Reducing Fruit Load Research Articles

Identification of potential regulators of cell production and early fruit growth in apple (Malus × domestica Borkh.)

Fruit size is a commercially valuable trait that is determined by the extent of fruit growth. In apple, (Malus × domestica Borkh.), early fruit growth is facilitated by intensive cell production, but mechanisms regulating these processes are not well understood. In this study, members of five gene families involved in growth regulation were identified and evaluated in apple: AUXIN-REGULATED GENE INVOLVED IN ORGAN SIZE (ARGOS); CELL NUMBER REGULATOR (CNR); GROWTH REGULATING FACTOR (GRF); GRF INTERACTING FACTOR (GIF); and KLUH. MdARGOS1 and MdARGOS2 transcript abundance was higher during early fruit growth but was also enhanced by up to 18-fold under conditions of reduced cell production during flower and fruit development, indicating that their gene products play complex roles in regulating growth mechanisms during early development. MdCNR20a and MdCNR20b transcript abundance decreased during early fruit growth and increased during the transition from cell production to cell expansion. MdCNR20a transcript abundance was negatively correlated with the relative cell production rate (RCPR; ρ = - 0.82; P = 0.002), was enhanced in response to shading, and reduced in response to lower fruit load, indicating that it's gene product negatively regulates cell production and early fruit growth. Transcript abundance of MdGRF11 and MdGRF16 was greater during cell production-mediated fruit growth, and higher in the cortex than in the pith. MdGIF3 transcript abundance was greater during early fruit development, higher in the cortex, enhanced under reduced fruit load conditions, and strongly correlated with RCPR (ρ = 0.93; P < 0.0001). Further, it was correlated with that of MdGRF11 and MdGRF16 (ρ = 0.87 and 0.89, respectively; P < 0.0001), indicating that the GRF11/16-GIF3 module is co-regulated and involved in spatio-temporal regulation of cell production and fruit growth. Transcript abundance of MdKLUH1 was low and not consistent with a role in regulating cell production and fruit growth. Together, this study demonstrates coordinated control of cell production during early fruit growth by multiple regulatory components, identifies candidates for functional characterization, and provides potential tools for enhancing growth of the apple fruit.

Thinning response of ‘Redhaven’ peaches to 1-aminocyclopropane carboxylic acid (ACC)

Peach trees bear an abundance of flowers which produce a surplus of fruit that the tree is unable to support. A self-regulatory mechanism enhances the abscission of immature fruitlets leading to a reduced fruit load, but this is often insufficient to achieve fruit of marketable size. Supplementary manual fruit thinning is typically required to optimize economic fruit load. This 2-yr study investigated the response of ‘Redhaven’ peach trees to sprays of 300 and 600 mg L−11-aminocyclopropane carboxylic acid (ACC) during the phenological stages of full bloom, shuck split, and ∼20 mm fruitlet diameter. The objective was to determine the efficacy of ACC on fruit set, fruit size, and yield at harvest and the amount of hand-thinning required at “June drop”. Although the response to ACC varied between the 2 yr, 600 mg L−1ACC spray at full bloom (2018) and at ∼20 mm fruit size (2019) reduced fruit set, the need for hand-thinning by 59%–66%, and crop load. Treatments also had varying but significant effects on leaf yellowing and leaf drop when measured shortly after application. ACC reduced total yield and number of fruit per tree in both study years and increased fruit weight in 2019. Overall, peaches were responsive to ACC at a range of timings from bloom to ∼20 mm fruit size. This study enhances our understanding of ACC on fruitlet abscission of peaches and is one of few studies to demonstrate the effectiveness of a chemical fruitlet thinner for peaches.

Response of Royal Gala apples to multiple applications of chemical thinners and the dynamics of fruitlet drop

Apple trees bear an abundance of flowers that produce a surplus of fruit that the tree is unable to support. A self-regulatory mechanism enhances the abscission of immature fruitlets, leading to a reduced fruit load, but this is often insufficient to achieve fruit of marketable size. Supplementary fruit thinning is usually required to optimize economic fruit load and annual bearing. This 2 yr study investigated the response of Royal Gala apple trees to primary single and combination sprays of 6-benzyladenine (6-BA) and carbaryl during fruit set, followed by secondary sprays of either treatment 7 d later. The objective was to determine the effect of a second application of chemical thinner on fruitlet abscission, which compounds are most efficacious, and to characterize the pattern of fruitlet drop. The combinations of chemical thinners varied in their effectiveness at reducing crop density. About 12–14 d were required from the time of the first application of chemical thinner to observed fruitlet beneath trees. A single application of both thinners applied at 8 mm advanced fruit drop by 7 d in most instances. The tank-mix of 6-BA and carbaryl applied at 8–10 mm followed by a secondary spray of carbaryl at 15 mm was the most efficacious thinning combination. Secondary sprays of 6-BA at 15 mm were ineffective at inducing additional fruit drop. Combination sprays of 6-BA and carbaryl were more effective than repeat sprays of the same product. This study enhances our understanding of the dynamics of fruitlet abscission and the benefits of multiple applications of post-bloom chemical thinners.

