Initial Fruit Set Research Articles

Correlative relation of yield and fruit quality with some phenological phases in peach

Ripening time of peach cultivars that are grown up in our country is extended over a time period of almost four months. In addition to that, one of more important objectives of the peach breeding is creation of the cultivars having either very early or very late ripening time. Our so far experience is that the peach cultivars which ripening time is in the extremes is of lower fruit quality. The aim of this study, therefore, was to determine relationship and the nature of the dependence between flowering time or ripening time from one side and yield, yield components (initial and final fruit set, fruit weight and stone weight) and chemical composition of fruit (content of total dry matter, content of soluble solids, content of total, invert and reduced sugar and content of total acid) on the other side. Twenty peach cultivars each having a different ripening time were using as material. The relationship between characteristics was determined on the basis of values of genetic and phenotypic correlation coefficients. Genetic and phenotypic coefficients of correlation were calculated based on the results of monofactorial analysis of covariance where the years considered as replications. It was confirmed that flowering time was positive genetic and phenotypic correlated with initial fruit set and with final fruit set. The existence of significant genetic and phenotypic correlation between ripening time and fruit weight, between ripening time and dry matter content and between ripening time and soluble solid content represented difficulty in creation of new peach cultivars of early ripening time and improved fruit quality .

EcoLyst Application Timing and Juice Corrected Soluble Solids (Brix) of Processing Oranges and Grapefruit in Florida

EcoLyst, a formulation of N-N-diethyl-2-(4-methylbenzyloxy) ethylamine hydrochloride containing 1 g/floz [4.5 oz/gal (33.8 g·L-1)] a.i., is a plant growth regulator that has been reported to increase soluble solids concentration (SSC) in juice oranges by 0.6% to 1.2%. Our objectives were to determine the effectiveness of EcoLyst application for increasing SSC in Florida oranges (Citrus sinensis) and grapefruit (C. paradisi), and to identify the optimum rate and time of application. Experiments were conducted for three seasons using `Hamlin,' `Pineapple,' and `Valencia' sweet oranges; and for two seasons using `Flame,' `Marsh,' and `Ray Ruby' grapefruit, all in commercial groves. EcoLyst was applied at 6 and 12 floz/acre (0.44 and 0.88 L·ha-1) for oranges and 16 and 32 ppm (mg·L-1) [effectively 9 and 18 floz/acre (0.66 and 1.32 L·ha-1) in most sprays] for grapefruit, and included Silwet L-77 adjuvant at 0.05%. Applications were made at several stages of development from prebloom to initial fruit set. In all cases, SSC was determined as juice corrected SSC, by adjusting refractometer readings based on titratable acidity. In 13 trials with sweet orange only five displayed significant increases in SSC (P ≤ 0.05) resulting from EcoLyst application. Two additional trials produced SSC increases significant at P < 0.10. Even where significant increases in SSC occurred they were typically observed in only one harvest and at one time of application and were always relatively low in magnitude (highest increase over controls was 0.38%). No rate or timing of EcoLyst application was consistently associated with best response, although eight of nine SSC increases observed in orange occurred with applications ranging from prebloom to 25% open flowers. Only one significant increase in SSC was observed in five trials with grapefruit. In these studies, increases in SSC resulting from EcoLyst application were neither sufficiently consistent nor large enough to justify a recommendation for commercial use in Florida citrus.

