scholarly journals Salvaging a Rabbiteye Blueberry Crop with GA3 following Sub-freezing Temperatures

HortScience ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 575d-575
Author(s):  
D. Scott NeSmith ◽  
Gerard Krewer ◽  
Orville Lindstrom
Keyword(s):  
Gibberellic Acid ◽  
Cold Exposure ◽  
Fruit Set ◽  
Temperature Limit ◽  
Flower Buds ◽  
Vaccinium Ashei ◽  
Growth Chambers ◽  
Freezing Temperatures ◽  
Flower Damage

Recent research in Georgia indicated gibberellic acid (GA3) could possibly be used to induce fruit set of freeze damaged rabbiteye blueberry (Vaccinium ashei) blooms. This research was conducted to determine the subfreezing temperature limit at which GA3 could be expected to be of use in salvaging a crop with freeze-damaged flowers. Rabbiteye blueberries with flower buds at stages 5 to 6 of development (fully elongated corollas and open blooms) were exposed to temperatures of 0, –1, –3, and –4.5°C in growth chambers to simulate overnight freezing events. After cold exposure, plants were placed in a greenhouse with a hive of bumblebees. Half of the plants were treated with GA3 and half were not. The number of flowers and subsequent fruit were recorded in order to calculate fruit set. Temperatures of –1°C and below caused fruit set resulting from pollination by bees to decline compared to control plants; whereas, flowers treated with GA3 had fruit set comparable to control plants down to –3°C. Plants exposed to –3°C had 50% to 80% fruit set when treated with GA3 compared to 5% to 19% fruit set for untreated plants. Temperatures of –4.5°C caused severe flower damage, and fruit set by pollination or GA3 was very poor (<2%). These results indicate that GA3 should be useful in salvaging a blueberry crop exposed to temperatures of – 1 to –3.5°C during bloom.

scholarly journals Flower Bud Stage and Chill Hours Influence the Activity of GA3 Applied to Rabbiteye Blueberry

HortScience ◽  
1992 ◽  
Vol 27 (4) ◽  
pp. 316-318 ◽  
Author(s):  
D.S. NeSmith ◽  
Gerard Krewer
Keyword(s):  
Gibberellic Acid ◽  
Growth Regulator ◽  
Flower Development ◽  
Fruit Set ◽  
Developmental Stages ◽  
Single Application ◽  
Flower Buds ◽  
Flower Bud ◽  
Vaccinium Ashei

Individual flower clusters of `Tifblue' rabbiteye blueberry (Vaccinium ashei Reade) were treated with 300 ppm GA at several flower bud stages to determine the activity of the growth regulator in promoting fruit set. Applications were made one time only at a specified stage of flower development, or once followed by a second application. A single application of GA when flower buds had elongated but corollas had not expanded (stage 5) led to the largest increase in fruit set. Two applications of GA, 10 to 18 days apart, increased fruit set compared with a single application at flower developmental stages other than stage 5. Fruit set promoted by a single spray of GA imposed on fully expanded corollas (stage 6) decreased with increasing number of chill hours (350, 520, 760, or 1150). Chemical names used: gibberellic acid (GA).

scholarly journals Fruit Set of Rabbiteye Blueberry (Vaccinium ashei) after Subfreezing Temperatures

1999 ◽  
Vol 124 (4) ◽  
pp. 337-340 ◽  
Author(s):  
D. Scott NeSmith ◽  
Gerard Krewer ◽  
Orville M. Lindstrom
Keyword(s):  
Gibberellic Acid ◽  
Cold Exposure ◽  
Fruit Set ◽  
Vaccinium Ashei ◽  
Different Temperatures ◽  
Freeze Damage

