Purple spot in loquat (Eriobotrya japonica Lindl.) is associated to changes in flesh-rind water relations during fruit development

Experiments were conducted to assess the link between purple spot in loquat fruit (Eriobotrya japonica Lindl.) and changes in the water relations of the flesh and the rind. Panicles were thinned to 1, 3 or 5 fruit or left unthinned (control), fruit wrapped in foil or exposed to the sun, or trees grown under plastic (night temperature >15 °C) or in the open (night temperature 5–3 °C) to induce different levels of the disorder. Typically, spotting increased with thinning (R² = 0.95), and was higher in exposed fruit (26.3% of fruit affected) than in wrapped fruit (nil), and higher with cool nights (16.2%) than with warm nights (2.7%). Mean tissue water potential (Ψ_w) was similar in the flesh and rind, whereas osmotic potential (π) was higher (less negative) in the flesh, and pressure potential (Ψ_p) lower in the flesh. There were no consistent effects of thinning on Ψ_w, whereas π of the rind decreased (more negative) with thinning during fruit color break. This response was associated with an increase in Ψ_p (more positive) in the rind at the same time. The external rind of exposed fruit had lower π than the external rind of warped fruit, and higher Ψ_p. Similarly, the fruit from trees grown under cool nights had lower rind π and higher rind Ψ_p than fruit under warm nights. These results suggest that low rind π and high rind Ψ_p are associated with purple spotting in loquat, and possibly reflect relatively high sugar concentrations in the flesh that increases the gradient of solute concentration between the flesh and the rind, making easy a dehydration process in the rind, which is responsible for purple spot.     

Application of 2,4-dichlorophenoxypropionic acid 2-ethylhexyl ester reduces mature fruit abscission in Citrus navel cultivars

Summary

2,4-dichlorophenoxyacetic acid (2,4-D) isopropyl ester has been used extensively, since the 1950’s, to reduce mature fruit abscission in Citrus navel cultivars. However, this synthetic auxin is no longer registered for this purpose in the European Union (EU). 2,4-dichlorophenoxypropionic acid (2,4-DP) 2-ethylhexyl ester has been registered in the EU for use in citrus growing and can be an effective replacement for 2,4-D to reduce pre-harvest fruit abscission. Use of the 2-ethylhexyl ester of 2,4-DP sprayed before mature fruit abscission significantly reduced fruit drop in sweet orange (Citrus sinensis L. Osbeck) ‘Washington navel’ and ‘Navelate’. The magnitude of the response depended on the concentration applied. At 15 mg l^–1, the percentage of abscised fruit was reduced by 50–75% compared to untreated trees, depending on the variety and the orchard. Increasing the concentration applied to 50 mg l^–1 did not improve this response. The response to this auxin was as effective as that obtained with 2,4-D applied on the same day at the same concentration (15 mg l^–1). 2, 4-DP treatment had no effect on skin colour or on the internal and external characteristics of the fruit at harvest.     

Effect of ethylene-releasing compounds on oleocellosis in ‘Washington’ navel oranges

Ethephon ((2-chloroethyl) phosphonic acid) and alsol (2-chloroethyl-tris-(2-methoxyethoxyl)-silane) caused a decrease in rind-oil-rupture pressure and thus increased susceptibility to oleocellosis in ‘Washington’ navel oranges (Citrus sinensis L.). This was probably caused by the increased fruit rind hydration brought about by stomatal closure. On the other hand, these compounds enhanced rind colour break, rendering the fruit less susceptible to handling-damage when picked after colour break.     

Shading decreases the growth rate of young apple fruit by reducing their phloem import

This study investigates the effects of shading on the biophysical mechanisms of apple (Malus Domestica Bork.) fruit growth by assessing how vascular and transpiration flows to/from the fruit are affected by shading. At 30 days after full bloom, a 90% neutral shading net was applied to four trees of the cv. Gala, for seven days, while four more trees, chemically thinned, were used as control. Fruit vascular and transpiration flows were assessed from two days before, to the end of shading. The daily patterns of fruit relative growth rate (RGR) and of phloem, xylem and transpiration flows were determined by continuous monitoring of fruit diameter by automatic fruit gauges. Before shading application, no differences between the two groups of trees selected were found for any of the parameters measured. Despite shading induced an immediate drop in canopy photosynthesis, both fruit daily RGR and phloem flow decreased gradually, until reaching 20% of the before treatment values after 7 days of shading. Differences in RGR and phloem flow appeared especially during the afternoon and night, i.e. post carbon assimilation by the tree, and fruit growth rates were higher in control trees. In the same period no, or very small differences were found between treatments for transpiration rates, while xylem flow was affected later than phloem and only at specific times during the day. These results suggest that the decrease in fruit growth rate under shading should be attributed to the reduction of canopy photosynthesis, rather than to a direct effect of shading on fruit sink strength.     

