Enhance Fruit Size Research Articles

Effect of Foliar Feeding with Nutrients and Bioregulators on Yield and Quality Attributes of Litchi cv. Bombai

Litchi (Litchi chinensis Sonn.) is considered one of the most important sub-tropical fruits of the world. In the western part of Odisha, India, litchi growers are facing problems of unstable and lower marketable yield and inferior quality due to a higher incidence of fruit cracking, fruit drop, low sugar content, and higher fruit acidity. Keeping in mind the positive effects of nutrients and bioregulators, the current study was conducted to elucidate their impact on fruit yield and quality in the farmers’ field of Jamankira block in Sambalpur district of Odisha, which is under the care of Odisha University of Agriculture and Technology, India. For this study, eight-year-old litchi trees were selected. With 12 treatments, the experiment was set up in a Randomized Block Design replicated thrice, as follows: T1: spray treatment with Borax—0.5%; T2: spray treatment with Borax—0.3%; T3: spray treatment with ZnSO4—0.75%; T4: spray treatment with ZnSO4—0.5%; T5: spray treatment with CaCl2—0.5%; T6: spray treatment with CaCl2—0.1%; T7: spray treatment with humic acid—1.5%; T8: spray treatment with humic acid—1%; T9: spray treatment with seaweed extract—0.5%; T10: spray treatment with seaweed extract—0.1%; T11: foliar spray with NAA—20 ppm; and T12: control (Water Spray). The current study compared foliar feeding treatments comprising different nutrient and bioregulators, which were applied during the first week of December, just after the completed formation of new leaves and the untreated control. The highest total number of fruits per plant was recorded in plants sprayed with 0.5% ZnSO4 (T4) followed by those treated with 1% humic acid (T8). The highest total fruit yield was recorded in plants subjected to foliar feeding with 0.3% Borax (T2) which was found to be statistically similar to plants treated with 0.1% seaweed extract (T10) and 0.5% seaweed extract (T9). Among the treatments, a better response, i.e., a higher number of marketable fruits and marketable yield, was recorded in litchi plants treated with 0.3% Borax (T2) followed by 0.5% zinc sulphate (T4), 1% humic acid (T8), and 0.1% CaCl2 (T6). The application of 1% humic acid (T8) followed by 1.5% humic acid (T9) enhanced fruit setting (%) and fruit retention rates (%) and reduced the fruit drop rate (%). The enhanced fruit size (fruit length and fruit width) and higher fruit weight was obtained in litchi plants treated with 0.3% Borax. The foliar application of 0.3% Borax (T2) also resulted in a higher TSS, total sugars, reducing sugar content, lower acidity, the highest aril weight, and lower seed weight in litchi cv. Bombai. In this research, among the five principal components, only PC1 demonstrated approximately 45.14% variability within the influential axes. PC1 contributed the highest proportion (48.9%) to the overall variability, followed by PC2 with 29.1%, PC3 with 11.9%, PC4 with 0.59%, and PC5 with 0.20%. Consequently, the outcomes of the principal component analysis indicate the presence of extensive variability among treatments.

Influence of Preharvest Bagging on Maturity Indices and Postharvest Quality of Cherry Tomato (Solanum lycopersicum var. cerasiforme)

The production of cherry tomato (Solanum lycopersicum var. cerasiforme) is negatively affected by harsh environmental conditions such as extremely high and low temperatures, wind and hail damage, and pest and disease infestation. These factors delay maturity and cause uneven ripening, fruit abrasion, and blemishes, which consequently result in poor fruit quality and reduced shelf life. Preharvest bagging is an environmentally friendly alternative technique for enhancement of fruit quality and hence alleviates the stated problems. The study evaluated the physico-chemical quality of ‘Tinker’ and ‘Roma VF’ cherry tomato as influenced by preharvest bagging (transparent and blue plastics) during 8 days of shelf life at ambient conditions. Five clusters of fruit per plant per cultivar with a diameter of 1.5 to 2.0 cm were bagged after 16 days of fruit set and harvested at the green maturity stage, 12 days after preharvest bagging for the assessment of postharvest quality. Preharvest bagging effectively accelerated fruit maturity and ripening as indicated by enhanced fruit size, uniform color development, high pH, dry matter (DM) content, soluble solid content (SSC), and low titratable acidity (TA) during shelf life. Bagged fruit had higher loss of firmness and weight mainly due to ripening and showed very slight incidence of diseases during shelf life of 8 days. Unbagged cherry tomato had delayed maturity and ripening; small-sized fruit; uneven color development; low pH, SSC, and DM; and high TA. Although unbagged cherry tomato had lower firmness and weight loss due to delayed ripening, fruit showed moderate to severe incidence of tomato bacterial canker disease (Clavibacter michiganensis subsp. michiganensis) during shelf life. These results indicated that preharvest bagging accelerated fruit maturity and ripening, improved physico-chemical quality, and reduced disease infestation on cherry tomato during shelf life.

