Strawberry Cvs Research Articles

Responses of two strawberry cultivars to NaCl-induced salt stress under the influence of ZnO nanoparticles

Salinity stress is one of the most serious impacts of climate changes on agriculture production, especially in salt sensitive crop plants, like strawberry. Currently, the utilization of nanomolecules in agriculture is thought to be a useful strategy to compact abiotic and biotic stresses. This study aimed to investigate the effect of zinc oxide nanoparticles (ZnO-NPs) on the in vitro growth, ions uptake, biochemical and anatomical responses of two strawberry cvs (Camarosa and Sweet Charlie) under NaCl-induced salt stress. A 2x3x3 factorial experiment was conducted, with three levels of ZnO-NPs (0, 15 and 30 mg 1-l) and three levels of NaCl-induced salt stress (0, 35 and 70 mM). The results showed that increased levels of NaCl in the medium had led to decrease in shoot fresh weight and proliferative potential. The cv Camarosa was found to be relatively more tolerant to salt stress. Additionally, salt stress leads to an accumulation of toxic ions (Na + and Cl-), as well as a decrease in K + uptake. However, application of ZnO-NPs at a concentration of 15 mg 1-l was found to alleviate these effects by increasing or stabilizing growth traits, decreasing the accumulation of toxic ions and the Na+/K + ratio, and increasing K + uptake. Additionally, this treatment led to elevated levels of catalase (CAT), peroxidase (POD) and proline content. The positive impacts of ZnO-NPs application were reflected on the leaf anatomical features, being better adapted to salt stress. The study highlighted the efficiency of utilizing tissue culture technique in screening of strawberry cultivars for salinity tolerance under the influence of NPs.

Repeated runner removal after harvest and floating row cover during fall affect carbohydrate status and yield potential of strawberry cvs. Polka and Wendy in the Northern climate

We investigated the impact of repeated runner removal after harvest and row cover during fall on strawberry (Fragaria × ananassa) cvs. Polka and Wendy cropping potential in the joint project of the University of Helsinki and the Rural Advisory Services Finland. Field trials were carried out in 2017 to 2019 on strawberry farms in Southern Ostrobothnia, Finland, at 62°49′N. The treatment effects on the crown carbohydrate reserves, flowering, and yield were recorded. Runner removal three times in three-week intervals after harvest decreased the crown starch reserves but increased the length of the apical inflorescence initials as observed through flower mapping in November, and the numbers of inflorescences and flowers in cv. Polka. Floating row cover after flower induction in September to October hastened floral development in the fall and increased the numbers of inflorescences, flowers, and fruit in cv. Wendy. Although the effects may depend on a cultivar and weather conditions during fall, repeated removal of runners after harvest and covering plants with a floating row cover after flower induction are recommended to increase strawberry yield potential in the Northern climate.

Genetic diversity in wild species and cultivars of strawberry for the FanAAMT gene controlling fruit flavor volatiles

Background. An important consumer trait of strawberry fruits is their aroma. Methyl anthranilate makes a considerable contribution to the fruit flavor. The methyl anthranilate content in strawberry fruits is controlled by the FanAAMT (аnthranilic acid methyltransferase) gene. Identification of genetic determinants for this trait facilitates targeted selection of promising forms based on diagnostic DNA markers. The purpose of this study was to study the allelic diversity of the FanAAMT fruit flavor gene in wild strawberry species and strawberry cultivars for identification of promising genotypes.Materials and methods. The objects of this study were wild species of Fragaria L. as well as F. × anaschata Kantor. and F. × ananassa Duch. cultivars of different ecogeographic origin. The FanAAMT gene was identified with the dominant marker FanAAMT.Results and conclusion. In the analyzed collection of strawberry genotypes, the FanAAMT gene was identified in 36.4% of the forms, including the wild species F. vesca L., F. moschata Duch. and F. virginiana subsp. platypetala (Rydb.) Staudt, and cv. ‘Kupchikha’ (F. × anaschata). Among the analyzed F. × ananassa cultivars, the FanAAMT gene was found in 31.6% of the tested forms, specifically in 27.3% of the 22 Russian cultivars, and 37.5% of the analyzed foreign ones. Promising sources of high methyl anthranilate content in fruits were identified: wild spp. F. moschata, F. vesca, and F. virginiana subsp. platypetala; cv. ‘Kupchikha’ (F. × anaschata); Russian garden strawberry cvs. ‘Bylinnaya’, ‘Zenit’, ‘Lastochka’, ‘Neznakomka’, ‘Feyerverk’ and ‘Tsarskoselskaya’; and foreign garden strawberry cvs. ‘Karmen’, ‘Ostara’, ‘Samson’, ‘Symphony’, ‘Troubadour’ and ‘Vima Tarda’, in which the functional allele of the FanAAMT gene was found. In the remaining studied strawberry genotypes the marker FanAAMT was not detected, which presumably indicates that the FanAAMT gene is absent. cells (R9.4.1).

