June Drop Research Articles

Nitrogen Fertilization Strategies for the ‘Hass’ Avocado that Increase Total Yield Without Reducing Fruit Size

Effects of nitrogen (N) fertilizer application times and rates on ‘Hass’ avocado (Persea americana) yield and fruit size were determined to resolve whether a single dose of soil-applied N [1x N (25 lb/acre)] at each of the five key stages of tree phenology (January, April, July, August, and November) (control) was as efficacious as soil-applied 2x N (50 lb/acre) at one or two key stages or soil- or foliar-applied 3x N (75 lb/acre) at only one stage. All trees received soil-applied N at 125 lb/acre as ammonium nitrate (NH4NO3) annually; trees receiving 2x or 3x N received the remaining N divided evenly at the same phenological stages (months) as trees receiving five 1x N applications. The importance of supplying N during the summer, when June drop, exponential fruit growth, vegetative shoot growth, and floral initiation occur, was determined by testing soil-applied 0.8x N in July plus August only (40 lb/acre N as NH4NO3 annually). Application time proved an important determinant of total yield. Yield of commercially valuable size (CVS) fruit was correlated with total yield (r = 0.80, P < 0.0001). Four-year cumulative total yields were equal for trees receiving soil-applied 1x N at five key phenological stages and trees receiving soil-applied 2x N in April and 18.75 lb/acre N at the four other stages (months). However, trees receiving soil-applied 2x N in April plus November and only 8.3 lb/acre N in the three other months, in particular July and August, had significantly lower 4-year cumulative total yields (P = 0.0362). Additional evidence of the importance of meeting avocado tree N demand in the summer is that trees receiving only 40 lb/acre N split in July plus August produced 4-year cumulative total yields equal to trees receiving 25 lb/acre N at the five key phenological stages; lower annual N would reduce fertilizer expense and protect the environment.

Physiological factors affecting flower and fruit abscission of ‘Hass’ avocado

‘Hass’ avocado (Persea americana Mill.) is characterized by distinct periods of excessive flower and fruit drop. Determining the cause(s) of these abscission events is critical for the development of strategies to increase fruit set and yield. Therefore, the objectives of this research were to determine pollination and fertilization rates of abscising flowers and to quantify the viability of developing ovules (seeds) and hormone concentrations of abscising versus persisting fruit through early and June drop of ‘Hass’ avocado. Experiments were conducted during sequential off- and on-crop years. Pollination, pollen germination, pollen tube growth and ovule viability of abscising flowers were determined by microscopic analysis. During early and June drop, cellular deterioration of developing ovules of abscising and persisting fruit was visualized with Evan’s blue stain. Abscisic acid (ABA), indole-3-acetic acid (IAA), and isopentenyladenine (IPA) concentrations were determined by radio-immuno assay (RIA) during the on-crop year only. On average≥70% of abscising ‘Hass’ flowers were pollinated but due to the failure of the pollen grains to germinate and produce pollen tubes, fertilization never occurred and the ovule deteriorated. Fruit abscission during early and June drop was also due primarily to a lack of fertilization. Fruit abscission was associated initially with deterioration of the nucellus within the developing ovule in early drop, and subsequently with deterioration of the integument (seed coat) in June drop; both occurred more frequently in abscising than persisting fruit. Abscising fruit had greater ABA concentrations during early drop, June drop and fall fruit drop compared to persisting fruit; IAA and IPA were greater in abscising fruit during June drop, but not early drop or fall fruit drop. Only 25% of the total number of fruit that abscised per crop year were fertilized. Taken together, these results provide strong evidence that the majority of flowers and fruit of ‘Hass’ avocado abscise due to a lack of pollen germination and subsequent fertilization. In addition, the results suggest that ABA accumulation is related to ovule (seed) abortion and reduced fruit growth in abscising fruit.