COMPARISON OF SPRING FROST TOLERANCE AMONG DIFFERENT HIGHBUSH BLUEBERRY (VACCINIUM CORYMBOSUM L.) CULTIVARS

ISHS XXVI International Horticultural Congress: Berry Crop Breeding, Production and Utilization for a New Century COMPARISON OF SPRING FROST TOLERANCE AMONG DIFFERENT HIGHBUSH BLUEBERRY (VACCINIUM CORYMBOSUM L.) CULTIVARS

Loquat fruit sink strength and growth pattern

Loquat fruit growth measured by increases of equatorial diameter adjusts to a logistic curve. By means of sequential measurements of tagged fruits of cultivar ‘Algerie’, curves were obtained that fit significantly to a single sigmoid model in unthinned as well as in heavily thinned trees. Equations defining growth pattern of fruits from thinned and from unthinned trees showed different slopes that reflect greater growth rates under thinning. On the contrary, small and large fruits within the same tree showed minor variations in growth rates, and fruit size at harvest was largely due to fruit size at initial fruit set. Differences in size among fruitlets of the same tree at the time of hand fruit thinning never reversed and led to different commercial categories related with initial size; that allows us to recommend fruit thinning on a size basis. A strong significant correlation was also found at harvest between fresh fruit weight and equatorial diameter. Size and number of seeds were the major determinants of final fruit size in loquat whereas number of leaves and leaf area index of the bearing shoots showed a weak correlation with final size of fruits.

Weed seed production and seedling emergence responses to late-season glyphosate applications

Seed production and seedling emergence of three broadleaf weed species were evaluated following glyphosate application at initial seed set, mid seed fill, and physiological maturity. In greenhouse experiments averaged across glyphosate rates of 0.42, 0.63, and 0.84 kg ae ha−1, Xanthium strumarium 100-bur weight and burs per plant were reduced at least 69 and 70%, respectively, for application at initial fruit set compared with later applications, and seedling emergence was 3% of the nontreated check. Glyphosate application at initial seed set reduced Sesbania exaltata 100-seed weight 73%, seed per plant 86%, and seedling emergence 94%. Senna obtusifolia 100-seed weight, seed per plant, and seedling emergence were reduced 46, 83, and 66%, respectively, when glyphosate was applied at initial seed set. In field experiments, X. strumarium and S. exaltata seed production were reduced only when glyphosate was applied at initial seed set. Compared with the nontreated check, seedling emergence following initial seed set application was reduced 82% for X. strumarium and 94% for S. exaltata. S. obtusifolia response in the field was inconsistent with no reductions in seed per plant or seedling emergence observed the first year. The second year, initial seed set application reduced seed per plant 88% and seedling emergence 72%.

Relationship of Flowering Intensity and Cropping in Fruit Species

The relationship between intensity of flowering and various aspects of cropping are reviewed for fruit species. Relatively light flowering can limit yield in most fruit species. This commonly occurs in young trees that have not achieved full production and in “off” years for varieties that display alternate bearing. When trees mature, many species will carry fruit numbers that exceed commercially desired levels, resulting in excessively small fruit and accentuating alternate bearing. The economic disadvantages of excess cropload have resulted in considerable research on fruit thinning and widespread commercial application of this practice. Heavy flowering intensity in some crop species results in economic disadvantages beyond the problems of excessive cropload and resultant small fruit size. Many species flower profusely and have initial fruit set that greatly exceeds tree capacity, resulting in abscission of numerous flowers and fruitlets. Abscised organs can represent a substantial amount of carbohydrates and nutrients, compromising availability of these materials at critical periods in flower and fruit development. The potential implications of this process are best exemplified in `Navel' orange [Citrus sinensis (L.) Osbeck], where an increase in flowering beyond intermediate intensity results in a reduction in both initial fruit set and final fruit yield at harvest. In several species, there is evidence that fruit size may be reduced by excessive flowering, even when cropload is quickly adjusted to an acceptable level. These data suggest that further research on the advantages of controlling flowering intensity is warranted.