Optimizing Nitrogen, Phosphorus, and Potassium Fertilization Rates for Fruit Performance of Chinese Cherry (Prunus pseudocerasus Lindl.)

ABSTRACT Attempts had been made to optimize nitrogen (N), phosphorus (P) and potassium (K) fertilization rates for increased fruit performance of Chinese cherry (Prunus pseudocerasus Lindl.). This study was conducted using a randomized block design (RBD) consisting of three factors and four levels, totaling to 14 treatments with each treatment repeated in triplicate. The results illustrated that the fertilization application increased the trunk, leaf, crown and new shoot growth, however, the optimal combination of N, P, and K (NPK) fertilization for growth varied among different parts of the young tree. Moreover, the fruit weight and size, internal quality, and fruit set rate (FSR) were positively affected by fertilization. Specifically, the no. 12 treatment (0.3 kg N + 0.4 kg P + 0.2 kg K) contained the optimal NPK combination for enhanced fruit size and cherry fruit set. Similarly, although the treatment is not the maximum of NPK concentration, the no. 12 treatment for mean daily values of Pn (MDVP) and the NPK concentration in leaf was significantly higher compared to other treatments. Additionally, Pearson’s correlation analysis suggests that the FSR was positively and significantly correlated with fruit weight (FW), fruit vertical diameter (FVD) and the soluble sugars (SS) in fruit. In general, the no. 12 treatment was the optimal NPK fertilization rates for young tree growth, fruit quality of Chinese cherry (Prunus pseudocerasus Lindl.) in the Karst region of southwest China.

Meloidogyne incognita population control and nutritional status and productivity of Thompson seedless grapevines managed with different treatments.

A two-year field trial was conducted in a vineyard (northern Egypt)cultivated with Thompson seedless grapevines to evaluate the effectiveness of four “alternative” (biological/chemical) treatments, Bacillus megaterium, boric acid, calcium nitrate and chitosan, against the root-knot nematode Meloidogyne incognita (Mi), compared to that of the nematicide oxamyl. The influence of these treatments on plant nutritional status and fruit yield and quality was also assessed. All treatments significantly inhibited Mi reproduction parameters in both seasons, decreasing the numbers of nematode galls and egg masses (roots) and of second-stage juveniles (soil). Oxamyl application resulted in the highest reductions in Mi-reproduction parameters, followed by boric acid, which also showed the highest relative nematicidal efficacy (respect to oxamyl). In the 1st season, the highest fruit yield (10.34 kg/grapevine) was recorded from boric acid-treated plants, followed by that from oxamyl-treated plants (7.50 kg/grapevine); in the subsequent season (2019), oxamyl use led to the highest yield, followed by boric acid + chitosan use (10.04 and 8.62 kg/grapevine, respectively). In both seasons, application of boric acid alone and combined with chitosan enhanced the total soluble solids (TSS)/total acidity ratio in grape juice. All treatments led to higher nutrient contents (leaf petioles) and chlorophyll levels (leaves) as well as enhanced fruit size and weight. We conclude that the tested treatments can be safely applied for nematode management in Thompson seedless grapevines, with positive effects on fruit yield and quality.