Interaction of Crop Load and Irrigation on Yield, Fruit Size, Color and Stem-end Splitting Ratio of Apple c.v. ‘Gala, Galaxy’

In this study, the interaction between crop load and irrigation level on yield, fruit size, skin color and stem-end splitting fruit ratio in the apple cultivar ‘Gala, Galaxy’ grafted on rootstock M9 were investigated. Six irrigation programs were applied during the whole growth season: deficit irrigation (rates of 0.25 kc, 0.50 kc, 0.75 kc), full irrigation (rate of 1.00 kc), excess irrigation (rate of 1.25 kc) and non-irrigation (rates of 0.00 kc of “Class A” pan evaporation coefficient). Four crop loads in each irrigation application were performed by hand thinning after the June drop as a- a low crop load (3 fruits cm−2 TCA), b- a medium crop load (5 fruits cm−2 TCA), c- a heavy crop load (7 fruits cm−2 TCA), and d- an un-thinned crop load (> 7 fruits cm−2 TCA). The total tree yield increased with crop load and irrigation levels. Fruit size was significantly increased by the low crop load. Irrigation increased the fruit size compared to non-irrigation treatment. Further 0.75 kc, 1.00 kc and 1.25 kc irrigation treatments significantly increased the fruit length. Irrigation reduced the fruit flesh firmness. While the low crop load increased the skin red color, it decreased the fruit skin brightness. The yellowness of skin decreased with increasing in the irrigation amount. Irrigation reduced the skin brightness and yellowness, but it increased red color. Crop load and irrigation significantly affected the stem-end splitting fruit ratio. While the splitting fruit ratio increased with a decrease in the crop load, it decreased with an increase in irrigation amount, relatively. Consequently, the low and medium crop load treatments would be beneficial to increase the ratio of marketable fruits without any significant losses in yield for ‘Gala’ apple, especially under 0.75 kc deficit irrigation treatment.

MECHANICAL THINNING OF 'LUCAS' AND 'CONFERENCE' PEAR IMPROVES FRUIT QUALITY

In the absence of any chemicals approved in Europe for flower thinning pears there is a market demand for large particularly ‘Conference’ fruit. The objective of the present study was to improve fruit quality i.e., achieve large fruit sizes. Therefore, 18-year-old ‘Conference’ and ‘Lucas’ pear trees, trained as super spindles, on quince A rootstock with a spacing of 4A—0.4 m were used in Klein-Altendorf near Bonn, Germany; un-thinned adjacent trees served as control. These pear trees with intense flowering were blossom-thinned on 15 April 2009 with rotor speeds of either 300 or 400 rpm both at 5 km h-1 tractor speed. The device with three horizontal rotors and front mounting of the tractor has been developed at the University of Bonn in 2005-2007. By selecting a range of combinations of brushes, rotor speeds (300-450 rpm) and tractor speeds (4-8 km h-1), its vertically operating brushes remove ca. 25-33% of flowers. Due to its use at early developmental stages, i.e., during flowering (between pink bud and petal fall), mechanical thinning on its own can break or prevent alternate/biennial bearing. Mechanical thinning on its own or in combination with either chemical or hand-thinning may improve fruit quality, particularly fruit size (by improving the source sink relationship and enlarging the photo-assimilates partitioned to the remaining fruit, sugar (taste), and sometimes firmness for better storability. June drop was stronger reduced in ‘A. Lucas’ (by -38%) than in ‘Conference’ (by -27% relative to the control). Mechanical blossom thinning reduced the June drop with increasing rotor speed. In ‘A. Lucas’, the natural June drop was as strong as mechanical thinning and resulted in large-sized 80-mm pear fruit in the control; mechanical thinning with 400 rpm further increased fruit mass by 16 g relative to the un-thinned control or 6 g larger than in the thinning with 300 rpm. In ‘Conference’, fruit fell within the next larger fruit size class after the stronger mechanical thinning with 400 rpm at 5 km h-1: the portion of pear fruit in the 75/80 mm size class was 2-fold and in the 80/85 mm size class was 6-fold that in the control. The portion of small fruit such as <60, 60/65 and 65/70 mm was halved relative to the control; the average fruit mass was increased by 40 g without affecting vegetative growth. The risk of both over-sized fruit and over-thinning appeared small, since mechanical thinning reduced the natural June drop without inducing a subsequent fruit drop after thinning. Mechanical thinning was more efficient in ‘Conference’, as intended, despite more intense flowering in ‘A. Lucas’. Overall, the results indicate the potential of mechanical thinning as a substitute or combination partner for chemical fruit thinning if approved such as BA in pear. The device saves labour costs, otherwise required for hand-thinning, in the order of 30-60 h ha-1, equivalent to € 150-300 ha-1, i.e., almost twice as much as the cost of mechanical thinning of ca. 120 € ha-1, based on 20 ha and 10 years depreciation.

