scholarly journals 251 The Effect of Simulated Stress on the Yield and Size of `Gala' and `Empire' Apple

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 485D-485
Author(s):  
S.L. Breitkreutz ◽  
J.A. Flore
Keyword(s):  
Total Yield ◽  
Fruit Size ◽  
Growing Season ◽  
Apple Fruit ◽  
Physiological Status ◽  
Crop Load ◽  
Pest Damage ◽  
Biological Stress ◽  
Foliar Damage ◽  
Current Standards

Pest damage to apple fruit is intolerable by our current standards. However, the effects of foliar damage on the plant's physiological status and fruit quality are not thoroughly understood. The objective of this work was to determine the time during the growing season when apple trees are most susceptible to foliar damage. Terbacil (50 ppm), an inhibitor of photosynthesis, was applied to 8-year-old `Gala'/Mark planted at 6 ×18-foot spacing or 14-year-old `Empire'/M106 planted at 18 × 20-foot spacing at 20- to 30-day intervals from petal fall until harvest to simulate environmental or biological stress. The work was conducted from 1995 through 1998. Photosynthesis was inhibited by 50% to 80% within 24 h of application of Terbacil but recovered to control levels 10 to 14 days after. The fruit were evaluated at harvest for total yield, size of fruit, and fruit number. Terbacil induced fruit abscission when applied at petal fall but not at later dates. The earlier the application, the greater the effect on current seasons yield and fruit size depending on crop load. For `Gala', there was a reduction in yield at petal fall of 30% to 70% over the control trees. Further detailed results will be presented.

scholarly journals 166 Influence of Crop Level on Growth and Quality of `Braeburn' Apple Fruit

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 418E-419
Author(s):  
P.I. Garriz ◽  
G.M. Colavita ◽  
H.L. Alvarez
Keyword(s):  
Fruit Size ◽  
Growing Season ◽  
Apple Fruit ◽  
Full Bloom ◽  
Cross Sectional ◽  
Crop Load ◽  
Commercial Crop ◽  
Source Sink ◽  
Fruit Diameter

Crop load and the genetic biological carrying capacity (source–sink relationships) determine the potential for fruit size development on apple; however, the environment within which the fruit grows attenuates this potential. The effects of different crop loads on the growth pattern and the progress of maturity in apples were evaluated at the Comahue National Univ., Argentina (lat. 38 56'S long 67 59'W), during the 1998–99 growing season. Our experiment was conducted on 6-year-old `Braeburn'/Malling Merton 111 apple (Malus domestica Borkh.) trees spaced 4.0 × 2.3 m and trained to palmette leader. Treatments were 1) light crop load (LC), 2.5 fruit/cm2 trunk cross-sectional area (TCSA), 2) moderate crop load (MC), 6.5 fruit/cm2 TCSA (standard commercial crop load) and 3) high crop load (HC), minimum 8 fruit/cm2 TCSA, no fruit removed from tree. Whole trees were hand-thinned 19 days after full bloom (DAFB). Fruit diameter (FD) was taken at two weekly intervals (n = 24 per date and treatment) and maturity indexes were determined at harvest. Analysis of variance was used and mean separations were computed with Student's t test. From 38 DAFB until harvest, fruit size was significantly reduced (P < 0.01) in the HC trees, indicating that they were source-limited during growth. At 166 DAFB, FD was 7.48, 7.14, and 6.89 cm for the LC, MC and HC treatments, respectively. Adequate carbon was apparently available to support a commercial crop load since no differences were found between LC and MC trees. Crop level influenced flesh firmness; at 173 DAFB, it was significantly lower in HC trees than MC and LC trees (84.33, 92.51, and 91.57 N, respectively). These results suggest some goals of thinning for ensuring sizable `Braeburn' fruit.

Interaction Between CPPU and NAA on Fruit Thinning and Fruit Development in Selected Apple Cultivars

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 513c-513 ◽  
Author(s):  
Martin J. Bukovac ◽  
Jerome Hull ◽  
John C. Neilsen ◽  
Michael Schroeder ◽  
Georg Noga
Keyword(s):  
Total Yield ◽  
Fruit Size ◽  
Frost Damage ◽  
Fruit Growth ◽  
Soluble Solids ◽  
Seed Number ◽  
Crop Load ◽  
Fruit Thinning ◽  
Carpel Development ◽  
Return Bloom