Regulation of flowering in guava (Psidium guajava L.) cv. Lucknow-49

Plant growth hormones play a vital role in guava production and are used in the induction of flowering, help in fruit set, fruit thinning, fruit elongation, premature fruit drop prevention, fruiting buds development and inhibiting ripening process. These can also influence the size, appearance and quality parameters of fruits. By using plant hormones, an experiment was carried out in the Experimental Farm and Laboratory, Department of Horticulture, College of Agriculture, Assam Agricultural University, Jorhat during 2016–18 to regulate the flowering of guava in the rainy season and to increase more production and productivity of guava fruit in the winter season. A total of six treatments with four replications and two seasons (rainy and winter) were laid out in a randomized block design. The effect in foliar application of different concentrations of plant growth hormones of T1-Naphthalene acetic acid (NAA at 100 ppm), T2-Naphthalene acetamide (NAD at 40 ppm), T3-Naphthalene acetamide (NAD at 60 ppm), T4-Urea (2%), T5-Urea (5%) and T6-Urea (10%) at flowering stage in the month of April, 2017 helped in deblossoming of flowers, enhanced fruit size, weight, number of flowers and fruits, reduced fruit drop (76.43% in rainy season to 38.26%), decreased the days required for maturity (118 days) and increased the yield (20.73 kg/plant) in the winter season. The effect of NAD @ 60 ppm gave the best result in fulfilling all the physical parameters of the guava fruit in the winter season.

CULTURAL PRACTICES ON TEMPERATE FRUITS GROWING IN TROPICAL AND SUBTROPICAL ZONES

Fruit production regions around the world are now experiencing significant changes in their growing conditions. Farmers already face greater challenges growing temperate fruits in subtropical and tropical regions compared to temperate regions, but time of production provides substantial farm gate returns. Climate variability is impacting on profitability, yields, fruit quality and phenological performance. Breeding of new low-chill cultivars and selection of new rootstocks have assisted farmers to negate some effects of climate variability. New cultivars have also allowed new growing regions to be developed. Market niches that were not previously considered accessible are now being targeted with temperate fruit from subtropical and tropical regions. New training systems that improving light penetration into the canopy and canopy management practices to control vegetative growth have substantially increased fruit size and enhanced fruit quality, providing consumers with a highly consistent product. Crop manipulation practices to enhance and concentrate flowering periods, decrease harvesting costs, improve fruit quality and increased the profitability of growing temperate fruits in subtropical and tropical regions. Furthermore, cultural practices, such as the use of new fertiliser and irrigation management practices and crop manipulators to delay fruit maturation have also significantly enhance fruit size and quality. The growing temperate fruits in subtropical and tropical of regions of Asia has significantly improve the socioeconomic status of poor ethnic minority groups living in areas where low-chill temperate fruits can be successfully grown.

A COMPARISON OF AGRONOMIC TREATMENTS TO IMPROVE AVERAGE BERRY SIZE IN EVERBEARING STRAWBERRIES (FRAGARIA × ANANASSA)

The total area of strawberry grown in the UK is nearly 5000 ha producing 110,000 t (DEFRA Basic Horticultural Statistics, 2011) of which approximately 40% is of everbearing cultivars. As everbearers are a very important component within the UK strawberry industry, it is essential to maximise the yield of class 1 berries for the growers. In many everbearer cultivars the average fruit size decreases as the season progresses. In 2010 and 2011 two trials were conducted to determine whether agronomic treatments could improve the average fruit size at harvest. The cultivar used for the study was ‘Finesse’, which is a recent release from East Malling Research that is becoming an important cultivar in the UK market place. Study 1 conducted in 2010 was designed to determine whether the removal of leaves and/or the removal of blooms could influence fruit size in the latter stages of harvest. In this study the oldest leaves of ‘Finesse’ were removed to a leaf area index (LAI) of 3.0 in an attempt to eliminate older, less-efficient leaves thereby diverting assimilates to enhance fruit size, while maintaining a full canopy of newer and more productive leaves. There was anecdotal evidence from UK growers that this treatment had been effective in some everbearing cultivars but this study concluded that a LAI of 3.0 and de-blooming three weeks after planting had the effect of reducing overall yield, due to a reduction in fruit size. Based on the same principle of relocating assimilates, study 2 conducted in 2011 compared four further treatments, which included a control, de-flowering at planting, picking only large berries followed by truss removal, and removing whole trusses from the plants. Harvesting continued until end of October 2011. Results showed that not harvesting the smaller berries increased significantly the percentage of larger fruit (above 45 mm) produced per plant. The production of larger berries in that treatment was also shifted towards the end of the harvest but that result was not consistent across the four replications.