Перлина - новий сорт суниці садової (Fragaria ananassa L.) для споживання ягід свіжими та для заморозки

Strawberry is the most spreaded small fruit crop in many countries. In Ukraine sn 2018 this crop total area was 8.3 thus. ha, among them 7.9 thus. ha fruit-bearing in all the categories of farms. The gross berries output was 62.3 thus. tons, the average yield being 7.7 t/ha. The Dutch bank «Rаdobank» carried out in April of 2016 the researches on the small fruit production in Europe and revealed that strawberry even now is the most popular small fruit crop. The strawberry Ukrainian and foreign cvs and elite forms were studied applying the methods of the primary strain inves-tigation and state strain testing in the small fruit patches planted in2012-2016 under the field conditions of the Northern part of the Ukraine’s Lisosteppe, namely: at the Institute of Horticulture NAAS of Ukraine. The varieties – standards were the Ukrainian Hercules, English Elegance, Dutch Elsanta and Italian Alba. As a result the new middle-ripening Ukraini-an cultivar Perlyna was selected as the best according to its signs. Perlyna was obtained by means of the intervarietal hybridization (cvs Present and Elsanta) sn 2004. The authors are V.V. Pavliuk, K. M. Kopan, V. H. Kopan. The berries ripe 2-3 days later than ’Elsanta’ and 2-3 days earlier than and ’Polka’. The bushes are high and vigour, not branchy, with firm high floriferous shoots and dark-green hardish leaves. Resistance to the leaves diseases is high. The berries are high marketable and large (the mass of average is 15 g, maximum 35 g), prolonged broad-conic, being ripe fully dark-red brilliant. The flesh is dense red aromatic of kind sour-sweet taste, in accordance with the multi-year data it contains 7.5 % of dry substances, 3.5 % of sugars, 0.95-1.0 % of organic acids as well as 0.440 mg of pectine substances and 45 mg of vitamin ’C ’ per 100 g of . Under the sufficient humid content the berries size exceeds that of ’Prysviata ’, ’Zenga Zengana’ and ’Polka ’. The yield is higher (18-20 t/ha) than that of the varieties ’Elsanta ’and ’Present ’ under the one-row planting ( 0.8x0.25 m). The cultivar is winter-hardy and drought- resistant. ’Perlyna’ is entered into the State Register of Plant Varieties Suitable for Dissemination in Ukraine. Certificate 181079 on the State Registration of the Plant Cultivar (December 4, 2018). Patent 190373 on the Plant Cultivar (April 12.2019).

Evaluation of Performances of Some Organic Waste in Organic Strawberry Cultivation

This trail aimed investigate the benefits of the use of wastes such as hazelnut husk and rice hull composts in organic strawberry cultivation and their effects on productivity and fruit. The research was carried out in the Ondokuz Mayis University’s (OMU) Faculty of Agriculture Research and Practice garden in Samsun in 2010 and 2011. In the research, effects of some organic wastes (hazelnut husk, hazelnut husk compost, rice hull, rice hull compost and farmyard manure) on yield and quality of strawberry cvs. “Camarosa”, “Sweet Charlie”, “Redlands Hope” and “Fern” were examined. In the experiment, yield per plan (g/plant), amount of rotten fruits (g/plant), fruit weight (g), total soluble solid (TSS) (%), titrable acid content (%) and vitamin C content (mg/100 g) were examined in order to determine impacts of organic wastes on yield and quality. No statistical difference could be established with regard to yield criteria among organic wastes in the experiment. Different organic waste practices have occasionally had significant impacts on some properties of fruit quality. In the experiment, the heaviest fruits were obtained from garden soil (S) and hazelnut husk compost (2010) application; the highest TSS content was obtained from the S and hazelnut husk compost (2011) applications and the highest vitamin C content was obtained from the hazelnut husk compost (2010), garden soil (2011) and hazelnut husk compost applications in 2011.