Plants of `Brightwell' and `Tifblue' rabbiteye blueberry (Vaccinium ashei Reade) were subjected to 0, -1, -3, or -4.5 °C for 1 hour during flowering. After treatment, half of the plants were exposed to bees (Bombus sp.) only, and half were exposed to bees and received applications of GA3. Fruit set of both `Brightwell' and `Tifblue' pollinated by bees declined sharply after exposure to -1 °C for 1 hour, but there was no visible damage to corollas, styles, and ovaries. Fruit set of GA3-treated plants of both cultivars equaled that of control plants (plants having no cold exposure) at temperatures ≥+-3 °C. Both pollinated and GA3-treated plants had ≤2% fruit set after exposure of flowers to -4.5 °C. Both prefreeze and postfreeze applications of GA3 were beneficial for fruit set. Assessment of flower part damage at the different temperatures indicated corollas were most sensitive to freeze damage, followed by styles, and then ovaries. Results suggest fertilization and fruit set of pollinated rabbiteye blueberries can be greatly impaired by even mild freezes (-1 to -2 °C), whereas, appropriately timed applications of GA3 can result in little reduction in fruit set even after moderate freezes (-3 to -4 °C) of blueberries during bloom. Chemical name used: gibberellic acid (GA3).

scholarly journals Response of Rabbiteye Blueberry (Vaccinium ashei Reade) to the Growth Regulators CPPU and Gibberellic Acid

HortScience ◽  
2002 ◽  
Vol 37 (4) ◽  
pp. 666-668 ◽  
Author(s):  
D. Scott NeSmith
Keyword(s):  
Gibberellic Acid ◽  
Growth Regulator ◽  
Fruit Set ◽  
Total Yield ◽  
Control Treatment ◽  
Single Application ◽  
Treatment Results ◽  
Vaccinium Ashei ◽  
Berry Size ◽  
Mature Field

Experiments were conducted during 1999 and 2000 at Griffin, Ga., with rabbiteye blueberries (Vaccinium ashei Reade) to determine how the growth regulator CPPU affected fruit set, berry size, and yield. CPPU (applied at two different timings) was used alone, and in conjunction with GA3 on mature, field-grown `Tifblue' plants. A control treatment without either growth regulator was also included. The CPPU concentration used was 10 mg·L-1 (a single application per treatment), and the GA3 concentration used was 200 mg·L-1 (two applications per treatment). Results from both years showed a positive benefit of CPPU with respect to fruit set and berry size, especially in the absence of GA3. Depending on timing, berry number per plant was increased by more than 200% in 1999 using CPPU. Berry size increases of more than 30% occurred in 2000 when CPPU alone was applied at 17 d after flowering (DAF). CPPU did not increase berry size of GA3-treated plants in either year. Total yield per plant during 2000 was 5.0, 7.1, and 8.3 kg for control, CPPU applied 7 DAF, and CPPU applied 17 DAF treatments, respectively, without GA3. While CPPU did substantially increase fruit set, berry size, and yield of `Tifblue', there was a notable delay in fruit ripening. These results suggest that CPPU may be useful for increasing yield of rabbiteye blueberries under conditions of inadequate fruit set (such as occurs in much of the Southeast), but a delay in ripening will likely result. Chemical names used: N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU); gibberellic acid (GA3).

scholarly journals Gibberellic Acid-induced Fruit Set of Rabbiteye Blueberry following Freeze and Physical Injury

HortScience ◽  
1995 ◽  
Vol 30 (6) ◽  
pp. 1241-1243 ◽  
Author(s):  
D. Scott NeSmith ◽  
Gerard Krewer ◽  
Mark Rieger ◽  
Ben Mullinix
Keyword(s):  
Gibberellic Acid ◽  
Field Experiments ◽  
Fruit Set ◽  
Field Trials ◽  
Fruit Weight ◽  
Physical Injury ◽  
Vaccinium Ashei ◽  
Freeze Injury ◽  
Green House ◽  
Series Of Experiments