657 Relationship between Intensity of Flowering and Cropping in Fruit and Nuts

The relationship between intensity of flowering and various aspects of cropping will be reviewed for fruit and nuts. Clearly, relatively light flowering can limit yield in most fruit and nut species. This commonly occurs before mature bearing commences and in “off” years for varieties that display alternate bearing. During mature bearing, many species will carry fruit numbers that exceed commercially desired levels, resulting in excessively small fruit and accentuating alternate bearing. The economic disadvantages of excess cropload have resulted in considerable research on fruit thinning and widespread commercial application of this practice. Heavy flowering intensity in some crop species results in economic disadvantages beyond the problems of excessive cropload and resultant small fruit size. Many species flower profusely and have initial fruit set far in excess of final tree capacity, resulting in abscission of numerous flowers and fruitlets. Abscised organs can represent a substantial investment in carbohydrates and nutrients, compromising availability at critical periods in flower and fruit development. The potential implications of this process are best exemplified in navel orange, where an increase in flowering beyond intermediate intensity results in a reduction in both initial fruit set and final fruit yield at harvest. In several crops, there is evidence that fruit size may be reduced by excessive flowering, even when cropload is quickly adjusted to an acceptable level. These data suggest that further research on the advantages of controlling flowering intensity is warranted.

Carbohydrate metabolism during early fruit development of sweet melon (Cucumis melo)

In sink tissues of cucurbits, including sweet melon fruits, the galactosyl‐sucrose oligosaccharides, stachyose and raffinose, together with sucrose, are the major translocated carbohydrates. In the present study we investigated the carbohydrate metabolism of young melon (Cucumis melo L. cv. C‐8) fruit during the period of initial fruit set and development, from 3 days prior to anthesis until 20 days after anthesis (DAA), prior to the onset of sucrose accumulation. The enzymes assayed could be classified into two categories according to developmental patterns. Two of the enzymes, alkaline α‐galactosidase I [EC 3.2.1.22], which hydrolyzes both raffinose and stachyose, and acid invertase [EC 3.2.1.26] either increased or remained stable during the first 10 DAA. The remaining measured enzymes (the stachyose‐specific alkaline α‐galactosidase form II, acid α‐galactosidase, alkaline invertase, sucrose synthase [EC 2.4.1.13], galactokinase [EC 2.7.1.6], UDP‐Gal PPase [EC 2.7.7.10], UDP‐Glc‐4 epimerase [EC 5.1.3.2], UDP‐Glc PPase [EC 2.7.7.9], phosphoglucomutase [EC 5.4.2.2] and phosphoglucoisomerase [EC 5.3.1.9]) all showed a similar developmental pattern of steady decrease in activity following anthesis. We also compared the saccharide metabolism of pollinated and non‐pollinated ovaries during the initial days following anthesis. In the absence of pollination, ovary growth dramatically decreased by the first DAA and was accompanied by a sharp decrease in the activity of UDP‐Glc PPase. Other enzymes in the pathway, including the enzymes of stachyose and raffinose hydrolysis, did not decrease in activity until 2 or 4 DAA, after ovary growth was affected. These results provide information to assess the possible regulating enzymes in cucurbit ovary development and fruit set.

Rate and Time of Boron Application Increase Almond Productivity and Tissue Boron Concentration

Previous studies with tree species have demonstrated that foliar boron (B) promotes flowering, fruit set, and yield. However, for most species the optimum time for foliar B application has not been determined. This investigation was undertaken to study the effects of time and rate of B application on almond [Prunus dulcis (Mill D.A. Webb)] tissue B concentration, fruit set, and yield. Solubor (Na2B8O13.4H2O), a commercial product containing 20.5% B, was applied with a handgun sprayer either in September (3 weeks postharvest), December (dormancy), or February (budbreak) at rates of 0, 0.8, and 1.7 kg·ha-1 B to almond cv. Butte at one site (Parlier, Fresno County, Calif.), and of 0, 0.8, 1.25, 1.7, and 2.1 kg·ha-1 B on the same cultivar in August, September, or February at a second site (Orland, Glenn County, Calif.) using Borosol, a polyboronated commercial product containing 10% B. At site 1, September application was more effective in increasing tissue B concentration, fruit set, and yield than were December or February applications. The optimal rate was 0.8 to 1.7 kg·ha-1 B when applied in September. At site 2, application in 1996 and 1997 increased tissue B concentration almost linearly, especially when applied in August and February. Application at the highest rate (2.1 kg·ha-1 B) in September produced the greatest final fruit set and yield in 1996. February applications increased initial fruit set at both sites but were less effective than September applications in increasing yield. Application of B did not affect any yield variable in 1997. These results suggest that B should be applied immediately postharvest (September) for optimal effect on tissue B concentration, fruit set, and yield in almond.

