Association between Fruit Development and Mature Fruit Drop in Huanglongbing-affected Sweet Orange

In the past decade, FL citrus industry has been struck by Huanglongbing (HLB), a disease caused by the phloem-limited bacterium Candidatus Liberibacter asiaticus (CLas). Besides tree decline, HLB causes a sharp increase in mature fruit drop before harvest, leading to a substantial reduction in citrus production. The aim of the study was to provide insights in HLB-associated mature fruit drop. For HLB-affected ‘Valencia’ and ‘Hamlin’ sweet orange (Citrus sinensis), trees exhibiting severe symptoms (“severe trees”) had a significantly higher rate of mature fruit drop compared with mildly symptomatic ones (“mild trees”). Interestingly, dropped fruit were smaller than those still attached to tree branches regardless of the symptom levels of trees; overall, fruit of severe trees were smaller than mild trees. The result suggests a negative effect of HLB on fruit growth that may lead to a high incidence to drop subsequently at maturity. This possibility is further supported by the difference in immature fruit size as early as 2 months after bloom between severe and mild trees. Although HLB-triggered phloem plugging due to callose deposition in citrus leaves, which results in disrupted carbohydrate transport, has been documented in literature, the results of the histological analysis demonstrated no consistent pattern of callose deposition in the mature fruit pedicel in relation to the drop incidence. Additionally, sugar concentration in juice was not significantly different between dropped and attached fruit, providing evidence that carbohydrate shortage is not the case for dropped fruit and thus not the predominant cause of HLB-associated mature fruit drop. Notably, the midday water potential was significantly lower for severe than mild trees during the preharvest period (2 weeks before harvest of the current crop) in late March, which was also the second week after full bloom of return flowering. This suggests that altered tree water status due to HLB might limit fruit growth during the initial stage of fruit development (immediately after flowering) and/or increase the incidence of mature fruit abscission, leading to elevated preharvest fruit drop. Together, the results suggest that in the presence of HLB, strategies to increase fruit size and minimize additional stresses (especially drought) for the trees may improve mature fruit retention.

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Magnitude, timing, and causes of immature fruit loss in Amelanchier alnifolia (Rosaceae)

Canadian Journal of Botany ◽

10.1139/b89-097 ◽

1989 ◽

Vol 67 (3) ◽

pp. 726-731 ◽

Cited By ~ 5

Author(s):

R. G. St. Pierre

Keyword(s):

Dry Weight ◽

Fruit Growth ◽

Total Loss ◽

Large Magnitude ◽

Mature Fruit ◽

Amelanchier Alnifolia ◽

Fruit Crop ◽

Immature Fruit

Despite a consistent and massive yearly bloom, the production of a fruit crop by Amelanchier alnifolia is highly variable. The objectives of this study were to characterize the magnitude and timing of fruit loss in A. alnifolia and to determine the causes of this loss, emphasizing factors that cause damage to flowers and immature fruit. Fruit loss was consistently of a large magnitude; for the 6 years that data were available, a mean of 81% of the potential fruit were lost. Mature fruit to flower ratios varied from 0.02 to 0.46 [Formula: see text]. The number of fruit per infructescence decreased within each season consistently and significantly. The period of decrease was initiated shortly after anthesis and was complete by mid-June, varying from 9 to 34 days [Formula: see text] in length. Fruit growth (mg dry weight) was only 16% complete by the end of the period of fruit loss. Of the abscised fruit collected and examined, a mean of 81% were damaged; 2–90% [Formula: see text] were damaged by a sawfly (Hoplocampa montanicola; Hymenoptera: Tenthredinidae) and 0–68% [Formula: see text] were damaged by frost. From 0 to 21% [Formula: see text] were damaged by other factors including a curculio (Anthonomus spp.) and unidentified insects and fungi. The cause of 19% of the total loss was undetermined.