In a series of experiments, gibberellic acid (GA3) was applied to rabbiteye blueberries (Vaccinium ashei Reade) under field and greenhouse conditions to determine if fruit set could be improved following physical or freeze injury to flowers. In field experiments, physically damaged flowers (i.e., corollas and styles removed, styles only removed, or ovaries lanced) of `Climax' and `Tifblue' treated with GA3 (4% ProGib at 250 mg·liter–1) set substantially more fruit than nontreated, damaged flowers. Under green-house conditions, GA3 applied postfreeze to `Tifblue' and `Brightwell' resulted in increased fruit set compared to unsprayed control plants of the same cultivars. Freeze-damaged plants had substantially reduced fruit set overall but to a much lesser extent for GA3-treated plants than for those not treated with GA3. Individual fruit weight was reduced by GA3 applications, as was berry seediness. Results from these greenhouse and field trials suggest that GA3 can be used to salvage a blueberry crop following a moderate freeze during bloom.

scholarly journals GIBBERELLIC ACID ENHANCES FRUIT SET OF PHYSICALLY DAMAGED BLUEBERRY FLOWERS

HortScience ◽  
1995 ◽  
Vol 30 (3) ◽  
pp. 430c-430
Author(s):  
Gerard Krewer ◽  
Scott NeSmith ◽  
Mark Rieger ◽  
Ben Mullinix
Keyword(s):  
Gibberellic Acid ◽  
Fruit Development ◽  
Fruit Set ◽  
The Other ◽  
Vaccinium Ashei ◽  
Freeze Damage ◽  
Corroborative Evidence ◽  
Better Than

Rabbiteye blueberry (Vaccinium ashei R.) flowers often suffer slight freeze damage that prevents fertilization and fruit development. To determine if gibberellic acid (GA3) might be useful in rescuing freeze-damaged flowers the following treatments were applied before anthesis to two cultivars at different locations: 1) undamaged control, 2) approximately two-thirds of the corolla and most of the style removed, 3) approximately half of the style removed, and 4) ovules lanced with an insect pin by driving it through the equator of the undeveloped berry until the point came out the other side. Half the bushes were not sprayed, and half were sprayed with GA3 (312 ppm, v/v) the night following treatment. `Climax' at Chula, Ga., had good fruit set for treatment 1 with and without GA3 (70% to 85%). Good fruit set also occurred for treatment 2, 3, and 4 where GA3 was applied (47% to 54%), but poor fruit set without GA3 (4% to 16%). `Tifblue' at Chula had significantly better fruit set for treatment 1 with GA3 (54% vs. 27%). Excellent fruit set occurred for treatment 2, 3, and 4 where GA3 was applied (81% to 96%), and poor fruit set without GA3 (6% to 7%). `Tifblue' fruit set by GA3 sized better than `Climax' fruit set by GA3. The experiments provide corroborative evidence that flowers that have suffered freeze damage to the stigma, style, corolla, and perhaps ovules can be set with GA3.

scholarly journals Effect of GA3 and Pollination on Fruit Set and Development in Rabbiteye Blueberry

HortScience ◽  
1998 ◽  
Vol 33 (4) ◽  
pp. 632-635 ◽  
Author(s):  
Raquel Cano-Medrano ◽  
Rebecca L. Darnell
Keyword(s):  
Gibberellic Acid ◽  
Fruit Development ◽  
Fruit Set ◽  
Fruit Size ◽  
Seed Mass ◽  
Parthenocarpic Fruit ◽  
Seed Number ◽  
Vaccinium Ashei ◽  
Development Period ◽  
Fruit Mass

To determine if multiple applications of GA3 would increase size of parthenocarpic fruit, and to assess the interaction between GA3 applications and pollination, `Beckyblue' rabbiteye blueberry (Vaccinium ashei Reade) flowers were treated with single or multiple applications of GA3 alone or in combination with full or partial pollination. Single or multiple applications of GA3 resulted in similar or increased fruit set compared with pollination, and increased fruit set compared with no pollination. GA3 applications decreased fruit mass and increased the fruit development period in comparison with pollination alone. Multiple, late applications of GA3 were ineffective in overcoming these effects. Partial (nonsaturating) pollination resulted in an average fruit set of 60%, while set following GA3 treatment in combination with full or partial pollination averaged 85%. Fruit mass was greater in the full pollination ±GA3 treatments than in all other treatments. The number of large seeds and seed mass per fruit were greatest in the full pollination treatment, and were significantly decreased by all treatments in which GA3 and/or partial pollination were used; however, there were no concomitant effects of GA3 in delaying the fruit development period. Our results indicate that under optimal pollination conditions, no detrimental effects of GA3 applications on fruit set, fruit size, or fruit development period in blueberry are to be expected, even though GA3 reduces seed number and seed mass. Furthermore, GA3 applications appear to be beneficial in increasing fruit set under suboptimal pollination conditions, although smaller fruit are to be expected under such conditions. Chemical name used: gibberellic acid (GA3).