A two-year study on chemical thinning agents for ‘Rocha’ pear (Pyrus communis L.)

In recent years, new chemical thinners have been introduced in the European market and researchers have tested them on apples and European pears. In Portugal, grower groups and academia jointly organized the thinning trials. Reported here are the results of two years' research (2015 and 2016) carried out in a commercial orchard of 'Rocha' pear planted in 2010. The following active ingredients: 6-benzyladenine (6-BA), naphthalene-acetic-acid (NAA) + 6-benzyladenine (6-BA), abscisic acid (ABA), and metamitron (MT) were tested at different concentrations and time of application. All the tested chemical thinners reduced fruit load, although the efficacy of some of them (NAA and 6-BA) was affected by the climatic conditions. ABA and Metamitron, the two newest chemical thinners introduced in Portugal, performed well and positively affected some fruit quality parameters.

Reduction of MDHAR activity in cherry tomato suppresses growth and yield and MDHAR activity is correlated with sugar levels under high light.

Ascorbate is oxidized into the radical monodehydroascorbate (MDHA) through ascorbate oxidase or peroxidase activity or non-enzymatically by reactive oxygen species. Regeneration of ascorbate from MDHA is ensured by the enzyme MDHA reductase (MDHAR). Previous work has shown that growth processes and yield can be altered by modifying the activity of enzymes that recycle ascorbate; therefore, we have studied similar processes in cherry tomato (Solanum lycopersium L.) under- or overexpressing MDHAR. Physiological and metabolic characterization of these lines was carried out under different light conditions or by manipulating the source-sink ratio. Independently of the light regime, slower early growth of all organs was observed in MDHAR silenced lines, decreasing final fruit yield. Photosynthesis was altered as was the accumulation of hexoses and sucrose in a light-dependent manner in plantlets. Sucrose accumulation was also repressed in young fruits and final yield of MDHAR silenced lines showed a stronger decrease under carbon limitation, and the phenotype was partially restored by reducing fruit load. Ascorbate and MDHA appear to be involved in control of growth and sugar metabolism in cherry tomato and the associated enzymes could be potential targets for yield improvement.

Bioactive compound composition of pomegranate fruits removed during thinning

Thinning consists of reducing fruit load at immature stage and thus allowing remaining fruits to develop to their maximum size and quality. The waste material produced during this farming practice was characterised in 9 pomegranate cultivars, by evaluating: weight, size, maturity index, pH, organic acids and sugars profiles, contents of minerals, punicalagin, and ellagic acid, total polyphenols and antioxidant activity. Citric and quinic were the main organic acids. Potassium was the predominant mineral, reaching up to 11gkg−1 dry weight (dw). Total polyphenol content ranged from 777 to 1660g GAE kg−1dw, α-punicalagin from 101 to 195 and β-punicalagin from 80.1 to 111gkg−1dw. The antioxidant activity was assessed by three methods and its values varied from 2923 to 4486 for ABTS, from 3153 to 4685 for FRAP, and from 2075 to 2934mmolTrolox kg−1dw for DPPH. Pomegranate thinning fruits, especially sour-sweet cultivars, are rich in bioactive compounds, with a potential use in the food, chemical and pharmaceutical industries.

Reduction of Fruit Load Affects Early Fruit Growth in Apple by Enhancing Carbohydrate Availability, Altering the Expression of Cell Production-related Genes, and Increasing Cell Production

