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Volume 3 Special Issue 1, 2009
ROSES
How to reference: MacPhail VJ, Kevan PG (2009) Review of the Breeding Systems of Wild Roses (Rosa spp.). In: Zlesak DC (Ed) Roses. Floriculture and Ornamental Biotechnology 3 (Special Issue 1), 1-13
Guest Editor
David C. Zlesak
University of Minnesota, USA
CONTENTS AND ABSTRACTS
Victoria J. MacPhail, Peter G. Kevan (Canada) Review of the Breeding Systems of Wild Roses (Rosa spp.) (pp 1-13)
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ABSTRACT
Invited Review: There are more than 150 wild rose species (Rosa spp.) known, but research into breeding systems (sexual reproduction) and pollination relationships has concentrated mostly on cultivars, with only a few exceptions. This review summarizes much of the known information about breeding systems for 94 wild species of rose around the world. Many roses can self-pollinate, a few can reproduce asexually (agamospermy), while some are obligate outcrossers even to the extreme of dioecy; however, many roses show combinations of breeding systems, particularly those that are polyploid. The most common type of breeding system among species is xenogamy, or cross-pollination, which allows for greater genetic variation within populations than methods such as autogamy or self-pollination. This review also presents information on: hip and seed production resulting from different breeding systems for selected species, factors affecting reproductive success including incompatibility, viability, receptivity, ploidy levels, and the Caninae meiosis, as well as the debate about the presence of agamospermy, and the features of achenes and seed production in Rosa.
Krasimir Rusanov, Natasha Kovacheva, Atanas Atanassov, Ivan Atanassov (Bulgaria) Rosa damascena Mill., the Oil-bearing Damask Rose: Genetic Resources, Diversity and Perspectives for Molecular Breeding (pp 14-20)
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Invited Mini-Review: Modern rose oil production is nearly all based on cultivation of Rosa damascena ‘Trigintipetala’, the oil-bearing damask rose. Although cultivated for centuries, the genepool of damask rose cultivars used for industrial cultivation has been poorly characterized. The development of new breeding lines was based exclusively on clonal selection from vegetatively propagated industrial populations. Utilization of crosses within the species and with other rose species was generally avoided due to the industry’s apprehension to changes in rose oil composition. This review summarizes the recent reports on DNA marker characterization of the genetic resources of industrially cultivated and naturally occurring damask roses. The needs and conditions for implementation of cross-breeding programmes in reference to the importance of this rose species for the perfume, cosmetic, pharmaceutical and food industries are presented. The opportunity for marker-assisted selection to assess the potential of the complex genome of R. damascena based on available molecular markers and the development of allele-/gene-specific markers is discussed.
Gun Werlemark, Ulrika Carlson-Nilsson (Sweden), Gerhard D. Esselink (The Netherlands), Hilde Nybom (Sweden) Studies of Intersectional Crosses between Pentaploid Dogrose Species (Rosa sect. Caninae L.) as Seed Parents and Tetraploid Garden Roses as Pollen Donors (pp 21-27)
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ABSTRACT
Original Research Paper: Intersectional crosses were performed between pentaploid dogrose species (Rosa sect. Caninae) as seed parents and different tetraploid garden roses as pollen parents. From 2810 crossings and with approximately 10% germination, 298 seedlings were obtained. Of these, more than 75% came from crosses with 10 different plants of R. rubiginosa as seed parents and either double flowering Rosa hybrida ‘André Brichet’ (cross 1) or the single flowering Canadian germplasm L83 (cross 2) as pollen parents. Selected seedlings from these two cross combinations together with their parents were used for a study with microsatellite markers. All studied seedlings obtained all alleles from their seed parents with two minor exceptions. In cross 1, 49% of the seedlings were hexaploid, and 51% were pentaploid, whereas in cross 2, 92% were hexaploid and only 8% were pentaploid. The pentaploid seedlings had not received any alleles from the pollen donor and were regarded as being of apomictic origin. The hexaploid seedlings had received two alleles from their pollen donor and were regarded as true hybrids. The alleles of the pollen donors appeared to segregate segregate randomly to the seedlings, both the specific and the ones in common with the seed parents. As the 10 R. rubiginosa plants used as seed parents were extremely homogenous, the differences in rate of true, hexaploid hybrids versus pentaploid apomicts appears to be governed mainly by the pollen donor. Approximately half of the cross 1 hybrid seedlings had flowers with more than 5 petals, consistent with ‘André Brichet’ being simplex for the gene governing double flowers, but none of the plants from any cross combination showed recurrent flowering. All seedlings were more susceptible to leafspot caused by the fungi Sphaceloma rosarum and/or Septoria rosae compared to their seed parents, but there was no increase in infection of blackspot caused by Diplocarpon rosae and only a slight decrease in powdery mildew in cross 1. There were three times more rosehip fly larvae in rosehips from cross 2 vs. cross 1, probably due to differences in chemical composition of hips.
