scholarly journals Use of GA3 to Manipulate Flowering and Yield of `Hass' Avocado

2000 ◽  
Vol 125 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Samuel Salazar-García ◽  
Carol J. Lovatt
Keyword(s):  
Early Stage ◽  
Persea Americana ◽  
Yield Reduction ◽  
Alternate Bearing ◽  
Concomitant Increase ◽  
Vegetative Shoot ◽  
Inflorescence Development ◽  
Initial Development ◽  
Shoot Number ◽  
Hass Avocado

Avocado trees (Persea americana Mill.) bearing a heavy crop produce a light “off” bloom the next spring. This results in a light crop and a subsequent intense “on” bloom the year after. The objective of the study was to quantify the effects of GA3 canopy sprays applied to `Hass' avocado trees during the months preceding an “off” or “on” bloom on inflorescence and vegetative shoot number and yield. The experiment was initiated approximately seven months before an anticipated “off” bloom in an attempt to increase flowering intensity and yield. GA3 (25 or 100 mg·L-1) was applied to separate sets of trees in September (early stage of inflorescence initiation), November (early stage of inflorescence development), January (initial development of the perianth of terminal flowers), March (cauliflower stage of inflorescence development; only 25 mg·L-1), or monthly from September through January (only 25 mg·L-1). Control trees did not receive any treatment. GA3 (100 mg·L-1) applied in September reduced inflorescence number in both years, but not yield. GA3 (25 or 100 mg·L-1) applied in November before the “on” bloom reduced inflorescence number with a concomitant increase in vegetative shoot number and 47% yield reduction compared to control trees. This treatment might provide avocado growers with a tool to break the alternate bearing cycle by reducing yield in an expected “on” crop year to achieve a higher yield the following year. GA3 (25 mg·L-1) applied in November or January stimulated early development of the vegetative shoot of indeterminate inflorescences. January and March applications did not affect the number of flowering or vegetative shoots produced either year. GA3 (25 mg·L-1) applied in March at the start of an “off” bloom increased 2-fold the production of commercially valuable fruit (213 to 269 g per fruit) compared to the control.

scholarly journals Inflorescence and Flower Development of the `Hass' Avocado (Persea americana Mill.) during “On” and “Off” Crop Years

1998 ◽  
Vol 123 (4) ◽  
pp. 537-544 ◽  
Author(s):  
Samuel Salazar-García ◽  
Elizabeth M. Lord ◽  
Carol J. Lovatt
Keyword(s):  
Flower Development ◽  
Persea Americana ◽  
High Yield ◽  
Reproductive Condition ◽  
Inflorescence Development ◽  
Apical Buds ◽  
Secondary Axis ◽  
Primary Axis ◽  
Hass Avocado ◽  
Flowering Process

Inflorescence and flower development of the `Hass' avocado (Persea americana Mill.) were investigated at the macro- and microscopic level with three objectives: 1) to determine the time of transition from vegetative to reproductive growth; 2) to develop a visual scale correlating external inflorescence and flower development with the time and pattern of organogenesis; and 3) to quantify the effect of high (“on”) and low (“off”) yields on the flowering process. Apical buds (or expanding inflorescences) borne on summer shoots were collected weekly from July to August during an “on” and “off” crop year. Collected samples were externally described and microscopically analyzed. The transition from vegetative to reproductive condition probably occurred from the end of July through August (end of shoot expansion). During this transition the primary axis meristem changed shape from convex to flat to convex. These events were followed by the initiation of additional bracts and their associated secondary axis inflorescence meristems. A period of dormancy was not a prerequisite for inflorescence development. Continued production of secondary axis inflorescence meristems was observed from August to October, followed by anthesis seven months later. In all, eleven visual stages of bud development were distinguished and correlated with organogenesis to create a scale that can be used to predict specific stages of inflorescence and flower development. Inflorescence development was correlated with minimum temperature ≤15 °C, whereas yield had little effect on the timing of developmental events of individual inflorescence buds. However, the high yield of the “on” year reduced inflorescence number and increased the number of vegetative shoots. No determinate inflorescences were produced during the “on” year. For the “off” year, 3% and 42% of shoots produced determinate and indeterminate inflorescences, respectively.

