Yield and fruit quality of ‘Gala’ and ‘Fuji’ apple trees protected by white anti-hail net

Covering apple orchards with nets protects them from hailstorms but this changes the amount and quality of the light supplied to the trees. This study was carried out to assess the effects of shade provided by white protection net on yield and fruit quality of apple orchards in Southern Brazil, along three growing seasons (2002/2003, 2003/2004, and 2004/2005). ‘Gala’ and ‘Fuji’ apple trees (on MM111 rootstock, raised as slender spindles, with a spacing of 5.5 m × 3 m) were left uncovered (control trees) or covered with white net. The white net reduced the photosynthetically active radiation (λ = 400–700 nm) accumulated over the trees’ canopy along a day by 18.4%, leading to a higher leaf chlorophyll content in both cultivars, and a higher specific leaf area in ‘Gala’. The shade provided by the net did not affect yield and increased fruit average weight in both cultivars. At harvest, the number of seeds per fruit and severity of russet were not affected by netting in both cultivars, as well as the incidence of watercore in ‘Fuji’. The main beneficial effects of the white net were the reduced incidence of sunburn on ‘Gala’, reduced incidence of bitter pit during cold storage in both cultivars, and reduced incidence of apple scab at harvest and of decay after cold storage in ‘Fuji’. Fruit fly damage in ‘Gala’ (assessed in one season) was reduced by netting. However, netting affected negatively some fruit quality attributes. ‘Gala’ and ‘Fuji’ apples from trees protected by the net had a poor skin color (pale blush and a more intense green background color) at harvest. The net reduced flesh firmness and SSC, and increased the starch index of ‘Gala’ apples at harvest, and reduced flesh firmness and SSC, assessed after cold storage and shelf life, in fruits of both cultivars.     

Effect of high temperature stress on the reproductive growth of strawberry cvs. ‘Nyoho’ and ‘Toyonoka’

High temperatures are known to reduce fruit size and fruit weight in strawberry, but cultivar differences in the response to high temperature stress during the reproductive stage up to the second inflorescence have not been sufficiently reported. We examined the effect of two day/night temperature regimes on fruit set and fruit growth in two cultivars, ‘Nyoho’ and ‘Toyonoka’. A high day/night temperature of 30/25 °C reduced the number of inflorescences, flowers, and fruits in both cultivars compared with plants grown at 23/18 °C. The percentage of fruit set in ‘Nyoho’ was not significantly different between the two temperature treatments, while that in ‘Toyonoka’ was much lower at 30/25 °C than at 23/18 °C. Days to ripening was shorter at 30/25 °C than at 23/18 °C, and no cultivar differences were observed. Fresh weight of primary, secondary, and tertiary fruits was greater at 23/18 °C than at 30/25 °C in both cultivars, and no cultivar differences were observed, except in tertiary fruits. The diameter of fruits from all positions was also reduced at 30/25 °C in both cultivars. Relative growth rates of fruits showed two peaks in both cultivars and in both temperature treatments. Both peaks appeared earlier at 30/25 °C than at 23/18 °C. Percentage of fruit set at 30/25 °C in the second inflorescence was also significantly lower in ‘Toyonoka’ than in ‘Nyoho’. These results indicate that high temperature stress negatively affects the reproductive process in strawberry and that plant response to high temperature stress is cultivar-related in such responses.     

Harvest parameters to improve the storability of high quality ‘Reinette du Canada’ apple

Summary

‘Reinette du Canada’ apple (Malus domestica Borkh.), which has been declared a Protected Designation of Origin (PDO) product throughout the European Community, is severely affected by bitter pit during storage, but increasing demand for organic produce requires chemical post-harvest treatments to be replaced with organic practices. The objective of this work was to determine the optimum stage of fruit maturity to improve the storability of high quality ‘Reinette du Canada’ apple during storage without applying post-harvest treatments. Seasonal conditions influenced fruit quality and the occurrence of storage disorders in ‘Reinette du Canada’. Harvest maturity also influenced the quality of ‘Reinette du Canada’ apple during storage, with later harvests reducing the development of bitter pit and increasing the soluble solids content:titratable acidity (SSC:TA) ratio. This study suggests that the SSC:TA ratio was a useful parameter for determining the optimum harvest maturity for high acidity, ‘Reinette du Canada’ apple. High quality fruit were obtained after long-term storage when the SSC:TA ratio exceeded 11.0, and fruit firmness at harvest exceeded 90 N. If these thresholds were not achieved, the quality of harvested ‘Reinette du Canada’ apples may not be sufficient to market fruit with the PDO designation. The results of our study also suggested that skin hue angle (hº) measurements may provide a quick and useful index that could replace fruit firmness measurements in the future.     