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Mechanical Harvesting Capacity in Sweet Orange Is Increased with an Abscission Agent

HortTechnology ◽

10.21273/horttech.15.4.0758 ◽

2005 ◽

Vol 15 (4) ◽

pp. 758-765 ◽

Cited By ~ 10

Author(s):

Jacqueline K. Burns ◽

Richard S. Buker ◽

Fritz M. Roka

Keyword(s):

Short Duration ◽

Citrus Sinensis ◽

Sweet Orange ◽

Mature Fruit ◽

Fruit Removal ◽

Ground Speed ◽

Detachment Force ◽

Fruit Drop ◽

Valencia Orange ◽

Significant Difference

An abscission agent [5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP)] was applied to `Hamlin' and `Valencia' orange (Citrus sinensis) trees at concentrations ranging from 0 to 500 ppm in a volume of 300 gal/acre. Four days after application, fruit were mechanically harvested with either a trunk shake-and-catch or a continuous canopy shake-and-catch system commercially used in Florida. Harvesting conditions were varied by limiting the actual trunk shake time of the trunk shaker to 2, 4, or 7 seconds, or by altering the ground speed of the canopy shaker (1.0, 1.5, or 2.0 mph). In general, increasing duration of shake and the application of CMNP increased percent mature fruit removal and decreased the amount of fruit remaining in the tree. Increasing CMNP concentration decreased fruit detachment force but increased post-spray fruit drop. Comparison of short duration shake times in CMNP-applied trees with trees harvested at longer durations either sprayed or not sprayed with CMNP indicated no significant difference in percent mature fruit removal. The results demonstrate that CMNP application increases harvesting capacity of trunk and canopy shakers by reducing time necessary to harvest each tree while maintaining high percent mature fruit removal.

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185 BIOASSAYS TO DETERMINE OF APPLE THINNING RESPONSE FROM APPLICATIONS OF NAA

HortScience ◽

10.21273/hortsci.29.5.455e ◽

1994 ◽

Vol 29 (5) ◽

pp. 455e-455

Author(s):

J. A. Flore ◽

M. Ventura ◽

D. Neri ◽

M. Sakin

Keyword(s):

Regression Analysis ◽

Growth Rates ◽

Environmental Conditions ◽

Fruit Size ◽

Fruit Growth ◽

Ethylene Evolution ◽

Fruit Drop ◽

Ethylene Response ◽

Golden Delicious ◽

Early Indicators

Auxin induction of ethylene, and fruit growth rates were investigated as early indicators of NAA thinning response for Golden Delicious, Red Delicious, McIntosh, Empire, and Tydeman's Red over a four period. Abscission at the end of the drop period was correlated with ethylene evolution from leaves 24-48 hours after NAA application and with changes in fruit growth at 2-3 day intervals through 10-14 days after application. Variation in ethylene evolution and fruit growth were also associated with environmental conditions prior to and at the time of NAA application to determine which factors have the greatest influence on response. Ethylene was a better predictor of final fruit drop than changes in fruit size for all varieties tested. However both performed very well. The ethylene bioassay requires more equipment, but the response is more-immediate. Bourse, and spur leaves as well as fruit were capable of producing ethylene in response to NAA application. Thinning response was greatest when all leaves and fruit were treated with NAA, followed by the bourse and spur leaves. Little or no response was produced when the fruit alone were treated. Concentration experiments and radioisotope data indicate that ethylene response is directly related to the amount of NAA absorbed. Regression analysis indicates that approximately 60% of the variation in response can be predicted by ethylene evolution

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THE EFFECT OF IRRIGATION STRATEGIES ON PEACH FRUIT GROWTH AND FINAL SIZE

HortScience ◽

10.21273/hortsci.27.6.572e ◽

1992 ◽

Vol 27 (6) ◽

pp. 572e-572

Author(s):

R. Scott Johnson ◽

Claude Phene ◽

Charles Medawar

Keyword(s):

Growth Stage ◽

Water Status ◽

Fruit Size ◽

Canopy Temperature ◽

Fruit Weight ◽

Fruit Growth ◽

Final Size ◽

Peach Fruit ◽

Early Stages ◽

Peach Trees

Six irrigation strategies were imposed on a block of O'Henry peach trees irrigated by fanjets. Treatments received different percentages of ET during the various stages of fruit growth and postharvest. ET was estimated by a large weighing lysimeter containing 2 trees and located in the center of the block. Fruit diameters were measured weekly and final fruit weights were determined at harvest. Adjusted fruit weights were estimated by statistically adjusting each treatment to the same fruit load. Adjusted fruit weight correlated well with soil water content during the month before harvest but not during early stages of fruit growth. Treatments which applied 50% ET during early stages of fruit growth showed reduced fruit size at that time. However, with applications of 150% ET during the final fruit growth stage, fruit size recovered. Adjusted fruit weight also correlated with measures of tree water status including midday leaf water potential and canopy temperature.

