Identification of gibberellins in leaf tissues of day-neutral strawberry (Fragaria × ananassa Duch.) cultivars

The endogenous gibberellins (GAs) in leaf tissues of two day-neutral cultivars (Rapella and Selva) of strawberry (Fragaria × ananassa Duch.) were analysed using combined gas chromatography -- mass spectrometry (GC-MS). Seven of the later members of the 13-hydroxylation GA biosynthetic pathway were identified, by comparison of Kovats retention indices and mass spectral data obtained for methyl ester trimethylsilyl ether derivatives, either with data obtained from authentic compounds or literature values. GA₁, GA₃, GA₈, GA₁₇, GA₁₉, GA₂₀ and GA₂₉ were detected in extracts of both cultivars.     

A new economical storage technique for strawberry (Fragaria × ananassa Duch.) in vitro

In Vitro Cellular & Developmental Biology - Plant - Strawberry plants grown in vitro are typically stored and maintained on agar containing Murashige and Skoog (MS) media and sucrose as a...     

Improved culture technique for strawberry (Fragaria × ananassa Duch.) protoplasts and the determination of DNA content in protoplast derived plants

A reproducible and efficient protoplast to plant-system has been developed for strawberry. By using young shoots growing on medium supplemented with cytokinin we were able to exclude the detrimental enzyme Pectolyase from our enzyme solution. The more gentle isolation procedure reported in this paper, together with the agarose-embedding system had a pronounced effect on protoplast viability and growth. Plant regeneration was enhanced by using thidiazuron instead of benzyladenine. Flow cytometric measurement of the DNA content in protoplast derived plants revealed that 27 out of 51 plants contained the amount of DNA corresponding to octoploid level. Fifteen plants exhibited chromosome doubling(16×), one was diplodecaploid(12×) and eight plants mixoploid.     

Identification of gibberellins in leaf tissues of strawberry (Fragaria × ananassa Duch.) grown under different photoperiods

In studies of the effect of long or short-day photoperiod treatments on the qualitative gibberellin (GA) content of mature leaves of a facultative short-day (SD) strawberry cultivar (Fragaria × ananassa Duch. cv. Elsanta), GA₁, GA₈, GA₁₇, GA₁₉, GA₂₀, GA₂₉ and GA₄₄ were identified by full-scan gas chromatography - mass spectrometry (GC-MS) in extracts from plants grown under long-day (LD) conditions, and GA₁, GA₅, GA₈, GA₁₉, GA₂₀ and GA₂₉ in similar extracts from plants subjected to eight SD cycles after growth under LD conditions. The early 13-hydroxylation GA biosynthetic pathway thus appeared to predominate, with the apparent absence of GA₅ in LD and of GA₁₇ and GA₄₄ in SD extracts providing evidence of modulation of this pathway by photoperiod. A search, including GC-MS with selected ion monitoring, failed to detect GA₃, or the polyhydroxylated GA₈₅, GA₈₆, GA₈₇ or GA₃₂ for which some extracts were specifically purified.This paper is respectfully dedicated to the memory of Gordon Browning, who died suddenly on the 1st July, 1993. He will be sorely missed, both as a friend and colleague.     

In vitro assessment of strawberry (Fragaria × ananassa Duch.) plant responses to water shortage stress under nano-iron application

In Vitro Cellular & Developmental Biology - Plant - Strawberry is a susceptible plant to water stress, and its growth is severely declined under water shortage. Therefore, the aim of this study...     

Positive effects of cold pretreatment, iron source, and silver nitrate on anther culture of strawberry (Fragaria × ananassa Duch.)

Androgenesis by anther culture or isolated microspore culture is the most efficient method for haploid production. In this study, the effects of cold pretreatment (4 °C), silver nitrate, and iron source in the medium were investigated on anther culture of five strawberry cultivars (Camarosa, Selva, Pajaro, Paros, and Gaviota) in three independent experiments, and three traits including percentage of androgenic anthers, embryogenesis, and callogenesis were determined. In the first experiment, cold pretreatment of 4 °C for 2 and 3 days produced the highest percentage of androgenic anthers in three cultivars (Camarosa, Selva, and Pajaro) and cold pretreatment of 4 °C for 2 days produced the highest percentage of androgenic anthers in cultivar Paros. In the second experiment, the effect of Fe-EDDHA was more effective than Fe-EDTA, and increased the percentage of androgenic anthers and embryogenesis. The use of 57.5 mg l^?1 Fe-EDDHA produced the highest percentage of androgenic anthers in cultivar Camarosa and the best embryogenesis in cultivars Camarosa and Gaviota. In the third experiment, the use of 15 mg l^?1 silver nitrate in medium significantly increased the percentage of androgenic anthers and embryogenesis in cultivar Camarosa.     

Jasmonic acid improved in vitro strawberry (Fragaria × ananassa Duch.) resistance to PEG-induced water stress

Plant Cell, Tissue and Organ Culture (PCTOC) - To investigate the influence of jasmonic acid (JA) on morpho-physiological and biochemical characteristics of strawberry cv. Queen Elisa, under in...     

