June Drop Research Articles

Effects of Ethrel and auxin applications on date palm fruit abscission during development

'Medjoul' is a large semidry date cultivar that is marketed as a special elite product. Fruit size and quality are determined by fruit load, which is dependent on the level of fruit set, fruitlet thinning protocols and natural drop. Currently there is no information on the process of natural fruit abscission in date palms and specifically not on abscission of 'Medjoul'. In the present study abscission levels were characterized through fruit development in vivo and in vitro. Fruit abscise throughout development. During two stages, at an 'Early fruitlet drop' and a 'June drop' (at 25–45 and 80–100 days after pollination respectively), specifically high rates of abscission were observed. The level of fruit set and the fruit load affects these two peaks respectively. Ethrel treatment, an ethylene releasing chemical, significantly induced fruitlet drop while Auxin (2,4-D) treatment reduced the rate of natural fruit drop in vitro, especially during the developmental stages with high natural abscission. A specific abscission zone located at the base of the fruit, just between the calyx and spikelet was detected. Following Ethrel treatment, breaks and cracks in this tissue were detected. This data will enable better understanding of fruitlet and fruit abscission in date palm, which is extremely important for a high quality production of 'Medjoul' dates.

Apple Fruitlet Abscission Prediction. I. Development and Evaluation of Reflectance Spectroscopy Models

Chemical thinning, the most common and cost-effective thinning method, is conducted during early apple fruit development over a 3- to 4-week period using multiple applications of plant growth regulators. It is critical to provide apple growers with tools to assess the efficacy of chemical thinners quickly and accurately because visible responses are not apparent for up to 2 weeks after application. The objective of this study was to build a model to predict apple fruitlet abscission following a chemical thinner application with in situ reflectance data obtained with a portable visible and near infrared (Vis/NIR) spectrophotometer. Developed models were compared with the currently available fruitlet growth model (FGM). ‘Honeycrisp’ fruitlet diameter and reflectance were measured on dates around a chemical thinner application across a 2-year period. After June drop, measured fruitlets were determined to have either persisted or abscised. Random forest, partial least squares regression, and XGBoost classification models were used to predict fruitlet abscission from reflectance data. Each classification model was developed with 2021, 2022, and combined 2021 + 2022 data. For each dataset, 5-fold cross validation was used to assess three model performance metrics: 1) overall accuracy, 2) recall, and 3) specificity. Datasets tested were either unbalanced, majority class down-sampled, or minority class up-sampled with synthetic minority oversampling technique. In both years, the FGM reliably estimated chemical thinner efficacy 9 days after application. Before this time point, the FGM had low prediction accuracy of the minority class in both years—persisting fruitlets in 2021 and abscising fruitlets in 2022. For reflectance spectroscopy, the developed random forest models that were balanced with synthetic minority over-sampling technique were found to be the best combination in predicting chemical thinner efficacy. The combined 2021 + 2022 dataset overall model accuracy ranged from 84% the day before to 93% at 9 days after thinner application. These results show that Vis/NIR is a promising tool to predict chemical thinner efficacy. This technology had high prediction accuracies over a range of fruitlet abscission potential and two growing seasons. Further development and testing of the model over cultivars, chemical thinner timings, and growing regions would facilitate commercialization of the technology.

Automatic flower cluster estimation in apple orchards using aerial and ground based point clouds

Chemical and mechanical thinning processes have long been used in stone and pome fruit production. During the thinning of apple flowers, growers use chemicals to regulate the tree load. Hand thinning is applied after the June drop to prune trees with excess crop load. The process of thinning can be unpredictable especially in biennial bearing cultivars. Thus, incentives to optimise chemical usage and to reduce expensive manual labour is ever increasing. Ground based machine vision systems have grown in popularity in orchard management due to the level of detail as well as plant coverage they can inspect with. Additionally, unmanned aerial vehicles (UAV) -based remote sensing technology is becoming a popular non-invasive quality inspection solution. This work proposes a framework for combining UAV and ground based RGB image data to detect flowering intensity in a Dutch Elstar apple orchard. The framework, based on point cloud reconstruction, presents automatic point cloud handling techniques as well as automated unsupervised flowering intensity estimation methods. Two linear regression models based on unsupervised machine learning methods were trained and validated from the framework that estimate flowering intensity in the orchard with both models having R 2 > 0.65, RRMSE < 20% and p-stat < 0.005 for the correlation between the image derived flower index and the flower cluster number counted in field. The proposed methods provide a novel strategy for guiding flower thinning using simple RGB images and location data only. Moreover, the proposed methods also reveal the flexibility of intra-tree inspection by checking its sub-volumes. • Automatic flower cluster estimation at the tree level with a R 2 = 0.7, RMSE < 20. • Ground and aerial point clouds have better performance when combined. • Novel strategy developed for guiding flower thinning in orchard management. • Dataset with aerial and ground images, and field sampling data released.