Maria Dolores Fernández-Romero, Alfonso Espín, Isabel Trujillo, Ana Maria Torres, Teresa Millán, Adoración Cabrera (Spain) Cytological and Molecular Characterisation of a Collection of Wild and Cultivated Roses (pp 28-39)
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Original Research Paper: A collection of 112 rose accessions, including wild species as well as ancient and modern cultivars were studied. Chromosome number was determined in 104 accessions. Overall, 33 diploid (2n=2x=14), 15 triploid (2n=3x=21), 47 tetraploid (2n=4x=28), 1 pentaploid (2n=5x=35) and 8 hexaploid (2n=6x=42) accessions were found. A selection of 27 accessions with ploidy level ranging from 2x to 6x were used to localize the NORs by FISH. A single NOR per genome was detected in 16 diploid species, 15 from subgen. Rosa (Sects. Rosa, Synstylae, Pimpinellifoliae, Banksianae, Bracteatae and Indicae) and one from subgen. Platyrhodon. However, in diploid Rosa majalis, two pairs of NORs per genome were found. Differences in hybridization signals in 3x, 4x, 5x and 6x polyploid accessions were detected. Based on these differences, the autoploid or alloploid nature of these accessions are discussed. In addition, 17 STMS were used to analyse 29 rose accessions. All markers presented high levels of polymorphism, generating a total of 219 different alleles ranging between 111 and 365 bp. The number of allelic patterns ranged from 9 to 22 and all of them presented unique patterns, with a minimum and maximum frequency of 40% and 95.2%, respectively. Based on PIC values obtained (from 0.778 to 0.935) all the STMS were classified as informative markers (PIC > 0.5). This set of microsatellite markers, with high discriminatory power, was used for cultivar identification and allelic patterns of twelve cultivars of roses. All the molecular and cytological data demonstrate the high genetic variability present in the subgenus Rosa. This study will help to clarify the origin and genomic relationships among species from this subgenus.
Parisa Koobaz, Maryam Jafarkhani Kermani, Zahra Sadat Hosseini, Mahboobe Khatamsaz (Iran) Inter- and Intraspecific Morphological Variation of Four Iranian Rose Species (pp 40-45)
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Original Research Paper: There are about 200 rose species in the world, but only a few of them have contributed to the breeding pool of today’s modern roses. In Iran there are 14 wild rose species with a few of them endemic to the region. In the present investigation 14 populations representing Rosa canina L. and R. iberica Stev. from the section Caninae and R. foetida Herrmann and R. hemisphaerica Herrmann from the section Pimpinellifoliae were studied. A multivariate statistical analysis was performed on 48 quantitative and qualitative morphological characters to investigate inter- and intraspecific variation. Cluster analysis indicated that inter- and intrasectional variation exists. Factor analysis and ordination based on principal component analysis revealed that intraspecific variation was present in both quantitative and qualitative characters. Traits such as presence or absence of hair on pedicle, prickle on sepal and hip shape were useful in the classification of these roses. Interspecific and intersectional relationships were comparable to the Rehder classification of rose.
