Morphological and molecular analyses of Rosa damascena × R. bourboniana interspecific hybrids

Rosa damascena Mill is the most important scented rose species cultivated for rose oil production. Rosa bourboniana L. (Edward rose), a related species, is popular on account of its longer blooming period and ease of propagation. With an aim to combine the oil quality of R. damascena and recurrent flowering habit of R. bourboniana, two cultivars (Jwala and Himroz) of R. damascena were crossed with R. bourboniana. The F1 hybrids obtained were evaluated using morphological, random amplified polymorphic DNA (RAPD) and microsatellite (SSR) markers. Twenty-two selected RAPD and three SSR primer pairs were utilized for hybrid identification. According to presence or absence of bands RAPD and SSR markers were classified into seven types of markers. The bands specific for the pollen parent and occurring in the hybrids were good markers to confirm the hybridity. The non-parental bands expressing uniquely in hybrids were effective in distinguishing the hybrids from each other. Cluster analysis, based on Jaccard's similarity coefficient using unweighted pair group method based on arithmetic mean (UPGMA), reliably discriminated the hybrids into two main clusters. These results indicate the practical usefulness of RAPD and SSR markers in hybrid identification in scented roses. The approach is advantageous for its rapidity and simplicity, for identification of hybrids at the juvenile stage. One of the studied morphological traits – prickle density, can also complement in the identification of interspecific hybrids between R. damscena (♀) and R. bourboniana (♂).     

Cold storage of oil rose (Rosa damascena Mill.) flowers

Oil rose flowers were stored at 0 °C in four different packaging materials [plastic box + stretch film (PB + SF), Xtend^®, Smartbag^® and polyethylene (PE)] for 60 days. During storage, weight loss, O₂ and CO₂ concentrations in the packages, petal color and sensorial attributes were investigated besides essential oil content and composition. Storage duration and packages had significant (p < 0.01) effects on weight loss. At the end of storage, the lowest weight loss was in PE package (1.696%) whereas the highest weight loss was in Xtend^® (10.081%). The essential oil content was significantly (p < 0.01) affected by storage duration and packages. In addition, the essential oil contents obtained from all packages for a storage period of 10 days and the essential oil contents obtained from unstored (control) petals were included in the same group. At the end of storage, the essential oil contents decreased by 91.3, 57.7, 80.0 and 64.3% in PB + SF, Xtend^®, Smartbag^® and PE packages, respectively as compared to control. In addition, storage duration and package types significantly (p < 0.01) affected petal color, O₂ and CO₂ concentrations in the packages and sensorial scores. The concentration of citronellol, a main component of rose oil, increased in all packages during storage of 10 days in comparison to the control group while it varied in other storage durations and package types. However, nerol and geraniol were lower than the control group during storage while concentrations of nonadecane, heneicosane and eicosane were higher. In conclusion, loss of oil yield and quality, due to various reasons and particularly due to fermentation in oil rose from the harvest of petals to their distillation, can be minimized with storage of petals in all package types for up to 10 days.     

Flower yield performance and stability of various Rosa damascena Mill. landraces under different ecological conditions

The flower yield stability of Damask rose as an important medicinal and aromatic plant at different environments has not been well documented. In order to evaluate flower yield and stability, 35 landraces of Damask rose were studied at 8 locations in Iran during 2007–2008. Analysis of variance revealed significant differences (p ≤ 0.01) among landraces (G), environments (E), locations (L) and for landrace × environment (GE) and landrace × location (GL) interactions. Both GE and GL interactions were mainly crossover, a large portion of which was accounted for by non-linear (unpredictable) component. The landraces of IS9, YZ2, WA1, IS7 and IS1 with 3120.63, 2941.63, 2894.62, 2769.15 and 2716.92 kg/ha respectively produced the highest flower yield among studied landraces. Kerman with average flower yield of 3635.46 kg/ha produced the highest yield among studied locations. According to the results, most of landraces that originated from temperate, warm temperate and arid regions produced higher flower yield than those from cool, cool temperate, semi-arid and humid regions. The landraces of YZ2, IS5, IS8, IS4, KZ1, AR1_, IS3 and BA1 were stable and YZ2, IS5, IS8, IS4, KZ1, AR1 IS6, IS3, BA1, IS10 and YZ1 were adaptable landraces for flower yield according to Eberhart and Russell (1966) model. The presence of some high flower yield and stable landraces such as YZ2 and IS5 suggests that a genotype can demonstrate high flower yield and stability for yield simultaneously. Thus, simultaneous selection for flower yield and stability using nonparametric methods could be possible. In addition, taking into consideration flower yield and stability potential, the landraces of YZ2, IS5, IS8, IS4 and KZ1 as general stable, adaptable, and high flower yield are recommended. Furthermore, the landraces of IS9 and WA1 as high flower yield and specific adaptable landraces can be recommended for temperate and arid areas and the landraces of IS7 and IS1 for semitemperate and cool areas.     