EFFECT OF PLANT GROWTH REGULATORS ON FRUIT SPLINTING IN THOMPSON NAVEL ORANGE

Fruit splitting is one of main problems extensively observed in citrus-growing area located in the northern parts of Iran. In order to investigate the effect of 2,4-D and GA3 on incidence of fruit splitting in Thompson ‘navel’ orange, an experiment, as a factorial arrangement in a randomized complete block design (RCBD) with three replications, was carried out in two consecutive years of 2016 and 2017. The main factors of this experiment included timing of spray at different growth stages (full bloom, petal fall, and June drop), 2, 4-D (0, 10, 20 mg L–1), and GA3 (0, 50, and 100 mg L–1). In the end of experiment, the characteristics including fruit length, fruit diameter, rind thickness, cellulase and polygalacturonase activities, total soluble solid, percentage of split fruit, and fruit yield were measured. Results showed that using 2, 4-D and GA3 not only decreased the rate of fruit splitting but also increased fruit yield as compared to controls. The highest fruit length, fruit diameter, rind thickness, total soluble solid and the lowest activities of cellulase and polygalacturonase were obtained using 100 mg L–1 GA3 and 20 mg L–1 2, 4 D during the full bloom. In general, the results revealed that using 2, 4-D and GA3 during the full bloom increased fruit yield while reduced fruit splitting and maintained the qualitative characteristics of Thompson ‘navel’ orange.

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.

Vegetative Growth and Quality of Washington Navel Orange as Affected by Shading Nets and Potassium Silicate Spraying

The experiment was conducted on Washington navel orange trees grown in sandy soil under a drip irrigation system at El Nubaria, Behera governorate during both experimental seasons of 2018 and 2019 to study the effect of applying a shading net, spraying potassium silicate, and their combination during fruit development to reduce high-temperature stress on fruit drop (%), number of fruits sunscald, number of fruits/ tree, and fruit quality, the experiment followed Randomized Complete Block Design(RCBD). The results showed that, T4 (Shading net (75%) and T7 (Shading net (75 %) + potassium silicate) caused the highest significant increase in shoot length. in the first season, the two shading treatments (T3 and T4) and the three combined treatments (T5, T6, and T7) caused a significant increase in leaf area compared to the control and the rest treatments. In the first season, Treatments (T4, T6, and T7) caused a significant increase in shoot diameter compared to the rest treatments and the control. In the two seasons, control, and the treatments of spray silicate only (one, two, or three times) caused the highest significant percentage of fruit June drop compared to the rest treatments. All treatments caused a significant increase in average fruit weight (g), juice weight (%), and fruit diameter (cm) compared to control. T2 (35% shading net) caused a significant increase in TSS and TA (%) compared to the control and the two shading treatments (65 and 75%). As for vitamin C shading treatments (T2, T3, and T4) did not show any significant differences among them or compared to the control. The highest value of total chlorophyll was obtained from T4 and T7.

Effect of Spraying with some Antioxidants on Growth, Yield, Fruit Quality and Nutritional Status of Navel Orange Trees