In vitro propagation using adventitious buds technique as a source of new variability in chrysanthemum

Eleven cultivars of Chrysanthemum × grandiflorum (Ramat.) Kitam.: ‘Richmond’ and its 10 radiomutants, representing the Lady group, were propagated in vitro with shoot tips and leaves as explants. The aim of this study was to investigate if the explant type used for micropropagation affects the genotype and phenotype of chrysanthemums. Plants grown from shoot tips and adventitious buds formed on leaves were rooted in vitro, acclimatized and cultivated in glasshouse up to full-flowering. The colour and shape of inflorescences of plants obtained from two different explant types were compared within the cultivars. All plants derived from shoot-tip explants showed the inflorescence colour and shape typical for the cultivars. Inflorescence colour of plants derived from adventitious buds were true-to-type in four cultivars: ‘Richmond’, ‘Lady Amber’, ‘Lady White’ and ‘Lady Yellow’. All plants of ‘Lady Apricot’ (originally: golden beet) and ‘Lady Salmon’ (salmon) propagated from adventitious buds technique showed altered inflorescence colour (respectively: purple gold; pink and white). ‘Lady Bronze’ (originally: reddish brown), ‘Lady Orange’ (orange brown) and ‘Lady Rosy’ (purple gold) propagated with adventitious buds had both typical and changed inflorescence colours (respectively: yellow; yellow and red; reddish pink). ‘Lady Vitroflora’ showed altered number of ligulate florets grown into tubes in inflorescence when propagated with shoot tips and leaves as explants. Those changes might be an effect of either chimeral structure or somaclonal variation of the plants investigated. The variation appears only if non-meristematical explants were used. The adventitious buds technique might be useful in chrysanthemum breeding as a source of a new variability.     

Effect of distance from early flowering pollinizers ‘Maypole’ and ‘Dolgo’ on ‘Fiji’ fruit set

An apple orchard consisting of a single cultivar under the condition of natural pollination must have suitable pollinizers such as Crab apples to ensure stable fruit production. We selected ‘Maypole’ and ‘Dolgo’ as pollinizers for the cultivar ‘Fuji’, and investigated the rate of fruit and seeds in ‘Fuji’ fruits produced by pollen of the pollinizers. We developed a method for tracing pollen flow based on the leaf color of progeny and S-RNase allele of ‘Maypole’, and on Simple Sequence Repeat (SSR) analyses of ‘Maypole’ and ‘Dolgo’. These were powerful tools for determining the distance insects (mainly Osmia cornifrons) carry pollen from the pollinizers to ‘Fuji’. Although the fruit set of ‘Fuji’ apples was not reduced with increasing distance between ‘Fuji’ apple trees and pollinizers (probably due to pollen flow from other commercial cultivars planted outside the area), the rate of ‘Fuji’ apple fruit produced by the pollen of the pollinizers decreased with increasing distance. The rate of fruit produced by the pollinizers was 84% and 77% when ‘Fuji’ was 2.5 m from ‘Maypole’ and ‘Dolgo’, respectively, and 71% and 64% when ‘Fuji’ was 5 m from ‘Maypole’ and ‘Dolgo’, respectively, but was reduced to 47% and 39% when ‘Fuji’ was 10 m from ‘Maypole’ and ‘Dolgo’, respectively. However, the spacing could cause reduced fruit size, and require extra fruit thinning for producing large fruits. It could also cause reduction of the yield for increasing the planting area of pollinizers. We recommend that pollinizers should be planted not more than 10 m from ‘Fuji’.     

Parameters of inner quality of the apple scab resistant and susceptible apple cultivars (Malus domestica Borkh.)