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Oleocellosis Injury of Fruitlets from Late-season Mechanical Harvesting of ‘Valencia’ Orange Trees after Different Irrigation Treatments Does Not Affect Internal Fruit Quality

HortScience ◽

10.21273/hortsci.46.3.457 ◽

2011 ◽

Vol 46 (3) ◽

pp. 457-459 ◽

Cited By ~ 2

Author(s):

Juan Carlos Melgar ◽

Jill M. Dunlop ◽

James P. Syvertsen

Keyword(s):

Drought Stress ◽

Surface Area ◽

Fruit Quality ◽

Sweet Orange ◽

Mechanical Injury ◽

Soluble Solids ◽

Juice Quality ◽

Mature Fruit ◽

Late Season ◽

Fruit Drop

Oleocellosis or oil spotting on the peel of citrus fruit is a common post-harvest injury caused by improper handling. Mechanical injury allows phytotoxic oil to leak out of oil glands and cause injury to surrounding flavedo cells, resulting in oleocellosis. Mechanical harvesting (MH) of ‘Valencia’ sweet orange is conducted in late spring, when the next season's fruitlets are in their early stages of development. There is a concern that mechanical injury from harvesting machines can cause oleocellosis and fruit drop of young, green ‘Valencia’ sweet orange fruitlets, especially late in the harvest season when fruitlets are relatively large. We evaluated the effects of winter drought stress and subsequent late-season MH with a canopy shaker on oleocellosis of ‘Valencia’ sweet orange fruitlets. In April, mature fruit size, juice content, total soluble solids, and acidity were unaffected by previous winter drought stress treatments. Mechanical harvesting removed ≈90% to 95% of mature fruit and 20% to 50% of fruitlets depending on previous drought stress treatments and harvesting date. Beginning 1 week after the late harvest (13 June), attached fruitlets were tagged and visually evaluated approximately every other month to determine oleocellosis injury until the late-season harvest 12 months later. Only 12% of the fruitlets had oleocellosis on more than 30% of their surface area. Up to 75% of the fruitlets from the previously drought-stressed trees had less than 10% of their surface area injured after MH and 11% of these fruitlets dropped before harvest. Nonetheless, there was no significant increase in fruit drop with increased surface area injured nor was juice quality affected at harvest. Overall, fruit surface oleocellosis decreased and healed as fruit expanded, but surface blemishes did not completely disappear. Thus, fruitlet oleocellosis in late-season mechanically harvested trees was cosmetic and did not increase fruit drop nor alter internal fruit quality.

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Fruit Development in Saskatoon (Amelanchier alnifolia Nutt.)

HortScience ◽

10.21273/hortsci.31.4.682f ◽

1996 ◽

Vol 31 (4) ◽

pp. 682f-682

Author(s):

Roisin McGarry ◽

Jocelyn A. Ozga ◽

Dennis M. Reinecke

Keyword(s):

Fruit Development ◽

Fruit Size ◽

Fruit Weight ◽

Growth Patterns ◽

Fruit Growth ◽

Seed Number ◽

Fresh Weight ◽

Canadian Prairies ◽

Developmental Patterns ◽

Growing Seasons

Saskatoon fruits, an emerging horticultural crop across the Canadian prairies, vary greatly in size among cultivars. In this study, we compare fruit development patterns among large, medium, and small fruited cultivars of saskatoon, and assess the role of seed number and pedicel diameter on fruit size. Fruit growth patterns of four cultivars (Thiessen, Northline, Regent, and Smoky) were determined from weekly measurements of fruit diameters and fresh and dry flower/fruit weights during two consecutive growing seasons. The developmental patterns of fruit growth determined using the above criteria were similar among cultivars and between years. At maturity, the largest fruits (fresh weight) obtained were from cv. Thiessen, followed by `Northline', `Smoky', and `Regent', in descending order. Pedicel diameters (one week prior to maturity) correlated linearly with increasing fruit diameter and fresh weight. At maturity, seed number per fruit correlated linearly with increasing fruit weight. Thiessen contained significantly more seeds per fruit (4.6) than `Northline' (3.7), `Smoky' (3.2), and `Regent' (3.2).