This study was carried out through two consecutive seasons 2016 and 2017 to investigate the effect of spraying with some antioxidants on vegetative growth, yield, fruit quality and nutritional status of twelve years old Navel orange trees on sour orange rootstock grown in a private orange orchard in Qalubia Governorate, Egypt cultivated in a silty clay loam soil. This experiment involved three antioxidant materials named (salicylic acid, citric acid and folic acid) and each one spraying by three levels of each of with (250, 500 and 1000 ppm) from each salicylic, citric and folic acid plus control treatment so the experiment included ten treatments. Selected trees were spraying three times (at the beginning of the growth cycle in March, just after fruit setting in May and just after June drop in July) by aqueous solution of salicylic acid, citric acid and folic acid until the point of runoff. The highest values of vegetative growth were obtained by spraying 500 ppm salicylic acid, 1000 ppm citric acid and 500 ppm folic acid. Regarding to yield, results pointed out that the foliar spraying with 500 ppm salicylic acid, 500 ppm citric acid and 250 ppm folic acid gave the highest values of yield. Treatments 500 ppm salicylic acid, 250 ppm citric acid and 250 ppm folic acid gave the highest values of physical and chemical fruit properties. In respect to nutrients content, the highest values of macronutrients were obtained by spraying 250 ppm folic acid, while that spraying 1000 ppm salicylic acid and 250 ppm folic acid gave the highest values of micronutrients. Therefore, using treatments 500 ppm salicylic acid, 500 ppm citric acid and 250 ppm folic acid may be recommended from economical point of view and as good treatments for enhancing Navel orange growth, yield, fruit quality and nutritional status especially under old citrus orchards.

Post petal fall applications of gibberellins improve fruit set on pear

Commercial pear production has become increasingly difficult over the last decade, with low fruit set being one of the main factors leading to poor yield of pear orchards. The use of gibberellins to increase fruit set has been widely reported, but in most of the cases these applications are made at full bloom or right after a spring frost has occurred. However, the increase in fruit set due to early applications of gibberellins such as at full bloom is often lost at June drop. Aim of this study was to assess dose and timing of different gibberellin applications made after petal fall to improve the final fruit set in pear orchards. Four experiments were conducted during four years (2010–2013) in mature pear orchards with ‘Conference’ as the scion cultivar. Fruit set and yield were increased when gibberellins were applied after petal fall, with a positive relationship with dose. Applications of GA4+7+BA tended to promote higher fruit set and yield than GA3, and in addition, they were less dependent to the moment of application. GA4+7+BA showed an additive effect when performing multiple applications. Return bloom was slightly affected when gibberellins were applied after petal fall. The strategy that showed a better behavior to increase fruit set was GA4+7+BA at 500 mL·ha−1 at H + 14, which coincides with the weeks of the natural fruit drop.

Crop Load Management with Blossom Thinners in ’Redchief’ Apple and Their Effects on Fruit Mineral Composition

The aim of this study was to determine the effect of ammonium thiosulphate (ATS) and potassium thiosulphate (KTS) on crop load, fruit quality and fruit mineral content of the eight-year-old ‘Redchief’/M26 apple. Seven different treatments were performed in the study as ATS (1%, 2%, 3%), KTS (1%, 2%, 3%) and hand thinning (after June drop) except for unthinned control. Thinning treatments were carried out as single application in full bloom period. Hand thinning and 3% ATS treatments were the best practices to increase fruit quality (diameter, weight). The fruit set ratio among the applications varied between 13.20% (2% ATS) and 23.46% (1% ATS). Yield was lowest in 2% and 3% ATS. Thinning with ATS was found more effective compared to KTS. The lowest Fe, Cu and Zn elements were determined in 2% ATS application, and the difference between the applications in terms of other elements was found to be insignificant. Phytotoxic effect was not observed for any ATS or KTS doses. As a result, flower thinners can be used as an alternative to hand thinning to improve fruit quality in ‘Redchief’ variety.

Genesis of ultra-specialized histology with stable traits in mesophyll of drought tolerant apple cultivars

Even if some biological defense responses are activated instantaneously after stress occurrence, but other mechanisms of drought tolerance could be probed, detected and diagnosed as sable traits at mesophyll level. The present observations demonstrated multilateral modifications in different leaf parts, specialized parenchyma tissues and cribro-vascular bundles that facilitate vital activities in tolerant apple cultivars. In 2006, long deficit irrigation occurred in commercial apple collection containing 93 cultivars located in Karaj-Iran. Entire bearing 16-Year-old trees lost completely the crop except 16 CVs which were assessed for yield per tree since June drop to physiological maturity. Based on thehypothesis, stable traits were developed against drought stress through phenomenon of genesis. 19 different anatomical traits of mesophyll were accurately assessed in the selected resistant CVs compared with the susceptible "Golden Delicious" and native "Assali" as the controls. Microscopic studies computed on the transversal sections of mesophyll prepared by microtome ascertained ultra-specialized histological traits in the selected CVs. Morphologically, basal part of the main vein was completely spherical, outfitted, highly ordered and tidy tissues. Epidermis underlying layer was composed of well-organized tissues containing uniform cells by shape and size, inserted consistently next to one another in neat order with no intercellular space. Contrarily, controls showed opposite rhythm in all examined characters. Also, the mean number of epidermis layers at leaf margin resulted higher related to susceptible CVs. The mean number of vascular bundles and stomata decreased in tolerant CVs. These observations put in evidence some stable ultra-specialized histological traits of mesophyll, as a result of genesis route.