Mechanical blossom thinning of apples and influence on yield, fruit quality and spur leaf area

McClure, K. A. and Cline, J. A. 2015. Mechanical blossom thinning of apples and influence on yield, fruit quality and spur leaf area. Can. J. Plant Sci. 95: 887–896. Apple (Malus×domestica Borkh.) trees tend to crop heavily, which often makes crop load adjustment necessary. This can now be achieved as early as bloom by mechanical removal/thinning of blossoms. High-density Empire/M.26 and Royal Gala/M.26 apple trees were mechanically (MBT) and hand blossom thinned (HBT) in 2010 and 2011, respectively, and their effects on fruit set, subsequent hand thinning, final crop load, and spur leaf area were measured. In both years, MBT effectively thinned trees and reduced fruit set, but did not reduce the requirement for follow-up hand fruitlet thinning after June drop in 2011. In 2010, harvest yields for MBT treatments decreased, while weight and diameter increased. In 2011, most harvest and fruit quality parameters were unaffected by thinning. Trees that were mechanically thinned had significantly reduced spur leaf area, but were similar to unthinned control trees with respect to many of the yield and quality parameters measured. Mechanical blossom thinning is a new crop load management option for apple growers looking to supplement more traditional chemical and hand thinning techniques.

Effect of Spraying Salicylic Acid on Fruiting of Valencia Orange Trees

Growth characters, tree nutritional status, fruit set %, June drop %, yield and fruit quality of Valencia orange trees inresponse to spraying salicylic acid at 0.0 to 400 ppm either applied once at growth start or twice at growth start and againjust after fruit setting were investigated during 2012 /2013 and 2013/ 2014 seasons.Spraying salicylic acid at 100 to 400 ppm once or twice considerably improved all growth characters , leaf pigments,N, P, K, Mg and Ca percentages, initial fruit set %, fruit retention %, yield and fruit quality over the check treatment. Allsalicylic acid treatments effectively reduced June drop. Using salicylic acid at 400 ppm once or twice caused a significantreduction on all the aforementioned parameters comparing with using salicylic acid at 100 to 200 ppm. Two sprays ofsalicylic acid were preferable than using it once in this connection.Treating Valencia orange trees twice at growth start and just after fruit set with salicylic acid at 200 ppm wasresponsible for promoting yield and fruit quality.

USE OF METAMITRON ALONE AND IN COMBINATION WITH 6-BENZYLADENINE FOR THINNING APPLES

Several experiments were conducted over a 3-year period to evaluate meta-mitron as a potential apple thinner. A block of 7-year-old 'CandyCrisp'/M.9 apples trees was selected in 2010. Metamitron rates between 50 and 400 mg/L were applied at the 15 mm fruit size stage. All rates of metamitron thinned excessively but this response was attributed in large part to very warm temperatures following applica-tion. Similar trees were used in 2011 but treatments were applied later at the 20 mm fruit size stage. At the end of June drop, crop load was reduced by nearly 50% which was a level considered to be nearly ideal for these trees. Metamitron had few fruit effects at harvest that could not be attributed to thinner-induced reduction in crop load. In a block of mature 'Pioneer McIntosh'/M.9 apple trees metamitron was applied at rates of 150 to 300 mg/L alone and in combination with 6-benzyladenine (BA) in two separate years but using different trees each year. Excessive thinning occurred when 300 mg/L metamitron was applied alone or in combination with BA. When 150 mg/L was applied less thinning occurred and the resulting crop load was reduced to a commercially acceptable level. Metamitron had minimal influence on fruit maturity parameters. It is concluded that metamitron may be a useful thinner on apples. Especially interesting is the observation that it was effective at thinning larger-sized fruit, a characteristic that is extremely rare for a mainstream apple thinner.