Relationships between bole and crown size for young urban trees in the northeastern USA

Knowledge of allometric equations can enable urban forest managers to meet desired economic, social, and ecological goals. However, there remains limited regional data on young tree growth within the urban landscape. The objective of this study is to address this research gap and examine interactions between age, bole size and crown dimensions of young urban trees in New Haven, CT, USA to identify allometric relationships and generate predictive growth equations useful for the region. This study examines the 10 most common species from a census of 1474 community planted trees (ages 4–16). Regressions were applied to relate diameter at breast height (dbh), age (years since transplanting), tree height, crown diameter and crown volume. Across all ten species each allometric relationship was statistically (p < 0.001) significant at an α-level of 0.05. Consistently, shade trees demonstrated stronger relationships than ornamental trees. Crown diameter and dbh displayed the strongest fit with eight of the ten species having an R² > 0.70. Crown volume exhibited a good fit for each of the shade tree species (R² > 0.85), while the coefficients of determination for the ornamentals varied (0.38 < R² < 0.73). In the model predicting height from dbh, ornamentals displayed the lowest R² (0.33 < R² < 0.55) while shade trees represented a much better fit (R² > 0.66). Allometric relationships can be used to develop spacing guidelines for commonly planted urban trees. These correlations will better equip forest managers to predict the growth of urban trees, thereby improving the management and maintenance of New England's urban forests.     

Growth regulator and low-volume irrigation effects on grapefruit quality and fruit-drop

‘Marsh’ (Citrus paradisi Macf.) grapefruit trees on rough lemon (C. jambhiri Lush.) rootstock received irrigated and unirrigated treatments. Half of each irrigation treatment received a GA₃ + 2,4-D spray at color break. Pre-harvest sprays of GA₃ and 2,4-D extended the grapefruit harvest season by increasing fruit removal and rind puncture force, delaying development of mature color and decreasing late-season and post-freeze fruit-drop. Although soil moisture content in the top 0.9 m of unirrigated blocks was reduced by approximately 40%, xylem pressure potentials of these trees and performance of GA₃ + 2,4-D were unaffected. Soil moisture content was not an accurate indicator of tree water status for large grapefruit trees.     

Characteristics and oleocellosis sensitivity of citrus fruits

The effects of variety, growth phase, and water loss on development of oleocellosis, and relationships between chromatism and Vis/NIR spectra were studied in ‘EarlyGold’ sweet orange (Citrus sinensis Osbeck), ‘Fukumoto’ navel (Citrus sinensis Osbeck), and ‘Cara Cara’ navel (Citrus sinensis Osbeck) oranges. The varieties showed significant differences in the rate (RO) and degree (DO) of oleocellosis development. The sensitivity of varieties (from most to least sensitive) was ‘EarlyGold’ > ‘Fukumoto’ > ‘Cara Cara.’ Growth phase and water loss had a significant influence on fruit sensitivity to oleocellosis. The order of sensitivity to oleocellosis was dependent on harvest time (i.e., at normal period > at delayed period > at uncolored period), and RO and DO decreased significantly with water loss. The RO and DO models for fruit water loss were established as y = 0.75 − 3.94x − 271.33x² (R² = 0.77) and y = 1.70 − 7.29x − 1025.83x² (R² = 0.583). The sensitivity of ‘EarlyGold’ to oleocellosis was significantly correlated with dL and dC of fruit chromatism. At the same time, there were significant differences at 480–575 nm, 650–720 nm, and 925–965 nm between varieties with low and high sensitivity to oleocellosis, and ‘EarlyGolds’ with a low RO and DO had a higher reflectance than those with a high RO and DO.     