scholarly journals Chemical Fruit Thinning of Vaccinium ashei Reade

1994 ◽  
Vol 119 (6) ◽  
pp. 1133-1136 ◽  
Author(s):  
Jose R. Cartagena ◽  
Frank B. Matta ◽  
James M. Spiers
Keyword(s):  
Gibberellic Acid ◽  
Fruit Set ◽  
Field Conditions ◽  
Application Time ◽  
Vaccinium Ashei ◽  
Fruit Thinning ◽  
Return Bloom ◽  
Presence And Absence ◽  
Fruit Diameter

The thinning potential of various chemicals sprayed on `Tifblue' rabbiteye blueberry was examined in the greenhouse in 1990 and under field conditions in 1991 and 1992. In the greenhouse, BA concentrations ranging from 25 to 500 mg·liter-1 and carbaryl concentrations ranging from 400 to 2100 mg·liter-1 reduced fruit set when treatments were applied 16 days after corolla drop (ACD). GA3 reduced fruit set only at 50 mg·liter-1 and NAA did not influence fruit set. In the field, BA at 75 mg·liter-1 and the combination of carbaryl at 400 mg·liter-1 and BA at 25 mg·liter-1 reduced fruit set in 1991 and 1992. Combinations of carbaryl and GA3 reduced fruit set, but the response depended on GA3 concentration and varied from year to year. GA3, NAA, and carbaryl also reduced fruit set, but the results were inconsistent. In 1991, greater thinning occurred when the treatments were sprayed 10 days ACD. BA at 25 mg·liter-1 increased fruit diameter at first harvest in 1991, and carbaryl at 400 mg·liter-1 increased fruit diameter in 1991 and 1992. Fruit diameter was increased in the presence and absence of thinning, depending on year and application time. Yield and return bloom were not influenced by any of the treatments. Chemical names used: 7 benzylamino purine (BA); gibberellic acid (GA3); 2-naphaleneacetic acid (NAA); 1-naphthyl N-methylcarbamate (carbaryl).

scholarly journals Vegetation-free Area Influences Growth and Establishment of Rabbiteye Blueberry

HortScience ◽  
1995 ◽  
Vol 30 (7) ◽  
pp. 1410-1412 ◽  
Author(s):  
D. Scott NeSmith ◽  
Gerard Krewer
Keyword(s):  
Festuca Arundinacea ◽  
Fruit Set ◽  
Growth Index ◽  
Shoot Length ◽  
Flower Buds ◽  
Vaccinium Ashei ◽  
Vegetation Control ◽  
Width Measurements ◽  
Hand Weeding ◽  
Free Area

`Tifblue' and `Brightwell' rabbiteye blueberries (Vaccinium ashei Reade) were planted in 1992 in a tall fescue (Festuca arundinacea Schreb.) sod. Vegetation-free areas of various sizes were maintained around plants to determine the area's influence on establishment and growth of young plants. Vegetation-free circles 0 (control), 0.6, 0.9, and 1.5 m in diameter were maintained from 1992 to 1994 by a combination of commercially recommended herbicides and hand-weeding. The treatments resulted in vegetation-free areas of 0, 0.3, 0.6, and 1.8 m2. Fall growth index values (derived from canopy height and width measurements) increased with size of vegetation-free area in each of the three years. The response was positive linear and negative quadratic, with little difference between the 0.6- and 1.8-m2 vegetation-free areas. Average shoot length in Fall 1992 showed a response similar to that of the growth index; total shoot count per plant was not affected by the treatments. Percent fruit set was not influenced by treatments; however, the number of flower buds per plant in Spring 1994 was correlated positively with size of vegetation-free area. The cultivars responded similarly. Thus, vegetation control seems to be important in establishing young rabbiteye blueberry plants, with the optimum vegetation-free area between 0.6 and 1.8 m2 during the first 2 to 3 years after planting.