Thinning Tall Spindle Apple Based on Estimations Made With a Hand-thinning Gauge

Trials were conducted in 2009 and 2010 to evaluate the use of a hand-thinning gauge [Equilifruit; Institut National de la Recherche Agronomique (INRA), Montpelier, France] on three cultivars of apple (Malus ×domestica) trees trained to tall spindle. Hand-thinning treatments were applied after June drop to trees with supra-optimal crop loads. Three hand-thinning treatments were applied using the hand-thinning gauge: 1) thinning to ≈6 fruit/cm2 branch cross-sectional area (BCSA) (F value), 2) subtracting the delta value [Δ (an adjustment factor to increase or decrease the number of fruit per BCSA] from the F value (F − Δ), and 3) F − 2Δ. These treatments were compared with a control and a traditional hand-thinning heuristic of spacing a solitary fruit every 7 to 8 inches of branch length. Use of the hand-thinning gauge generally improved fruit weight and maintained whole tree yields when compared with the control. Hand-thinning based upon traditional fruit-spacing heuristics reduced crop density and increased final fruit weight of apple, but significant reductions in yield were observed in two of four studies when compared with the control. We find the hand-thinning gauge a useful tool in adjusting final crop load of apple.

Influence of M9 Rootstock on the Reproductive Behaviour of Apple Cultivars under Dry, Semi-arid Growing Conditions

In the last decade, apple has been intensively cultivated in the western coast of Albania. The scope of this research was to study the influence of M9 rootstock on the reproductive behaviour of apple cultivars ‘M. Gala’, ‘Golden Delicious’, ‘Starking’, ‘Fuji’ and ‘Pink Lady’. The trial was conducted from 2010 – 2011 in 5-year old orchards with 2,250 trees/ha grown as French axe and in full production located in Lushnja. The following indicators were measured: diameter of two main branches, number of fruits/branch, fruit growth dynamic and sugar content (%). Global radiation, temperature and humidity were recorded. The reproduction behaviour has also been measured by fruiting spurs in the general structure of the canopy as well as the number of fruits formed for each cultivar. The results have shown that in terms of fruit set, cultivars are ranked as follows: ‘M. Gala’ with the highest number of fruits, then ‘Golden Delicious’, ‘Fuji’, ‘Pink Lady’ and ‘Starking’, respectively. The dynamic of fruit dropping shows that ‘Starking’, having the lowest fruit set, after the June drop is more stable while ‘M. Gala’, with the highest fruit set, besides an abundant June drop, had another drop in July. This is due to higher competition among the fruits and failure of the rootstock to supply the adequate quantities of sap. In terms of fruit growth dynamic, it was observed that intensive growth was measured for all the cultivars during the end of July after which fruit growth slowed down. Changes between cultivars were observed in relation to the maturation period of each cultivar, with ‘M. Gala’ maturing in August, ‘Fuji’ and ‘Pink Lady’ in October and November. ‘Starking and ‘Golden Delicious’ cultivars had a more rapid maturation (20 September), accompanied with a higher sugar content which is far more related to climatic factor rather than M9 rootstock. In conclusion, it was found that the cultivars under study have different reproductive behaviour with M9 rootstock. It can also be stated that ‘Starking’ is not appropriate for this coastal region due to inadequate fruiting behaviour.

EFFECT OF FOLIAR SPRAY WITH GIBBERELLIC ACID AND AMCOTONE ON FRUIT SET, DROPPING, COMPONENT YIELD AND FRUIT QUALITY OF WASHINGTON NAVEL ORANGE TREES