Carbohydrate availability is a key factor determining fruit growth in apple (Malus ×domestica) and other fruits. However, the molecular mechanisms regulating fleshy fruit growth in response to changes in carbohydrate availability are not well understood. In this study, carbohydrate availability was manipulated by reducing fruit load, and its effects on apple fruit growth, cell production and expansion, and the expression of genes associated with these processes was investigated. Reduction of fruit load during early fruit development led to a rapid increase in early fruit growth. The increase in fruit growth was associated with a transient increase in sorbitol and fructose concentrations and altered expression of sorbitol dehydrogenase and sucrose synthase genes. Increase in early fruit growth was mediated primarily by an increase in cell production. The aintegumenta gene, MdANT1, an AP2-domain transcription factor associated with the regulation of cell production and fruit growth, displayed an increase in expression by up to 5-fold during early fruit development in response to the reduction in fruit load. Additionally, multiple cell cycle genes positively associated with cell production such as the cyclins, MdCYCA2;1, MdCYCA2;3, MdCYCB1;1, and MdCYCB2;2, and the B-type cyclin-dependent kinases, MdCDKB1;1, MdCDKB1;2, and MdCDKB2;2, displayed higher expression by up to 5-fold under reduced fruit load conditions during early fruit growth. These data indicate that carbohydrate availability affects the expression of key transcription factors and cell proliferation genes, thereby regulating cell production during early fruit growth. Several genes associated with cell expansion such as the expansins, and cobra and cobra-like genes, also displayed altered expression in response to the reduction in fruit load. The expression of three expansin genes was higher under reduced fruit load conditions at maturity, a stage at which a minor increase in cell size was apparent. Together, data from this study indicate that fruit load reduction induces changes in carbohydrate availability and metabolism, which in turn affect cell production-related mechanisms, thereby enhancing early fruit growth.

Agronomic and physiological responses of a tomato crop to nitrogen input

Two field experiments were carried out during 2005 and 2006 to study the effect of four N-fertilization rates (0 (N0), 100 (N100), 200 (N200), and 300 (N300)kgha−1) on yield, growth, N uptake, and N use efficiency of processing tomato in a silty-clay soil under Mediterranean conditions. N supply positively affected LAI (leaf area index), radiation use efficiency (RUE), above-ground dry weight (DW) and N accumulation. The respective maximum values 4.6, 1.16gMJ−1, 13.4Mgha−1, and 383kgha−1 were detected with N300. However, passing from the N200 to the N300 rate, the DW and the N tissue content mostly increased in the vegetative organs resulting in lower total and marketable yield, attributable mainly to the lower number of fruit in N300 plants. N excess exacerbates the unbalanced vegetative/reproductive plant growth which occurred when seasonal temperatures negatively affected crop productivity by reducing fruit load. Maximum total and marketable yield were obtained with the N200 rate and were respectively 155 and 119Mgha−1 in 2005 and 135 and 104Mgha−1 in 2006 season. N supply quadratically decreased the agronomical (NUEa) and physiological (NUEp) N use efficiency, these indices reaching a maximum with the N200 rate (NUEa=11.8kgkg−1, NUEp=15.1kgkg−1). However, increasing N supply decreased partial factor productivity and the efficiency in N fertilizer recovery linearly to 24 and 0.55kgkg−1. Nitrogen nutrition index (NNI) was 0.8 in N0 plants and increased up to 1.3–1.4 with N300. Under Mediterranean conditions and with the specific tomato cultivar, the N200 rate can be considered the most efficient both in terms of yield and NUE, and the respective NNI values of 1.15–1.23 (in the period from maximum LAI to harvest) could be associated with the optimal N nutritional status of the crop indicating that the minimal N concentration to obtain the maximum above-ground DW is higher than that proposed as critical for this crop. From an environmental standpoint, a 200kgha−1 of nitrogen fertilizer dose would put this production system in N balance, with N removal from the field being close to 200kgha−1 with a yield goal of 100–120kgha−1 of marketable fruits containing 1.97kgMg−1 of N.

Role of carbohydrate reserves in yield production of intensively cultivated oil olive (Olea europaea L.) trees

Olive (Olea europaea) has a very high tendency for year-to-year deviation in yield (alternate bearing), which has a negative economic impact on the olive oil industry. Among possible reasons for alternate bearing, depletion of stored carbohydrates (CHO) during the On-year (high yield) has often been mentioned. The objective of the present study was to verify the role of CHO reserves, as a cause or effect, in the alternate bearing of intensively cultivated olives. A monthly survey of soluble sugar and starch concentrations in the leaves, branches, bark and roots of On- and Off-trees (cv. Barnea) was carried out during a complete reproductive cycle from November 2005 to October 2006. Carbohydrate concentration in the sapwood was determined in January, as well as an estimate of whole-tree biomass. The trunk and limbs possess the largest portion of CHO reserves. The influence of reduced fruit load on CHO reserves was also investigated. Starch, mannitol and sucrose concentrations increased from December to March in all tissues, and then declined along with fruit development. Leaves, branches and bark have a significant role in CHO storage, whereas roots accumulated the lowest CHO concentrations. However, fluctuations in reserve content suggested considerable involvement of roots in the CHO budget. Nevertheless, there were no meaningful differences in the annual pattern of CHO concentration between On- and Off-trees. Even a 75-100% reduction in fruit number brought about only a minor, sluggish increase in CHO content, though this was more pronounced in the roots. Carbohydrate reserves were not depleted, even under maximum demands for fruit and oil production. It is concluded that in olives, the status of CHO reserves is not a yield determinant. However, they may play a significant role in the olive's survival strategy, ensuring tree recovery in the unpredictable semiarid Mediterranean environment. This suggests that CHO reserves in olive act like an active sink, challenging the common concept regarding the regulation of CHO reserves in plants.