Roger E. Mitchell II (USA) The Inheritance of Juvenile Recurrence in Rosa Species Hybrids (pp 46-52)
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Original Research Paper: The current market for roses demands that new cultivars bloom throughout the growing season. The form of recurrence found in most modern roses can be termed juvenile recurrence, because bloom begins only months after germination. Previous studies have observed that juvenile recurrence is conferred by a recessive allele at a single locus. Most species in the genus Rosa have not yet been used to produce commercialized hybrids, in part because they carry the dominant allele for non-recurrence. Furthermore, only a few species have been tested for their effect on recurrence when used for hybridization. This study investigated the inheritance of juvenile recurrence by crossing several hardy tetraploid species and near-species hybrids with modern roses, and then backcrossing the resulting hybrids with modern roses to recover recurrence. For all species, and all but one first-generation hybrid, juvenile recurrence was recovered. This suggests that using non-recurrent species in a rose breeding program is feasible. The numbers of recurrent and non-recurrent second-generation backcross offspring produced by each first-generation hybrid varied. Some progeny groups did not differ significantly from the theoretically predicted 1 recurrent: 5 non-recurrent ratio, while the number of recurrent offspring was lower than predicted in the rest. The ability of some species and near-species hybrids to produce some late blooms did not affect the frequency of juvenile recurrence in the second generation.
David C. Zlesak (USA) Pollen Diameter and Guard Cell Length as Predictors of Ploidy in Diverse Rose Cultivars, Species, and Breeding Lines (pp 53-70)
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Original Research Paper: Roses range from diploid to hendecaploid and determining sporophytic and gametophytic ploidy levels can aid in breeding efforts and genotype and population characterization. Direct chromosome counts require specialized skill and are time consuming. The objectives of this study were to determine the usefulness of pollen diameter and guard cell length to predict sporophytic and gametophytic ploidy levels in a diverse collection of roses (n=428) and demonstrate the utility of pollen size in understanding ploidy transmission in a breeding program. The diameters of 30 pollen grains using acetocarmine staining and the lengths of ten guard cells were recorded per genotype. Sixty-seven roses with reported chromosome counts provided ploidy size ranges from which to predict ploidy of 361 rose genotypes. Root tip squashes were performed to determine actual sporophytic ploidy. Ploidy transmission was documented using breeding lines with known pedigrees and tetraploid female x triploid male crosses to characterize ploidy contribution from triploids. Guard cell length was variable and not useful for generalized ploidy prediction. Pollen diameter accurately predicted 100% of diploid, 91.1% of tetraploid, 80.0% of hexaploid, and 100% of octoploid roses not in or recently derived from section Caninae species. Recommended pollen diameter ranges for sporophytic ploidy prediction are: diploid (<35.6 μm), tetraploid (35.6 μm to <43.7 μm), hexaploid (43.7 μm to 47.0 μm), and octoploid (>47.0 μm). Sporophytic ploidy estimation based on pollen diameter was not effective for triploid, pentaploid, and section Caninae species and hybrids, although it was useful for gametophytic ploidy estimation. Clones producing 2n or 4n pollen were identified. Ploidy transmission trends and breeding implications are discussed. Pollen diameter is a fast and useful tool to predict sporophytic and gametophytic ploidy in rose.
Abolfazl Jowkar, Maryam Jafarkhani Kermani, Mohsen Kafi, Mohsen Mardi, Zahra Sadat Hoseini, Parisa Koobaz (Iran) Cytogenetic and Flow Cytometry Analysis of Iranian Rosa spp. (pp 71-74)
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Original Research Paper: Since the ploidy level and nuclear DNA amounts are less exposed to natural selection than most morphological traits, and are more stable in the stages of evolution, they are used to study variation among different species. In order to study the diversity of Iranian Rosa spp., chromosome counting and flow cytometry (FCM) analyses were carried out on 10 species collected from different parts of the country. For each plant, cuttings were rooted and young leaves were collected. Root tips were pretreated in 8-hydroxyquinolin, fixed in Lewitsky solution and macerated in cellulase. Chromosome number and ploidy level of the investigated species ranged from diploid (2n = 2x = 14) to hexaploid (2n = 6x = 42). FCM analysis was conducted with propidium iodide (PI) on R. moschata, R. beggeriana, R. persica, R. foetida, R. hemisphaerica, R. pimpinellifolia, R. canina, R. boissieri, R. orientalis and R. pulverulenta. The mean 2C-value of different species showed a varying degree from 0.83 pg (s.d. ± 0.08 pg) in R. persica from subgenus Hulthemia to a four-fold higher amount of 3.54 pg (s.d. ± 0.08 pg) in R. pulverulenta from subgenus Rosa (=Eurosa). Finally, the PI measurements were compared with measurements obtained from 4', 6-diamidino-2-phenylindole (DAPI) staining, which indicated that DAPI ratios (p1/p2) were lower, but closely correlated (r2 = 0.98) with PI ratios (p1/p2).
