another in each block on 7 Sept. Internal ethylene was measured on 7, 14, 21, and 28 Sept. Increasing the portion of the crop initially harvested linearly delayed subsequent fruit ripening. Approximately 6 days separated the ripening of fruit from the control and the 80%-removal treatments.
A series of experiments were initiated to evaluate the influence of notching on improving lateral branching of young apple trees. Buds on 2-year-old wood of `Redspur' Delicious/MM.111 were notched at 2-week intervals from 6 weeks before bloom to 2 weeks after. Notching increased lateral branching cubically with the greatest response occurring when notching was done 2 to 4 weeks before bloom. Bud break occurred equally well and shoots grew comparably when `Redcort'/M.7 were notched at the tip, middle, or base. Bud break and shoot growth from unnotched buds was greatest at the tip, intermediate in the middle and least at the base. Limbs of `Spygold'/M.7 were spread to a 45 degree angle then one bud from each 1-year-old shoot was notched at either the top, side or on the bottom of the shoot. Notching increased lateral branching from all bud positions, but the greatest response was from buds notched at the top and least from those located at the bottom of a branch. Buds of `Marshall McIntosh' were notched on either 1 or 2-year-old wood. Notching increased lateral branching more on 2-year than on 1-year old wood.
Abstract
A planting of ‘Starkrimson Delicious’ (Bisbee strain) apple trees was established in 1981 on M.27 EMLA, P.2/KA313, P.22/KA313, and C.6/KA313. After 6 years, trees on P.2/KA313 and C.6/KA313 were similar in size and larger than those on M.27 EMLA and P.22/KA313. P.22/KA313 induced profuse suckering, whereas trees on M.27 EMLA were virtually sucker-free. Cumulative yields per tree (1984–86) were the highest on P.2/KA313 and C.6/KA313. However, cumulative production efficiencies were highest for trees on M.27 EMLA and P.2/KA313. The least efficient trees were on P.22/KA313. Foliar analyses indicated that trees on M.27 EMLA had the highest levels of N, Ca, Mn, and Zn.
In 1991, experiments were conducted to assess the effects of several growth controlling techniques on tree growth and fruit set, abscision, ripening, and other qualities. The first two experiments assessed the effects of root pruning (4-8 days after petal fall, 1 m from the trunk, 30 cm deep) in commercial orchards. Compared to controls, root pruning reduced fruit abscision from mature `Cortland'/M.7A trees by 70% on 17 Sept. In another orchard, root pruning reduced fruit abscision from mature `McIntosh'/MM.106 trees by 47% on 24 Sept. The third experiment utilized vigorous `Gardiner Delicious'/MM.106 trees. Treatments included root pruning (as described above), trunk scoring (single, complete circle, approximately 40 cm from the soil), trunk ringing (single, complete circle, 1 mm wide, approximately 40 cm from the soil), ethrel spray treatment (500 ppm), and dormant-pruned and unpruned controls. Treatments were applied on 15 May, when terminal growth was 12-15 cm. No treatment affected fruit set. Trunk growth was less for ringed and scored trees than other treatments. Ringing and scoring advanced ripening compared to controls, and ethrel resulted in intermediate ripening. Treatments had no effect on fruit size, flesh firmness, or the development of bitter pit and cork spot. Fruit abscision was least from controls and root-pruned trees. Trees that were treated with ethrel in May had the most rapid abscision rate.
There is a general increase in interest in planting new apple cultivars. The loss of daminozide has provided an additional stimulus for growers in New England to find an alternative to McIntosh. Promising new apple cultivars have been identified from around the world and from breeding programs in Arkansas, British Columbia, New York, New Jersey and the PRI Program. Trees were propagated and planted in a cultivar evaluation block at the University of Massachusetts Horticultural Research Center. In 1992 we evaluated over 80 new cultivars. Fruit assessment consisted of laboratory analysis and visual and sensory evaluation. All cultivar were given an overall rating, and several were identified as being worthy of further evaluation. These apple cultivars include: Arlet, BC 9P 14-32, BC 8M 15-10, BC 17-30, Ginger Gold, Honeycrisp, Kinsei, NJ 55, NY 75414-1, and Sansa.
BA, NAA, and carbaryl at 75, 6, and 600 mg·liter-1, respectively, were applied alone or in combination to `Starkrimson Delicious' in 1989 and `Redspur Delicious' apples (Malus domestica Borkh.) in 1990. BA was effective alone, but when combined with carbaryl it thinned excessively. Thinning failed when BA was combined with NAA because many seedless pygmy fruit were formed and they persisted until harvest. BA and carbaryl were more effective than NAA at increasing return bloom. Return bloom was more closely related to total seed count than to final set. BA improved flesh firmness at harvest and after cold storage. None of the treatments influenced the development of calcium-related storage disorders following air storage. Chemical names used: benzyladenine (BA); naphthaleneacetic acid (NAA).