Reproductive Responses of Capsicum annuum to High Temperatures

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 543c-543
Author(s):  
Ami N. Erickson ◽  
Albert H. Markhart
Keyword(s):  
Capsicum Annuum ◽  
High Temperatures ◽  
Fruit Development ◽  
Flower Development ◽  
Fruit Set ◽  
Fruit Production ◽  
Yield Reduction ◽  
Bud Size ◽  
Growth Chambers ◽  
Constant Growth

Fruit yield reduction due to high temperatures has been widely observed in Solanaceous crops. Our past experiments have demonstrated that Capsicum annuum cultivars Ace and Bell Boy completely fail to produce fruit when grown at constant 33 °C. However, flowers are produced, continually. To determine which stages of flower development are sensitive to high temperatures, pepper buds, ranging in size from 1 mm to anthesis, were exposed to high temperatures for 6 hr, 48 hr, 5 days, or for the duration of the experiment. Fruit set for each bud size was determined. Exposure to high temperatures at anthesis and at the 2-mm size stage for 2 or more days significantly reduced fruit production. To determine whether inhibition of pollination, inhibition of fertilization, and/or injury to the female or male structures prevents fruit production at high temperatures, flowers from pepper cultivars Ace and Bell Boy were grown until flowers on the 8th or 9th node were 11 mm in length. Plants were divided between 25 °C and 33 °C constant growth chambers for 2 to 4 days until anthesis. At anthesis, flowers from both treatments were cross-pollinated in all combination, and crosses were equally divided between 33 or 25 °C growth chambers until fruit set or flowers abscised. All flower crosses resulted in 80% to 100% fruit set when post-pollination temperatures were 25 °C. However, post-pollination temperatures of 33 °C significantly reduced fruit production. Reduced fruit set by flowers exposed to high temperatures during anthesis and pollination is not a result of inviable pollen or ovule, but an inhibition of fertilization or initial fruit development.

Cyclamen Leaf Unfolding Rate in Response to Temperature

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 447d-447
Author(s):  
Meriam Karlsson ◽  
Jeffrey Werner
Keyword(s):  
Day Length ◽  
Leaf Number ◽  
Cyclamen Persicum ◽  
Flower Buds ◽  
Flower Bud ◽  
Leaf Unfolding ◽  
Significant Difference ◽  
Number Of Leaves ◽  
Growth Chambers ◽  
Response To Temperature

Nine-week-old plants of Cyclamen persicum `Miracle Salmon' were transplanted into 10-cm pots and placed in growth chambers at 8, 12, 16, 20, or 24 °C. The irradiance was 10 mol/day per m2 during a 16-h day length. After 8 weeks, the temperature was changed to 16 °C for all plants. Expanded leaves (1 cm or larger) were counted at weekly intervals for each plant. The rate of leaf unfolding increased with temperature to 20 °C. The fastest rate at 20 °C was 0.34 ± 0.05 leaf/day. Flower buds were visible 55 ± 7 days from start of temperature treatments (118 days from seeding) for the plants grown at 12, 16, or 20 °C. Flower buds appeared 60 ± 6.9 days from initiation of treatments for plants grown at 24 °C and 93 ± 8.9 days for cyclamens grown at 8 °C. Although there was no significant difference in rate of flower bud appearance for cyclamens grown at 12, 16, or 20 °C, the number of leaves, flowers, and flower buds varied significantly among all temperature treatments. Leaf number at flowering increased from 38 ± 4.7 for plants at 12 °C to 77 ± 8.3 at 24 °C. Flowers and flower buds increased from 18 ± 2.9 to 52 ± 11.0 as temperature increased from 12 to 24 °C. Plants grown at 8 °C had on average 6 ± 2 visible flower buds, but no open flowers at termination of the study (128 days from start of treatments).

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