Zhiqiong Zhou, Weikai Bao, Ning Wu (China) Effects of Scarification, Stratification and Chemical Treatments on the Germination of Rosa soulieana Crépin Achenes (pp 75-80)
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Original Research Paper: Most rose achenes are dormant at maturity and require pretreatment to stimulate germination. To develop effective methods to improve germination of Rosa soulieana Crépin, its achenes were subjected to mechanical and acid (H2SO4) scarification, cold stratification (5°C), and GA3 and smoke water combined with mechanical scarification or stratification. Achene morphology and imbibition also were investigated to help determine the class of dormancy. Freshly harvested R. soulieana achenes displayed some dormancy by having a low germination percentage (41.0 ± 1.9%, mean ± SE) and slow germination rate (mean germination time, MGT; 52.0 ± 2.7 days). The embryo was fully developed, and the pericarp was permeable. Thus, the achenes did not have physical, morphological, or morphophysiological dormancy. Mechanical and acid scarification significantly increased germination percentage and rate. Germination percentage increased with an increase in duration of soaking in H2SO4, reaching the highest value after 2 h and then decreasing, while germination rate increased continuously with increased time of acid scarification. A short duration (4 weeks) of cold stratification significantly improved germination percentage, while prolonged stratification durations (12-16 weeks) only increased germination rate and had no influence on percentage. Light during stratification had no effect on achene germination. Neither GA3 nor smoke water improved germination percentage and rate, regardless of combination with scarification or stratification, but highly concentrated GA3 (500 ppm) and smoke water (1:50) inhibited germination percentage. The highest germination percentage (75.33 ± 5.21%) was obtained when achenes were soaked in H2SO4 for 3 h, while the highest germination rate (MGT 9.8 ± 0.4 days) was obtained when achenes were stratified with water in darkness for 16 weeks. The results suggest that R. soulieana achenes have non-deep physiological dormancy which can be overcome by scarification or a short period of cold stratification.
Tammy Estabrooks, Robin Browne, Zhongmin Dong (Canada) The Effect of 2,4,5-T on Embryogenic Tissue Formation in Rose (pp 81-85)
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Original Research Paper: 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) has recently been reported to induce somatic embryogenesis in Rosa hybrida L. ‘HARwelcome’ (Livin’ EasyTM). This study takes a closer look at the effect 2,4,5-T on embryogenic tissue and somatic embryo morphology in ‘HARwelcome’ (Livin’ EasyTM). Anatomical studies were conducted to gain insight into the types of tissue initiated by treatment with 2,4,5-T. The findings showed that only two out of 10 morphologically different presumptive embryogenic tissue (PET) types were embryogenic. The morphological traits of PET described in this study could be useful as early selection criteria for embryogenic tissue in rose. Somatic embryo morphology in ‘HARwelcome’ (Livin’ EasyTM) was heterogeneous in cotyledon number. There was no significant difference in germination rates amongst somatic embryos with varying numbers of cotyledons indicating that cotyledon number would not be a useful indicator of germination potential. A histological study showed that shoots arose from cotyledon axillary meristems or adventitiously from hypocotyl regions, thus suggesting that cotyledon development occurred despite a lack of shoot apical meristem formation. 2,4,5-T and 2,4-dichlorophenoxyacetic acid (2,4-D) were compared to gauge their effectiveness to induce embryogenic tissue in eight other rose cultivars. Five out of the eight cultivars produced embryogenic tissue when treated with 2,4,5-T compared to only two cultivars when treated with 2,4-D. The results support the premise that individual genotypes within a given species vary greatly in terms of the conditions required for embryogenic induction. These findings also demonstrate that 2,4,5-T may be useful for initiating embryogenic tissue in cultivars unresponsive to 2,4-D.