Dynamics of phytohormone and DNA methylation patterns changes during dormancy induction in strawberry (Fragaria?×?ananassa Duch.)

Changes in endogenous phytohormone levels, DNA methylation patterns, and expression levels of related genes during induction of dormancy in two strawberry cultivars, Darselect and All Star, were studied under controlled environmental conditions. At 12°C, regardless of day length, potted, runner-derived plants of both cultivars gradually exhibited morphological traits typical of dormancy after treatment for 8 weeks. These morphological changes were accompanied by a synchronous significant decline in indole-3-acetic acid (IAA) level and increases in abscisic acid (ABA) content and global genomic DNA methylation in young leaves. Exposed at 15°C and a short-day photoperiod, the changes in morphology, phytohormone levels and DNA methylation of both cultivars were similar to those observed at 12°C. Slight but non-significant changes in IAA and ABA levels and genomic DNA methylation occurred in young leaves at both 15°C with long days and 18°C with short days. These results indicated that temperature alone was sufficient to induce strawberry to enter the typical dormant phase, and day length had no impact at 12°C. The higher temperature permissible for dormancy induction in strawberry was 15°C, but at this temperature dormancy induction was modified by day length. The expression patterns of FaPIN1, FaNCED1, FaDRM and FaROS1 were coincident with the changes in phytohormone levels and DNA methylation. Although the two tested cultivars have different temporal responses with the different degree of cold tolerance and depth of dormancy, both the endogenous phytohormone and DNA methylation were changed when induced by external environmental factors.     

The influence of photoperiodic growth condition on isolation of RNA from strawberry (Fragaria × ananassa duch.) tissue

Purification of high-quality RNA from different strawberry tissues is often affected by the presence of high levels of contamination by polysaccharides and phenolic compounds. With the protocol detailed here we describe for the first time total RNA purification from petiole tissue. Treating the plants used as source of material with short-day light regime prior the extraction we are able to obtain RNA suitable for further applications such as in vitro translation, RT-PCR, and RNA blot analysis. The yield of total RNA extraction is significantly enhanced when tissue from plants grown under short-day photoperiodic condition is used compared with that taken from plants grown under long day photoperiod.     

Silver nanoparticles improved explant disinfection,in vitro growth,runner formation and limited ethylene accumulation during micropropagation of strawberry (Fragaria × ananassa)

Plant Cell, Tissue and Organ Culture (PCTOC) - One of the common problems in strawberry (Fragaria?×?ananassa) micropropagation is the vitrification phenomenon (succulent plantlets,...     

Tissue-specific expression of the β-glucuronidase reporter gene in transgenic strawberry (Fragaria × ananassa) plants

The strawberry ( Fragaria spp) is regarded as a false fruit because it originates from the receptacle, which is a non-ovarian tissue. For this reason, fruit-specific promoters isolated from plant species in which the fruit is derived from the ovary wall might not be suited to control gene expression in a fruit-specific way in strawberry. In order to achieve (false) fruit-specific expression in strawberry, we tested the petunia FBP7 (floral binding protein7) promoter, which proved to be active in the receptacles of petunia flowers, in transgenic strawberry fruits. In strawberry plants containing the FBP7 promoter fused to the ß-glucuronidase (GUS) reporter gene ( gus), GUS activity was found in floral and fruit tissues of all developmental stages tested but not in leaf, petiole and root tissue . Surprisingly, Northern blot analysis showed the presence of gus-derived mRNAs in root (strong) and petiole (weak) tissue of fbp7- gus plants in addition to the floral and fruit tissues. Therefore, it is concluded that the histological GUS phenotype does not necessarily correspond with expression at the mRNA level. mRNA quantification using the TaqMan polymerase chain reaction technology confirmed the Northern results and showed that in red strawberry tissue the cauliflower mosaic virus 35S promoter is at least sixfold stronger than the FBP7 promoter.     

Detachment-accelerated ripening and senescence of strawberry (Fragaria × ananassa Duch. cv. Akihime) fruit and the regulation role of multiple phytohormones

To study the detachment stress on the ripeness of strawberry fruit, physiological characteristics of strawberry fruit on and off plant during ripeness and senescence processes were investigated. The results indicated that the ripeness of strawberry fruit upon detachment was accelerated, in terms of firmness, soluble solid content and especially color development. The color of fruit off plant changed rapidly from white to full red in 1–2 days. The respiratory rate in fruit off plant was strengthened, higher than that on plant. Abscisic acid level and ethylene production in fruit off plant were also higher than those on plant and auxin degradation was exacerbated by detachment. Expression levels of FaMYB1, FabHLH3 and FaTTG1 were generally reduced with phenotypes of redder color and more anthocyanin accumulation in fruit off plant. Results also suggested that the detachment initially stimulated ethylene and abscisic acid production and auxin degradation, which modulated ripening-related gene expression and at last enhanced fruit pigmentation.     