Phenology and drought affects the relationship between daily trunk shrinkage and midday stem water potential of peach trees

Summary

The relationship between maximum daily shrinkage in trunks (MDS), daily trunk growth (DTG), predawn water potential (Ψ_pd) and midday stem water potential (Ψ_stem) were studied in an irrigation experiment in peach trees. Control trees were irrigated to replace evapotranspiration, with trees receiving regulated deficit irrigation (RDI) watered at 35% of this rate during Stage II of fruit development and after harvest. The RDI trees were watered as controls during Stage III of fruit development. Minimum (Ψ_pd and Ψ_stem fell to –0.6.MPa and –1.2 MPa, respectively in RDI plots compared with –0.2 and –0.6 MPa in the controls. Trunk growth was less in the RDI plots than in the controls during drought. In contrast, MDS was higher when deficit irrigation was applied in the RDI trees. When site differences were considered the correlation between (Ψ_pd and accumulated trunk growth over an ample period was loose, while maximum daily shrinkage and midday stem water potential remarkably improved such a correlation. However, pooling all available data, the correlation between Ψ_stem and MDS was very poor (R²=0.44) and it substantially improved only when using data from specific phenological periods (i.e. R²=0.75). A seasonal drift in MDS values was observed and it was related to the seasonal changes in trunk growth rates, (i.e. highest shrinkage was found when growth rates were lowest). We concluded that phenology in combination with drought reduce the reliability of the water status information obtained from MDS.     

Induction of resistance in Yali pear (Pyrus bretschneideri Rehd.) fruit against postharvest diseases by acibenzolar-S-methyl sprays on trees during fruit growth

The objective of this work was to evaluate how disease resistance in harvested fruit of Yali pears (Pyrus bretschneideri Rehd.) may be affected by acibenzolar-S-methyl (ASM) sprays on trees. Results showed that disease incidence and lesion diameter in mature pears from trees sprayed with ASM for three times during growth and inoculated with Penicillium expansum or Alternaria alternata after harvest were 27.9 and 42.7%, or 29.1 and 23.4% lower, respectively, than in control fruit 17 days after inoculation. Mature fruit from ASM-treated trees exhibited higher activities of defense enzymes including phenylalanine ammonia-lyase (PAL), chitinase and β-1,3-glucanase than in control at harvest. In young pears, activities of peroxidase, polyphenoloxidase, PAL, chitinase and β-1,3-glucanase were significantly enhanced by ASM after first spray on trees. The ASM spray also significantly increased H₂O₂ level and glutathione reductase activity, but reduced activities of catalase and ascorbate peroxidase in young pears. The study indicated that enhancement of disease resistance in harvested Yali pear fruit could be the result of multiple effects of several factors related to plant defenses induced by ASM sprays on trees during fruit growth. Application of ASM in the field holds great promise for controlling postharvest diseases of the fruit.     

西瓜新品种农科大10 号的选育

农科大10 号是以自交系M04-1-2 为母本、以F03 为父本配制而成的西瓜一代杂种。早熟,
果实发育期32 d（天）,全生育期108 d（天）;易坐果,果实圆形,果形指数1.0;果皮深绿色,覆墨绿
色齿状条纹,皮厚0.9 cm,较韧,较耐贮运;果肉红色,肉质酥脆,纤维较少,口感风味佳,中心可溶性
固形物含量10.5%～12.5%;单瓜质量4.7～6.8 kg,每667 m² 产量3 500 kg 左右。中抗枯萎病,耐低温弱
光,适宜早春保护地栽培。     

Effects of growth retarding treatments on apple tree growth,fruit maturation and fruit abscission

SUMMARY

Eight days after petal fall in 1991, mature 'Delicious'/MM. 106 apple trees and four days after petal fall in 1992, mature 'McintoshVMM. 106 were ringed, scored, root pruned (1 m from the trunk, two sides, 30 cm deep), or treated with ethephon (500 mg 1¹). Only ringing and scoring reduced vegetative growth. Ethephon advanced fruit maturation and fruit abscission, but root pruning did not affect the trees or fruit significantly. Mature 'Cort-land'/M.7a apple trees were root pruned 8 d after petal fall in 1991 and/or at full bloom in 1992. Root pruning reduced shoot growth, even in the year after treatment. Fruit abscission was reduced in 1991 and 1992 by root pruning in 1991, but root pruning in 1992 had no impact on abscission, in 1992. In an additional experiment, mature 'Mcintosh'/ MM.106 were root pruned 4 d after petal fall in 1991 or root pruned both in 1991 and at full bloom in 1992. Growth and preharvest fruit abscission were reduced in both the year of root pruning and the year after.     

Effects of Certain Cultural Practices on Tree Growth,Yield and Fruit Quality of Valencia Oranges in Cyprus

The winter-grown covercrop Vicia sativa increased the growth and yield of Valencia orange trees as compared with clean cultivation in summer and complete weed control without cultivation. A winter covercrop resulted in trees that were 8·6 and 26·5% larger and produced 15·0 and 26·0% more fruit than trees under clean cultivation and no-cultivation respectively. Treatments did not affect fruit quality except that the rind of fruits from trees under the winter covercrop was significantly thinner than that of fruit from the other two treatments. Leaf analyses for 12 elements did not show significant differences.     