Effects of 2,4-DP- P (2,4-Dichlorophenoxypropionic Acid-P) Plant Growth Regulator on Fruit Size and Yield of Star Ruby Grapefruit (Citrus paradisi Osb.)

Star Ruby is the main grapefruit (Citrus paradisi) variety grown in Turkey; however, small fruit size is a common problem in ‘Star Ruby‘ grapefruit. Fruit size is a decisive external quality parameter in citrus at the marketing of fresh citrus fruits. Fruit size can be enhanced by several techniques such as girdling and thinning. Various plant growth regulators are known to affect the growth and size of citrus fruit. The objective of the present study was to observe the effects of 2,4 dichlorophenoxypropionic acid-p (2,4-DP-P) on the fruit size, yield and quality of Star Ruby from 20-year-old trees budded on sour orange rootstock in Adana, Turkey in 2007. Four concentrations (50, 100, 150 and 300 ppm) of 2,4-DP-P were applied 8 weeks after anthesis during physiological fruit drop when the mean fruit diameter was 13-15 mm. The results indicated that the application of 2,4-DP-P increased the fruit size of Star Ruby grapefruit without reducing yield. The application had a significant effect on fruit yield except for trees treated with 50 ppm 2,4-DP-P. Compared with the control trees, applications of 2,4-DP-P increased the number of large, commercially valuable Star Ruby (&gt;93 mm, 89-93 mm and 84-89 mm). No effects were determined on fruit internal quality parameters. Thus, the results of the present study revealed that 2,4-DP-P can be used to improve the fruit size of Star Ruby fruitlets during the June drop.

Effect of non-chemical crop load regulation on apple fruit quality, assessed by the DA-meter

Abstract The objective of the present work was to investigate alternatives to chemical crop load management (CLM) for cv. ‘Gala Mondial’ to improve fruit quality, particularly fruit size and portion of class I and its effects on June drop and return bloom as well as evaluate fruit maturation with the new, non-invasive DA-meter. Moderately flowering apple trees cv.’Gala Mondial’ at Klein Altendorf under white hail net in 2016 were subjected to four crop load motions: a) shading (90% for 77 daylight hours) at the end of May, b) mechanical blossom thinning with the Bonner device with three horizontal rotors at the balloon stage, and c) hand thinning at the end of June, with d) a combination trial of b) and c) adjacent un-thinned apple trees served as control. The weaker (320 rpm) and the stronger (360 rpm) mechanical thinning both at 5.5 km h−1 tractor speed caused a 5% or 22% reduction in fruit set, followed by shading with 27% reduction in comparison with the control trees. After June drop, the stronger mechanical thinning reduced fruit set by 23% and the combined mechanical and hand-thinning by 67%, while shading caused a reduction of 99% at 50°N and without spring frosts. The best pack-out viz. greatest percentage (86.8%) of fruits >70 mm diameter was achieved in the combined mechanical and hand thinning followed by 53.8% in the hand thinning, the strong mechanical thinning with 21.4% and control fruit with only 19.4% resulting in a ca. 68% increase in both class I and II fruit with an additional economic net gain of 3500 €/ha. The relationship between the DA-meter and Streif index is delineated to determine optimum harvest date (OHD). Although apple cv. ‘Gala’ appears insensitive to alternate bearing, return bloom in the control was 4–6, in the stronger mechanical thinning (360 rpm) 5–7, in the hand thinning 6–8 and in the combined mechanical and hand thinning as strong as 8–9 on the 0 (no flowers) − 9 (white blossom) scaleand reflects the physical response of the tree to the previous CLM.© Elsevier B.V.