Shogo Matsumoto (Japan) Plantlet Regeneration via Organogenesis from Immature Seeds of Rosa rugosa Thunb. ex. Murray (pp 86-88)
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Original Research Paper: Rosa rugosa Thunb. ex. Murray possesses unique and value traits including: large, fragrant flowers, a long flowering period, disease resistance, and winter hardiness. An improved regeneration system is essential to exploit the potential of this species utilizing transgenic applications. The development of an efficient plantlet regeneration system was explored using different combinations and rates of 2,4-dichlorophenoxy acetic acid (2,4-D) and trans-zeatin (ZT) during the shoot induction stage. Immature seeds (14-28 days after pollination) were cut transversely in half and placed onto a medium containing Murashige and Skoog (MS) basal salts plus vitamins, 0.25% (w/v) Gellan gum, and varying concentrations and combinations of 2,4-D and ZT for 33 to 49 days. The treatment producing the highest frequency of explants with calli containing shoot primordia (14.4%) contained 2.0 mg/l 2,4-D and 1.5 mg/l ZT. Explants were transferred to the same medium without phytohormones for 56 to 67 days, each differentiating ~12 adventitious shoots. The shoots were easily separated and rooted after 28 days on medium without phytohormones or medium with 0.1 mg/l 1-naphthaleneacetic acid (NAA).
Susanne Baldermann, Ziyin Yang, Miwa Sakai (Japan), Peter Fleischmann (Germany), Naoharu Watanabe (Japan) Volatile Constituents in the Scent of Rose (pp 89-97)
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Invited Review: The cultivation of roses as an ornamental plant has a long history. Apart from floricultural purposes, roses also have an economic importance as a source of natural fragrance in perfume and cosmetic industry and for medical applications. Rose hips, flowers, and their extracts are used for tea infusions and for flavouring of a broad variety of foods. In the scent of roses, more than 400 volatiles have been identified and this review focuses on the key classes of these compounds. There are several possibilities to classify rose volatile compounds, for example by their biosynthetic pathways or their chemical structures. Beginning with cellular compartmentalization, we summarize the recent findings of volatiles derived from the methylerythritol phosphate- and mevalonic acid pathways, the shikimate pathway, and the formation of fatty acid and carotenoid derived volatiles. Additionally, we review recent knowledge about the enzymes involved in these pathways, i.e. methyltransferases, decarboxylases, reductases, carotenoid cleavage enzymes, and β-glycosidases. In the light of recent findings, we also summarize the rhythmic release of volatile compounds. Finally, the evolution of scent metabolic pathways of roses and future research aspects are discussed.
Adnan Younis, Atif Riaz, M. Aslam Khan, Asif Ali Khan (Pakistan) Effect of Time of Growing Season and Time of Day for Flower Harvest on Flower Yield and Essential Oil Quality and Quantity of Four Rosa Cultivars (pp 98-103)
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Original Research Paper: The performance of four Rosa cultivars representing different species (R. damascena ‘Gulqandi’, R. centifolia ‘Sahiwal’, R. borboniana ‘Lahori’ and R. hybrida ‘Gruss an Teplitz’) was evaluated with respect to their floral characteristics under Faisalabad, Pakistan agro-climatic conditions. There was a positive and highly significant interaction between temperature and number of flowers for ‘Sahiwal’. As temperature increased, so too did the number of flowers, with a maximum number of flowers/plant in March, April and May. This was significantly more than other months of the year. ‘Sahiwal’ formed the most flowers, followed by ‘Gruss an Teplitz’ then ‘Gulqandi’. The effect of time of day of flower harvest (05:00 or 17:00 hr) on the quality and quantity of rose oil produced from these four roses was examined to determine the best harvest time for maximum oil yield, ideal oil content and suitable oil composition. Harvest time significantly affected the quantity and quality (i.e. oil profile and composition) of the oil recovered. Early morning was the best time to harvest flowers for maximum quality and yield of essential oil from all four roses. ‘Sahiwal’ showed the greatest potential for commercial production of rose essential oil by Faisalabad farmers due to an overall high flower yield over an extended flowering period and relatively high yield of high quality essential oil.