Morphological and oil content variations amongst Damask rose (Rosa damascena Mill.) landraces from different regions of Iran

Forty landraces of Damask rose were collected from 28 provinces (13 origin sites) in Iran and evaluated to determine the diversity among them. The investigated characters were: flower weight, flower diameter, peduncle length, number of petals, number of stamens and oil content. Pearson's coefficients showed that number of petals was positively correlated with flower weight (r = 0.642) and number of stamens (r = 0.630), while its correlation with peduncle length was negative (r = −0.53). A negative correlation was obtained between oil content and number of stamens (r = −0.60) which is useful for indirect selection of landraces with low number of stamens and therefore high amount of oil content. Cluster analysis based on five botanical characters and oil content separated the origin site 12, which included Guilan, Mazandaran and Golestan provinces with a specific climate condition of temperate humid, from other origin sites. This distinctiveness was already confirmed by the bi-plot of the principal components. The distribution of Damask rose landraces provided useful information for the future collection and for the genetic resource management in these origin sites.     

African spider flower (Cleome gynandra L./Gynandropsis gynandra (L.) Briq.) as a red spider mite (Tetranychus urticae Koch) repellent in cut-flower rose (Rosa hybrida L.) cultivation

Companion planting of Cleome gynandra, of Kenyan origin, in beds of cut-flower roses reduces significantly red spider mite (Tetranychus urticae Koch) infestation without any detrimental effect on productivity or flower quality. The level of reduction is dependent upon the density of the C. gynandra plants with 15 plants in a 1.8 m² bed (8.3 plants m²) being the most effective, planted either around the bed perimeter or within the rows of roses. The relatively high density of C. gynandra plants required may limit the direct application of this technology in export-focused, greenhouse rose production yet may be of significant value as a supplement to other mite-control strategies. The potential benefits of such companion planting for growers of field roses and those involved in some domestic markets are also evident. Research into the nature and extraction of the active, volatile mite-repellant components of C. gynandra is indicated.     

Effects of thermoperiodicity and plant population density on stem and flower elongation, leaf development, and specific fresh weight in single stemmed rose (Rosa hybrida L.) plants

Thermoperiodicity, i.e. growth in the alternating temperature regime with the same diurnal mean compared with growth at the constant temperature at which optimal growth occurs, was studied at three plant population densities in four cultivars of Rosa hybrida L. Single-node cuttings with five-leaflet leaves were excised and grown as single-stemmed rose plants at an average photosynthetic photon flux density of about 260 μmol m⁻² s⁻¹ and supplied with carbon dioxide at about 1000 μmol mol⁻¹. The optimal constant temperature regime was 22 °C day (20 h)/22 °C night (4 h); alternating temperatures were 23 °C day (20 h)/18 °C night (4 h). The plant population densities were 100, 131 and 178 plants m⁻² of bench area. Thermoperiodicity was absent, or could not be detected, in the parameters related to the growth period, the formation of fresh biomass, the bloom quality, and most parameters related to shoot elongation. However, classic thermoperiodic effects of alternating regime were significant in the cultivars Red Velvet and Sonia, with shoot elongation promoted (7.1 and 10.5%, respectively) in the growth phase from onset of axillary bud growth until the flower bud became visible. Compared with the other two cultivars, plants of Red Velvet and Sonia tended to develop longer internodes. The results, obtained concurrently at three different plant population densities, suggest that thermoperiodicity can affect (single-stemmed) plant growth and development in R. hybrida. Increased plant population density also increased plant height at visible flower bud, but the bloom quality, expressed as specific fresh weight, and the flower height at anthesis was decreased at the highest density. Increased plant population density increased the number of five-leaflet leaves developed in Red Velvet, but had no effect on leaf number in Texas and Sonia, while, in Lambada the leaf number was decreased at the highest density.     