Individual organic acids and sugars were analysed in the fruits of scab resistant and susceptible apple cultivars. The total sugars ranged between 128.2 and 191.6 g/kg, and the total organic acid between 5.1 and 13.4 g/kg. In the flesh and peels of different apple varieties single phenolics (gallic, protocatehuic, chlorogenic, caffeic, ferulic and p-coumaric acid, phloridzin, epicatechin, catechin, quercitrin and rutin) were analysed together with their total phenolic content (TPC). ‘Golden Delicious’ was the cultivar with the lowest TPC whereas ‘Rubinola’, ‘Jonagold’ and ‘Goldrush’ had the highest level of TPC in the pulp. Peels showed a 2–9 times higher phenolic content than the pulp. ‘Goldrush’ had the highest content of TPC in its peel. The total antioxidant capacity of peels was about 2–5 times higher than respective pulps. Scab resistant apple cultivars had significantly higher content of some single and total phenolic contents in comparison with the scab susceptible, especially the pulp.     

Effect of plant growth temperature on membrane lipids in strawberry (Fragaria × ananassa Duch.)

Changes in membrane lipid composition are important in the acclimation of plants. The influence of four day/night growing temperature combinations (18/12, 25/12, 25/22, and 30/22 °C) on membrane lipids of ‘Earliglow’ and ‘Kent’ strawberry (Fragaria × ananassa Duch.) were studied. The monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG) were the major galactolipids in the strawberry leaves. ‘Earliglow’ contained a higher amount of galactolipids in the leaves than ‘Kent’. The major phospholipids in the strawberry leaves, roots, and fruit were phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE). PC and PE were the two predominant phospholipids in the strawberry. The leaves and fruit of ‘Earliglow’ contained higher amounts of phospholipids compared to those of ‘Kent’, whereas ‘Kent’ strawberry roots had higher phospholipids. Palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2), and α-linolenic (C18:3) acids were major fatty acids in galacto- and phospholipids of the ‘Earliglow’ and ‘Kent’ strawberry. PC is very rich in linolenic acid in leaves compared to the fruit and root tissues. PC had the highest ratio of unsaturated to saturated fatty acids among all phospholipids. There was a significant increase in the content of galactolipids (MGDG, DGDG) and phospholipids (PC, PI, PG and PE) and unsaturation of their fatty acids in the cool day/night growth temperature. Increasing day/night growth temperatures decreased MGDG/DGDG ratios. The shifts in saturation and composition of fatty acids observed with strawberry may be an adaptation response of plants to the temperature changes.     

Modeling plant morphology and development of petunia in response to temperature and photosynthetic daily light integral

The effects of mean daily temperature (MDT) and mean photosynthetic daily light integral (MDLI) on flowering during the finish stage of two petunia (Petunia × hybrida) cultivars were quantified. Petunia ‘Easy Wave Coral Reef’ and ‘Wave Purple’ were grown in glass-glazed greenhouses at 14–23 °C or 14–26 °C and under 4–19 mol m⁻² d⁻¹ with a 16-h photoperiod. The flower developmental rate was predicted using a model that included a linear MDT function with a base temperature multiplied by an exponential MDLI saturation function. The flower developmental rate increased and time to flower decreased as MDT increased within the temperature range studied. For example, under a MDLI of 12 mol m⁻² d⁻¹, as MDT increased from 14 to 23 °C, time to flower of ‘Easy Wave Coral Reef’ and ‘Wave Purple’ decreased from 51 to 22 d and 62 to 30 d, respectively. Flower developmental rate increased as MDLI increased until saturation at 14.1–14.4 mol m⁻² d⁻¹. Nonlinear models were generated for effects of MDT and MDLI on flower bud number and plant height at flowering. The number of flower buds at flowering increased as MDT decreased and MDLI increased. For example, at an MDT of 14 °C with 18 mol m⁻² d⁻¹, plants had 2.5–2.9 times more flower buds than those grown at 23 °C and 4 mol m⁻² d⁻¹. Models were validated with an independent data set, and the predicted time to flower, flower bud number, and plant height were within ±7 d, ±20 flowers, and ±4 cm, respectively, for 96–100%, 62–87%, and 93–100% of the observations, respectively. The models could be used during greenhouse crop production to improve scheduling and predict plant quality of these petunia cultivars.     