Effects of fruit thinning,pollination and paclobutrazol on fruit set and size of persimmon (Diospyros kaki L.) in subtropical Australia

Summary

A factorial combination of three cultural factors (± hand-pollination, ± growth retardant, ± fruit thinning) were evaluated for their effects on fruit set and fruit size of ‘Fuyu’ persimmon (Diospyros kaki L.) in subtropical Australia (Lat. 27° S). Treatments were applied to individual shoots on mature seven year old trees. Fruit set of pollinated flowers was high compared with non-pollinated flowers (91% vs. 47%). Pollinated fruit also grew faster at all stages of fruit development and, at harvest, fresh weights were 25% heavier. Palcobutrazol significantly (P<0.05) increased fruit weight by 7% compared with controls but did not increase fruit set. Irrespective of treatment, fruit weight was not correlated (r<0.3, n.s.) with shoot length, number of nodes per shoot, fruit nodal position, shoot dry weight, leaf area per shoot, and number of leaves per shoot. Fruit fresh weight was only poorly correlated with shoot base diameter (r = 0.41*). Pollinated fruit had significantly (P<0.05) higher concentrations of nutrients (N, K, Ca, and Zn).     

Influence of nitrogenous fertilization on the protein content of flavedo of ‘Navelina’ oranges and its relationship with rind colour

Summary

Nitrogenous fertilization effects on the protein concentration of flavedo of ‘Navelina’ oranges during ripening was studied in an experimental greenhouse, using cuttings grown in pots with inert sand and nutrient solution. Two types of nutrient solution were used: a nitrate solution (all nitrogen in nitrate form) and an ammoniacal-nitrate solution (40% nitrogen in ammonium form and 60% in nitrate form). The protein concentration of fresh flavedo of fruits irrigated with ammoniacal-nitrate solution was higher than that of fruits irrigated with nitrate solution. When the protein concentration of flavedo is high, the rind of fruits reach a yellow or orange-yellow colour earlier during development. In both types of nutrient solution, the quantity of nitrogen applied did not influence the total protein concentration of fresh flavedo nor the timing of fruit rind colour change from green to orange-yellow. After fruit set, the sooner the ammoniacal- nitrate nutrient solution was supplied, the sooner fruits reached an orange-yellow colour, and the higher was the total protein concentration of fresh flavedo, although there were no significant differences between the protein concentrations of flavedo of fruits from cuttings whose irrigation started with the ammoniacal-nitrate solution at different time. Results of this and a previous study suggest a relationship between the rind colour change and the protein concentration in the flavedo of fruit.     

西瓜YUCCA 基因家族鉴定及在果实成熟过程中的表达分析

以栽培西瓜自交系97103 为试材,测定不同发育时期果肉及果皮中游离态吲哚-3- 乙酸（IAA）含量。结果显示：果实发育后期,果肉中IAA 含量显著上调,果皮中IAA 含量则一直保持较低水平,推测果肉中IAA 可能对西瓜果实成熟与含糖量积累起重要作用。利用生物信息学手段,鉴定了西瓜生长素合成色氨酸依赖途径限速酶基因家族YUCCA,并对其在果肉与果皮组织的表达水平进行qRT-PCR 检测。结果表明：西瓜YUCCA 基因家族包含 10 个成员,所有YUCCA 基因均含有FMOs 保守结构域,聚类分析表明其分为两大类。基因结构分析显示这些基因包含 2～5 个外显子。ClYUCCA4、ClYUCCA6、ClYUCCA10b 及 ClYUCCA10c 等4 个YUCCA 基因在西瓜果肉中表达,且都在果实发育后期表达明显上调。ClYUCCA4 及ClYUCCA10c 在果肉与果皮中的表达量变化与IAA 含量变化趋势一致,且在其他组织中几乎检测不到表达,推测其可能参与调控西瓜果实的成熟。     

西瓜新品种农科大5号的选育

农科大5号是以自交系M18为母本,自交系F23为父本配制而成的西瓜新品种一代杂种。早熟,果实发育期28～30d(天),全生育期90～92d(天);易坐果,果实圆形,果形指数1.1;果皮深绿色,覆墨绿色中细条带,皮厚0.93cm,硬韧,耐贮运;果肉红色,肉质沙细,汁多纤维少,口感佳,品质优,中心折光糖含量12.4%,中边糖梯度小;田间调查表明对蔓枯病的抗性强于对照京欣2号,枯萎病零星发生,未见炭疽病和白粉病发生;单瓜质量5.9kg,产量3200kg·(667m2)-1。适宜在陕西及同类生态区早春设施西瓜种植区种植。     