Identification of differentially expressed genes in fragrant rose Jinyindao with suppressive subtraction hybridization

To investigate the floral fragrance new genes, scent mutant of rose was used here. The suppressive subtraction hybridization (SSH) technique and micoarray analysis of the clones were used to isolate the cDNA fragments, which showed differential expression between the rose scent mutant ‘Wangriqinghuai’ and wild type ‘Jinyindao’ (Rosa × hybrida), and RT-PCR was used to identify up-regulated expressed genes. 16 positive contigs of JSSH were obtained. Some ESTs such as RcOMT1, RcOMT2, RhMYB92 and RhGP1 were known to regulate scent metabolism, and 5 ESTs with no homology in NCBI may represent new genes involved in rose flower fragrance metabolism. SSH technique combined with cDNA micoarray would be useful for analysis and isolation of the genes related to rose floral scent.     

Effect of shade regime on flower development,yield and quality in lisianthus

The effects of shading on lisianthus (Eustoma grandiflorum) floral transition, plant development, flower yield and quality, and content of starch and soluble sugars were assessed in three cultivars, over two consecutive years. Shading nets affording 67% or 88% reduction in light intensity, were fitted at planting in the greenhouse for periods ranging from 3 to 8 weeks. Meristem morphology at floral transition was characterized by apical meristem widening and the appearance of two bract primordia. Floral transition time was affected by cultivars, but in general, longer and heavier shade treatments delayed floral transition; the longest delay (6 weeks) being recorded in Mariachi White under 88% shade for 7 weeks or under a combined shade treatment of 88% for 3 weeks followed by 67% for 5 weeks. Despite interactions between cultivar and shade treatment, consistent trends were discerned: the heaviest and most prolonged shading reduced yield (up to 40%), cut stem length (up to 15%), and number of flower buds/stem (up to 26%), within cultivar. Total carbohydrates levels were very low, and it is questionable whether changes observed in carbohydrate quantity following shade treatments had any effect on plant growth or flower yield. Rather, it appears that lisianthus is very dependent on current photosynthesis, so that even a brief shading interlude could reduce branching and flower quality. It may be concluded that the intensive shading usually applied is detrimental for lisianthus.     

Levels of physiological dormancy and methods for improving seed germination of four rose species

Low seed germination is a major problem in commercial rose propagation and breeding and is species-dependent. The present work selected four rose species previously un-examined to explore effective methods for improving seed germination and the relevant dormancy mechanism and its levels in seven experiments. The results showed that both pulp and achenes from the four rose shrubs had chemical substances that significantly inhibited seed germination with the inhibitory effect was more pronounced in pulp extract than of achenes. Single treatments of H₂SO₄ scarification, short-term cold stratification (<16 weeks) or warm stratification were less effective in breaking dormancy as indicated by lower germination index than their combinations. Comprehensive comparisons showed that among the six treatments the most effective for breaking dormancy was H₂SO₄ scarification followed by warm plus cold stratification, then H₂SO₄ scarification followed by cold stratification and finally warm plus cold stratification. Scarification with H₂SO₄ for 2–4 h ordinal followed by warm stratification at 20 °C for 4 weeks and cold stratification at 5 °C for 8 weeks was the best pretreatment for increasing seed germination percentage for Rosa multibracteata (81.4 ± 2.9%), Rosa hugonis (13.1 ± 6.0%), and Rosa filipes (62.7 ± 5.7%); and H₂SO₄ scarification for 4 h followed by cold stratification at 5 °C for 12 weeks was the best pretreatment for Rosa sericea (46.7 ± 8.7%). Our results suggest that these four species have only physiological dormancy caused by integrative roles of pulp, pericarp and embryo. The level of physiological dormancy was ranked as R. hugonis > R. sericea > R. filipes > R. multibracteata.     

Early flower initiation allows ample manipulation of flowering time in cherimoya (Annona cherimola Mill.)