The present study was carried out during 2007 and 2008 on 15 years old Washington navel orange trees (C. sinensis Osbeck) grafted on sour orange (C. aurantium L.) rootstocks. Trees were grown under north delta conditions. The results could be summarized in the following points: 1) The trees which sprayed with 100 g amcotone /100 L+ 20 ppm (GA3) gave the highest initial and final fruit set % and the lowest (June drop% and preharvest drop%) followed by the trees which sprayed with 50 g amcotone /100 L+ 20 ppm (GA3) which obtained the second order in this regard in both studied seasons. Also, there are no significant effects on number sprayed doses in this respect. 2) The trees which sprayed with 100 g amcotone /100 L+ 20 ppm (GA3) gave the highest {fruits number and yield (kg) /tree} followed by the trees which sprayed with 50 g amcotone /100 L+ 20 ppm (GA3) which possessed the second order in this regard in both seasons. Also, the trees which sprayed with three doses (mid-March, late April and the beginning of August) obtained the highest {fruits number and yield (kg) /tree}. 3) Fruit shape (H/D ratio) was the highest in trees which sprayed with100 g amcotone /100 L+ 20 ppm (GA3) followed by trees which sprayed with 100 g amcotone /100 L+ 15 ppm (GA3) with insignificant effect of three treatments. Whereas, non- significant effects of the number of doses . 4) Physical properties of fruits under this study as { fruit weight (g), fruit size (cm3) and fruit juice weight (g) } the highest values obtained in trees which sprayed with100 g amcotone /100 L+ 20 ppm (GA3) followed by 50 g amcotone /100 L+ 20 ppm (GA3).Moreover, trees which sprayed with three doses (mid-March, late April and the beginning of August) gave the highest values in this respect. 5) Regarding to the chemical properties of fruits which studied as ( T.S.S. %, total acidity % and Vitamin C mg/100 ml juice) the treatments which sprayed with100 g amcotone/100 L+ 20 ppm (GA3) gave the highest values followed by the trees which sprayed with 50 g amcotone /100 L+ 20 ppm (GA3) . Also, the trees which sprayed with three doses (mid-March, late April and the beginning of August) gave the highest values in this respect . 6) Trees which sprayed with Amcotone/100L+20 ppm GA3 treatment gave the highest values of T.S.S. /acid ratio with insignificant effect when compared with other treatments under this study. Moreover, trees which sprayed with three doses (mid-March, late April and the beginning of August) gave the highest T.S.S. / acid ratio. The recommendations: It could be recommended that spraying “Washington” navel orange trees with100 g amcotone /100 L+ 20 ppm (GA3) three times at (mid-March, late April and the beginning of August) gave the highest values of initial and final fruit set %, decrease of June and preharvest drop %, increase of yield as fruit number and weight (kg) /tree, improvement fruit physical and chemical properties as {fruit weight (g) and size (cm3) and fruit juice weight (g),TSS% , total acidity % ,Vitamin C. and TSS/Acid ratio }.

Development of a Fruitlet Growth Model to Predict Thinner Response on Apples

Previous reports have provided evidence that measuring fruit growth rate may be a viable method to predict if a fruit will abscise or persist through the June drop period. A series of experiments were carried out over several years to develop a procedure that could be used to predict the response to a chemical thinner application within 7 to 8 days after application and before thinners exhibit their final effect. The procedure developed involves tagging 105 spurs on seven individual trees distributed appropriately in the orchard. A minimum of two measurements must be made, one 3 to 4 days after application and again 7 to 8 days after application. This model requires that fruit measurement should not start before fruit grow to a diameter of 6 mm and individual fruit within a spur should be numbered and identified. The model is based on the assumption that if fruit growth rate of a particular fruit over the measurement period is less than 50% of the growth rate of the fastest growing fruit on the tree during the same growth period, it will abscise, whereas if fruit growth rate exceeds 50% of the growth rate of the fastest growing fruit, it will persist. All data can be entered into an Excel spreadsheet and the output in the summary page gives the predicted fruit set expressed as percentage of the total number of fruit present. The strategy for crop load adjustment with chemical thinners has evolved over the years to a point where most orchardists plan and are prepared to make two or more thinner applications. The dilemma associated with this approach is to determine if additional thinner applications are necessary. Up to this point a tool designed specifically to provide this information has not been developed.

RESULTS OF POLLINATION STUDIES OF SOME NEW PLUM CULTIVARS IN LATVIA

One of the most important factors for the success of plum pollination and fertilization is the availability of a suitable pollinator. The aim of this study was to find the best pollinators in field conditions for new plum cultivars 'Adelyn', 'Lotte' and 'Sonora', which were submitted for registration in Latvia in 2010. Cultivars 'Experimentalfaltets Sviskon’, 'Jubileum', 'Julius', 'Minjona' and 'Victoria' were tested as pollinators in 2008-2010. Significant differences were found among cultivars and pollination combinations. The results were significantly different between years. The best pollination results for 'Adelyn' were with pollinator 'Victoria' (average fruit set after june drop - 66.5%). ‘Lotte’ showed the best results with ‘Minjona’ as pollinator (46.6%). 'Sonora' showed the best results of fruit set with ‘Experimentalfaltets Sviskon’ as pollinator (53.9%). The least suitable pollinator in all crosses was 'Julius'. An open pollination experiment was also established. Average fruit set after June drop for 'Adelyn' was 49.5%, for 'Lotte' 37.7%, and for 'Sonora' 53.3%. Only 'Sonora' showed self-fertility (33.5%) in the self-pollination experiment. Significantly higher results of pollination for all the cultivars (70.8% average fruit set) were obtained in 2008 while the results did not differ significantly in 2009 and in 2010.