Large bugs damage pistachio nuts most severely during midseason

“Large bug” damage to pistachio nuts varies by season, as well as among insect species and development stages, with larger bugs typically causing more damage than smaller bugs. We investigated pistachio damage by three large bug species (leaffooted bug, redshouldered stink bug and flat green stink bug) at different development stages and throughout the season, using field surveys and cage studies. Before fruit set occurs in June, most damaged nuts are dropped from the cluster without reducing fruit load. The midseason period (June to July) is the most critical because the damaged nuts remain in the cluster. After shell hardening, the kernel is largely protected from bug feeding.

Effect of Irrigation Regimes on Disease Expression in Melon Plants Infected with Monosporascus cannonballus

The effect of irrigation regimes on disease expression in melon plants infected with Monosporascus cannonballus was studied during two summer growing seasons (1998 and 1999) in the Arava region of southern Israel. Less frequent and reduced irrigation postponed the onset of plant collapse and lowered disease incidence. Delaying disease development in infested fields by reducing irrigation frequency allowed crop harvest before plant collapse. However, reduced irrigation regimes reduced yields, as shown in methyl bromide fumigated plots. Fruits from melon plants grown under reduced irrigation in the infested plots were also of lower quality due to water shortage. The delay in plant collapse under the reduced irrigation treatments was attributed to a combined effect of reduced fruit load and the development of a deeper root system, which could support the increased water demand of the mature, fruiting plant.

Seasonal Evolution of the Quality of Fresh Glasshouse Tomatoes under Mediterranean Conditions, as Affected by Air Vapour Pressure Deficit and Plant Fruit Load

Changes in yield and quality of fresh tomatoes in response to air vapour pressure deficit (VPD) and plant fruit load were studied under Mediterranean summer conditions. Plants thinned to three or six fruits per truss were grown in two compartments, one at a VPD below 1.5kPa, the other without VPD control. The seasonal trend in fruit yield and quality was assessed from April to September by weekly measurement of number, fresh weight and dry matter content of harvested fruits, together with the occurrence of blossom-end-rot (BER) and cracking. On two occasions, in July and September, sugar and acid content was measured at three ripening stages. The seasonal decrease in fresh yield was attenuated at low VPD, because of higher individual fruit fresh weight, especially at low fruit load. Low VPD decreased occurrence of BER but like low fruit load, it increased fruit cracking. Fruit dry matter content was lower at low VPD, but was unaffected by fruit load. Sugar content and the ratio of sugars:acids was increased at high VPD and low fruit load, with interactive effects depending on season and ripening stage. The influence of VPD on acid content differed with fruit load and also changed during ripening and between seasons. Results showed that water was the main limiting factor for growth of fruits picked in July; at this time, reducing fruit load to promote mean fruit size had negative effects on BER and cracking. Reducing VPD reduced BER but had a negative effect on cracking and diluted both the dry matter and sugar content. For fruits harvested later in summer, these negative effects were attenuated because fruit growth was also carbon limited.

Effects of supplemental light duration on greenhouse tomato ( Lycopersicon esculentum Mill.) plants and fruit yields