Daily Dynamics of Sugar and Phenol Contents in Apple Fruitlets during June Drop

The occurrence of the abscission signal in young developing fruits on apple trees (Malus domestica) was studied. Apple has a natural system of fruitlet shedding, so called June drop. Although physiological fruit drop is unable to guarantee production of marketable apples and avoid alternate bearing, knowledge of this is a key background for successful fruit thinning. A study was carried out on apple trees cv. ‘Golden Delicious’ during June drop. On three dates (beginning, middle and after June drop), the daily dynamics of HPLC detected individual sugar and spectrophotometrically detected total phenolic contents were investigated in central (K) and lateral (L) fruitlets. The results of daily dynamics showed the highest sugar contents at 2 p.m. On the final sampling date, on 2nd July 2015, we observed a significant difference between sugar contents at 2 p.m. and the morning and afternoon measurements. Contents of sugars in K and L fruitlets were not significantly different. Total phenolic content at the beginning of June drop was higher than at the end. There was no statistically significant difference between K and L in an individual time period, while there were statistically significant differences in total phenolic content among the sampling dates. Although sugar and phenolic contents in K and L fruitlets were rarely statistically different, their contents changed during June drop. In general, sugar contents increased and phenolic contents decreased during the process, while the daily dynamic depended on weather conditions.

Bearing behaviour and correlation of fruit development stages with weather parameters in Kinnow mandarin under semi-arid irrigated conditions

The present investigations were carried out with the objective to find the basic understanding of bearing behavior of Kinnow and correlation of fruit development stages with weather parameters. During four years of study, two years were observed as on years (high yield) and two years off years (low yield). There was 20–25 per cent yield reduction in off year. It was observed that during off years, flowering was delayed (19th March) with reduced flowering duration (12 days) and days to form flower (15 days) as compared to early flowering (11th and 14th March) with more flowering duration (15 and 14 days) and days to form flower (18) during on years. No much variation in flowering density was observed in on and off years. Among yield parameters June drop was higher (66.97% and 69.77%) which results in less fruit retention (16.96% and 14.78%) during off years in comparison to less June drop (53.60% and 59.50%) and more fruit retention (21.37% and 19.54%) during on years. Average fruit weight was also less in off years (153.44 and 162.18g) as compared to on years (174.12 and 178.14g). During off years’ leaf potassium content was found in deficient range. So, it may be concluded that delay in flowering, more June drop, less fruit weight and deficient leaf potassium content are responsible for low yield in Kinnow during off year. However, no significant involvement of peel content, juice content and residue content was observed. Temperature and pan evaporation were positively correlated with fruit growth parameters (diameter, fresh weight and dry weight) during early fruit growth stage (April-May) and a negetive correlation with mid (June-Sept.) and late fruit growth stages (Oct-Dec). Whereas, Temperature and pan evaporation showed significantly positive correlation with peel thickness during early and mid fruit growth stages and negative during later growth stages.

Calcium Absorption during Fruit Development in ‘Honeycrisp’ Apple Measured Using 44Ca as a Stable Isotope Tracer

Calcium (Ca) sprays are commonly used to control Ca-related disorders such as bitter pit in apple. Increases in the frequency and the amount of Ca applied directly to the fruit have increased fruit Ca levels and are associated with a reduction in bitter pit incidence. However, the absorption efficiency at different fruit developmental stages is poorly understood. Here, the absorption efficiency was measured using 44Ca stable isotope applied to 30 individual fruit at five different times every 2 weeks between June drop and 2 weeks before harvest in a medium-density ‘Honeycrisp’ orchard. Fruit size, spray adhesion, and Ca and potassium (K) content were monitored weekly for 12 weeks between 26 May and 13 Aug. 2015. At harvest, the 44Ca-labeled fruit was picked and separated into peel and inner fruit for mass balance analysis of 44Ca absorption to regions of the fruit that are important to prevent Ca-related disorders. As expected, δ44Ca was greater in the peel than the interior of the fruit. However, there was a significant amount of 44Ca present in the inner fruit at harvest for all five applications applied during the growing season. Using a stable isotope tracer approach, we present evidence that Ca is absorbed throughout fruit development. These findings support current recommendations for frequent Ca applications in low concentrations throughout fruit development to increase fruit Ca levels and reduce the incidence of bitter pit in ‘Honeycrisp’ apple.