Rootstock influence on the incidence of rind breakdown in ‘Navelate’ sweet orange

Summary

The influence of three rootstocks, Carrizo citrange (Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.), Cleopatra mandarin (Citrus reshni Hort. ex Tanaka) and sour orange (Citrus aurantium L.) on the incidence and severity of rind breakdown in ‘Navelate’ sweet oranges was studied over seven years in four orchards. The proportion of affected fruit was greater in trees on Carrizo citrange (60% on an average) followed by Cleopatra mandarin (38%) and then on sour orange (9%). There were also significant differences in the severity of the disorder among rootstocks; more than 35% and 20% of fruit from trees on Carrizo citrange and Cleopatra mandarin, respectively, were rejected for commercialization, whereas only 4% of fruit on sour orange was rejected. Cryo-scanning electron microscopy (SEM) of fruit peduncles showed that average diameter of xylem vessel elements of peduncles of fruits on Carrizo citrange rootstock were 6% and 17% larger than those on Cleopatra mandarin and sour orange, respectively. Defoliation of fruit-bearing branches reduced water loss from fruit, maintained fruit peel water potential at a higher value than that of fruit on undefoliated branches and reduced the proportion and severity of affected fruit. It is concluded that fruit-tree water relationships are related to rind breakdown in ‘Navelate’ oranges and low fruit water content might be responsible for the disorder.     

高档礼品西瓜新品种美月的选育

美月是以优良自交系MH-35-1为母本,MH-9-1为父本配制而成的小型西瓜一代杂交种.早熟,生长势强,全生育期冬季75～80 d,秋季63～65 d,果实椭圆形,果形指数1.29,平均单果质量1.5～2.0 kg,深绿果皮覆14～15条墨绿细齿条带;皮厚0.5 cm,果肉鲜红色,中心糖含量12.5%～13%,边糖含量9%～10%,肉质细脆,多汁,品质佳,抗性好,产量高.     

The Effects of Fruit Thinning on the Development of Cox’s Orange Pippin Apples in Relation to the Incidence of Storage Disorders

Severe hand thinning of fruitlets on Cox’s Orange Pippin trees five weeks after full blossom led to a doubling of fruit weight by harvest. Although the rate of cell division was stimulated slightly, the larger fruit size was due mainly to an increased rate of cell enlargement.

The respiration rate of whole fruits was slightly higher after thinning and the onset of the climacteric rise was advanced. Respiration per cell was correspondingly higher in the larger cells of the thinned fruit and respiration per unit protein was similar to that of fruit from unthinned trees.

Potassium, magnesium, and phosphorus contents, expressed on a fresh weight basis, were higher in the cortical tissue of the thinned fruits. Calcium per unit fresh weight was unaffected by thinning and the ratio of calcium to cell surface remained relatively constant throughout development in both types of fruit.

Senescent breakdown and bitter pit developed during storage only in the thinned fruit. Slight differences in the incidence of rotting and low temperature breakdown between the two types of fruit are attributed to the effects of maturity rather than of fruit size.     

Annual dry-matter production by three apple cultivars at four within-row spacings in New Zealand

Summary

Annual dry-matter production was estimated from eight year old apple trees of ‘Fuji’, ‘Braeburn’ and ‘Royal Gala’ on rootstock M.9, trained as slender spindles, in a spacing trial with trees spaced at 1.3, 1.5, 1.9 and 2.4 m within the row with tree rows 3.5 m apart. Light interception was recorded at intervals during the season. Both fresh weight yield and total dry-matter production were linear functions of light interception, with a higher slope recorded for the two late season cultivars compared with the early maturing ‘Royal Gala’. Comparison of the relationship between mid-season light interception and apple yields with published values from elsewhere, reveals that the slope of the relationship is enhanced under New Zealand conditions. The relationship suggests an upper limit of yield of 169 t ha^–1 at 90% light interception, slightly higher than the maximum yield recorded of 163 t ha^–1. Energy conversion of intercepted light over the growing season into dry-matter production was similar to that observed in the United Kingdom, suggesting that the major climatic advantage in New Zealand over the United Kingdom is the higher growing season radiation integral. Dry matter was allocated in the order fruit>woody tissue>leaves, with partitioning to the fruit of 74, 72 and 63% for ‘Braeburn’, ‘Fuji’ and ‘Royal Gala’, respectively. Under New Zealand conditions, sustainable 70% harvest index values may be achievable for mature apple trees on dwarfing rootstock with late maturing cultivars.