The efficacy of 6-benzyladenine, gibberellins4+7 and prohexadione-calcium to increase fruit size in ‘Forelle’ and ‘Abate Fetel’ pear

Fruit size is an important marketing and quality parameter and has a significant effect on the economic value of fruit. The application of synthetic cytokinins are believed to enhance fruit size by stimulating and extending the cell division stage in fruit when applied at the correct time during fruit growth. In addition, a combination of prohexadione-calcium (P-Ca) with gibberellins4+7 (GA4+7) was used successfully on Japanese pear (Pyrus pyrifolia Nakai) and ‘Bing’ sweet cherry to improve fruit size. This combination of GA4+7 and P-Ca was evaluated and combined with 6-benzyladenine (6-BA) treatments on European pear (Pyrus communis L.) cultivars Forelle and Abate Fetel to determine whether fruit size can be improved under the Mediterranean-type growing conditions in South Africa. On both ‘Forelle’ and ‘Abate Fetel’ the combination of GA4+7 and P-Ca increased fruit size but the effect was more pronounced in ‘Abate Fetel’; further addition of 6-BA did not improve fruit size in these two cultivars over two consecutive seasons.

INFLUENCE OF CHLORINE ON SHOOT GROWTH OF KIWIBERRY (ACTINIDIA ARGUTA (SIEB. ET ZUCC.) PLANCH. EX MIQ.)

Actinidia species show a relatively high uptake of N, K, Cl and Ca. Nitrogen is an important nutrient for good cane growth, but too much nitrogen causes excessive vegetative growth, poor yields, and increased winter injury. Applications of nitrogen at the end of the fruiting season enhance fruit size but are discouraged as fruit then tend to store poorly. Special attention should also be paid to boron (B) and sodium (Na) as the kiwifruit is extremely sensitive to excess of both elements in the soil. Actinidia deliciosa needs comparatively high concentrations of chloride for optimum growth. Therefore, unless the natural soil is high in Cl (>150 mg/kg) and/or low in N, K should be preferably applied as KCl. K is more readily absorbed by kiwifruit in its chloride form than as sulfate. Yield differences up to 30% have been recorded in relation to the chloride content of the soil. Until now there were only few studies examining chlorine effects and content in Actinidia arguta. Some experiments with young plants in pot culture were performed. The vegetative plant parts were analyzed to study the effects of chloride on the growth and development of 3 cultivars ('Jumbo', 'Ken's Red' and 'Maki'). The results clearly show that also this species has a great demand of chloride for optimal growth.

Bearing Branch Units Developed on Branches Hedged During Flowering Produce Large ‘Washington’ Navel (Citrus Sinensis L. Osbeck) Oranges

Citrus growers in Australia need to be able to produce large fruit size for premium returns in domestic and overseas markets. Therefore, it is important to manipulate the tree canopy by hedging in a “heavy-flowering” year to decrease crop load and enhance fruit size the following year. A two-year study was conducted on the relationship of fruit size to different inflorescence types that developed on bearing branch units (BBU) that developed in the summer following mechanical hedging during flowering in spring compared with non-hedged branches. Spring hedging produced a “stronger” vegetative growth flush compared to the non-hedged branches: BBU developing on hedged branches produced more sprouts, flowers, leafy inflorescences and 3.6 to 5 mm larger fruit size than BBU from non-hedged branches. Moderate severity mechanical hedging in the spring of “on-flowering” years is recommended as a practical means to manage the existing crop load, enhance fruit size and alleviate alternate bearing for the following year.

Increase in fruit size of a spontaneous mutant of ‘Gala’ apple (Malus×domestica Borkh.) is facilitated by altered cell production and enhanced cell size

Fruit size regulation was studied in the apple cultivar ‘Gala’ and a large fruit size spontaneous mutant of ‘Gala’, ‘Grand Gala’ (GG). GG fruits were 15% larger in diameter and 38% heavier than ‘Gala’ fruits, largely due to an increase in size of the fruit cortex. The mutation in GG altered growth prior to fruit set and during fruit development. Prior to fruit set, the carpel/floral-tube size was enhanced in GG and was associated with higher cell number, larger cell size, and increased ploidy through endoreduplication, an altered form of the cell cycle normally absent in apple. The data suggest that the mutation in GG promotes either cell production or endoreduplication in the carpel/floral-tube cells depending on their competence for division. Ploidy was not altered in GG leaves. During fruit growth, GG fruit cells exited cell production earlier, and with a DNA content of 4C suggesting G2 arrest. Cell size was higher in GG fruits during exit from cell production and at later stages of fruit growth. Final cell diameter in GG fruit cortex cells was 15% higher than that in ‘Gala’ indicating that enhanced fruit size in GG was facilitated by increased cell size. The normal progression of cell expansion in cells arrested in G2 may account for the increase in cell size. Quantitative RT-PCR analysis indicated higher MdCDKA1 expression and reduced MdCYCA2 expression during early fruit development in GG fruits. Together, the data indicate an important role for cell expansion in regulating apple fruit size.