Rajinder S. Ranu, Dong Wang, Jianguo Fan (USA) Role of 1-aminocyclopropane-1-carboxylate (ACC) Synthases Genes and Genes Involved in Ethylene Signal Transduction in Rose Flower Senescence (pp 104-110)
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Invited Mini-Review: This review focuses on the expression patterns of genes involved in ethylene perception (ethylene receptors and signal transduction) and ethylene biosynthesis. Special emphasis is placed on 1-aminocyclopropane-1-carboxylate synthases (ACS) and their involvement in rose flower petal senescence. The role of ethylene in rose flower opening and petal senescence, including some cultivar-dependent variations, is well documented. Three full-length and a number of partial length ACS genes from Rosa hybrida L. have been analyzed and compared; and their differential expression patterns are consistent with the presence of an ACS multi-gene family in roses. As more full-length ACS genes from the Rosa multi-gene family are identified, a better picture of their differential regulation will emerge. These findings may allow for specific genetic manipulation of ACS gene(s) to enhance the vase-life of rose cut flowers and allow growers to reduce their losses during transportation.
Giancarlo Fascella (Italy) Long-Term Culture of Cut Rose Plants in Perlite-Based Substrates (pp 111-116)
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Original Research Paper: Perlite is often used in soilless systems for horticultural crops but is rarely employed for pluriannal culture of ornamental species. The aim of this research was to test the changes in the physical and chemical properties of two perlite-based growing media during a 36-month greenhouse cultivation period and their effects on the production of cut roses. ‘Anastasia’, ‘Nirpbredy’ (New Fashion®), ‘Nirpinwin’ (Fenice®) and ‘Sunluck’ (Gold Strike®) roses were grown in 80L plastic bags filled with pure perlite or perlite mixed with coconut coir dust (1:1, v/v) in an open-loop system. Chemical and physical characteristics of the two substrates were determined at the beginning and at the end of the experiment. Bulk density and water holding capacity gradually increased, whereas total porosity and air content diminished. The mixture with perlite and coir dust provided higher water retention capacity throughout the trial, though pure perlite maintained a more stable physical condition. Number of rose stems/plant, stem length and thickness and flower bud height and width were monitored during the trial. The prolonged cultivation period was characterized in both media by an increase of yield (60%) and cut rose quality during the second year and by a decrease (26%) in yield in the third year. Growing media affected yield and qualitative traits: best results were achieved with plants grown in medium composed of perlite and coir dust as compared to pure perlite. The mixed medium had a higher number of flowers (21.2 vs. 16.3 stems/plant/year) and longer (63.2 vs. 57.5 cm) and thicker (7.5 vs. 6.8 mm) stems. Significant differences were also observed among cultivars: ‘Anastasia’ produced the highest number of stems (21.5 per plant) and the tallest buds (5.7 cm) and ‘Nirpinwin’ produced the longest (65.4 cm) and thickest (0.8 cm) stems.
Juliette Pijnakker, Pierre Ramakers (The Netherlands) Development of Integrated Pest Management in Greenhouse Cut Roses (in the Netherlands) (pp 117-120)
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Invited Mini-Review: Generalist predatory mites were tested for controlling mites and small insects in greenhouse grown cut roses. Euseius ovalis, Amblyseius swirskii, Typhlodromalus limonicus, Amblyseius andersoni and Iphiseius degenerans were found to establish persistent populations year-round. They were associated with two-spotted spider mites, greenhouses whiteflies and/or western flower thrips. No effect on mealybugs could be demonstrated. Current IPM practices as applied by Dutch rose growers in the year 2008 are briefly described.