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Interlinked regulatory loops of ABA catabolism and biosynthesis coordinate fruit growth and ripening in woodland strawberry

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1812575115 ◽

2018 ◽

Vol 115 (49) ◽

pp. E11542-E11550 ◽

Cited By ~ 30

Author(s):

Xiong Liao ◽

Mengsi Li ◽

Bin Liu ◽

Miaoling Yan ◽

Xiaomin Yu ◽

...

Keyword(s):

Fruit Ripening ◽

Fruit Development ◽

Fruit Size ◽

Fruit Growth ◽

P450 Monooxygenase ◽

Woodland Strawberry ◽

Rate Limiting Step ◽

Aba Catabolism ◽

Repressive Effect ◽

Rate Limiting

Fruit growth and ripening are controlled by multiple phytohormones. How these hormones coordinate and interact with each other to control these processes at the molecular level is unclear. We found in the early stages of Fragaria vesca (woodland strawberry) fruit development, auxin increases both widths and lengths of fruits, while gibberellin [gibberellic acid (GA)] mainly promotes their longitudinal elongation. Auxin promoted GA biosynthesis and signaling by activating GA biosynthetic and signaling genes, suggesting auxin function is partially dependent on GA function. To prevent the repressive effect of abscisic acid (ABA) on fruit growth, auxin and GA suppressed ABA accumulation during early fruit development by activating the expression of FveCYP707A4a encoding cytochrome P450 monooxygenase that catalyzes ABA catabolism. At the onset of fruit ripening, both auxin and GA levels decreased, leading to a steep increase in the endogenous level of ABA that drives fruit ripening. ABA repressed the expression of FveCYP707A4a but promoted that of FveNCED, a rate-limiting step in ABA biosynthesis. Accordingly, altering FveCYP707A4a expression changed the endogenous ABA levels and affected FveNCED expression. Hence, ABA catabolism and biosynthesis are tightly linked by feedback and feedforward loops to limit ABA contents for fruit growth and to quickly increase ABA contents for the onset of fruit ripening. These results indicate that FveCYP707A4a not only regulates ABA accumulation but also provides a hub to coordinate fruit size and ripening times by relaying auxin, GA, and ABA signals.

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Effects of Water Stress on Vegetative Growth and Productivity of Fruit Trees

HortScience ◽

10.21273/hortsci.32.3.550b ◽

1997 ◽

Vol 32 (3) ◽

pp. 550B-550

Author(s):

R. Scott Johnson ◽

Claude J. Phene ◽

Dale Handley

Keyword(s):

Water Stress ◽

Fruit Size ◽

Late Summer ◽

Fruit Trees ◽

Fruit Growth ◽

Mature Fruit ◽

Annual Crops ◽

Early Maturing ◽

Increase In Productivity ◽

The Right

Generally, water stress reduces yield in annual crops. However, for mature fruit trees, this relationship may not hold in many situations, thus providing the opportunity for saving water without losing production. Indeed, even an increase in productivity may be achieved as we better learn how to manipulate processes within the tree through moderate water stress. Several areas of research have shown promising results. The reduction of irrigation after harvest of early maturing peaches and plums has demonstrated substantial savings of water with no loss of production. Peaches can suffer fruit quality problems such as doubling and deep suturing, but these can be overcome with well-timed irrigations in the previous late summer. Water stress imposed before harvest has also shown some promise. Reports from Australia have demonstrated significant increases in yield and fruit size in peach and pear, although researchers in other locations have generally been unable to replicate these results. The timing and/or rate of stress development appear to be critical factors. Under the right conditions, stress can alter the allocation of resources between vegetative and fruit growth. Before implementation of these practices can be achieved, further research will need to focus on developing good tools for measuring stress in the trees, obtaining a better understanding of adaptation of trees to rapidand slow-developing stress, documenting the effects of stress on vegetative and fruit growth during different times of the season, and understanding the interaction of stress with other factors such as fruit load.