181 Studies on Fruit Thinning and Growth in Apple Cultivars

Experiments were carried out for 3 years on `Gala' and `Fuji' apple cultivars. The efficacy of the compounds applied during blooming (ATS, Armothin) and at 10 mm king fruit diameter (BA, CPPU, and NAA) was studied. Results showed a poor efficacy of the chemicals applied during bloom, while compounds applied at fruit set showed interesting results. Among the new chemicals, citokinins were the most effective, although their effects were related to the cultivar: BA performs better than CPPU on `Fuji' while vice versa on `Gala'. In addition, both chemicals induced a slightly higher °Brix content, and acidity level showed the tendency to increase L/D ratio of the fruits as compared to controls. Fruit thinning and the strategies to enhance fruit size are applied early in the season and the problem remains, to assess their effectiveness as early as possible in order to adapt the management techniques (e.g., further thinning, if applicable, or fine-tuning of nutrition and irrigation, etc.) to enable the fruit to reach their maximum potential development. A modelling approach proposed by Lakso et al. (1995) postulates that apples grow in weight according to an equation termed “expolinear” (Goudriaan and Monteith, 1990) because after an initial phase of exponential growth (cell division), the apple enters a phase of linear growth (cell expansion) lasting up to harvest. The effectiveness of a thinning agent can therefore be evaluated-and explained-in terms either of the number of cells of the cortex tissue, or of their volume, or both. In addition, assessing the slope of the linear phase as early as possible might provide a prediction tool to evaluate size at harvest. This paper presents data from apple thinning trials on several cultivars. The effectiveness of these applications has been evaluated via an analysis of the cell parameters (number, volume and intercellular spaces) of the fruit's parenchyma cortex tissue. Also, fruit growth data have been used to test the possibility to predict fruit size at harvest once the fruit reaches the phase of linear growth.

564 The Influence of Preharvest Treatments with ReTain™ (An Ethylene Biosynthesis Inhibitor) on the Fruit Maturation and Quality of `Royal Gala' Apple in New Zealand

ReTain™ is a plant bioregulator containing the active ingredient aminoethoxyvinylglycine (AVG), which inhibits the ethylene biosynthesis pathway. In 1997, the first efficacy studies on `Royal Gala' apple with ReTain™ were conducted under New Zealand conditions in Hawkes Bay. ReTain™ was applied 4 weeks before the anticipated start of harvest on `Royal Gala' at 850 and 1700 g·ha–1 with or without adjuvants. ReTain™ application delayed the onset of `Royal Gala' fruit maturation between 1 and 2 weeks, resulting in enhanced fruit size and fruit flesh firmness at harvest. The optimum response for delaying the onset of fruit maturation was achieved using ReTain™ at 850 g·ha–1 if applied in combination with a wetter. Fruit were also graded for fruit quality and air-stored at 0.5 °C. Fruit after 10 weeks of storage showed no difference in fruit flesh firmness, but all ReTain™ treatments had fruit with less yellow background colour compared with untreated fruit. In 1998, efficacy studies were undertaken in three geographical locations on `Royal Gala'. ReTain™ was applied at a rate of 830 g·ha–1 in combination with Silwet L-77 at 0.1%. All trees with the exception of `Royal Gala' grown in the Hawkes Bay had not received any ReTain™ previously. In all regions, seasonal changes in background color and starch pattern index were delayed by ReTain™ treatment. A concurrent delay of an increase in soluble solids concentration and retention of higher flesh firmness were also induced by ReTain™ treatment.