Adele Salamone, Giuseppa Scarito, Giulia Camerata Scovazzo, Giancarlo Fascella (Italy) Control of Powdery Mildew in Cut Roses using Natural Products in the Greenhouse (pp 121-125)
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Original Research Paper: Roses grown under greenhouse cultivation are commonly affected by diseases and regular fungicide applications are commonly used. The aim of this research was to identify natural products that can substitute and reduce the health and environmental impacts of typical chemical treatments in the control of powdery mildew [(Podosphaera pannosa (Wallr. Fr.) de Bary] and grey mould (Botrytis cinerea Pers.). Treatments were applied in the greenhouse on the cut rose cultivars Sunluck (Gold Strike®) and Nirpbredy (New Fashion®) growing in a soilless system. Oregano and clove essential oil at 0.5 ml/l (an emulsifier was added) and sodium bicarbonate (NaHCO3) at 4 g/l were sprayed on rose plants to runoff. The controls were untreated roses and a standard chemical control (the fungicides Dinocap, Triadimenol, Dimethomorph+Sulphur, Bupirimate, Dithianon, Iprodione and Thiram) was applied in rotation. Sprays were applied every 7-10 days after the first symptoms of disease appeared. Disease incidence was checked on 100 leaflets and symptoms were evaluated using a scale from 0 (no disease) to 7 (76-100% infection). At three different times (June and November 2005 and January 2006) biometric data (stem height, stem diameter, stem flexibility, flower diameter, number of petals/flower and thorniness) and colorimetric analysis of the leaves were evaluated in order to determine the effect of treatments on cut rose quality. Treatment with essential oils and NaHCO3 was able to control the incidence and the severity of powdery mildew on roses. Ambient infection of grey mould was low and comparisons between treatments were not possible. Significant differences among the chemical and natural product treatments were found for all traits examined. Although NaHCO3 treatment controlled powdery mildew to a greater extent than essential oils, it resulted in slight phytotoxicity. These results indicate the potential use of natural products to control powdery mildew of roses and could be a good alternative to chemical fungicides. However, differences in response to powdery mildew depend on the cultivar susceptibility, period of treatments and level of control needed.
Maryam Jafarkhani Kermani (Iran), Andrew V. Roberts, Kazutomo Yokoya (UK) Morphological Investigations and Infection Studies of the Rust-Causing Fungi of Roses (pp 126-130)
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Original Research Paper: Rose rust is caused by members of the genus Phragmidium, four of which are: P. mucronatum (Pers.) Schlect., P. tuberculatum Mull., P. fusiforme Schroet. and P. rosae-pimpinellifoliae (Rabh.) Diet. In the present study, the preliminary identification of species of Phragmidium was based on host range. Identification was then supported by a measurement of the dimensions of urediospores and teliospores. Axenic cultures of P. tuberculatum were initiated on culture media but these cultures were unable to reinfect rose leaves, therefore cultures of P. tuberculatum on leaf discs of ‘Mme. Grégoire Staechelin’ were initiated from urediospores. The infectivity of dry spores and spore suspensions of urediospores of P. tuberculatum directly from host tissue did not differ significantly; however, spore densities of 30 × 104 per ml proved to be more infective than higher or lower densities. Surface-sterilized detached leaves showed significantly lower infection rates than leaves that were not surface sterilized. The urediospores on the leaf discs, survived when stored at 4°C for four weeks, but when stored for 12 weeks at the same temperature, they lost their viability and were not able to infect leaf discs.
Leen Leus, Johan Van Huylenbroeck (Belgium) Developing Resistance to Powdery Mildew (Podosphaera pannosa (Wallr.: Fr.) de Bary): A Challenge for Rose Breeders (pp 131-138)
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Invited Review: Powdery mildew is the major fungal pathogen of roses in greenhouses and also an important disease on field-grown roses. In the past decade different tools have been developed allowing breeders to develop resistant roses in a more efficient way. Different pathotypes of the fungus, important for resistance testing, were detected. Resistance mechanisms in rose leaves were found and characterized. Screening techniques to evaluate powdery mildew resistance are available. These methods allow pathotype specific inoculation on detached leaves or can be used for the selection of resistant genotypes within a population of thousands of seedlings. New information on the genetic background of powdery mildew resistance became available. Genetic maps providing information on resistance markers are currently being developed and integrated. Marker-assisted selection is expected to be ready soon for use in rose breeding programs for powdery mildew resistance among other traits. This review aims to provide an overview on fundamental information and methodology available and necessary to make progress in breeding for powdery mildew resistance in roses.