New strategies for the chemical thinning of apple (Malus domestica Borkh.) cultivars Queen Cox and Royal Gala

SummaryHigh volume sprays of ammonium thiosulphate (ATS), endothal, sulfcarbamide and pelargonic acid, applied at full bloom, were compared as flower thinners for the apple cultivars Queen Cox and Royal Gala grown on M.9 rootstocks in the south-east of England. Sprays of ATS (10,000 or 15,000 mg l–1) or endothal (500 to 200 mg l–1 reduced initial and final fruit set per 100 floral buds in each of two consecutive years when applied to the same set of trees. Sulfcarbamide reduced fruit set only when applied at concentrations higher than those recommended (4000 mg l–1), and sprays of pelargonic acid had no significant effect on the final set of these two cultivars. The ATS and endothal treatments increased fruit size in the first year of application, but effects in the subsequent year were inconsistent. Sprays in the first year increased floral density in the second year. In both years of treatment, sprays of benzyladenine (BA), applied when fruitlets were approximately 12.mm in diameter, increased the percentage of fruitlets abscinding. As with the ATS and endothal sprays, the effects of the BA spray treatments on fruit size at harvest were variable. Possible reasons for the inconsistencies in fruit size recorded in the thinning trials are discussed.

The Influence of Temperature and Low Light on Fruit Set and Chemical Thinning of Apple Trees

Fruit trees grown in the eastern U.S. environment are typically exposed to low light conditions from cloudy/rainy periods that can reduce PAR to 10% to 15% of full sun for 2 to 3 days. To magnify or concentrate the effect of temperature during low light stress, fruit trees were moved from the field into total darkness for 2 to 4 days at various temperatures and then returned to the field. This provided low light stress while eliminating the need for treatments involving various levels of light and temperature during the day on photosynthesis. To reduce transplanting shock, bearing apple trees used were grown in the field in 25-cm-diameter root bags and were on M.27 rootstock. After initial fruit set (at about 15 mm fruit diameter) trees were dug and transplanted into 5-gal buckets and moved for short periods of time (2 to 4 days) into various dark environments or sprayed with various thinning chemicals and placed in growth chambers at 5, 10, 16, and 21 °C in the dark. Immediately after dark treatments, trees were returned to the field and placed in the original holes. In 1995, we found that Elstar/M.27 apple trees placed in the dark for 3 or 4 days and returned to natural sunlight conditions abscised all of their fruit at 21 °C dark temperature but were retained at 5 °C. In 1996, we found that Braeburn/M.27 apple trees placed in the dark for 2 days and returned to natural sunlight conditions abscised all of their fruit at 16 and 21 °C dark temperature, but were retained if the dark period was 5 °C. These data indicated that the dark period temperature was very important for fruit retention. In addition, trees sprayed with Carbaryl+Accel 3 h before placing in the growth chambers caused the development of more pigmy fruit at all temperatures. Pigmy fruit also appeared to be related to the combined effects of digging trees, treating with Carbaryl + Accel, and colder temperatures. In 1997, we found that Stayman/M.27 apple trees placed in the dark for 2 days and returned to natural sunlight conditions abscised most of their fruit at 21 °C dark temperature, but were retained if the dark period was 5 °C. Fruit thinning occurred at 10 and 16 °C. Additional fruit thinning was significantly promoted by Carbaryl or NAA + Regulaid over the range of temperatures (5 to 21 °C), but thinning appeared to be most promoted at 21 °C dark temperature. Unexpectedly, ethephon caused fruit thinning at all temperatures from 5 to 21 °C, and thinning did not appear to be affected by temperature (ethephon defruited all trees at all temperatures). We suspect that higher dark temperatures caused either higher respiration rates or higher natural ethylene production, which promoted fruit abscission whether treated with a thinner or not. In one field experiment, Carbaryl sprays were applied at 2-h intervals beginning at 6 a.m. until 8 p.m. to Empire/Mark trees. Similar fruit thinning occurred when applied at temperatures ranging from 18 to 36 °C. These data suggest that no differences in thinning were related to daytime temperature.

