scholarly journals Effects of Exogenous Gibberellic Acid in Huanglongbing-affected Sweet Orange Trees under Florida Conditions – I. Flower Bud Emergence and Flower Formation

HortScience ◽  
2021 ◽  
pp. 1-11
Author(s):  
Lisa Tang ◽  
Garima Singh ◽  
Megan Dewdney ◽  
Tripti Vashisth
Keyword(s):  
Gibberellic Acid ◽  
Sweet Orange ◽  
Fruit Production ◽  
Colletotrichum Acutatum ◽  
Flower Formation ◽  
Flower Bud ◽  
Climate Conditions ◽  
Bloom Period ◽  
Flower Bud Formation ◽  
Orange Trees

Under Florida conditions, sweet orange (Citrus sinensis) affected by Huanglongbing {HLB [Candidatus Liberibacter asiaticus (CLas)]} frequently exhibits irregular flowering patterns, including off-season flowering and prolonged bloom period. Such patterns can increase the opportunity for temporal and spatial proliferation of pathogens that infect flower petals, including the fungal causal agent for postbloom fruit drop (PFD) Colletotrichum acutatum J.H. Simmonds. For the development of strategies to manipulate flowering, the effects of floral inhibitor gibberellic acid (GA3) sprayed monthly at full- and half-strength rates (49 and 25 g·ha−1, or 33 and 17 mg·L−1, respectively) with different regimens, starting from September and ending in November, December, or January, on the pattern of spring bloom were evaluated in field-grown HLB-affected ‘Valencia’ sweet orange at two locations in subsequent February through April for two separate years in this study. To further examine whether GA3 effects on flowering patterns vary in different cultivars, early-maturing ‘Navel’ sweet orange trees receiving no GA3 or full-strength GA3 monthly in September through January were included. Overall, for ‘Valencia’ sweet orange, monthly applications of GA3 at 49 g·ha−1 from September to December not only minimized the incidence of scattered emergence of flower buds and open flowers before the major bloom but also shortened the duration of flowering, compared with the untreated control trees. In addition, exogenous GA3 led to decreased leaf flowering locus t (FT) expression starting in December, as well as reduced expression of its downstream flower genes in buds during later months. When applied monthly from September through January at 49 g·ha−1, similar influences of exogenous GA3 on repressing flower bud formation and compressing bloom period were observed in ‘Navel’ sweet orange. These results suggest that by effectively manipulating flowering in HLB-affected sweet orange trees under the Florida climate conditions, exogenous GA3 may be used to reduce early sporadic flowering and thereby shorten the window of C. acutatum infection that causes loss in fruit production.

scholarly journals Development of Peach Flower Buds under Low Winter Chilling Conditions

Agronomy ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 428 ◽  
Author(s):  
Gener A. Penso ◽  
Idemir Citadin ◽  
Silvia Scariotto ◽  
Carlos E. Magalhães dos Santos ◽  
Américo W. Junior ◽  
...  
Keyword(s):  
Flower Development ◽  
Crop Management ◽  
Fruit Production ◽  
Flower Formation ◽  
Flower Bud ◽  
Bud Formation ◽  
Bud Induction ◽  
Exogenous Factors ◽  
Flower Bud Formation ◽  
Winter Chilling

Here, we reviewed both endogenous and exogenous factors involved in the processes of flower bud formation and flower development in peach, analyzing how they can be affected by climatic change in temperate zones, explored the expansion of peach to tropical or subtropical zones. The process of flower bud formation in peach differs between low winter chilling and temperate conditions. Although the main steps of flower development are maintained, the timing in which each one occurs is different, and some processes can be altered under low winter chilling conditions, with a great impact on fruit production and crop management. Further studies on flower bud induction and differentiation under warmer conditions are fundamental for addressing the alterations in flower bud development that negatively impact on next season’s harvest. In the future, horticulturalists and scientists will face several challenges, mainly how high temperatures affect the expression of the main genes regulating flower formation and how to improve crop management in these conditions.