Changes in anatomical structure of apple fruitlet pedicels preceding June drop

The anatomical structure of pedicels of apple fruitlets was investigated. The fruitlets of cv. 'Mcintosh' and 'Bancroft' were collected on June 8th, 16th an 24th. The middle date coincided with the beginning of June drop. The pedicel structure of larger fruitlets which tended to be retained on the tree was compared with that of smaller fruitlets which tended to be shed of. In the pedicels of larger fruitlets, development of the xylem, especially secondary one, was more intensive. This difference increased in time. Lignification of cortex sclereids, phloem fibers, xylem parenchyma cells and pith cells was also more advanced. The differences in the amount of phloem tissue between both kinds of fruitlets were not large but usually significant. The mentioned differences especially in pedicel xylem development are considered to be partly responsible for the fact that smaller fruitlets loose gradually their ability to compete for nutrients. This finally leads to their starvation and shedding.

Using colour features of cv. ‘Gala’ apple fruits in an orchard in image processing to predict yield

New apple fruit recognition algorithms based on colour features are presented to estimate the number of fruits and develop models for early prediction of apple yield, in a multi-disciplinary approach linking computer science with agricultural engineering and horticulture as part of precision agriculture. Fifty cv. ‘Gala’ apple digital images were captured twice, i.e. after June drop and during ripening, on the preferred western side of the tree row with a variability of between 70 and 170 fruit per tree, under natural daylight conditions at Bonn, Germany. Several image processing algorithms and fruit counting algorithms were used to analyse the apple images. Finally, an apple recognition algorithm with colour difference R − B (red minus blue) and G − R (green minus red) was developed for apple images after June drop, and two different colour models were used to segment ripening period apple images. The algorithm was tested on 50 images of trees in each period. Close correlation coefficients R2 of 0.80 and 0.85 were obtained for two developmental periods between apples detected by the fruit counting algorithm and those manually counted. Two sets of data in each period were used for modelling yield prediction of the apple fruits. In the calibration data set, the R2 values between apples detected by the fruit counting algorithm and actual harvested yield were from 0.57 for young fruit after June drop to 0.70 in the fruit ripening period. In the validation data set, the R2 value between the number of apples predicted by the model and actual yield at harvest ranged from 0.58 to 0.71. The proposed model showed great potential for early prediction of yield for individual trees of apple and possibly other fruit crops.

Effects of 2,4-DP (2,4-dichlorophenoxypropionic acid) plant growth regulator on fruit size and yield of Valencia oranges (Citrus sinensis Osb.)

The Valencia orange is a high-quality fruit grown in Turkey; however, small fruit sizes and high fruit discard percentages are common in Valencia oranges. Small fruit size is the main factor limiting the marketing of Valencia oranges; thus, synthetic auxins are commonly used to enhance the size of citrus fruit. The objective of the present study was to observe the effects of 2,4-dichlorophenoxypropionic acid (2,4-DP) on the fruit size, yield and quality of Valencia oranges from 29-year-old trees budded on sour orange rootstock in Adana, Turkey during 2005–06. Three concentrations (50, 100 and 150 ppm) of 2,4-DP were applied during the June drop, when the mean fruit diameter was 13–15 mm. The results indicated that the application of 2,4-DP increased the fruit size of Valencia oranges without reducing yield. The application had a significant effect on fruit yield. Compared with the control trees, applications of 2,4-DP increased the number of large, commercially valuable Valencia oranges (75–80 mm). Moreover, an increase in the concentration of 2,4-DP increased the yield and weight of the fruits. As a result, fruit retention was highest in trees sprayed with 150 ppm 2,4-DP. Except for the titratable acid content (TA), which increased with an increase in the 2,4-DP concentration, the internal characteristics of the fruit were not affected by treatment with 2,4-DP. Thus, the results of the present study revealed that 2,4-DP can be used to improve the fruit size of Valencia fruitlets during the June drop.