Precision thinning of ‘Royal Gala’ apple trees using the fruit growth model

Abstract In 2013 we thinned mature ?Royal Gala? apple trees on M.9 rootstock using the precision thinning protocol developed by Robinson. To assess the initial flower bud load we counted the number of flower buds on 5 trees per treatment at the pink bud stage. We then thinned the trees with one of 2 thinning protocols using sequential chemical thinning sprays: 1) Promalin (benzyl adenine + GA 4+7 ) at full bloom (FB) followed by three successive sprays of benzyl adenine (BA)+carbaryl at petal fall, 12 mm fruit size and 18 mm fruit size; 2) BA at FB then three sprays of BA + carbaryl at petal fall, 12 and 18 mm; and 3) untreated control. After each spray we used the fruit growth rate model developed by Greene to predict cumulative thinning efficacy to that point. We implemented this model by tagging 15 representative spurs tree -1 on the 5 test trees of each treatment at full bloom. At petal fall each fruit within each tagged cluster was marked with a dot to identify its position in the cluster. On the third day after each thinner spray and the seventh day after each spray we measured the diameter of each fruit in the 15 clusters on each of the 5 trees. These data were analyzed with the fruit growth rate model to determine the number of fruits still growing on the tree after each spray. The model indicated that BA sprayed at FB reduced the fruit number tree -1 32% compared to the untreated control. Promalin at FB did not reduce fruit number tree -1 . When the successive thinning treatments were completed and fruits were 25 mm diameter we again measured fruit diameters of the tagged spurs and calculated the number of fruits persisting on each tree. Treatment 2 had the lowest fruit number tree -1 (44% of the untreated control) while Treatment 1 had slightly greater fruit number tree -1 than treatment 1 (52% of the untreated control). At harvest the final number of fruits per trees was significantly less than we estimated by using the model when fruits were 22 mm. This overestimation of final fruit set by the fruit growth rate model could be due to later climatic conditions, which induced a ?June drop?.

Early Yield Prediction Using Image Analysis of Apple Fruit and Tree Canopy Features with Neural Networks

(1) Background: Since early yield prediction is relevant for resource requirements of harvesting and marketing in the whole fruit industry, this paper presents a new approach of using image analysis and tree canopy features to predict early yield with artificial neural networks (ANN); (2) Methods: Two back propagation neural network (BPNN) models were developed for the early period after natural fruit drop in June and the ripening period, respectively. Within the same periods, images of apple cv. “Gala” trees were captured from an orchard near Bonn, Germany. Two sample sets were developed to train and test models; each set included 150 samples from the 2009 and 2010 growing season. For each sample (each canopy image), pixels were segmented into fruit, foliage, and background using image segmentation. The four features extracted from the data set for the canopy were: total cross-sectional area of fruits, fruit number, total cross-section area of small fruits, and cross-sectional area of foliage, and were used as inputs. With the actual weighted yield per tree as a target, BPNN was employed to learn their mutual relationship as a prerequisite to develop the prediction; (3) Results: For the developed BPNN model of the early period after June drop, correlation coefficients (R2) between the estimated and the actual weighted yield, mean forecast error (MFE), mean absolute percentage error (MAPE), and root mean square error (RMSE) were 0.81, −0.05, 10.7%, 2.34 kg/tree, respectively. For the model of the ripening period, these measures were 0.83, −0.03, 8.9%, 2.3 kg/tree, respectively. In 2011, the two previously developed models were used to predict apple yield. The RMSE and R2 values between the estimated and harvested apple yield were 2.6 kg/tree and 0.62 for the early period (small, green fruit) and improved near harvest (red, large fruit) to 2.5 kg/tree and 0.75 for a tree with ca. 18 kg yield per tree. For further method verification, the cv. “Pinova” apple trees were used as another variety in 2012 to develop the BPNN prediction model for the early period after June drop. The model was used in 2013, which gave similar results as those found with cv. “Gala”; (4) Conclusion: Overall, the results showed in this research that the proposed estimation models performed accurately using canopy and fruit features using image analysis algorithms.