Low attractiveness of avocado (Persea americana Mill.) flowers to honeybees (Apis mellifera L.) limits fruit set in Israel

SummaryAvocado in the Western Galilee region of Israel was found to be dependent on honeybees for fruit set. A significant initial fruit set required a density of at least five bees per tree during the female stage of flowering. The early-blooming avocado cultivars were visited by enough honeybees on fewer than one-third of their blooming days. Because they were visited mostly at the end of their blooming season, and due to rainy days, not more than 5% of their entire season’s flowers were exposed to sufficient pollination to set fruit. The late-blooming cultivars however, were visited by many bees and exhibited high initial fruit set. The attractiveness to honeybees of various avocado cultivars and some other plant species, which were found to compete for pollination, was measured by the coefficient “r” obtained from correlations between bee density and reward measures of these plants, over the course of a day or season. At the beginning of the blooming season, the avocado flowers competed for nectar-foraging bees mainly with flowers of Citrus spp., and for pollen foragers with Brassicaceae and Fabaceae, all of which were more attractive to the bees. Since pollination was carried out only by nectar-collecting bees, Citrus spp. flowers presented the main limiting factor for initial fruit set in avocado. However, toward the end of its blooming season, the avocado competed with Poaceae, Asteraceae and Apiaceae flowers, and its relative attractiveness increased.

Compatibility Relationships in `Manzanillo' Olive

We investigated pollination and fruit set parameters in `Manzanillo' olive (Olea europaea L.) following self-pollination and pollination with `Sevillano', `Ascolano', and `Mission' pollen. Results of analyses and experiments conducted over 2 years in central California indicated that `Manzanillo' behaves as a self-incompatible cultivar (index of self-incompatibility = 0.22 to 0.24). Pollination with `Sevillano' resulted in a more than 4-fold increase in fruit set over self-pollination. When `Mission' or `Ascolano' pollen was used, there was no increase over self-pollinated samples. Analyses of pollen tube growth, fertilization, initial fruit set, and final fruit set were consistent with `Manzanillo' being considered as a self-incompatible cultivar cross-incompatible with `Mission' and `Ascolano'. Our results indicate that `Manzanillo' is likely to be more productive when interplanted with `Sevillano' rather than when planted without a pollinizer or with `Mission' or `Ascolano'.

Boron Does Not Increase Hazelnut Fruit Set and Production

In a 3-year experiment in two drip-irrigated orchards on the Mediterranean coast, boron (B) sprays applied at rates of 0.6 and 1.2 g per tree and a soil B application of 12 g per tree did not increase fruit set or production of Corylus avellana L. `Negret' and `Pauetet' hazelnuts with mid to low foliar B levels (14.3 to 21.8 μg·g-1 dry mass). The average fruit set and nut yields of the trials were, respectively, 66% and 3.54 kg per tree for `Pauetet', and 50% and 4.54 kg per tree for `Negret'. The lack of response to B applications might be due to 1) initial fruit set levels were high; 2) the current B recommendation guidelines (25 to 30 μg·g-1 dry mass) might be adequate for fruit set and yield; 3) the rates of B applied might be too low; and 4) weather and soil conditions, cultivars, and biennial bearing may have masked any response to foliar B application.