scholarly journals The Relationship Between Flower and Fruit Abscission and Alternate Bearing of ‘Hass’ Avocado

2008 ◽  
Vol 133 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Lauren C. Garner ◽  
Carol J. Lovatt
Keyword(s):  
Developmental Stages ◽  
Weather Conditions ◽  
Nutrient Status ◽  
Persea Americana ◽  
Alternate Bearing ◽  
Immature Fruit ◽  
Fruit Abscission ◽  
Reproductive Structures ◽  
Independent Process ◽  
Hass Avocado

Despite profuse flowering, ‘Hass’ avocado (Persea americana Mill.) yields are low because of excessive flower and fruit abscission. Whether the dynamics of flower and fruit abscission are influenced by or contribute to alternate bearing, the production of a heavy on-crop followed by a light off-crop that is characteristic of many avocado cultivars, remains unresolved. The objective of this research was to determine whether abscission of reproductive structures from ‘Hass’ avocado trees during specific developmental stages, including flowering, fruit development, and fruit maturity, was influenced by crop status of the current or preceding year. Abscised reproductive structures were collected from commercially bearing trees during two complete crop years. Flower abscission began at about the same time but peaked 1 month later in the off-crop year compared with the on-crop year. Peak abscission rates were lower during the off-crop year than the on-crop year (compare 1836 ± 403 to 5378 ± 856 flowers per day and 50 ± 18 to 280 ± 23 immature fruit per day, respectively). The off- or on-crop status of the tree did not influence the percentage fruit set, average fruit diameter, or biomass of individual fruit that abscised at similar phenological stages. Furthermore, flower and fruit abscission were not influenced by the number of mature fruit from the previous year's crop. In both years of the research, as immature fruit abscission declined, abscission of the preceding year's crop increased, indicating that the processes were controlled independently. During the study, neither weather conditions nor tree nutrient status were associated with key abscission events. Taken together, these results provide evidence that the previous year's yield does not influence flower or fruit abscission and the seasonal abscission of reproductive structures is an independent process that does not contribute to alternate bearing of ‘Hass’ avocado.

scholarly journals The Impact of Outcrossing on Yields of ‘Hass’ Avocado

2008 ◽  
Vol 133 (5) ◽  
pp. 648-652 ◽  
Author(s):  
Lauren C. Garner ◽  
Vanessa E.T.M. Ashworth ◽  
Michael T. Clegg ◽  
Carol J. Lovatt
Keyword(s):  
Microsatellite Markers ◽  
Fruit Set ◽  
Persea Americana ◽  
Primary Factor ◽  
Alternate Bearing ◽  
Fruit Abscission ◽  
Significant Relationships ◽  
Outcrossing Rates ◽  
Hass Avocado ◽  
The Impact

‘Hass’ avocado (Persea americana Mill.) is characterized by excessive flower and fruit abscission, resulting in extremely low fruit set. Low outcrossing rates might be a factor contributing to low yields. It is hypothesized that self-fertilized flowers and resulting fruit abscise at a much higher rate than fruit that are the product of outcrossing. However, significant relationships between outcrossing rates and yields have only been established in a few avocado studies. The objective of this research was to investigate the importance of outcrossing to yield in a commercial ‘Hass’ orchard containing ‘Bacon’, an effective pollinizer of ‘Hass’. Microsatellite markers were used to determine the rate of outcrossing of fruit persisting to harvest on ‘Hass’ trees. Experiments were conducted during sequential on- and off-crop years. During both years, outcrossing rates were not related to yield or alternate bearing. These results indicate that outcrossing was not the primary factor affecting flower and fruit persistence and ultimately yield in this orchard for the two sequential years of this research.