5-Aminolevulinc acid increases tree yield and improves fruit quality of ‘Rabia’ and ‘Sukkariat-Yanbo’ date palm cultivars under hot arid climate

Date palms growing in hot arid regions are generally facing several kinds of environmental stresses which limit tree growth and productivity and negatively affect fruit quality. During 2009 and 2010 seasons, the effects of 5-aminolevulininc acid (5-ALA) application at different rates on yield, fruit quality, pigment contents and nutrient uptake of ‘Rabia’ and ‘Sukkariat-Yanbo’ date palm cultivars were studied. In both cultivars, the application of 5-ALA significantly increased bunch weight and yield per tree compared to control. The highest bunch weight and yield per tree was achieved by 5-ALA at 200 ppm followed by 250 ppm applied on both fruit bunches and leaves. These were reflected on higher fruit and flesh weight and fruit length, at the bisir and rutab stages. However, the application of 5-ALA at 250 ppm only on fruit bunches without leaves significantly increased bunch weight and yield per tree compared to control only in ‘Sukkariat-Yanbo’ but not in ‘Rabia’ cultivar. There were significant interaction effects between treatments and seasons on bunch weight and yield in ‘Rabia’ but not in ‘Sukkariat-Yanbo’ cultivar. The rutab % was not significantly affected by any of the applied treatments and it was higher in 2009 than in 2010 season in ‘Rabia’, however, the opposite was true in ‘Sukkariat-Yanbo’ cultivar. Most of the physical parameters of fruit quality at both the bisir and rutab stages were significantly improved in both cultivars by 5-ALA application compared to control, in contrast to the biochemical parameters that were not affected. In both cultivars, chlorophyll a concentration significantly increased by 5-ALA application especially at 200 and 250 ppm on both leaves and fruits compared to control. While chlorophyll b concentration was not significantly affected by the 5-ALA application, total chlorophyll concentration was significantly higher at 250 ppm 5-ALA application than control in both cultivars. There were no significant differences among the different rates of 5-ALA application. Chlorophyll a/b ratio was not significantly affected by 5-ALA application compared to control. The concentrations of N, P and K in the leaves of both cultivars were not significantly affected by the 5-ALA application compared to control. It was concluded that 5-ALA application has promotive effects on yield, fruit quality and chlorophyll concentration of both ‘Rabia’ and ‘Sukkariat-Yanbo’ date palms under hot arid climate.     

Volatile production by ‘Golden Delicious’ apples is affected by preharvest application of aminoethoxyvinylglycine

The effect of AVG application on the quality and volatile production of ‘Golden Delicious’ apples, grown in Chihuahua Mexico, was evaluated. AVG (125 g AVG/ha) was applied on apple trees four weeks before harvesting. Apples were harvested 176 days after full bloom and stored at 8 °C for 35 d. Quality parameters and volatile compounds were periodically evaluated. AVG application retarded color changes, and preserved acidity of apples during storage. Ethylene synthesis was also delayed by AVG. Control apples presented higher total soluble solids content than AVG-treated apples at the end of cold storage. Volatile production was affected by AVG application, especially in the case of esters and alcohols, which presented 59% and 33% lower values in AVG-treated apples at the end of storage. A higher concentration of aldehydes was observed at harvest time in AVG-treated apples; however, no difference was observed between treatments during storage. Higher correlations between ethylene production and aldehydes and alcohols were found in control apples (0.98, and 0.98, respectively), than in AVG-treated apples (0.6 and 0.90, respectively). AVG application on ‘Golden Delicious’ apples conferred a variety of benefits, such as delaying maturation, maintaining color, and reducing changes in acidity and total soluble solids. However, AVG treatment negatively affects the production of some volatile compounds.     