Flower initiation date and readiness to flowering in buds of different age were studied in ‘Fino de Jete’ cherimoya (Annona cherimola) cultivar in order to establish the limits for the manipulation of its flowering date. Flower initiation was analyzed by light and scanning electron microscopy (SEM) collecting axillary buds from May to the following February, whereas the bud readiness to produce perfect flowers was determined by forcing buds of different age to sprout by means of leaf removal and tipping the new growth. SEM images confirm that cherimoya buds are differentiated into flowers almost a year before blooming. In this regard, axillary buds have already formed the sepals when the subtending leaf has just begun unfolding (week 0), while the petals are clearly visible in 1-week-old buds. Sectioning of paraffin-embedded buds illustrate that cherimoya buds are in fact a bud complex that 1 week after its inception comprises 4–5 buds of different size of which the two largest ones are reproductive, while the 2–3 smallest buds often remain undifferentiated at that time. The high capacity of flowering expressed by young buds that have been forced to grow proves that cherimoya meristems are early competent for flowering. No differences in fertility or in the time needed to reach anthesis after leaf removal were found among buds of different ages. Node position had no effect on bud break and flowering potential. The early flower initiation in cherimoya deduced from this work opens a wide temporal window for the experimental manipulation of flowering and harvest dates in this crop.     

Cross-transferable polymorphic SSR loci in Prunus species

This work reports the transferability and polymorphism of previously reported SSRs in 10 Prunus species. The availability of a large number of SSRs in the genus Prunus makes marker choice random, while preventing comparison of results in fingerprinting studies. The availability of SSR markers, polymorphic in a wide sample of Prunus species, would facilitate marker choice, while allowing the comparison of results. In this work, microsatellite markers useful for analyzing 10 different Prunus species (P. persica, P. dulcis, P. armeniaca, P. domestica, P. insititia, P. salicina, P. cerasifera, P. avium, P. cersus and P. mahaleb) were searched through screening SSRs previously reported to be conserved and/or polymorphic in more than one Prunus species. A selected group of 13 SSRs, transferable to the 10 species, was analyzed in terms of their usefulness for analyzing these species. The amplification range, polymorphism and variability detected by these loci are reported. The information provided will be useful for Prunus genetic studies as well as conservation and management of Prunus germplasm resources.     

Interacting effects of temperature integration and light intensity on growth and development of single-stemmed cut rose plants

Energy conservation in horticulture can be achieved by allowing temperatures to fluctuate within predefined bandwidths instead of using rigid set points for heating and ventilation. In temperature integration, plants are supposed to compensate effects of temporarily deviations of the average temperature some time later by deviations in the opposite direction. However, little is still known on the effects of integration periods exceeding 1 day. In this study, effects of temperature integration on growth and development of single-stemmed cut rose plants were determined. Pruned rose shoots were placed in climate chambers in which light levels switched daily (2 days integration period) or weekly (14 days integration period) from high light intensity (300 μmol m⁻² s⁻¹) to low light (150 μmol m⁻² s⁻¹). Temperatures were kept continuously at 20 °C (control) or changed with the light intensity (phase, high temperature at high light intensity, low temperature at low light intensity) or changed opposite to the light intensity (counter phase). Bandwidths of temperature integration were 0, 6 or 10 °C. Under these conditions, buds grew out to harvestable shoots in approximately 45 days. At both integration periods, shoot length was significantly reduced with increasing bandwidths of temperature integration. Shoot dry weights were reduced when a bandwidth of 10 °C was applied. At both integration periods, rates of photosynthesis were primarily determined by light intensity. However, in the counter phase treatments, photosynthesis rate at high light and low temperature was reduced compared to the high light condition of the control. Under these conditions, starch content increased to approximately 10%, suggesting a feedback inhibition of the rate of photosynthesis. However, this did not (yet) affect plant growth or development.     

Effect of climatic conditions on the overcoming of dormancy in apricot flower buds in two Mediterranean areas: Murcia (Spain) and Tuscany (Italy)