Inflorescence development in Amelanchier alnifolia

1990 ◽  
Vol 68 (8) ◽  
pp. 1680-1688 ◽  
Author(s):  
Margaret W. Steeves ◽  
Taylor A. Steeves
Keyword(s):  
Shoot Growth ◽  
Early Stage ◽  
Axillary Buds ◽  
Vegetative Shoot ◽  
Inflorescence Development ◽  
Amelanchier Alnifolia ◽  
Inflorescence Size ◽  
Fruit Crop ◽  
Terminal Flower ◽  
Foliage Leaf

The morphology and development of the inflorescence of Amelanchier alnifolia, a potential fruit crop, are described. Although racemelike in appearance, the 8- to 12-flowered inflorescence is determinate, and the occasional branching of the basal member indicates its compound nature. This basal member in the axil of a foliage leaf frequently bears three to four bracteoles instead of the two characteristic of the remaining lateral flowers, and an arrested bud may be found in the axil of one or more of the bracteoles. The inflorescence is thus interpreted as a much reduced panicle. The phenology of inflorescence development in relation to seasonal shoot growth has been documented. Transformation of vegetative shoot apices to the flowering condition begins after the differentiation of a set of cataphylls and as the current fruit crop is ripening. It is marked by the accelerated formation of bract primordia with precocious axillary buds, culminating after about 2 weeks with the initiation of a terminal flower. Although the last to be formed, the terminal flower at all subsequent stages is equivalent in development to those at the base of the inflorescence. The buds in the axils of three to five bracts immediately below the terminal flower are arrested at an early stage and variation in inflorescence size may in part be due to variability in their development.

scholarly journals Influence of gibberellin inhibitors applied during flowering of nonirrigated 'Hass' avocado trees

2018 ◽  
Vol 53 (8) ◽  
pp. 918-923 ◽  
Author(s):  
Bruna do Amaral Brogio ◽  
Simone Rodrigues da Silva ◽  
Tatiana Cantuarias-Avilés ◽  
Sérgio Figueiredo Angolini ◽  
Edypol Guilherme Baptista ◽  
...  
Keyword(s):  
Shoot Growth ◽  
Block Design ◽  
Fruit Shape ◽  
Persea Americana ◽  
Fruit Yield ◽  
Gibberellin Biosynthesis ◽  
Alternate Bearing ◽  
Water Control ◽  
Hass Avocado ◽  
Prohexadione Calcium

Abstract: The objective of this work was to evaluate the effect of different gibberellin biosynthesis inhibitors on shoot growth above the panicle, as well as on fruit yield, size, and shape of nonirrigated 'Hass' avocado (Persea americana) trees. The experiment was carried out in a randomized complete block design, with five treatments, four replicates, and 40 trees. From 2013 to 2015, the following treatments were applied at full bloom, as foliar sprayings: water (control), 250 mg L-1 prohexadione-calcium, 2,500 mg L-1 trinexapac-ethyl, 1,750 mg L-1 paclobutrazol, and 350 mg L-1 uniconazole; the first two are acylcyclohexanediones and the last two, triazoles. Fruit yield, yield efficiency, and alternate bearing were not affected by the application of plant growth regulators. However, the gibberellin inhibitors increased fruit size and modified the fruit shape of nonirrigated 'Hass' avocado. Uniconazole reduces shoot growth above the panicle, and this effect may vary depending on environmental conditions, especially water supply.

scholarly journals Timing Citrus and Avocado Foliar Nutrient Applications to Increase Fruit Set and Size

1999 ◽  
Vol 9 (4) ◽  
pp. 607-612 ◽  
Author(s):  
Carol J. Lovatt
Keyword(s):  
Foliar Application ◽  
Persea Americana ◽  
Flower Initiation ◽  
Cumulative Yield ◽  
Phenological Stages ◽  
Inflorescence Development ◽  
Nutrient Demand ◽  
Washington Navel ◽  
Foliar Nutrient ◽  
Hass Avocado