B. Ulrika Carlson-Nilsson (Sweden), Campbell G. Davidson (Canada) A Three Year Study of Winter Hardiness and Blackspot Resistance (Diplocaron rosae Wolf) of Roses in Two Climatically Different Environments (pp 139-151)
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Original Research Paper: Most of the garden rose cultivars available today are not fully winter hardy in cooler climates. Besides insufficient winter hardiness, susceptibility to multiple fungal diseases is a major problem as it reduces the ornamental value as well as the vigour of the infected plant. Blackspot, caused by the fungus Diplocarpon rosae, is often regarded as the most destructive disease of outdoor grown roses. A cooperative field trial in Balsgård, Sweden (56° N; 14° E) and Morden, Canada (49° N; 98° W) was performed from 1995 to 1999 with the objective of studying the variation in winter survival, winter injury and blackspot resistance among a common group of rose genotypes chosen to represent a diversity of rose germplasm. Significant differences were obtained between genotypes regarding winter injury and blackspot infection at both sites. Differences between the cultivars were also noted for the diseases leaf spot, powdery mildew and rust. The survival rate at Balsgård was lower compared to Morden after the first winter. This was most striking for cultivars belonging to the floribunda and polyantha horticultural groups. Absence of snow cover is a likely reason for the higher mortality rate at Balsgård. Significant differences were also obtained for amount of winter injury on surviving genotypes. Surviving genotypes at Balsgård suffered less winter injury compared to Morden. The most hardy genotypes at both sites belonged to the alba, damask and hybrid gallica horticultural groups and species within the sections Rosa (=Cinnamomeae)and Synstylae. In addition, the same groups and sections contained the most blackspot tolerant genotypes. The degree of blackspot infection was the highest in Morden all three years of the study and possible explanations are discussed, e.g. existence of different races of the fungus. The results obtained indicated a competition between different fungi on rose plants. Significant correlations between high blackspot infection rates and a high degree of winter injury after the following winter were also observed.
Anna Speranza, Fabiana Antognoni, Gian Lorenzo Calzoni (Italy) Rosa for the Environment (pp 152-165)
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ABSTRACT
Invited Review: Recently, increasing attention is being paid to the use of ornamental plants within the context of environmental technologies such as biomonitoring and phytoremediation. Different aspects concerning the potential of Rosa plants in this context have been reviewed here. The tolerance of a number of Rosa species towards critical environments and their usefulness as active biomonitors of some metals originated from either soil or air sources have recently been found. Rosa rugosa pollen was demonstrated to be an effective and more precocious indicator of environmental pollutants than vegetative plant portions. Moreover, Rosa flowers and seeds are efficient as biosorbents in removing metals from contaminated water, thus representing low cost biomasses available for an environmentally-friendly use. These studies demonstrate that a wide array of significant benefits may be derived from ornamental horticultural products, in addition to the fact that they represent a useful resource for people’s psychological well-being and recovery from stress.
Derald A. Harp, David C. Zlesak, Gaye Hammond, Steve George, Wayne Mackay (USA) EarthKind™ Rose Trials – Identifying the World’s Strongest, Most Beautiful Landscape Roses (pp 166-175)
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ABSTRACT
Invited Mini-Review: “EarthKindTM” is the most prestigious horticulture designation bestowed by the Texas AgriLife Extension Service (part of the Texas A&M System). This designation is awarded based on multi-year scientific research studies, combined with extensive, regional field trials, conducted by or in collaboration with Texas A&M horticulturists. Only rose cultivars possessing an extremely high level of landscape performance, coupled with outstanding disease and insect tolerance and/or resistance may receive the designation. The EarthKind™ philosophy is based on the premise that it is possible to identify beautiful plants that tolerate harsh, low-maintenance environments without fertilizers, pesticides, and other agricultural chemicals along with a significant reduction in irrigation. This cutting-edge, environmental effort is the most popular and fastest growing, research-based environmental university program of its kind in the U.S. and directly benefits all sectors of horticulture: growers, retailers, landscapers, and consumers. EarthKind™ rose research is underway in 25 states and four foreign countries, including Bermuda, Canada, India and New Zealand.
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