CAPS markers improved by cluster-specific amplification for identification of octoploid strawberry (Fragaria × ananassa Duch.) cultivars, and their disomic inheritance

Cleavage amplified polymorphic sequence (CAPS) markers of strawberry (Fragaria × ananassa Duch.) can be useful for identifying mislabeled or patent-infringing cultivars in the marketplace. However, CAPS markers in octoploid strawberry tend to give unclear bands because multiple homologous sites are simultaneously amplified by the non-selective PCR. To overcome this problem, we used cluster-specific amplification based on the nucleotide sequences of PCR products and were able to improve the band clarity of 18 CAPS markers. By analyzing the marker segregation ratio, we demonstrated that 13 clarified markers were derived from single diploid loci that were transmitted to progeny in a manner consistent with Mendelian inheritance. We discuss the genomic structure of octoploid strawberry from the viewpoint of cluster and segregation analysis and suggest that it comprises independent genomes. We tested the utility of all of the markers we developed for cultivar identification and confirmed their ability to distinguish among 64 strawberry cultivars.     

Identification of gibberellins in leaf exudates of strawberry (Fragaria ×ananassaDuch.)

Leaf exudates from the short-day (SD) strawberry (Fragaria × ananassa Duch.) cv. Elsanta were analysedfor gibberellin (GA) content using combined gaschromatography – mass spectrometry (GC-MS). Comparison of full-scan mass spectra and Kovatsretention indices (KRIs) with those of standardsrevealed the presence of GA₁, GA₃, 3-epiGA₁ and GA₃-isolactone.     

Effect of nickel concentration and soil pH on metal accumulation and growth in tropical agromining ‘metal crops’

Plant and Soil - Phosphorus (P) deficiency is a major constraint for rice production in the tropics. Field-specific P management is key for resource-limited farmers to increase yields with minimal...     

Physiological and growth responses to water deficits in cultivated strawberry (Fragaria × ananassa) and in one of its progenitors,Fragaria chiloensis

Cultivation of strawberry (Fragaria × ananassa) requires irrigation. Improving crop water use efficiency (WUE) is important for future production. Fragaria chiloensis, a progenitor of cultivated strawberry, grows in sandy soils, and may prove useful in breeding for improved WUE. Little, however, is known about variation in drought tolerance within this species. This research explores drought tolerance in a range of F. chiloensis and F. × ananassa genotypes. Four cultivars of F. × ananassa and four accessions of F. chiloensis were compared when well watered, and when subjected to a water deficit (65% of evapotranspiration). New leaf production, stomatal conductance, and photosynthetic rate were significantly reduced under water deficit, and also significantly differed between genotypes. A significant interaction of genotype and irrigation was found for transpiration rate, leaf area and dry mass, production of runners, predawn water potential, a measure of transpiration efficiency (shoot biomass produced per litre water transpired), and carbon isotope composition, indicating that some genotypes were more severely affected by water deficit than others. The South American F. chiloensis accession ‘Manzanar Alto’ had a similar rate of transpiration to the commercial cultivars, but the remaining (North American) F. chiloensis accessions used far less water than the F. × ananassa. Well-watered F. chiloensis plants used less water than water-limited plants of the F. × ananassa cultivar ‘Florence’. Transpiration efficiency of the F. chiloensis accession ‘BSP14’ was improved by water deficit: this was the only genotype not to show a reduction in leaf area and dry mass under water deficit. Greater drought resistance in three F. chiloensis accessions compared to F. × ananassa results from a conservative vegetative growth strategy, reducing loss of water.     

Effects of Elevated CO(2) and Temperature on Yield and Fruit Quality of Strawberry (Fragaria × ananassa Duch.) at Two Levels of Nitrogen Application

We investigated if elevated CO(2) could alleviate the negative effect of high temperature on fruit yield of strawberry (Fragaria×ananassa Duch. cv. Toyonoka) at different levels of nitrogen and also tested the combined effects of CO(2), temperature and nitrogen on fruit quality of plants cultivated in controlled growth chambers. Results show that elevated CO(2) and high temperature caused a further 12% and 35% decrease in fruit yield at low and high nitrogen, respectively. The fewer inflorescences and smaller umbel size during flower induction caused the reduction of fruit yield at elevated CO(2) and high temperature. Interestingly, nitrogen application has no beneficial effect on fruit yield, and this may be because of decreased sucrose export to the shoot apical meristem at floral transition. Moreover, elevated CO(2) increased the levels of dry matter-content, fructose, glucose, total sugar and sweetness index per dry matter, but decreased fruit nitrogen content, total antioxidant capacity and all antioxidant compounds per dry matter in strawberry fruit. The reduction of fruit nitrogen content and antioxidant activity was mainly caused by the dilution effect of accumulated non-structural carbohydrates sourced from the increased net photosynthetic rate at elevated CO(2). Thus, the quality of strawberry fruit would increase because of the increased sweetness and the similar amount of fruit nitrogen content, antioxidant activity per fresh matter at elevated CO(2). Overall, we found that elevated CO(2) improved the production of strawberry (including yield and quality) at low temperature, but decreased it at high temperature. The dramatic fluctuation in strawberry yield between low and high temperature at elevated CO(2) implies that more attention should be paid to the process of flower induction under climate change, especially in fruits that require winter chilling for reproductive growth.