Effect of cultivar and storage temperature on identification and stability of polyphenols in strawberry cloudy juices

The effect of strawberry (Fragaria x ananassa Duchesne) cultivars (cvs) and storage temperature on the stability of polyphenols in cloudy juices was determined. Identification of phenolic compounds by ultra performance liquid chromatography-electrospray ionization/mass spectrometry (UPLC–ESI/MS), as well as quantitative analysis by ultra-performance liquid chromatography–photodiode array–fluorescence (UPLC–PDA–FL), were carried out on fresh and stored products (6 months, 4°C and 20°C) from 7 different strawberry cvs. A total of 32 polyphenolic compounds were identified: flavan-3-ols (6), anthocyanins (8), flavonols (4) and flavones (3), hydroxycinnamic acids (4), and ellagic acid derivatives (7). Total polyphenol content ranged from 642.08mg/L in fresh ‘Florence’ cv. juice to 296.72mg/L in ‘Honeoye’ cv. juice after 6 months of storage at 20°C. Anthocyanins (max. 161.40mg/L in ‘Honeoye’ juice) demonstrated the greatest degree of degradation (31–100%, depending on the molecular structure and temperature). Cyanidin-3-malonylglucoside was less labile than 3-glucoside. In the case of pelargonidin glycosides, 3-glucoside was more stable. The degradation process was the least advanced in ‘Kimberly’ cv. juice (58.53% at 4°C). Storage conditions also influenced the decrease in p-coumaroyl-hexose, and quercetin-glucuronide content. However, low temperatures limited this process. This was especially noticeable in ‘Florence’ and ‘Honeoye’ cvs. In turn, proanthocyanidins showed the most stability and were the main polyphenols identified in juices (212–434mg/L). Generally, it was observed that the total content of polyphenols and their stability in juices was dependent on the cultivar, and the duration of storage conditions.

Abscisic acid-mediated leaf phenolic compounds, plant growth and yield is strawberry under different salt stress regimes

The present research was conducted to evaluate the interaction effects of exogenous abscisic acid (ABA) and salt stress on phenolic compounds, growth and yield of two short day strawberry cvs "Queen Elisa" and "Kurdistan". Plants were subjected to control, gradual salt stress (up to 20 mmol L-1 over 5 weeks) and salinity shock (20 mmol L-1). ABA treatments included: 0 (control), 5, 10, 20 and 40 µmol L-1. The experiment was carried out based on a complete randomized design in factorial experiment. The highest level of ferulic acid was observed by applying 40 µmol L-1 ABA in "Queen Elisa" under salt stress shock but effective increase in caffeic acid and p-coumaric acid was shown at gradual salt stress for both cultivars at the same ABA level. Maximum level of ABA led to the highest gentisic acid and gallic acid at gradual salt stress in "Kurdistan". Methyl gallate and flavonoid content showed a striking increase at the same conditions in "Queen Elisa". The interaction effect of salt stress regimes and ABA resulted in an increase in ellagic acid content for both cultivars. The interaction effect of ABA and salt shock caused higher reduction in root and shoot fresh dry weights and decrease in fruit yield in "Kurdistan". The results of this experiment accounts for the important role of exogenous ABA in the activation of antioxidant defense mechanism, growth and yield maintenance under gradual salt stress in strawberry.