Attempts to control alternate cropping of Valencia orange by inhibiting flower formation with gibberellic acid

1978 ◽  
Vol 18 (91) ◽  
pp. 309 ◽  
Author(s):  
PT Gallasch
Keyword(s):  
Gibberellic Acid ◽  
No Reduction ◽  
South Australia ◽  
Flower Formation ◽  
Mature Fruit ◽  
Mature Trees ◽  
Valencia Orange ◽  
Orange Trees

Gibberellic acid (GA) was sprayed on whole Valencia orange trees in 1971 at Loxton in South Australia with the aim of reducing the size of the heavy crop and the alternate cropping cycle. Sprays were applied in June or July at 25 p.p.m. but there was no reduction in mature fruit weights in 1972. In 1973, sprays of GA at 25 p.p.m, were applied twice, about two weeks apart, commencing on either May 7 or 22. In the following November treated trees had 75 per cent fewer fruitlets, but by the time fruit were mature, trees had fully compensated for this early reduction in fruit numbers by increased set and reduced December drop. Again the weight of mature fruit was not reduced at the timings and concentrations used and hence GA cannot be recommended for the control of alternate cropping.

scholarly journals Citrus Viroids: Symptom Expression and Performance of Washington Navel Sweet Orange Trees Grafted on Carrizo Citrange

Plant Disease ◽  
2015 ◽  
Vol 99 (1) ◽  
pp. 125-136 ◽  
Author(s):  
N. Murcia ◽  
S. M. Bani Hashemian ◽  
P. Serra ◽  
J. A. Pina ◽  
N. Duran-Vila
Keyword(s):  
Sweet Orange ◽  
Fruit Production ◽  
Symptom Expression ◽  
Trifoliate Orange ◽  
Carrizo Citrange ◽  
Hop Stunt Viroid ◽  
Washington Navel ◽  
Canopy Volume ◽  
Viroid Infection ◽  
Orange Trees

Citrus are natural hosts of several viroid species. Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd) are the causal agents of two well-known diseases of citrus, exocortis and cachexia. Other viroids have been found to induce specific symptoms and different degrees of stunting in trees grafted on trifoliate orange and trifoliate orange hybrids. A field assay was initiated in 1989 to establish the effect of CEVd, HSVd, Citrus bent leaf viroid (CBLVd), Citrus dwarfing viroid (CDVd), and Citrus bark cracking viroid (CBCVd) on Washington navel sweet orange trees grafted on Carrizo citrange rootstock. Here we report the effect of viroid infection on symptom expression, tree size, fruit production and quality evaluated from 2004 to 2007. Vegetative growth was affected by viroid infection with height and canopy volume being reduced. No bark scaling symptoms were observed in CEVd-infected trees albeit they presented lesions and blisters in the roots. Bark cracking symptoms were consistently observed in CBCVd-infected trees that were smaller with enhanced productivity and fruit size. No major effects were found as a result of infection with CBLVd, HSVd, or CDVd. The quality of the fruits was not affected by viroid infection, except for the low diameter of the fruits harvested from HSVd-infected trees. An interesting effect was identified in terms of tree productivity increase (yield/canopy volume) as a result of infection with CEVd, CDVd, and especially CBCVd.

Promoting fruit-set and yield in sweet orange using plant growth substances

1972 ◽  
Vol 12 (54) ◽  
pp. 96 ◽  
Author(s):  
GI Moss
Keyword(s):  
Gibberellic Acid ◽  
Fruit Set ◽  
Sweet Orange ◽  
Fruit Size ◽  
Growth Substances ◽  
Biennial Bearing ◽  
Small Fruit ◽  
Washington Navel ◽  
Fruit Size And Shape ◽  
Orange Trees