Flowering and changes in respiration in Asiatic hybrid lilies as influenced by bulb vernalization

Asiatic hybrid lilies, Lilium × elegans Thunb., ‘Red Carpet’ and ‘Sunray’ were used to investigate the effect of bulb vernalization at 2.5 °C on plant growth, flowering, and CO₂ production (respiration), and to use the CO₂ production pattern to monitor the time of flower bud initiation and development. Lily shoot emergence and flowering were accelerated when bulbs received 2.5 °C bulb vernalization; however, flowering was delayed when bulbs were stored at 20 °C before treatment at 2.5 °C; this indicated that bulbs were de-vernalized. The maximum CO₂ level, and the minimum level, reached in 78 h in non-vernalized bulbs and in 110 h in 6 weeks of 2.5 °C (6 weeks/2.5 °C) treated bulbs, was increased as the 2.5 °C duration was increased; this indicated that CO₂ level can be an useful parameter to measure the cold stimulus (i) accumulated in bulbs following bulb vernalization. The respiration rate higher than the predicted values of the best-fit curves derived from the quadratic equations was designated as Blip A and this was correlated to the time of flower bud initiation and development. Shoot elongation may follow the rise in carbon dioxide levels after reaching the minimum level. It is proposed that increased carbon dioxide levels higher than the predicted levels (Blip A), was correlated to the time of flower bud initiation and development. Measurement of carbon dioxide production upon receipt of bulbs may be a useful technique to provide important information for optimum vernalization treatments for bulbs that have accumulated different levels of low temperature stimulus after bulb vernalization.     

Susceptibility of several Japanese plum cultivars to pests and diseases in a newly established organic orchard

The susceptibility of 14 Japanese plum cultivars to an aphid pest and three fungal diseases was analysed during 2007 and 2008 in two experimental orchards, one in organic and the other in conventional management. There was a significantly higher incidence of green peach aphids [Myzus persicae (Sulzer)] for most of the cultivars in the organically managed treatment. ‘Fortune’, ‘Primetime’, ‘Larry Ann’ and ‘Sapphire’ were the cultivars most affected, and ‘Souvenir’ suffered the lowest attack in both treatments. Shot hole disease (Wilsonomyces carpophilus) affected both orchards at low levels, and only two cultivars, ‘Santa Rosa’ and ‘Larry Ann’, suffered a moderate attack. Powdery mildew (Sphaerotheca pannosa) incidence was significantly higher in the conventionally managed orchard and only the ‘Red Beaut’ cultivar was affected. Rust disease (Tranzschelia spp.) incidence was significantly higher in the organic treatment. The cultivars in which the rust disease appeared earliest and reached the highest levels were ‘Showtime’, ‘Santa Rosa’, ‘Friar’, and ‘Larry Ann’. An intense rust infestation in leaves provoked a premature defoliation in the organic plot, indicating that proper control of this disease is important to maintain tree vigour and yield.     

Fruit set and embryo rescue in crosses using parthenocarpic ‘Mopanshi’ persimmon

The ‘Mopanshi’ persimmon is a seedless, astringent parthenocarpic cultivar that does not produce male flowers. After pollination using four non-astringent cultivars (‘Zenjimaru’, ‘Nishimurawase’, ‘Okugosho’ and ‘Hanagosho’), seeds were produced to different degrees. ‘Mopanshi’ fruits pollinated with ‘Zenjimaru’ produced far more seeds than those pollinated with the other three cultivars. The ratio of abnormal seeds obtained from the fruits pollinated with ‘Hanagosho’ was higher than that obtained from the fruits pollinated with the other three cultivars. Most embryos degenerated in the early to late stages of seed development. Immature embryos were cultured in a modified MS medium (half of NO₃ in MS medium + 0.4 μM BA + 0.1 μM IBA) with the greatest success (52–80%) from embryos taken from fruits 60–80 days after pollination. Seedlings failed to initiate radicles so they were transferred to dark culture conditions for 8 days or to a rooting media that contained 3% sucrose and 1% Chinese ink. The seedlings on the medium darkened with ink rooted at greater than 90.83% compared to 75.83% for dark cultured seedlings. This study demonstrated that ‘Mopanshi’ persimmon could be used as a female parent in crosses, but embryos needed to be moved to tissue culture conditions to continue to develop and form plantlets.     