The goal of this research was to identify the role essential nutrients play in the physiology of tree crops, and then to apply the nutrient as a foliar fertilizer to stimulate a specific metabolic process at phenological stages when nutrient demand is high. This approach has proven successful. A single winter prebloom foliar application of nitrogen as low-biuret urea [0.16 kg N/tree (0.35 lb N/tree)] to 30-year-old `Washington' navel orange (Citrus sinensis L. Osbeck) trees during flower initiation significantly increased yield and fruit number per tree for each of 3 consecutive years (P ≤ 0.05). The number of commercially valuable largesize fruit also increased significantly with yield increases (r2 = 0.88). Sodium tetraborate applied foliarly to `Hass' avocado (Persea americana Mill.) trees at the cauliflower stage of inflorescence development (elongation of inflorescence secondary axes, pollen and ovule development) increased the number of pollen tubes reaching the ovule, ovule viability and cumulative yield (P ≤ 0.05). Additional examples are presented.

scholarly journals Inflorescence Development of the `Hass' Avocado: Commitment to Flowering

1999 ◽  
Vol 124 (5) ◽  
pp. 478-482 ◽  
Author(s):  
Samuel Salazar-García ◽  
Elizabeth M. Lord ◽  
Carol J. Lovatt
Keyword(s):  
Low Temperature ◽  
Developmental Stage ◽  
Persea Americana ◽  
Inflorescence Development ◽  
Apical Buds ◽  
Secondary Axis ◽  
Primary Axis ◽  
Hass Avocado ◽  
Old Trees

The developmental stage at which the shoot primary axis meristem (PAM) of the `Hass' avocado (Persea americana Mill.) is committed to flowering was determined. Three-year-old trees were subjected to low-temperature (LT) treatments at 10/7 °C day/night with a 10-h photoperiod for 1 to 4 weeks followed by 25/20 °C day/night at the same photoperiod. Before LT treatment, apical buds of mature vegetative shoots consisted of a convex PAM with two lateral secondary axis inflorescence meristems lacking apical bracts each associated with an inflorescence bract. Apical buds did not change anatomically during LT treatment. However, the 3- and 4-week LT treatments resulted in inflorescences at 17% and 83% of apical buds, respectively. Trees receiving 2 weeks or less LT, including controls maintained at 25/20 °C, produced only vegetative shoots. Apical buds of 2-year-old trees receiving 3 weeks at 10/7 °C plus 1 week at 20/15 °C produced 100% inflorescences. GA3(100 mg·L-1) applied to buds 2 or 4 weeks after initiation of this LT treatment did not reduce the number of inflorescences that developed. `Hass' avocado apical buds were fully committed to flowering after 4 weeks of LT, but were not distinguishable anatomically from those that were not committed to flowering.

scholarly journals GA3 Application Alters Flowering Phenology of `Hass' Avocado

1998 ◽  
Vol 123 (5) ◽  
pp. 791-797 ◽  
Author(s):  
Samuel Salazar-García ◽  
Carol J. Lovatt
Keyword(s):  
Vegetative Growth ◽  
Flowering Phenology ◽  
Persea Americana ◽  
Field Conditions ◽  
Axillary Buds ◽  
Vegetative Shoot ◽  
Full Bloom ◽  
Hass Avocado ◽  
Precocious Development ◽  
Stimulation Of

The objectives of the present research were to quantify 1) the contribution that vegetative shoots produced in the summer vs. fall and indeterminate vs. determinate inflorescences make to yield and 2) the effects of GA3 on flowering expression and inflorescence phenology of summer and fall shoots of `Hass' avocado (Persea americana Mill.) under field conditions. Anthesis started earlier on fall than summer shoots of 10-year-old `Hass' avocado trees; however, no difference in the date of full bloom was observed. Indeterminate inflorescences that underwent early anthesis set more fruit than those with delayed anthesis, conversely, determinate inflorescences with delayed anthesis set more fruit. Indeterminate inflorescences comprised 90% of total inflorescences and contributed 73% of total fruit yield, but individual determinate inflorescences were at least three times more productive than the indeterminate ones. Summer and fall shoots were sprayed with 0, 50, 100, or 1000 mg·L-1 GA3 in November, December or January. GA3 stimulated apical growth of all shoots. If secondary axes of an inflorescence bud were differentiated at the time of GA3 application, the inflorescence developed in advance of inflorescences on branches not treated with GA3. In addition, GA3 caused precocious development of the vegetative shoot of indeterminate inflorescences relative to the flowers in the same inflorescence and relative to the vegetative shoot of indeterminate inflorescences from untreated branches. Stimulation of vegetative growth at the inflorescence apex by GA3 inhibited growth of axillary buds. GA3 at 50 mg·L-1 had no effect on the number of determinate or indeterminate inflorescences produced by either summer or fall shoots. Higher concentrations of GA3 increased the number of vegetative shoots and inactive buds produced by both shoot types.