Experiments were done over four years to see if certain growth substances would increase the yields of sweet orange by increasing fruit-set. The main object was to find a method to increase yields during an off-year, and so control biennial bearing. Gibberellic acid (GA) was the most promising substance and under glasshouse and controlled environment conditions increased fruit-set when several applications were made, but had only a temporary effect when a single spray was applied. In the first instance a greater volume of fruit was produced although the mean size of the fruit was less. In the second instance some changes in fruit size and shape were found. In the field, a single spray (to part of a tree) of 400 p.p.m. GA at petal fall in one season on both Late Valencia and Washington Navel increased fruit-set, and in the following season 100 p.p.m. GA applied at petal fall increased fruit-set in Washington Navels. When a 50 p.p.m. GA spray was applied to whole Washington Navel trees in successive seasons there was a 20 per cent increase in the number of fruit harvested, but this was barely significant. However, there was a greater percentage of small fruit from the treated trees. This treatment had no effect the following season. Single applications of GA from 25 to 200 p.p.m. applied to Late Valencia trees from petal fall onwards in an 'off year' had relatively little effect. Some treatments retarded fruit-drop, but had insignificant or only minor effects on yield. Applying gibberellic acid to improve fruit-set is not a practical means for controlling yields of sweet orange trees.

The use of gibberellic acid to control alternate cropping of Late Valencia sweet orange

1977 ◽  
Vol 28 (6) ◽  
pp. 1041 ◽  
Author(s):  
GI Moss ◽  
KB Bevington
Keyword(s):  
Gibberellic Acid ◽  
Sweet Orange ◽  
Poncirus Trifoliata ◽  
Minimum Concentration ◽  
Rough Lemon ◽  
Small Fruit ◽  
Valencia Orange ◽  
Orange Trees ◽  
Long Term Adverse Effects

The effect of spraying commercial gibberellic acid (GA) on alternate cropping and yield of Late Valencia orange trees was studied in detail at three sites over three seasons. Two applications of GA were applied at a minimum concentration of 25 ppm (in two experiments 0.75% emulsifiable oil was used as an adjuvant) 3 weeks apart during April and May for Dareton (on the River Murray) or June and early July for Yanco (Murrumbidgee Irrigation Areas) prior to the heavy-crop blossom. These sprays partly inhibited flowering and the subsequent heavy crop was reduced by up to 22% (by fruit number). In the next season there were more flowers and the light crop was increased by up to 57% at Dareton and 228% at Yanco. Some treatments practically eliminated alternate cropping while all reduced considerably the heavyllight crop ratio. Mean weight yields over 2 years were increased by up to 17% at Yanco and 16% at Dareton with mean increases for all successful GA treatments of 12.6% and 7.2% respectively. This represented an increase of 34 and 24 kg fruitltree. No long-term adverse effects on yield were found.Apart from re-greening of the fruit present at the time of spraying, fruit quality was not affected. There were fewer non-saleable small fruit at Yanco in the heavy crop as a result of the GA treatments, and a better range of fruit sizes in both the heavy and light crops. Trees on Rough Lemon rootstock responded well to GA treatments, especially in terms of increased yield in the light crop. Poncirus trifoliata rootstock was less responsive than Sweet Orange. This method might be used for the commercial control of alternate cropping of Late Valencia orange trees.

scholarly journals UTILIZATION OF POSTHARVEST GIBBERELLIC ACID SPRAYS TO REDUCE HAND THINNING IN `PATTERSON' APRICOT

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1167a-1167
Author(s):  
Stephen M. Southwick ◽  
James T. Yeager
Keyword(s):  
Gibberellic Acid ◽  
Fruit Size ◽  
Fruit Production ◽  
Prunus Armeniaca ◽  
Growth Responses ◽  
Flower Bud ◽  
Growing Seasons ◽  
Fruit Species ◽  
Bud Initiation ◽  
Whole Tree