Harvest and post-harvest apple fruit quality following applications of kaolin particle film in South African orchards

Sunburn on apples in the Western Cape region of South Africa can result in yield losses of up to 50%. Application of kaolin-based particle film (Surround^® WP) increases leaf and fruit surface reflectivity, thus potentially reducing heat load and sunburn. Trials were performed during 2002/2003 and 2003/2004 to assess the effectiveness of kaolin particle film in controlling sunburn on ‘Granny Smith’, ‘Braeburn’, ‘Fuji’, ‘Royal Gala’ and ‘Cripps’ Pink’ apples. Fruit quality and ripening were monitored following 1–4 months in regular atmosphere cold storage at −0.5 °C. Sunburn on exposed fruit was significantly reduced in ‘Granny Smith’ and ‘Fuji’. Kaolin treatment improved fruit colour of ‘Granny Smith’ and ‘Royal Gala’, and delayed starch conversion in ‘Granny Smith’ at harvest and during the early storage period but not thereafter. Incidence of watercore at harvest was significantly reduced by kaolin treatment, but this disorder disappeared during cold storage in both treatments. There were no effects on skin anthocyanin or phenolic concentrations in any cultivar compared to unsprayed fruit.     

The fruit pitting disorder—A physiological anomaly in mango (Mangifera indica L.) due to deficiency of calcium and boron

A new disorder known as fruit pitting has been observed in some Indian mango orchards during the recent years. In this disorder, there is a development of some sunken pits on fruit peel, which distract consumers. Based on preliminary observations, it was observed that deficiency of nutrients could be the cause, and hence systematic studies were conducted in five indigenous cultivars such as ‘Alphonso’, ‘Amrapali’, ‘Dashehari’, ‘Mallika’ and ‘Neelum’, and five exotic mango cultivars such as ‘Edward’, ‘Irwin’, ‘Rosari’, ‘Sensation’ and ‘Tommy Atkins’ with the aim to observe the fruit pitting incidence and degree, and to investigate its probable causes. Our studies indicated that nearly 13% of the mango fruit was affected by fruit pitting with variable degree and magnitude. All indigenous cultivars had higher incidence of fruit pitting than exotic cultivars. ‘Dashehari’ had the maximum incidence of fruit pitting (30.3%), followed by ‘Amrapali’ (28.6%), and ‘Rosari’ the least (3.4%). Our studies indicated that the incidence of fruit pitting in mangoes was nearly 13% with a significant variability among the cultivars (Table 1). Although the concentrations of most of the major nutrients such as N, P, K, Mg, and minor nutrients such as Cu, Mn, Fe, Zn, did not differ significantly. However, the pitted fruit had lower Ca (1.53%) and B (22 mg kg⁻¹) concentrations than normal fruit (2.47% and 38 mg kg⁻¹, respectively), indicating that deficiency of Ca and B probably is the cause for fruit pitting in mangoes.     

Cultivar variation in apple peel and whole fruit phenolic composition

The quali-quantitative distribution of phenolic compounds varies considerably between apple flesh and peel, but the concentration of phenolics is substantially higher in the peel than flesh. Because the peel comprises only a small percentage of the entire fruit weight, its significance as a donor of phenolics is disputable. We assessed the contribution of the peel to the total phenolic yield of 19 apple cultivars. Calculations were based on the weight of the whole fruit and the peel (which is frequently discarded) and the concentration of individual phenolic compounds. On average, 8, 24, 32, 50 and 66% of chlorogenic acid, (+)-catechin, (−)-epicatechin, phloridzin, and rutin, respectively, were present in the peel, which constitutes about 6–8% of the whole apple weight. With the exception of chlorogenic acid, 50% or more, on average, of the above phenolics were present in the peel of ‘Granny Smith’, ‘Idared’, ‘Red Rome’, ‘Jonamac’ and ‘Gloster’ apples; the highest percentage was found in ‘Starking Delicious’ apple peel (82%). The lowest peel contribution to total phenolic content per whole apple ranged between 26 and 29% and was observed in ‘Pilot’, ‘McIntosh’ and ‘Prima’ apples. Presented results may be useful for further investigations of the relationship between phenolics and agronomical parameters or future selection of apple genotypes having improved nutritional quality when consumed as fresh or as processed apple products.     