REDUCTION IN JUNE DROP, A WAY TO REDUCE LOSSES OF SATSUMA MANDARIN (CITRUS UNSHIU)

Citrus is one of the most important horticultural crops in Iran with area and annual production placing Iran as the 10th country in world citrus production. In spite of suitable climate, high crop losses, before and after harvest, cause reduction citrus average yield in Iran. Abscission of flower, fruitlet and fruit, is one reason of these problem. To evaluate the possibility of reducing June drop in Satsuma mandarin, an experiment was conducted in randomized complete block design with 8 treatments include: 1. control; 2. urea (1%); 3. urea + 2,4-D (15 mg/L); 4. urea +GA3 (15 mg/L); 5. urea + sucrose (1%); 6. urea + zinc sulfate (0.5%); 7. urea + zinc sulfate + 2,4-D and 8. urea + zinc sulfate + GA3 and 4 replications. Treatments were applied before starting June drop in 20 May 2006. After spraying until the end of June drop, number of abscised fruitlets was counted. Then percent of fruitlet abscission was determined in each treatment. Results showed that treatments 3, 5 and 8, reduced abscission significantly compare to the control. Treatment 8 reduced abscission and increased yield about 58 and 57% respectively. Also abscission and yield in treatment 8 were significantly better compared to all other treatments. However, average fruit weight and diameter in this treatment showed a significant reduction compare to the control. Treatments 3 and 5 had about 19.5% abscission reduction, 17 and 13% yield improvement, respectively, and didn’t have any significant difference in fruit weight and diameter compared to the control and therefore were the two efficient treatments in this experiment.

Phenolic compounds profile, carbohydrates and external fruit quality of the ‘Concorde’ pear (Pyrus communisL.) after bagging

Hudina, M., Stampar, F., Orazem, P., Mikulic Petkovsek, M. and Veberic, R. 2012. Phenolic compounds profile, carbohydrates and external fruit quality of the 'Concorde' pear ( Pyrus communis L.) after bagging. Can. J. Plant Sci. 92: 67–75. The practice of pre-harvest bagging has been extensively used in several fruit crops to improve the commercial value of the fruit. The purpose of this study was to investigate the effect of fruit bagging on internal and external quality of the European pear (Pyrus communis L.) cv. ‘Concorde’. Fruit quality was determined by chemical analyses (individual sugars, organic acids and phenolic compounds) and physical characteristics in 2005 and 2006. Bagging of pear fruit after June drop until harvest significantly reduced fruit length in both observed years. Fruit bagging resulted in increased firmness of the fruit only in 2006. Soluble solids content was significantly lower in bagged fruit in 2006. In 2005, bagging had no influence on firmness and soluble solids content. Bagging improved fruit surface lightness, since L* was higher in the bagged than in the control fruit in both years. Also the a* parameter was higher in bagged fruit. We noted significant influence of bagging on total sugars content. Bagging European pear fruit decreased the content of phenolic compounds in skin (catechin, chlorogenic acid, epicatechin, p-coumaric acid, quercetin 3-O-galactoside, quercetin 3-O-glucoside, quercetin 3-O-rhamnoside). The removal of bags 7 d before harvest significantly increased glucose, shikimic and fumaric acids.

Phenolic compounds profile, carbohydrates and external fruit quality of the ‘Concorde’ pear (Pyrus communis L.) after bagging

Hudina, M., Stampar, F., Orazem, P., Mikulic Petkovsek, M. and Veberic, R. 2012. Phenolic compounds profile, carbohydrates and external fruit quality of the 'Concorde' pear (Pyrus communisL.) after bagging. Can. J. Plant Sci. 92: 67-75. The practice of pre-harvest bagging has been extensively used in several fruit crops to improve the commercial value of the fruit. The purpose of this study was to investigate the effect of fruit bagging on internal and external quality of the European pear (Pyrus communis L.) cv. ‘Concorde’. Fruit quality was determined by chemical analyses (individual sugars, organic acids and phenolic compounds) and physical characteristics in 2005 and 2006. Bagging of pear fruit after June drop until harvest significantly reduced fruit length in both observed years. Fruit bagging resulted in increased firmness of the fruit only in 2006. Soluble solids content was significantly lower in bagged fruit in 2006. In 2005, bagging had no influence on firmness and soluble solids content. Baggi...