The Effects of Exogenous Bioregulators and Environment on Regular Cropping of Apple

The use of exogenous plant bioregulators or plant hormones to adjust crop load in apple (Malus ×domestica Borkh.) and promote regular cropping remains challenging to both researchers and producers. Responses to these hormones are sensitive to the rate and timing of application, to physiological status of the tree, orchard system, variety, rootstock, and a myriad of cultural practices and environmental factors. Of the environmental factors, temperature plays the most important role in determining response and efficacy of a given material. All classes of plant bioregulators have been used over the past 30 to 40 years as postbloom chemical thinning materials. Most of the standard postbloom thinning programs involve application of a synthetic auxin, such as naphthalene acetic acid (NAA) in combination with carbaryl (Sevin), a commonly used insecticide. The mode of action of these two compounds is not clearly understood. Gibberellins generally have not been effective thinning materials for apple because of their negative impact on return bloom. Ethylene-releasing compounds have been used successfully as postbloom thinning materials. Cytokinins, particularly synthetic sources such as 6-benzyladenine (6-BA), have been shown to effectively thin fruit and enhance fruit size on many commercial varieties. The rate and timing of 6-BA applications are critical to obtain desirable thinning and fruit size responses. The use of these different bioregulators is essential for regular cropping of apple, particularly for spur `Delicious', `Fuji' and other varieties that are difficult to thin chemically and which are prone to severe alternate bearing. The focus of this discussion is the use of these bioregulators in commercial apple production areas in the United States.

The Effects of Exogenous Bioregulators and Environment on Regular Cropping of Apple

Use of exogenous bioregulators (“hormones”) to adjust crop load in apple remains challenging to both researchers and producers. These hormones are sensitive to the rate and timing of application, to the physiological status of the tree, the choice of orchard system, variety and rootstock, and a myriad of cultural practices and environmental factors. All classes of plant bioregulators have been used over the past 30 to 40 years as chemical thinning materials. Most of the standard postbloom thinning programs involve application of a synthetic auxin, such as naphthalene acetic acid (NAA) in combination with carbaryl, a commonly used insecticide. The mode of action of these two compounds is not clearly understood. Gibberellins generally have not been effective thinning materials because of the negative impact on return bloom. Ethylene-releasing compounds have been used successfully as postbloom thinning materials. And cytokinins, particularly synthetic sources such as 6-BA, have been shown to effectively thin fruit and to enhance fruit size on many commercial varieties. The rate and timing of 6-BA applications are particularly critical to obtain the desirable thinning and size responses. Overall, these bioregulators are sensitive to temperature. The use of bloom thinning compounds and their efficacy in the Pacific Northwest will be discussed in the context of return bloom.

Effects of Application Conditions and Adjuvants on Chemical Fruit Thinning of Apple

In 1995, effects of adjuvants on fruit thinning with Accel [10:1 ratio of 6-benzyladenenine (BA):GA4&7] at 75 ppm BA were studied. Silwet L-77 was used at 0.027% (v/v). Regulaid and ultrafine spray oil were used at 0.125% (v/v). Treatments also included unthinned controls, NAA (naphthalene acetic acid) at 7.5 ppm plus 600 ppm carbaryl, and Accel plus 600 ppm carbaryl. `Empire' apple trees on M.9/MM.111 rootstock in Milton, N.Y., were used in the 6th leaf. Trees were blocked by number of blossom clusters/cm2 trunk cross sectional area. Applications were made at 1.5x concentration, using tree-row volume to calculate appropriate dilute volume. Each spray treatment was applied near the high temperature on each of three consecutive days around 10-mm king fruitlet diameter. Conditions were as follows: day 1–high temperature of 19°C with moderate drying time, and rain several hours after application; day 2–high temperature of 15.5°C and prolonged drying; and day-3–high temperature of 21.1°C and moderate drying. All treatments significantly thinned and enhanced fruit size compared to unthinned controls. Application conditions (treatment day) did not significantly affect response when compared within any spray treatment. However, in combined analyses, treatment with Accel or Accel with Regulaid resulted in significantly smaller fruit on day 1, when rain followed application, compared to these treatments on other days, or compared to Accel with other adjuvants on day 1. Accel with carbaryl resulted in largest fruit size and cropload reduction, but significantly reduced seed number/fruit. It is postulated that prolonged drying times occurring in cool conditions can compensate for reduced uptake rate at lower temperatures.