Temperature responses,flowering and fruit yield of the June-bearing strawberry cultivars Florence,Frida and Korona

The effect of night temperature on short day (SD) floral induction has been studied in three June-bearing strawberry cultivars of different geographic origin and compared with yield performance in the cool Nordic environment. At the optimum day temperature of 18 °C, the SD flowering response of the cultivars ‘Florence’ and ‘Korona’ increased significantly with increasing night temperature from 9 to 18 °C, while an optimum was reached at 15 °C in the cultivar ‘Frida’ that is selected under cool-environment conditions in Norway. Also, while saturated flowering response was obtained with 3 weeks of SD treatment at all temperatures in ‘Frida’, several plants of ‘Florence’ and ‘Korona’ failed to initiate flowers at 9 °C night temperature even with 5 weeks of SD. The effect of extended SD period was particularly pronounced in ‘Florence’. The slow SD floral induction response of ‘Florence’ was associated with a 2 week delay of anthesis in subsequent long day (LD) conditions at 21 °C. Yield performance of the same cultivars during 2 years under field conditions at Nes Hedmark and in North Norway also demonstrated that the yield potential of ‘Florence’ was not realized under the climatic conditions prevailing at these locations. In both years the yields varied significantly among the cultivars, ‘Frida’ having the highest yields followed by ‘Korona’, with ‘Florence’ far below. It is concluded that, in the Nordic environment, autumn (September) night temperatures are obviously sub-optimal for yield performance of some June-bearing strawberry cultivars, and that this effect is mediated by autumn temperature effects on flower initiation responses.     

Effect of set-size and storage temperature on bolting,bulbing and seed yield in two onion cultivars

The effects of three set-sizes (12.5, 17.5 and 22.5 mm in diameter) and seven storage temperatures (0, 5, 10, 15, 20, 25 and 30 °C) on bolting, bulbing and seed yield in two onion (Allium cepa L.) cultivars ‘Hygro’ and ‘Delta’ were investigated. The incidence of bolting increased linearly with set-size and curvi-linearly with decreasing storage temperature. Time to inflorescence emergence and floret opening showed a curvi-linear response to storage temperature with the earliest inflorescence emergence and floret opening occurring at 5 °C and the latest at 30 °C for ‘Hygro’ and at 25 °C for ‘Delta’. Seed yield per umbel also showed a curvi-linear response to storage temperature with the lowest seed yield occurring at 30 °C for ‘Hygro’ and at 25 °C for ‘Delta’ and the highest seed yield at 5 °C. For a seed crop, storage of large sets (22.5 mm) of these cultivars at 5 °C for 120 days appeared to be optimum with 5–12% higher seed yield per umbel than that of 90 days storage. Bulb yield showed a curvi-linear response to storage temperature with the highest bulb yield occurring at 25 °C and the lowest at 5 °C.     

Changes of physicochemical quality,phenolics and vitamin C content in hardy kiwifruit (Actinidia arguta and its hybrid) during storage

The effect of storage and the stage of maturity of hardy kiwifruits on the physicochemical quality, phenolics (TPC) and ascorbic acid content (AAC), as well as antioxidant activity (AA) were studied in this work. The phenolic compounds in hardy kiwifruits were separated and characterized by HPLC. The investigation was carried out on the two cultivars of Actinidia arguta – ‘Weiki’, ‘74-49’ and the hybrid of A. arguta and Actinidia purpurea (‘D14’). Fruit firmness rapidly decreased and the soluble solid content (SSC) increased for all cultivars during the first 14 days of storage at 1 °C. The AAC and TPC in vine ripe fruits were similar to the ones of the fruits of storage harvest maturity (8–10% SSC). AA content depended on the clone and either decreased during storage or remained almost unchanged. There was an increase in TPC after 7 days of keeping the fruits in a cold store chamber at the temperature 1 °C, but a longer period of storage caused a decrease in these compounds. AA (at harvest for storage purposes) was higher than that of vine ripe fruits and the ability to absorb free radicals slightly decreased during storage. There was a strong correlation between AAC, TPC and AA. That means that phenolics and vitamin C affect the antioxidant activity of hardy kiwifruits.