MANAGING OPEN FIELD PRODUCTION OF PERENNIAL HORTICULTURAL CROPS WITH TECHNOLOGICAL INNOVATIONS

Technological innovations appear under-utilised in many fruit tree crops, whereas viticulture, citriculture and vegetable crops have largely automated planting, pruning, thinning and harvesting and integrated GPS and/or GIS in their cultivation practises. As a consequence of the trend from pedestrian to tall orchards, innovation and technology is required to overcome shading, particularly in the lower part of the tree canopy. Types, properties and prices are presented of reflective ground covers (textile, aluminium and paper) as well as organic alternatives (lime, straw) as well as titanium dioxide and bio-degradable white line marker paint with additives. To combat sunburn, kaolin, carnauba-wax and other products are available, which can be combined with evaporative cooling. Mechanisation includes new machinery for mechanical thinning, pruning and harvesting to save labour. An autonomous prime mover (APM) is being developed for camera systems for assessment of flowering intensity, alternate bearing, fruit set, June drop, leaf nutrient status, pest and disease control and yield estimation/prediction. The two approaches for better light utilisation in row systems include reducing the spacing of every row from the current 14 feet (4.3 m) to 10-12 feet (3.0 to 2.6 m) or maintaining the spacing of a centre row at 14 feet (4.3 m) or ease of access, but narrower row spacing either side to less than 10 feet (3.0 m) The OTR (over the tree rows) developed by Washington State University and two commercial European multi-row sprayers are presented and new harvesting techniques with pre-sorting in the orchard.

Influence of Aminoethoxyvinylglycine (AVG) on Yield and Quality of Nut Crops from a Commercial Pecan Orchard

Excessive fruit drop (i.e., June drop) can limit orchard profitability of certain pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars. The present study examines efficacy of aminoethoxyvinylglycine (AVG; formulated as ReTain®; Valent BioSciences, Libertyville, IL), a natural ethylene inhibitor, for increasing nutmeat yield in a commercial ‘Desirable’ pecan orchard over a 2-year period. The 30-ha experiment consisted of two treatments (nontreated versus ReTain) in the first year, an “off” year in the orchard's alternate bearing cycle. The second year's study, an “on” year, consisted of four treatments (i.e., “08 nontreated + 09 nontreated,” “08ReTain + 09 nontreated,” “08 nontreated + 09 ReTain,” and “08ReTain + 09 ReTain”). AVG, as ReTain [132 mg·L−1 a.i. (11.7 oz/acre)], was applied as two post-pollination canopy sprays (937 L·ha−1) 2 weeks apart in both years. During the “off” year, ReTain increased nut yield parameters with ReTain increasing kernel yield by 36% (704 kg·ha−1 versus 516 kg·ha−1) over that of nontreated trees. In the subsequent “on” crop year, the trees exhibiting a ReTain-associated previous year yield increase of ≈36% exhibited a reduction in yield of ≈25%, thus largely negating the previous season's yield increase over a 2-year alternate bearing cycle. Additionally, ReTain-treated trees during the “on” year failed to exhibit an increase in yield parameters over that of the nontreated control. As a result of a lag effect on subsequent year yield parameters, ReTain offers potential as a crop-load management tool for ‘Desirable’ orchards in “off” years such as a year of relatively high nutmeat price followed by a year of relatively low price. There appears to be no positive effect on yield when used in a heavy crop-load “on” year of an alternate bearing cycle. Thus, ReTain might have benefit for stabilizing alternate bearing in ‘Desirable’ pecan orchards. Kernel quality (defined as percentage of nut weight as kernel) of individual nuts from “on” year trees was not as sensitive to units of yield increase as for individual nuts of “off” year trees, thus implying that the rate of assimilate partitioning to individual reproductive structures in “off”-year trees is not as great as that in “on”-year trees.