Heavy fruit set of apricot (Prunus armeniaca) cultivars grown in California often require hand thinning to insure that adequate fruit size is obtained. Alternatives to costly hand thinning would be welcome. GA treatments made during flower bud initiation/differentiation have been previously shown to inhibit the development of floral and vegetative buds in a number of different tree fruit species. The effects of post-harvest limb and whole tree aqueous gibberellic acid (GA) sprays on flower and fruit production were investigated over a 3 year period in `Patterson' apricot. Limb treatments indicated the potential for utilizing postharvest GA sprays to reduce the number of flowers produced in the following season. Harvest fruit size (June 1989) was increased by a 100 mg·liter-1 GA whole tree spray applied 7 July 1988 when compared to non-thinned and hand thinned trees. Yield per tree was reduced by that GA spray, but not enough to show statistical differences. No abnormal tree growth responses have been observed in GA-sprayed trees to date. These results and those from the 1989 and 1990 growing seasons will be presented in effort to identify a role for whole tree postharvest GA sprays in a chemical thinning program suitable for commercial apricots.

scholarly journals 659 Reducing Floral Initiation and Return Bloom in Fruit Trees— Applications and Implications in Fruit Production: Pome Fruit

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 561E-561
Author(s):  
Duane W. Greene
Keyword(s):  
Fruit Set ◽  
Fruit Size ◽  
Fruit Trees ◽  
Fruit Production ◽  
Alternative Methods ◽  
Pome Fruit ◽  
Flower Bud ◽  
Bud Formation ◽  
Biennial Bearing ◽  
Flower Bud Formation

Pome fruit display a biennial bearing tendency that is characterized by heavy flowering and fruit set one year followed by a year with reduced bloom and fruit set. This tendancy results in a year with heavy cropping with small fruit, and a subsequent year with large fruit and a small crop. Both situations are undesirable. Chemical thinners in the “on” year are frequently used to modify this cropping behavior. Alternative methods to control cropping by flower bud inhibitions will be discussed. Gibberellin application in the “off” year at or soon after bloom will inhibit flower bud formation and encourage moderate flowering. This method of crop regulation has been used infrequently. Gibberellins differ in their ability to inhibit flowering. Therefore, selection of a specific gibberellin and an effective concentration range may provide greater flexibility in controlling flowering. The cytokinins CPPU and thidiazuron inhibit flower bud formation, increase fruit size, and also thin fruit. Appropriate application of these cytokinins will be discussed where beneficial effects on fruit size may be achieved while maintaining a moderate level of flower bud formation.

scholarly journals Flower Bud Induction of Sweet Orange Trees [Citrus sinensis (L.) Osbeck]: Effect of Low Temperatures, Crop Load, and Bud Age

2004 ◽  
Vol 129 (2) ◽  
pp. 158-164 ◽  
Author(s):  
Juan I. Valiente ◽  
L. Gene Albrigo
Keyword(s):  
Citrus Sinensis ◽  
Sweet Orange ◽  
Weather Conditions ◽  
Flower Bud ◽  
Crop Load ◽  
Flowering Response ◽  
Reproductive Response ◽  
Bud Induction ◽  
Winter Temperatures ◽  
Orange Trees

Citrus flowering is a complex phenological process influenced by a number of interacting factors. Low winter temperatures are recognized as an important factor, but the flowering response has not been quantified under Variable natural conditions. A study was conducted to monitor the flower bud induction response of `Valencia' and `Hamlin' sweet orange trees [Citrus sinensis (L.) Osbeck] to naturally occurring winter weather conditions during the 1999 and 2000 seasons. The flowering response was quantified and related to shoot age, bud position along the shoot, local weather information, and crop load status. Results indicate that buds on previous summer shoots developed 2.52 and 3.59 to 1 flower on spring shoots, for `Hamlin' and `Valencia', respectively. In addition, buds at apical positions produced more flowers than buds located far from the apex. These basal positions buds required higher induction levels. Under Florida conditions, greater accumulation of hours of temperatures 11 to 15 °C increased floral intensity by the combined effect on the number of sprouting buds with reproductive growth and the number of flowers per flowering bud. Some statistical analyses indicated that high winter temperatures reduced flowering in `Valencia' and `Hamlin' oranges. The presence of fruit consistently reduced reproductive response for both cultivars. Crop load reduced flowering by an average of 41.5% compared to no crop and varied by cultivar. A discussion on the different induction requirements as well as on the differential effect of crop load on flowering by cultivar is presented.

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