Supplemental LED growth light in remontant strawberry at high latitudes

BACKGROUND: To grow remontant strawberries at high latitudes in autumn is challenging because of short days and low light levels. Nevertheless, current day and night temperatures in Norwegian coastal areas up to 63 degrees N are normally sufficient for growth and fruit development till early October, and even higher temperatures can be expected in the future according to climatic scenarios, with potential to prolong the growing season. However, light would be a minimum factor. It is therefore of interest to examine the effects of providing supplemental light when photosynthetic active radiation (PAR) falls below critical level for development of high fruit quality. OBJECTIVE: To examine effects on fruit yield parameters, fruit tension, Brix ◦ and arthropod numbers, in order to investigate the potential of LED lighting using diodes giving red and blue light, as a means to prolong the growing season at northern latitudes. METHOD: In this two-year study remontant strawberry cvs ‘Everest’ and ‘Rondo’ were grown in high polytunnels. Two LED lighting levels (LED100 and LED300) were applied from 7 Pm to 7 AM, whenever light intensity fell below 400mol m −2 s −1 from first week of September, and compared to ambient light (control). The LED300 was peaking at wavelengths of 460 nm and 660 nm, respectively blue and red, and the relation between blue and red light was 1 : 8; LED100 delivered similar wavelengths but the blue to red relation was 2 : 8. Fruit yield, soluble solids (Brix ◦ ), fruit firmness, temperature ( ◦ C), dew point ( ◦ C), and PAR light (mol m −2 s −1 ) were recorded. The experimental design was block with four replications. The lamps were hung with the light source 40 cm above top of canopy, giving a PAR radiation at top of canopy of LED100 and LED300 of respectively 900 and 258mol m −2 s −1 . RESULTS: LED improved fruit yield and quality, but more at 900 than at 258mol m −2 s −1 . However, highest light level was probably beyond the saturation point for photosynthesis, at least in early morning and late evening and the last three weeks of the harvesting season, because of low temperatures. Some fruit yield was not harvested because of too low temperatures to achieve ripen fruits after mid-October. Arthropods were sampled from ‘Rondo’ leaves 2–3 times per season, and aphids, spider mites and predatory mites (introduced) were the most numerous groups. LED significantly decreased the number of spider mites in the autumn. CONCLUSIONS: LED lighting has potential as light source growing remontant strawberries in high polytunnels, when PAR radiation is below 400mol m −2 s −1 . However, to benefit fully of the light it would be necessary to grow the plants in winter tunnels and add heating. That would increase the yields significantly compared with our results.

Influence of media and growth regulators on regeneration and morphological characteristics of strawberry cvs Kurdistan and Merck

To evaluate the best media and growth regulator combinations for the regeneration and morphological characteristics of strawberry, meristems of Kurdistan and Merck strawberry cultivars were cultured on Murashige and Skoog (1962), Gamborg et al. (1968) and Nitsch and Nitsch (1969) media supplemented with various growth regulator combinations including B1: (BA 1.0 mg/l + IBA 0.05 mg/l + GA3 0.05 mg/l), B2: (Kinetin 5 mg/l + 2,4-D 0.5 mg/l + GA3 0.05 mg/l) and B3: (BA 2 mg/l + IBA 0.2 mg/l + GA3 0.05 mg/l). The largest number of shoots was obtained on NN medium supplemented with B1 followed by MS and B5 media with the same growth regulator combination. In the media, B2 increased shoot elongation rate in both cultivars, but caused a low frequency of shoot formation. There was significant difference among various media and growth regulator combinations in regards to morphological traits such as leaf length, width of terminal leaflets and number of terminal leaflets teeth, whereas little differences were observed in the length of terminal leaflets and the length of terminal leaflet petiolate. Key words: Strawberry, growth regulator, regeneration, cultivar.

Seasonal alteration of sugar metabolism in strawberry (Fragaria × ananassa) plants during cold-acclimated and non-acclimated stages

Plants of strawberry cvs Aromas and Diamante were removed from the field in cold acclimated (CA, January) and non-acclimated (NA, July) stages. Crown parts of the plant were used for analysis. Apoplastic total soluble sugar (TSS), reducing sugars and sucrose contents did not change in both cultivars in both sampling stages. Symplastic TSS, reducing sugars and sucrose contents were higher in CA stage than that in NA stage in all samples. Considering the cultivars, TSS, reducing sugars and sucrose contents were higher in Diamante than Aromas. The activity of acid invertase (EC 3.2.1.26) enzyme was higher in NA stage than that in CA stage in the apoplast of crown tissues. In general, acid invertase activity in the symplast of crown tissues in both cultivars was higher in CA stage compared with that in NA stage although not significantly, as a function of hardening. In addition generally, the cultivars had significantly higher sucrose synthase (SS) (EC 2.4.2.13) activity in the symplast of crown tissues when sampled at the CA than at the NA stage. In conclusion, cold-hardiness of strawberry was suggested by increasing their TSS, reducing sugars and sucrose contents significantly in the symplast of crown tissues in the CA stage. Moreover, both acid invertase and SS are regulated by coldacclimation and deacclimation.