In one experiment, tomato plants were grown under natural light or extended photoperiods of 14, 16, 20 and 24 h. Compared to natural light, extended photoperiod treatments increased shoot fresh weight and yields of tomato plants by, respectively, 40–57% ( P<0.05) and 15–20% ( P>0.05). However, photoperiods longer than 14 h did not further improve growth and yields. In the second experiment, tomato plants were exposed to a 14 or 24 h photoperiod and clusters were either pruned to 1 fruit or not. Tomato plants exposed to continuous light (24 h photoperiod) started developing leaf chloroses after 7 weeks of treatments. We observed that, for the first 5 to 7 weeks of treatments, tomato plants grown under continuous light had better growth and higher yields than plants receiving the 14 h photoperiod. During the second half of the experiment, continuous lighting decreased the growth rate of tomato plants. At the end of the experiment, total growth and yields of tomato plants grown under continuous light were generally lower than plants exposed to 14 h photoperiod. Reducing fruit load increased vegetative growth and decreased yields, but had no influence on the response of tomato plants to the photoperiod treatments. Photoperiods did not influence leaf mineral composition. Therefore, plant mineral nutrition did not explain the leaf chloroses, reduced growth and yields observed under 24 h photoperiod. Continuous light increased leaf starch and sugar contents. Fruit pruning treatments did not alter plant response to photoperiod treatments regarding leaf starch and sugar contents and had no influence on the date of appearance and the severity of leaf chloroses noted under continuous light. Our data suggest that growth and yield reductions as well as leaf chloroses of tomato plants grown under continuous light are possibly explained by starch and sugar accumulation due to leaf limitations rather than a sink limitation.

Effects of Root Pruning and Benzyladenine Application on Tree Growth and Fruit Size in 'Empire' and 'McIntosh' Apple

In three trials over three years, postbloom applications of benzyladenine (BA) thinned young fruitlets of both “Empire” and “McIntosh” apples trees, increased fruit weight, and reduced yield per tree. Increases in shoot growth and/or trunk enlargement were observed in BA-treated trees in some of the trials. Root pruning consistently reduced shoot growth and /or trunk enlargement in all trials reported here. In most of the trails, root pruning reduced fruit load rather than fruit size. The absence of an increase in fruit size under reduced fruit-load conditions is consistent with a negative effect of root pruning on fruit size. BA consistently increased fruit size and improved fruit-size gradeout in 1991. Return bloom was promoted in some of the trials by BA and in al but one trial by root pruning. Effects of BA and root pruning largely were independent. These results suggest that BA can be used to improve fruit size in root-pruned apple trees, but only at the expense of a reduction in yield. Chemical name...

Effect of Concentration and Time of Accel Application on Cropping of Selected Cultivars

The effect of Accel concentration and time of application on fruit size and yield was studied using `Delicious' (Redchief), `Empire', `Jonathan', and `Gala'. High-volume sprays of Accel were applied at 25 to 150 mg·liter–1 to `Delicious' and `Empire' at king fruit diameter (KFD) of 5 to 20 mm. `Jonathan' and `Gala' were treated at KFD of 5 to 20 mm with 10 to 40 g/A. The effect of spray volume (500 to 2000 liters·ha–1) and surfactant (Regulaid) was studied using `Jonathan'. Response was indexed by yield and fruit size distribution at harvest. Although yield in `Delicious' was reduced with all concentrations of Accel, the percentage of fruits in the larger-size classes (3”+) was not significantly increased. In contrast, with `Empire', Accel reduced fruit load similar to hand-thinning (HT) and percentage of large fruit equaled or exceeded that of the HT treatment. Increasing concentration of Accel was related to an increase in fruit size; early application (5 mm KFD) was more effective than late (10, 20 mm KFD) application. There was no significant effect of spray volume or Regulaid. Increasing Accel rate (10 to 20 g/A) resulted in significant yield reduction and increase (4% to 9%) in mean fruit weight in `Gala'.

Size, flowering and fruiting of maturing own-rooted ‘Gala’ apple trees treated with paclobutrazol sprays and trunk drenches

Four-year-old, own-rooted, micropropagated cultivar ‘Gala’ apple ( Malus domestica Borkh.) trees were, (1) untreated, (2) treated with paclobutrazol (paclo) sprays (SP) at 500 or 1000 mg l −1 2, 4 and 6 weeks after full bloom or (3) treated with the 500 or 1000 mg l −1 paclo sprays plus a paclo trunk drench (TD) at 2.9 g per tree (SP + TD) in mid-May. Fruit load on trees of one treatment set was left intact (normal load) whereas 30–40% of the fruit was removed annually from the other set (reduced load) after ‘June drop’. Reducing fruit load in late May or early June over the 6-year period had little influence on vegetative growth, flower density, or fruit quality but fruit yields and the 6-year yield efficiency index were reduced. There were few differences between paclo 500 and paclo 1000 SP treatments. Compared with paclo SP + TD, paclo SP treatments caused fewer and less persistent changes. Over the 6-year period, paclo SP reduced trunk cross-sectional area (TCSA) 17% whereas paclo SP + TD reduced it by 49%. Flowering, fruit size and yield were minimally altered by paclo SP but paclo SP + TD reduced flower clusters over two seasons and reduced the 6-year average number of fruit per tree. Trees treated with paclo via sprays plus the trunk drench, especially paclo 1000 SP + TD, tended to develop biennial flowering patterns. Weight per fruit was reduced in two seasons by paclo SP + TD but it was greater in seasons when fruit numbers were reduced (low number of flowers). Fruit yields were reduced over four seasons by paclo SP + TD resulting in an overal yield reduction of 27% however, because TCSA was reduced by paclo SP + TD, the 6-year yield efficiency index (fruit yield per unit TCSA) was increased. Six-year average fruit length to width ratios were lower and russeting ratings were higher for fruit from trees receiving paclo SP + TD treatments compared with controls. Paclobutrazol did not alter net photosynthesis, stomatal conductance, leaf chlorophyll content or specific leaf weight the third season after treatment.