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Physiological Changes during Maturation, Ripening, and Storage of Asian Pears Grown in Southeastern United States

HortScience ◽

10.21273/hortsci.30.4.816g ◽

1995 ◽

Vol 30 (4) ◽

pp. 816G-817

Author(s):

Nihal Rajapakse ◽

William C. Newall

Keyword(s):

United States ◽

Ethylene Production ◽

Southeastern United States ◽

Fruit Size ◽

Physiological Changes ◽

Mature Fruit ◽

Immature Fruit ◽

Early Maturation ◽

Nonclimacteric Fruit ◽

Harvest Maturity

Morphological and physiological changes during maturation and ripening of eight Asian pear cultivars grown in the southeastern United States were evaluated. Fruit size increased throughout maturation. Flesh firmness decreased as fruit matured and averaged ≈30 to 35 N at harvest maturity. The average TSS in mature fruit ranged from 10% to 13%, with `Shinko' having the lowest and `Shinsui' having the highest. TSS increased during 4 weeks of storage at 1C, but the increase was greater in immature fruit than in mature fruit. Respiration rate declined as fruit matured. Ethylene production was low in `Hosui', `Kosui', `Nijisseiki', `Shinseiki', `Chojuro', and `Shinko' fruit. Mature `Ichiban' and `Shinsui' fruit produced high amounts of ethylene. `Kosui', `Shinsui', `Chojuro', and `Ichiban' fruit showed a climacteric rise in respiration and ethylene production at 20C, while `Hosui', `Nijisseiki', `Shinseiki', and `Shinko' behaved as nonclimacteric fruit. Ethylene production by 1C-stored `Kosui', `Shinsui', `Chojuro', and `Ichiban' fruit was increased on removal to 20C. Glucose and fructose were low during early maturation but sharply increased ≈80 to 85 days after full bloom (DAFB). Sucrose was low in immature fruit but accumulated rapidly late in maturation ≈100 to 107 DAFB. In mature `Hosui', `Kosui', `Nijisseiki', `Shinsui', `Shinko', and `Ichiban' fruit, fructose was the predominant sugar, while in `Shinseiki' and `Chojuro' fruit, sucrose was the predominant sugar.

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Peach Rusty Spot Epidemics: Temporal Analysis and Relationship to Fruit Growth

Plant Disease ◽

10.1094/pdis.2003.87.4.366 ◽

2003 ◽

Vol 87 (4) ◽

pp. 366-374 ◽

Cited By ~ 4

Author(s):

Laura A. Furman ◽

Norman Lalancette ◽

James F. White

Keyword(s):

Disease Progression ◽

Fruit Development ◽

Disease Incidence ◽

Fruit Size ◽

Temporal Analysis ◽

Logistic Function ◽

Fruit Growth ◽

Data Sets ◽

Growing Seasons ◽

Physical Changes

Incidence and severity of peach rusty spot were monitored throughout the growing seasons of 1999 to 2001. Graphical and statistical analysis revealed that disease increased from the shuckoff stage of fruit development until 60 days after full bloom; epidemics typically lasted from 17 to 30 days. An analysis of fruit growth indicated that the early-season epidemic coincided with the first stage of stone fruit development, physiologically characterized as the period of cell division. During this period, as fruit growth slowed and approached initiation of pit-hardening, the rate of disease increase slowed. Since fruit infection was greatest during the period of fruit growth, disease progression was modeled as a function of plant growth instead of time. Temporal analysis revealed that the logistic function was appropriate for describing both growth processes, and a synchronous logistic/logistic composite disease progression/fruit growth model was fit to all data sets. No change in disease levels occurred during midseason, which coincided with the second stage of fruit development, a period of slow growth. Subsequently, disease incidence and severity significantly declined on average by 26% and 1.3 lesions per fruit, respectively, during the 20 to 30 days prior to harvest. This decline phase coincided with the third stage of fruit growth, the period of cell enlargement and coloration. These disease reductions may be related to physical changes in fruit size and pigmentation, as opposed to resistance development, causing younger, less established lesions to become undetectable.

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