NAA is used extensively for fruit thinning of apples to increase fruit size and to promote return bloom. In some cultivars, even if thinning is achieved, fruit size at harvest may be less than expected based on crop load. CPPU, N-(2-chloro-4-pyridinyl)-N.-phenylurea, has been shown to increase fruit growth in apples, grapes, and kiwi. We evaluated combinations of NAA and CPPU on thinning, fruit growth and return bloom in Redchief `Delicious', `Elstar', and `Gloster'. CPPU was applied at 5 mgμL–1 (based on 0 to 10 mgμL–1 response curve) in combination with 15 mgμL–1 NAA as high-volume sprays at 7 to 10 mm KFD. Yield and fruit size distribution (on total yield) were used as index of response. In `Delicious', CPPU (3-year study) increased % large (70 mm+) fruit, but in the presence of NAA % large fruit was reduced 2 of the 3 years. CPPU did not induce significant thinning. There were no significant effects on color or soluble solids; firmness was increased slightly and seed number reduced. The L/D ratio was increased and uneven lobe and carpel development was common. CPPU had no significant effect on return bloom in presence or absence of NAA, but NAA increased bloom in both the presence and absence of CPPU. With `Elstar' (2-year study) there was no significant thinning with either chemical, but CPPU increased mean fruit size and % large (70–80 mm) fruit over nonthinned, but not significantly greater than NAA alone. There were no significant differences in firmness, color, soluble solids or seed number. NAA + CPPU did not inhibit fruit growth or cause excessive uneven carpel development. Frost damage reduced crop load in `Gloster' where results were similar to `Elstar' except seed number was reduced by the NAA + CPPU combination.

The Effects of Exogenous Bioregulators and Environment on Regular Cropping of Apple

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 554e-555
Author(s):  
Kathleen M. Williams
Keyword(s):  
Pacific Northwest ◽  
Cultural Practices ◽  
Negative Impact ◽  
Fruit Size ◽  
Physiological Status ◽  
Naphthalene Acetic Acid ◽  
Crop Load ◽  
The Past ◽  
The Pacific ◽  
Return Bloom

Use of exogenous bioregulators (“hormones”) to adjust crop load in apple remains challenging to both researchers and producers. These hormones are sensitive to the rate and timing of application, to the physiological status of the tree, the choice of orchard system, variety and rootstock, and a myriad of cultural practices and environmental factors. All classes of plant bioregulators have been used over the past 30 to 40 years as chemical thinning materials. Most of the standard postbloom thinning programs involve application of a synthetic auxin, such as naphthalene acetic acid (NAA) in combination with carbaryl, a commonly used insecticide. The mode of action of these two compounds is not clearly understood. Gibberellins generally have not been effective thinning materials because of the negative impact on return bloom. Ethylene-releasing compounds have been used successfully as postbloom thinning materials. And cytokinins, particularly synthetic sources such as 6-BA, have been shown to effectively thin fruit and to enhance fruit size on many commercial varieties. The rate and timing of 6-BA applications are particularly critical to obtain the desirable thinning and size responses. Overall, these bioregulators are sensitive to temperature. The use of bloom thinning compounds and their efficacy in the Pacific Northwest will be discussed in the context of return bloom.

The effect of irrigation and crop load on stem water potential and apple fruit size

1997 ◽  
Vol 72 (5) ◽  
pp. 765-771 ◽  
Author(s):  
A. Naor ◽  
I. Klein ◽  
I. Doron ◽  
Y. Gal ◽  
Z. Ben-David ◽  
...  
Keyword(s):  
Water Potential ◽  
Fruit Size ◽  
Apple Fruit ◽  
Stem Water Potential ◽  
Crop Load ◽  
Stem Water

scholarly journals Native Variation in Bloom and Crop Density in Spur-type `Delicious' and Effect of Ethephon Applied in High Crop Years

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1096D-1097
Author(s):  
Martin J. Bukovac ◽  
Jerry Hull ◽  
Paolo Sabbatini
Keyword(s):  
Apple Tree ◽  
Cultural Practices ◽  
Total Yield ◽  
Fruit Size ◽  
Alternate Bearing ◽  
Full Bloom ◽  
Crop Load ◽  
Fruit Thinning ◽  
Crop Density ◽  
Return Bloom