Effects of some growing media on the growth of strawberry cvs. 'Camarosa' and 'Fern'

This study evaluated the development of above and under ground parts of strawberry plants cvs. 'Fern' and 'Camarosa ' in a glasshouse using perlite, forest soil, finpeat, peat, finpeat+perlite (1:1) and peat+perlite (1:1) as substrates. The effects of different growing media on development of above and under ground parts of plant were statistically significant. The highest number of primary roots per plant, length of the most developed roots and number of crowns per runner were obtained from perlite, finpeat+perlite and peat medium, respectively, in both cultivars. The runner length, number of runners per plant, leaf area, fresh root weight and dry root weight varied between cultivars according to growth medium. In general peat, finpeat or finpeat+perlite gave the best results in terms of above and under ground parts of plants in both cultivars. Some important properties such as water retention capacity, cation exchangeable capacity, pH, porosity etc. of growing media using in this study were also determined.

Quality of fresh-cut strawberry

The aim of this work was to study the physical, chemical, physiological and microbiological changes during the flow chart of fresh-cut strawberry. Strawberry cvs. Camarosa, Dover and Tudla, derived from experimental area of the Universidade Federal de Viçosa, were selected by color (red ¾) and absence of wound. Afterwards, the minimal processing was evaluated, as follows: fast cooling, water and ice, removal of the calyx followed by conservation at 5±0.5°C and 90-95% RH for 13 days, sanitation, drainage, cut in halves. Removal of the calyx did not result significant difference for fresh weight, total soluble solids, total titratable acidity, pH and ratio TSS/TTA. The rapid cooling resulted in lower electrolyte leakage and respiratory rate, especially sanitized fruits. Sanitization by immersion in chlorine solution slowed the growth of fungi and yeast. Drainage for 20 minutes eliminated practically all water on the surface of the fruits. The fresh-cutting did not affect the visual and nutritional quality of strawberries like appearance, microbiot, vitamin C, anthocyanins and phenolic compounds, consisting of alternative market potential economically viable.

First Report of Fusarium Wilt Caused by Fusarium oxysporum on Strawberry in Spain.

In the spring of 2007, wilted and dead strawberry plants (Fragaria × ananassa Duch. cvs. Camarosa and Ventana) were observed in a soilless culture system in Huelva, southwestern Spain. Approximately 8% of the plants in the field died. Isolations from necrotic crowns and roots and necrotic flowers were made on potato dextrose agar after disinfestation in 0.6% NaOCl for 30 s. Colonies with light purple mycelia and beige or orange reverse colony colors developed after 9 days of incubation at 25°C. Colonies produced abundant microconidia, macroconidia, and chlamydospores. Microconidia were hyaline and oval-ellipsoid to cylindrical (5.9 to 9.2 × 2.1 to 3.4 μm). Macroconidia were 3 to 5 septate and fusoid-subulate with a pedicellate base (28.8 to 37.3 × 3.2 to 4.3 μm). Morphology and growth matched descriptions of Fusarium oxysporum Schlechtend emend. Snyder & Hansen (2). A PCR assay for amplification of r-DNA using primers PFO2 and PFO3 established the identity of the isolate as F. oxysporum (1). To confirm the pathogenicity of the fungus, roots of 30-day-old strawberry cvs. Camarosa and Ventana (20 plants each) were inoculated by dipping the roots into a conidial suspension (107 conidia per ml) for 15 min. The inoculated plants were transplanted into plastic pots containing sterilized peat and maintained at 25°C and 100% relative humidity in a growth chamber with a daily 12-h photoperiod of fluorescent light. The pathogenicity test was conducted twice. Within 30 days, all inoculated plants developed wilt symptoms similar to that observed in the field and eventually 75% of the plants died. No symptoms were observed on plants dipped in distilled water. The fungus was successfully reisolated from crowns, roots, and necrotic flowers, fulfilling Koch's postulates. To our knowledge, this is the first report of the occurrence of Fusarium wilt caused by F. oxysporum on strawberry plants in Spain.