Spur behavior in Almond trees (Prunus dulcis [Mill.] DAWebb): effects of flowers, fruit, and “June drop” on leaf area, leaf nitrogen, spur survival and return bloom

Effects of flowering, fruiting, and fruit drop on leaf area, leaf nitrogen, probability of spur survival and return bloom were studied in an 11 year-old highly productive almond orchard. Six different spur categories (spurs with no fruit, spurs with flowers removed at full bloom, spurs with fruit removed at 14days after full bloom (DAFB), spurs with fruit removed at 28 DAFB, spurs with one fruit, spurs with two fruits) were labeled on a total of forty-eight trees, variety Nonpareil. Spurs were tracked from winter 2011 to spring 2012. Spur survival and spur return bloom data were collected by visually inspecting each labeled spur in 2012. Results showed that the competition for nitrogen between fruit and leaves at the spur level occurs during the whole season. Fruiting spurs had 50% less leaf area than non-fruiting spurs because they had smaller and less leaves. Spurs whose fruit was removed early in the season reached similar survival probabilities to spurs that had no fruit throughout the season. However, the return bloom probabilities were lower on spurs whose fruit was removed than in non-fruiting spurs. Two fruiting spurs had the lowest chance to either survive or return bloom.

Calyx biochemical changes and possibility of reducing thomson orange June drop by nutrition elements and growth regulators

Summer fruit drop (June drop) is one of the main reasons for low yield in some citrus varieties in northern Iran. Recognition of physiological changes in fruit abscission zone (calyx) and application of suitable treatments would reduce or control abscission. Hence, the changes of auxin, cellulose, and polygalacturonase in calyx of Thomson navel fruitlets were measured and their relations with abscission and mineral nutrition of fruitlets as well as the effect of different treatments on them at June drop were evaluated. A randomized complete block design (RCBD) experiment was performed with 8 treatments and 4 replicates. Treatments were as follows: 1. control; 2. urea (1%); 3. urea + 2,4-D (15 mg l-1); 4.urea + GA3 (15 mg l-1); 5.urea + sucrose (1%); 6.urea + ZnSO4 (0.5%); 7. urea + ZnSO4 + 2,4-D; and 8. urea + ZnSO4 + GA3. Results showed that abscission had a significant negative correlation with auxin and a significant positive correlation with cellulase and polygalacturonase of the calyx. The control group had the lowest auxin and the highest cellulase in calyx. Maximum effect (Approximately 24% reduction in abscission) was obtained after foliar application of urea + sucrose (treatments 5). The use of urea alone or in combination with 2, 4-D and GA3 had no effect on abscission; however, using it in combination with sucrose was the most efficient treatment in this experiment. Furthermore, the combination of urea and Zn provided an effective treatment. A majority of micronutrients (Mg, Fe, Mn, Zn, Cu and B) had a positive correlation with auxin and a negative correlation with enzymes. Therefore, nutritional management and providing an appropriate condition to maximize photosynthesis can balance physiological metabolism and reduce fruitlets abscission.

Effects of different leaf-fruit ratios on uptake and partitioning of N and K in 'Uenishiwase' persimmon trees

To supply appropriate amount of nutrients to persimmon trees with high crop load is critically important for the stable production year after year. This study was conducted to determine absorption and partitioning of nitrogen (N) and potassium (K) in 13-year-old ‘Uenishiwase' persimmon trees with different crop loads. The leaf-fruit (L/F) ratio was adjusted to 20 (high) and 10 (low) by fruit thinning on July 2 after the June drop. The trees were harvested in early spring and late autumn, and increases of dry weight (DW) and N and K in different tree parts during the growing season were calculated. As the L/F ratio decreased from 20 to 10, total fruit DW increased from 4.3 to 7.6kg per tree. Of the total DW increase in a season, fruit accounted for 14% in a high and 24% in a low L/F tree. DW in older than 1-year-old woods accounted for 44% in a high and 41% in a low L/F tree. Different L/F ratios did not significantly affect the increase of tree total DW. Upon decreasing the L/F ratio, the amount of fruit N increased by 1.7-fold where N partitioning to fruit increased from 10% to 17% of the tree total, whereas fruit K increased by 2-fold, increasing its partitioning from 25% to 44%. It was noted that N and K increases were lower in aerial woods of the low L/F trees. Total N per tree increased by about 170g in both the high and low L/F trees, but the total K increases were 175g and 202g in a high and low L/F tree, respectively. The results suggested that a fertilization program for high crop-load trees should take two points into consideration, namely, the magnitude of nutrients removed from the tree by fruit harvest and the reduced nutrients in woody organs essential for tree development the next season.