Effect of CPPU and NAA on Fruit Growth and Cropping of Redchief `Delicious'

NAA is commonly used for fruit thinning of apples. However, with spur-type `Delicious' fruit, size may be less than expected based on the remaining crop load. Attempts to enhance fruit size on NAA-thinned trees with benzyladenine (BA) resulted in an interaction causing an increase in small (≤64 mm) fruit. CPPU [N-(2-chloro-4-pyridinyl)-N'-phenylurea], a highly active cytokinin in promoting parthenocarpy and growth of a number of fruit, was evaluated alone and with NAA for its effects on cropping and fruit growth in Redchief `Delicious'. High-volume sprays of CPPU were applied at 0, 2.5, 5, and 10 mg·L–1 to 13-year-old trees at 7.26 mm king fruit diameter. NAA was applied at 15 mg·L–1 with and without CPPU at 5 mg·L–1. Each treatment consisted of a single tree replicated four times. Response was evaluated by determining yield per tree and fruit size distribution at harvest. CPPU increased the amount of large (≥70 mm) fruit produced without significantly reducing yield. The amount of large fruit produced was 35, 71, 91 and 85 kg/tree for the nonthinned control (NTC) and CPPU at 2.5, 5, and 10 mg·L–1, respectively. NAA (15 mg·L–1) reduced yield by 39 kg/tree and increased amount of large fruit by 44 kg/tree. When CPPU (5 mg·L–1) was oversprayed with NAA (15 mg·L–1), yield was reduced by 30 kg/tree, and amount of large fruit was increased by 56 kg/tree compared to the NTC. The interaction was not significant for yield but was significant (P = 0.01) for amount of large fruit produced. Seed content was significantly reduced by NAA and CPPU, the effect being greater for NAA and in small (51 to 56 and 57 to 63 mm) than in large (76 to 82 mm) fruit. These data showing no significant inhibition of fruit growth with a combination of NAA and CPPU in Redchief `Delicious' are in contrast with findings for a related cytokinin, BA, where fruit growth was depressed significantly when combined with NAA.

952 PB 449 HYDROGEN CYANAMIDE ENHANCEMENT OF FRUIT SET

The state of Texas suffers from a lack of chilling one out of every five years. Reduced yield in temperature fruit crops such as peach (Prunus persica) is one detrimental effect associated withinadequate chilling. Field trials with hydrogen cyanamide (Dormex) have demonstrated that a one to two percent solution applied six weeks prior to bloom will substitute for inadequate chilling of up to 150 hours. Field trials with this chemical have provided further insight into some other possible benefits associated with its use such as: increased marketable yields of fruit crops, enhanced fruit size, and an earlier more concentrated harvest. Advantages noted by the use of this product include a possible earlier crop and reduced labor costs.

CPPU control of fruit morphogenesis in apple

CPPU, a cytokinin-like substance derived from phenylurea, was applied to shoots, fruits, and to shoots + fruits of mature trees of apple cultivars ‘Golden Delicious’ clone B and ‘Red Delicious’ clone Clear Red 25 days after full bloom. While no influence on fruit morphogenesis was detected for the shoot only treatment, the fruit only and shoot + fruit applications enhanced fruit size and weight, though often inducing irregular elongation, a slight delay in colouring and a lower sugar content. No differences were recorded in the contents and degradation of pectic substances.

Split-Pit of ‘Dixon’ Cling Peaches in Relation to Cultural Factors1

Abstract Split-pit of ‘Dixon’ cling peaches was correlated with all 3 variables in a multivariable cultural system study involving differential N applications, irrigations, and crop loads. Any factor that enhanced fruit size contributed to increased split-pit. Fruit size at reference date was more important than fruit size at harvest. In different years fruits of the same size at reference date or at harvest did not necessarily have the same amount of split-pit. Fruit set was more important than other factors in determining fruit size at thinning. Crop load after thinning influenced split-pit where fruit set was moderate; however, where fruit set was light split-pit was severe regardless of thinning and where fruit set was heavy split-pit was of minor concern regardless of thinning. Early thinning accomplished about reference date (10 days after beginning of pit hardening in 80% of fruit) increased split-pit over thinning 2 weeks later. Maintenance of high soil moisture (< 40% used) after reference date increased split-pit over that of less frequently irrigated plots. Manipulation of cultural factors cannot satisfactorily control split-pit, but may considerably influence its occurrence.