Contribution of amino acids to strawberry fruit quality and their relevance as stress indicators under NaCl salinity

Strawberry cvs Korona and Elsanta, differing in their sensitivity to salt stress, were exposed to 0, 40, or 80 mM NaCl in the root medium from the end of April to mid-August. Although fruits of both cultivars contained comparable amounts of Na + and Cl −, fruit quality was more impaired in cv. Elsanta, as indicated by the larger reductions of fruit size and sugar/acid ratios. Malondialdehyde levels started to rise significantly at 40 mM NaCl in the more sensitive cv. Elsanta, but at 80 mM in cv. Korona. Total amino acid levels, especially contents of essential amino acids, rose significantly in both cvs. Salt stress also increased contents of free proline, asparagine, and glutamine. Their increases may contribute to osmotic adjustment. The results of the present study favour the interpretation that elevated levels of proline, asparagine and glutamine are indicative of salt stress damage.

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.

Effect of Organic and Conventional Growing Systems with Different Mulching on Yield and Fruit Quality in Strawberry cvs. Sweet Charlie and Camarosa

ABSTRACT This study was carried out to determine yield and fruit quality of cvs. Sweet Charlie and Camarosa in conventional and organic growing systems in 2003–2005. Organic agriculture is an alternative production system that uses no synthetic pesticide or fertilizer and, therefore, it may benefit human health and the environment. This study consisted of the following eight treatments: (1) Sweet Charlie using the conventional system mulched with a black plastic (SC-CL-BP), (2) Sweet Charlie using conventional system mulched with a floating sheet (SC-CL-FS), (3) Sweet Charlie using organic system mulched with a black plastic (SC-Or-BP), (4) Sweet Charlie using organic system mulched with a floating sheet (SC-Or-FS), (5) Camarosa using conventional system mulched with a black plastic (CAM-CL-BP), (6) Camarosa using conventional mulched with a floating sheet (CAM-CL-FS), (7) Camarosa using organic system mulched with a black plastic (CAM-Or-BP), (8) Camarosa using organic system mulched with a floating sheet (CAM- Or-FS). Yield was higher in the conventional system than in the organic system in 2004, but no significant difference between the two was found in 2005. Soluble solid and vitamin C contents were higher in fruits grown using the organic system in both years. Also, the amount of rotten fruit was lower in the organic system. There was no difference between conventional and organic growing from the point of view of fruit weight and titreable acidity contents. It was shown that Camarosa when considering yield and fruit quality was superior to Sweet Charlie in the organic system. Thus, organic strawberry growing is recommended because of the benefical effects on the environment, human health and its higher price in market.

Influences of day and night temperatures on flowering of Fragaria x ananassa Duch., cvs. Korona and Elsanta, at different photoperiods

Abstract The effects of photoperiod (12, 13, 14, 15 or 16 h), day temperature (12, 15, 18, 24 or 27 °C) and night temperature (6, 9 or 12 °C) and their interactions on flower and inflorescence emergence were investigated by exposing 4 week old runner plants of strawberry cvs. Korona and Elsanta during a period of 3 weeks. A daily photoperiod of 12 or 13 h resulted in the highest number of plants with emerged flowers. A photoperiod of 14 h or more strongly reduced this number, while no flowers emerged at a photoperiod of 16 h. Plants exposed to photoperiods of 12 or 13 h flowered earlier and had longer flower trusses. A day temperature of 18 °C and/or a night temperature of 12 °C were optimal for plants to emerge flowers and resulted in the shortest time to flowering. A night temperature of 6 °C strongly reduced the number of plants that emerged flowers, especially when combined with lower day temperatures. Photoperiod and temperature had no effect on the number of inflorescences, all flowering plants produced on average one inflorescence. The number of flowers on the inflorescence increased with decreasing day temperature and when photoperiod was raised from 12 to 15 h. In general, ‘Korona’ was more sensitive to photoperiod and temperature as ‘Elsanta’, and had a lower optimal day temperature for flower emergence. Results of this experiment may be used to produce high quality plant material or to define optimal conditions when combining flower induction and fruit production.