Properly Timed Foliar Nutrient Applications Provide an Efficient Means to Meet Nutrient Demand to Increase Flowering, Fruit Set, and Size of Citrus and Avocado

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 556f-557 ◽  
Author(s):  
Carol J. Lovatt
Keyword(s):  
Persea Americana ◽  
Cumulative Yield ◽  
Inflorescence Development ◽  
Ongoing Research ◽  
Horticultural Crops ◽  
Nutrient Demand ◽  
Washington Navel ◽  
Foliar Nutrient ◽  
Essential Nutrient ◽  
Hass Avocado

The goal of our research is to identify the role that specific essential nutrient elements play in the physiology of horticultural crops and then to apply the nutrient as a fertilizer to the foliage at key times in the phenology of the tree, i.e., a time when the demand for the nutrient is likely to be high, in order to stimulate a specific physiological process. This approach proved successful in the following completed studies. A single winter prebloom application of nitrogen as low-biuret urea made to the foliage of 30-year-old `Washington' navel orange (Citrus sinensis L. Osbeck) trees at the time of irreversible commitment to flowering significantly increased yield and fruit number per tree for each of three consecutive years. In addition, the number of commercially valuable fruit with diameters of 6.1 to 8.0 cm significantly increased as yield increased (r2=0.88). Applications of boron as sodium tetraborate to the foliage of a commercial orchard of `Hass' avocado (Persea americana Mill.) trees at the cauliflower stage of inflorescence development (gametogenesis) increased the number of pollen tubes reaching the ovule, ovule viability and cumulative yield (P ≤ 0.05). Additional examples from ongoing research also will be presented.

scholarly journals Mechanism and Underlying Physiology Perpetuating Alternate Bearing in Citrus

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1117C-1117
Author(s):  
Johannes S. Verreynne ◽  
Carol J. Lovatt
Keyword(s):  
Phase Transition ◽  
Shoot Growth ◽  
Indoleacetic Acid ◽  
Alternate Bearing ◽  
Vegetative Shoot ◽  
Fruit Removal ◽  
Inflorescence Development ◽  
Shoot Initiation ◽  
Shoot Production ◽  
Return Bloom

Alternate-bearing trees produce a heavy on-crop followed by a light off-crop. Whereas climatic events initiate alternate bearing, it is perpetuated by endogenous tree factors. For citrus, the mechanism and underlying physiology by which fruit influence floral intensity the next spring was unresolved. To determine whether reduced return bloom of on-crop trees was due to inhibition of vegetative shoot production and, thus, a lack of “wood” on which to bear next spring's inflorescences or, alternatively, to inhibition of phase transition and inflorescence development on an adequate number of vegetative shoots, fruit were removed from individual shoots monthly or from entire on-crop `Pixie' mandarin trees during periods critical to shoot initiation (summer) and phase transition (winter). Fruit removal provided clear evidence that the on-crop exerted a significant effect on return bloom during the summer by reducing summer–fall shoot growth and, hence, the number of flowers borne on these shoots as well as on old wood of fruit-bearing shoots. The on-crop had less effect in winter on phase transition and return bloom. Buds collected during the summer from on-crop `Pixie' mandarin trees were characterized by high indoleacetic acid and low isopentenyladenosine concentrations compared to buds from off-crop trees. The starch level of the buds was not affected. No differences in hormone concentrations were detected for buds collected during winter from on- and off-crop trees, but buds of on-crop trees had less starch. The results demonstrate that the on-crop reduces return bloom predominantly by inhibiting summer-fall vegetative shoot growth by a mechanism similar to apical dominance, not a lack of available carbohydrate.

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