For studies on blossom/fruit thinning in apple, tree selection is often based on uniformity of bloom/crop load, assuming that such trees exhibit greater uniformity to treatment. However, the literature is replete with data showing marked variation for a given treatment. We followed variation in bloom/crop density of spur-type `Delicious'/MM.106 and effect of ethephon applied in high crop years on return bloom/yield. Uniform trees (n = 95), under identical cultural practices, were selected for varying crop load. Return bloom, yield and fruit size were monitored over six years. General mean (X) for yield was 94 ± 25 kg/tree and bloom density, rated 1 to 10 (highest), was 5.4 ± 1.7. Annual yield deviated from X by +56 to –40% and bloom density by +49 to –42%. All trees were ranked (decreasing yield) and assigned to five percentile (PCTL) groups (1st, 81-100; 2nd, 61-80; 3rd, 41-60; 4th, 21-40; 5th, 0-20 kg/tree). Trees in each group were reassigned annually to the five PCPL groups for the next five years. Of trees in 1st PCTL (n = 19, X = 187 ± 10 kg/tree) in year one, 5, 5, 24, 0 and 63% placed in PCPL 1, 2, 3, 4, and 5, respectively, in year two. Of trees in 1st PCTL (5%) in year two, all placed in PCTL 2 in year three. Effect of ethephon [200 mg·L-1 at 3, 3 + 6, 3 + 6 + 9 weeks after full bloom (WAFB)] applied in on years to `Redchief', with strong alternate bearing, were evaluated for six years. Ethephon at 3 WAFB had no effect. Yield from multiple applications differed from control (NTC) in off years, but not from each other. Total yield (3 on + 3 off years) for the NTC and ethephon at 3 + 6 WAFB was similar (479 vs. 471 kg/tree). However, 64% of the total yield was produced in the on years and 36% in the off years in NTC vs. 56 and 44% in 3 + 6 WAFB, respectively.

scholarly journals Effect of Sterol-demethylation Inhibiting Fungicides on Apple Fruit Set, Fruit Size, Total Yield, and Gross Returns

HortScience ◽  
2003 ◽  
Vol 38 (4) ◽  
pp. 601-604 ◽  
Author(s):  
D.A. Rosenberger ◽  
T.L. Robinson ◽  
J.R. Schupp ◽  
C.A. Engle-Ahlers ◽  
F.W. Meyer
Keyword(s):  
Plant Growth Regulator ◽  
Fruit Set ◽  
Total Yield ◽  
Apple Scab ◽  
Fruit Size ◽  
Apple Fruit ◽  
Fruit Weight ◽  
Dmi Fungicides ◽  
Apple Production ◽  
Fruit Size And Shape

Effects of three sterol-demethylation inhibiting (DMI) fungicides and a contact fungicide were compared over two years at each of two locations to determine if fungicide treatments had differential effects on productivity, fruit size and shape, or gross returns for `Empire' apples (Malus ×domestica Borkh.). Treatments were applied four to five times per year during the primary apple scab season. Effects of treatments were assessed by comparing fruit set efficiencies, number of fruit per tree, total harvested fruit weight, and fruit length: diameter ratios at harvest. No significant differences were noted among individual treatments in any of the four trials. However, when treatments were contrasted by grouping individual treatments, significantly larger fruit size was noted for triflumizole treatments vs. combined fenarimol and myclobutanil treatments in one of the four trials and for captan or mancozeb compared to fenarimol and myclobutanil treatments in two trials. None of the DMI fungicides compared in these trials had any consistent adverse affect on fruit size, total yield, or estimated gross return per hectare. We conclude that the plant growth regulator effects of DMI fungicides are inconsistent and are unlikely to have significant economic impact on commercial apple production.

scholarly journals Irrigation and Crop Load Interactions in Relation to Apple Yield and Fruit Size Distribution

1997 ◽  
Vol 122 (3) ◽  
pp. 411-414 ◽  
Author(s):  
A. Naor ◽  
I. Klein ◽  
I. Doron ◽  
Y. Gal ◽  
Z. Ben-David ◽  
...  
Keyword(s):  
Size Distribution ◽  
Total Yield ◽  
Fruit Size ◽  
Fruit Tree ◽  
Pan Evaporation ◽  
Crop Load ◽  
Evaporation Coefficient ◽  
Irrigation Level ◽  
Class A ◽  
Class A Pan