Effect of Ammonium: Nitrate Ratio on Yield, Calcium Concentration, and Photosynthesis Rate in Strawberry

ABSTRACT The effect of ammonium:nitrate (NH4:NO3) ratio in nutrient solution on growth, photosynthesis (Pn), yield, and fruit quality attributes in hydroponically grown strawberry (Fragaria × ananassa Duch) cvs. ‘Camarosa’ and ‘Selva’ was evaluated. There were four nutrient solutions of differing NH4:NO3 ratios as follows: 0:100, 25:75, 50:50, and 75:25. Plants grown in solution with 75% NH4 had lower leaf fresh and dry weights and leaf area than those with 25% NH4 in both cultivars. High ratios of NH4 and NO3 in the solution always reduced the yield. The yield was increased by 38% and 84% in ‘Camarosa’ and ‘Selva,’ respectively, when the plants were grown in the 25NH4:75NO3 solution compared with plants grown in a higher NH4 ratio solution. The increased yield at the 25 NH4:75NO3 ratio was the result of the increase in fruit size, i.e., length and fresh weight of fruits. Plants grown in the 25NH4:75NO3 solution had the highest rate of Pn, while those grown in 75NH4:25NO3 solution had the lowest Pn rates in both cultivars. Increasing the NH4 ratio in the solution from 0 to 75% significantly reduced the calcium (Ca) concentration and postharvest life of the fruits in both cultivars. Both higher leaf area and Pn rate appeared to be the reason for the increased yield and plant growth in the 25:75 ratios of nitrogen (N). The results indicate the preference of strawberry plant growth toward a greater nitrate N form in a hydroponic solution. Therefore, a combination of two forms of N in an appropriate ratio (25NH4:75NO3) appears to be beneficial to plant growth, yield, and quality of strawberry fruits.

(431) Evaluation of Anti-transpiration Organic Materials on Strawberry Performance

Interactive effects of different temperature regimes and anti-transpiration organic materials, Surround WP (kaolinite clay) and Raynox (sun-protectant), on two strawberry (Fragaria ×ananassa) cvs. Chandler and Sweet Charlie were investigated under controlled environmental conditions. Newly planted strawberries treated with Surround and Raynox were subjected to 20/15, 30/25, and 40/35 °C (day/night) temperature regimes and 16 day/8 night photoperiod in growth chambers for 42 d. Photosynthesis (A) and photochemical efficiency (Fv/Fm) were measured at 7-d intervals during the experiment. Plants treated with Raynox displayed greater resistance to high temperature (40/35 °C) compared to those treated with Surround. Net photosynthesis of both cultivars decreased significantly with time at 40/35 °C. There was no significant difference in photosynthetic rate between the two cultivars. Nevertheless, there was difference in plant biomass between the cultivars. Raynox provided more protection against high temperature, specifically in reducing stomatal conductance and limiting transpiration, than Surround.

Allelopathic effects of juglone and walnut leaf extracts on growth, fruit yield and plant tissue composition in strawberry cvs. ‘Camarosa’ and ‘Sweet Charlie’

SummaryWe conducted an experiment in a heated greenhouse to investigate the effects of juglone (5-hydroxy-1,4-naphthoquinone) and walnut (Juglans regia L.) leaf extracts on yield, growth, chemical and plant nutrient element composition of short-day strawberry cultivars ‘Camarosa’ and ‘Sweet Charlie’. Strawberry plants were treated with 1 mM juglone or walnut leaf extracts (undiluted, or diluted 1:2, 1:4, 1:8). Vegetative and generative plant growth was inhibited strongly by treatment with both juglone and undiluted walnut leaf extracts. Fruit yield per plant, numbers of fruit per plant, average fruit weight, crowns per plant, numbers of leaves, leaf area, fresh root weight, total soluble solids, vitamin C, and acidity were all lower for juglone-treated plants compared to controls. All nutrient elements analysed in leaves were generally lower than in controls for all treatments except 1:8 diluted walnut extract. Results from this study should address concerns about growth inhibition of strawberry plants under walnut-based intercropping systems.