Intra- and Inter-specific Pollination of Santalum spicatum and S. album

The flower morphology, receptivity and sexual compatibility between genotypes and species were determined in Western Australian sandalwood (Santalum spicatum) and Indian sandalwood (S. album). The results showed that the stigma of both species became receptive at anthesis and reached a peak at 3 or 4 days after anthesis. Pollen tubes took 2 days to grow to the ovary when pollinated at anthesis, and 1 day when pollinated 2 or 3 days after anthesis. The egg apparatus matured at least 2 days after pollination and varied between genotypes. Fertilisation occurred 2 or 3 days following cross pollination. Although 10–40% of ovules were fertilised following intra-specific crosses of both species, the average initial fruit set was much lower: 4% in S. spicatum and 19% in S. album. Most immature fruit (75–80%) abscised following intra-specific pollination. The number of pollen tubes that grew in styles after self-and inter-specific pollination was lower than that for intra-specific pollination. Following self and inter-specific pollination, growth of pollen tubes was arrested in the style, ovary and around the embryo sac; a few penetrated the embryo sac. Initial fruit set was low and developing fruit abscised prematurely. The results indicated that pre- and post-fertilisation mechanisms control self-incompatibility and inter-specific incompatibility between the sandalwood species.

Assessing Vascularization Response of Three Tomato (Lycopersicon esculentum Mill.) Cultivars to Soil Type, Nutrient Stress, and Water Stress

Amount of vascular development (veininess) is an important quality factor for processing wholepack tomatoes. The influences of nutrient and soil moisture stress on the amount of vascular development in `Chico III', `Dorchester', and `Roma' tomato fruit were studied. Fruit subjected to nutrient stress showed the highest amount of veininess. Fruit exposed to moisture stress after initial fruit set did not differ from controls in amount of veininess. Amount of vascularization did not differ among cultivars. A method for quantifying veininess was developed and compared with a traditional subjective rating scale. There was a high correlation (r2 = 0.77) between the subjective rating and quantitative measurement of veininess.

Pollination effects on fruit mineral composition, seeds and cropping characteristics of ‘Braeburn’ apple trees

‘Braeburn’ apple ( Malus domestica Borkh) trees were supplementary hand-pollinated or partially netted over a 3–4 week period during early and mid-blossom and compared with trees pollinated only by bees. Trees were later hand-thinned to a moderate or heavy level. In addition, individual fruit from flower clusters which had reached king petal fall in the first or fourth week of bloom were compared on supplementary hand and bee-only pollination treatments which had been moderately thinned. Partially netting trees reduced, while supplementary pollination increased, initial and final set on spur and terminal sites, seed number and final fruit Ca concentrations. Final set on 1-year axillary sites was increased by partial netting but reduced by supplementary pollination. Final yield, fruit Mg and K concentrations and average fruit size were unaffected by pollination treatment while hand-thinning level had no effect on fruit distributions, cropping or fruit mineral concentrations. For fruiting sites in trees and fruit of known blossom dates, initial fruit set and seed number per fruit were greater for later flowering sites but fruit Ca concentrations and bourse leaf areas were less than those from early flowering sites. Supplementary hand-pollination increased initial fruit set, seed numbers and fruit Ca concentrations on early flowering sites but had little effect on late flowering sites. These results show that poor pollination during the early blossom period can reduce fruit Ca concentrations for the ‘Braeburn’ cultivar. This effect may occur by reducing seed numbers in fruit as well as by altering fruit distributions on the tree.