Phomopsis Seed Infection and Nutrient Accumulation in Pods of Soybean with Reduced Fruit Loads

AbstractActive infection of soybean [Glycine max (L.) Merr.] fruits by Phomopsis longicolla Hobbs is associated with physiological changes occurring during senescence. The purpose of this research was to determine the relationship of carbohydrate and mineral nutrient composition of pod tissue to seed infection by P. longicolla. Varying carbohydrate and mineral nutrient levels in pod tissue were created by different fruit removal and debranching treatments. Reducing fruit load in plants from three to four pods per node to one per node increased seed infection by P. longicolla 42% and decreased seed germination 35%. Total nonstructural carbohydrates, N, and P concentrations in pod walls at physiological maturity were increased 56, 40, and 77%, respectively, by pod reduction. Seed total nonstructural carbohydrates were reduced 13% and seed N increased 15% by reduced fruit loads. Fruit removal delayed plant maturation up to 2 to 3 wk. A lower incidence of P. longicolla and moldy seed from upper nodes (vs. lower nodes) of plants was associated with lower K and greater Ca and total nonstructural carbohydrates in pod walls. Decreasing seed infection by P. longicolla might be achieved by maximizing fruit loads and shortening the time interval between physiological maturity and harvest maturity.

VEGETATIVE AND REPRODUCTIVE GROWTH OF DETERMINATE TOMATOES AS INFLUENCED BY APPLICATIONS OF ETHEPHON, DCIB, NAA AND SADH AT THE SIX-CLUSTER STAGE

In an attempt to control fruit set and thereby increase fruit size, 2-(chloroethyl) phosphonic acid (ethephon), sodium 2,3-dichloroisobutyrate (DCIB), naphthaleueacetic acid (NAA) and N-dimethylaminosuccinamic acid (SADH) were applied as sprays to plants of the determinate tomato Lycopersicon esculentum Mill. ’Summit’ when fruit was set on six clusters. In comparison, one set of plants was deblossomed manually after the six-cluster stage, and another untreated. Although none of the chemicals provided perfect control of fruit load, NAA (100 ppm), SADH (4,000 ppm) + NAA (100 ppm), DCIB (4,000 ppm) + ethephon (500 ppm) and DCIB (6,000 ppm) were approximately 81, 77, 75 and 73% effective, respectively, in reducing fruit load. However, decreases in fruit load were not accompanied by corresponding increases in fruit size. In all probability, this was due to the impairment of normal growth by the chemicals. Several of the treatments produced substantial increases in early and total yield, by maturing a greater number of fruits and thus may be of potential use to commercial growers.

The Influence of (2-Chloroethyl)phosphonic Acid on Peach Quality and Maturation1

Abstract Ethephon ((2-chloroethyl)phosphonic acid) at 50 to 200 ppm hastened the maturation of peach fruit of the cvs. ‘Cardinal’, ‘Ranger’, ‘Redhaven’, ‘Blake’, and ‘Richhaven’ over a range of application times. Stimulation of maturation was not attributed solely to reduced fruit load, since an influence on maturation was found even when ethephon-treated trees bore no fewer fruits than hand-thinned controls. When treated and nontreated ‘Richhaven’ fruit were harvested at a comparable maturity based on firmness, ground and flesh color a and a/b values were increased by ethephon, as were soluble solids. No differences were found in b values for ground or flesh color or in total titratable acidity. Fruit treated with ethephon exhibited more uniformity in firmness and color than untreated fruit at shipping maturity, a characteristic which has potential value in facilitating once-over mechanical harvesting operations.