The interaction between irrigation and crop load with respect to fruit size distribution was investigated in a `Golden Delicious' apple (Malus domestica Borkh) orchard located in a semi-arid zone. Irrigation levels during the main fruit expansion phase ranged from 0.42 to 1.06 of the Class A pan evaporation coefficient. Crop load was adjusted to 100 to 450 fruit/tree in the 1250 trees/ha orchard by hand thinning. Total yield was not affected by irrigation level up to a crop load of 200 fruit/tree. Yield of all grades >65 mm was affected by irrigation level for higher crop densities. The yield of fruit of diameter <75 mm was not affected by increasing the Class A pan evaporation coefficient above 0.75. Our data indicate that availability of assimilates may limit the size of fruit with potential to grow larger than 70 mm in diameter at all crop loads higher than 200 fruit/tree. This limitation increases with decreasing irrigation level. The volumetric relative growth rate (VRGR) increased with irrigation level and with decreasing crop load. VRGR was more affected by crop load than by irrigation level in the ranges studied.

scholarly journals Growth Response of Apple Fruit to NAA and Accel: Effect of Intraspur Competition and Position on a Spur

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 765D-765
Author(s):  
Brent L. Black ◽  
Martin J. Bukovac ◽  
Matej Stopar
Keyword(s):  
Growth Response ◽  
Fruit Size ◽  
Apple Fruit ◽  
Fruit Growth ◽  
Crop Load ◽  
Commercial Thinning ◽  
Whole Tree ◽  
Fruit Diameter

Apple fruit size is influenced by position on the spur, and location and number of competing fruits. King fruit appear to have the greatest potential to size and grow best in the absence of intraspur fruit competition (ISFC). Accel (A) and NAA (N), commercial thinning chemicals, influence fruit size beyond their effects on crop load. A 2-year study was conducted to determine the effect of ISFC and position (king, K, or lateral, L) on fruit growth in response to A and N. Branches from `Redchief Delicious' were thinned, after petal fall, to one K, one L, one K + one L, or two L fruits per spur. Whole-tree treatments of N (15 mg·liter–1), A (50 mg·liter–1, 1993; 25 mg·liter–1), and a combination (N+A) were applied at 10-mm king fruit diameter. A nontreated control was included. In 1993, N and N+A reduced fruit size only with ISFC, while A increased fruit size in the absence of ISFC. In 1994, A had no effect, but N and N+A reduced fruit growth with ISFC. In both seasons, A and N decreased the frequency of spurs bearing multiple fruit, while N+A dramatically increased number of spurs with multiple fruits (branch survey).

scholarly journals Responses of apple fruit size to tree water status and crop load

2008 ◽  
Vol 28 (8) ◽  
pp. 1255-1261 ◽  
Author(s):  
A. Naor ◽  
S. Naschitz ◽  
M. Peres ◽  
Y. Gal
Keyword(s):  
Water Status ◽  
Fruit Size ◽  
Apple Fruit ◽  
Crop Load

scholarly journals 683 Contributions of Early Season Environment and Crop Load to Apple Fruit Development

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 516D-516
Author(s):  
C.J. Stanley ◽  
D.S. Tustin
Keyword(s):  
Cell Division ◽  
Fruit Size ◽  
Cell Number ◽  
Apple Fruit ◽  
Fruit Weight ◽  
Full Bloom ◽  
Crop Load ◽  
Early Season ◽  
Growth Partitioning ◽  
Load Conditions

Many factors contribute to final apple fruit size. Researchers have studied these factors and have developed models, some very complex. Results from many New Zealand regions over several years suggest that early season temperature along with crop load are the key factors driving final fruit size. Accumulated growing degree days from full bloom to 50 days after full bloom (DAFB), accounted for 90% of the variance in fruit weight of `Royal Gala' apples at 50 DAFB under nonlimiting low-crop-load conditions. In turn, fruit weight at 50 DAFB accounted for 90% of the variance in final fruit size at harvest under the low-crop-load conditions. We hypothesise that a potential maximum fruit size is set by 50 DAFB, determined by total fruit cell number, resulting from a temperature-responsive cell division phase. Under conditions of no limitations after the cell division phase, we suggest that all cells would expand to their optimum size to provide the maximum fruit size achievable for that cell number. Factors which affect growth partitioning among fruits, e.g., higher crop loads, would reduce final fruit size, for any given cell number, when grown in the same environment. In Oct. 1999, four different crop loads were established at full bloom on `Royal Gala' trees (M9 rootstock) in four climatically different regions. In Hawkes Bay, similar crop loads were established at 50 DAFB on additional trees. Hourly temperatures were recorded over the season. Fruit size was measured at 50 DAFB and fruit will be harvested in Feb. 2000. These data should provide fresh insight and discussion into the respective roles of temperature and competition during the cell division fruit growth phase on apple fruit size.

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