Bat and hummingbird pollination of an AUTOTETRAPLOID COLUMNAR CACTUS, Weberbauerocereus weberbaueri (Cactaceae)

I present data on flower morphology, pollination, breeding system, and genetic diversity of the columnar cactus Weber‐bauerocereus weberbaueri at 2500 m elevation in southwestern Peru. Weberbauerocereus weberbaueri is a self‐compatible columnar cactus that is visited and pollinated by one species of rare endemic bat, Platalina genovensium, and two species of hummingbirds, Patagona gigas and Rhodopis vesper. W. weberbaueri exhibits pronounced interplant variation in floral color and size, and flowers exhibit traits corresponding to both bat and hummingbird pollination syndromes. Starch‐gel electrophoresis of flower bud tissue indicated that W. weberbaueri is an autotetraploid and that genetic diversity (Hep = 0.257) of the study population was high relative to diploid plants but similar to other tetraploid species. Initial fruit set from pollinator exclusion experiments conducted in 1991 and 1993, at the onset of and after a drought associated with the El Niño event of 1991–1992, revealed that bats were the most important pollinators in 1991, but that hummingbirds and diurnal insects were most important in 1993. In both years, however, autogamy and lepidopteran larval infestation of fruits reduced differences in mature fruit production among pollinator exclusion treatments so that differences in mature fruit set were not statistically significant. Reduced bat pollination in 1993 is attributed to the reduced abundance of bats at the study site during a drought caused by El Niño. I hypothesize that interaction among several factors, including tetraploidy, autogamy, larval infestation of developing fruits, and variation in pollinator abundance, may not result in strong selection for a bat vs. hummingbird floral morph, thus allowing the persistence of floral variation in this cactus.

Root and Stem Extension of Young Papaya Plants

`Red Lady' and `Tainung #1' papaya plants were grown in nursery trays with cells 5.1 cm in diameter. After 10 weeks, mean height of the `Red Lady' plants was 10.1 cm and that of the `Tainung #1' plants was 9.3 cm. Each of five plants per cultivar was planted between two root observation windows, one at 45 cm and the other at 95 cm. Roots reached the 45-cm observation window in 30 days, when mean height of the `Red Lady' plants was 18.7 cm and that of the `Tainung #1' plants was 13.0 cm. Roots reached the 95-cm observation window in 55 days, when mean height of the `Red Lady' plants was 55.4 cm and that of the `Tainung #1' plants was 40.6 cm. Thus, root extension during these initial 55 days was 17 to 18 mm per day for both cultivars, and stem extension during this period was 8.7 mm·d–1 for `Red Lady' and 5.5 mm per day for `Tainung #1'. Root extension declined for both cultivars to ≈12 mm·d–1 by the initial bloom period, then further declined to ≈4 mm·d–1 during and after the initial fruit set stage. Stem extension increased to about 19 mm·d–1 after the plants were established and remained at this rate until well into the stage of heavy fruit set and growth, when it declined to about 8 mm·d–1. The amount of fruit set influenced root characteristics more than cultivar.

Effects of shoot variables and canopy position on fruit set, fruit quality and starch reserves of persimmon (Diospyros kakiL.) in subtropical Australia

SummaryThe influence of canopy position (sectors: N, S, E, W; tree height: top, middle and base) and shoot growth on fruit set, yield and fruit quality of the non-astringent persimmon cultivar ‘Fuyu’ trained to standard modified central leader system was evaluated in subtropical Australia (Lat. 26°S). The main aim of the study was to determine if different sections of the tree canopy produce greater quantities of export-quality fruit. Light interception, net CO2 assimilation, leaf nutrients, and starch were also measured for each canopy position. Generally, there was little or no effect of canopy position on fruit quality. In contrast, initial fruit set was highest in upper parts of the tree canopy exposed to higher irradiance. Weight of fruit removed from any position was primarily dependent on fruit set at that position. Fruit weight was poorly correlated (r<0.30, n.s.) with leaf area, leaf number per fruit, shoot length, and shoot base diameter of fruiting shoots indicating that these variables are not useful criteria for determining thinning levels or final fruit size. The fruit disorder, calyx cavity, was least in the middle canopy. In contrast, average fruit weight, Brix, colour, texture and flavour were only slightly affected by canopy position. It was concluded from the study that, in Australia, light influences yield but not fruit quality. Export-quality fruit can be harvested from any position within the tree canopy.