For temperate-zone fruit species such as apricot, when winter cold requirements are not adequately satisfied, negative repercussions on productivity occur. The aim of this research was to study the effect of, mainly temperature on the overcoming of dormancy in different apricot cultivars growing in two areas (Italy, Tuscany: lat. 43°02′N, long. 10°36′E; Spain, Murcia: lat. 38°16′N, long. 1°16′W) representative of the Mediterranean climate. Trials were conducted for two consecutive years on the same genotypes: ‘Currot’, ‘San Castrese’, ‘Goldrich’, ‘Stark Early Orange’ and ‘Orange Red’. These genotypes cover the range of chilling requirements (CR) in the apricot species in these Mediterranean areas. The CR (measured by chill units, CU and portions) for breaking of dormancy, heat requirements, flowering date and flowering and fruit-set percentages were measured. Temperatures were recorded and transformed into the corresponding CU and portions by the Utah Model and the Dynamic model, respectively. The winter climatic conditions determined a dissimilar chill unit accumulation in Tuscany (Italy) and Murcia (Spain) as well as an important effect of the year in both areas. While all cultivars with the exception of Stark Early Orange overcame dormancy, significant differences regarding the CR of cultivars for two different years and growing in two environments were observed, depending also on the cultivar. The results showed that both the Utah Model and Dynamic Model were not completely accurate with regard to establishing the CR for dormancy release under a Mediterranean climate. Temperature should be analysed together with other climatic factors in order to improve the CR assessment.     

The effect of sucrose on the expression of the VvTFL1 and VFL genes during flower development in the “Xiangfei” grapevine

VFL and VvTFL1 genes expression patterns and the effects of sucrose on the expression of VFL and VvTFL1 genes in different organs of the “Xiangfei” grapevine (Vitis vinifera L.) were investigated. VvTFL1 gene expression was detected in the meristem of the apical bud and lateral bud, but was not detected during inflorescence differentiation and flower organ development. After sucrose treatment, VvTFL1 gene expression increased in the apical bud, but decreased in the lateral bud. These results suggested that the VvTFL1 gene might be mainly involved in the apical growth process of shoots, and exogenous sucrose had an effect on the VvTFL1 gene by increasing shoot apical meristem initiation of apical buds. The VFL gene was expressed primarily during inflorescence differentiation and early flower organ development, but it gradually reduced in later flower development. After sucrose treatment, VFL gene expression increased in the inflorescence and small or middle flower, but a little change was seen in the large flower. These results suggested that the VFL gene plays important roles in the initiation of inflorescence meristems and the morphological formation of flower organs. Exogenous sucrose had an effect on VFL gene expression at the early stage of flower development.     

The effect of forcing temperature on peony shoot and flower development

Pre-chilled potted plants of Paeonia ‘Coral Sunset’, ‘Monsieur Jules Elie’, ‘Sarah Bernhardt’, and ‘Karl Rosenfeld’ were placed in a range of controlled temperature regimes to ascertain the effect of temperature on the timing of shoot emergence and floral development. For all cultivars, warmer temperatures up to 25 °C lead to more rapid shoot emergence and flower development. Linear temperature responses adequately described the rate of development from shoot emergence to flower bud appearance, and from bud appearance to flower opening, but a curvilinear response was required to describe the time taken for shoots to emerge. There were significant differences between cultivars in the number of heat units required for shoot emergence, with the shoots of the slowest-developing cultivar, ‘Monsieur Jules Elie’, taking 50% longer to emerge than those of the most rapid, ‘Coral Sunset’. No significant differences were found among cultivars in the time taken from shoot emergence to flower opening, although the ‘split’ stage (when the bud opens sufficiently for petal colour to be observed) was slightly earlier in ‘Karl Rosenfeld’.     

Application of treated wastewater for cultivation of roses (Rosa hybrida) in soil-less culture

No information is available today concerning the effect of irrigation with secondary treated sewage water on growth, production or quality of roses or other cut flowers. In the present study we investigated the effect of irrigation with treated sewage water on roses cultivated in two soil-less medium, perlite, an inert mineral medium and Choir (coconut fibers), an organic medium of high ion absorption capacity. During 12 months of exposure to the treated water, the visible appearance of the plants, their growth, the quantity and size of the flowering stems and their postharvest performance were not affected by the irrigation treatments. Contents of macroelements in the leaf tissues were unaffected by the irrigation with the secondary treated sewage water. At the same time, Cl contents increased 47% in perlite and 73% in Choir grown plants reaching levels characteristic of exposure to moderate salinity. Mn, Cu and B contents increased as well under cultivation in both perlite and Choir under irrigation with treated sewage water. On the other hand, contents of Fe, Zn, Mo and Al, were similar in all treatments. In all treatments contents of all the examined micro and macroelements were within the range accepted for proper plant function.