Rosa Hybrida Research Articles

Cotyledonary somatic embryo is one kind of intermediate material similar to callus in the process of in vitro tissue culture from Rosa hybrida ‘John F. Kennedy’

BackgroundRose is recognized as an important ornamental plant worldwide, and it is also one of the most widely used flowers in gardens. At present, the improvement of rose traits is still difficult and uncertain, and molecular breeding can provide new ideas for the improvement of modern rose varieties. Somatic embryos are quite good receptors for genetic transformation. However, little is known about the molecular mechanisms underlying during the regeneration process of rose somatic embryos. To elucidate the molecular regulation mechanism of somatic embryo plantlet regeneration, the relationship between the differences in traits of the two different regenerated materials and the significantly differentially expressed genes (DEGs) related to phytohormone pathways in the process of regeneration were be investigated.ResultsThese representative two regenerated samples from single-piece cotyledonary somatic embryo (SPC) culture of Rosa hybrida ‘John F. Kennedy’, were harvested for transcriptome analysis, with the SPC explants at the initial culture (Day 0) as the control. The differentially expressed genes (DEGs) in the materials from two different types for regeneration approach (SBF type: the regeneration approach type of single bud formed from SPC explants; MBF type: the regeneration approach type of multiple buds formed from SPC explants) were be screened by means of the transcriptome sequencing technology. In this study, a total of about 396.24 million clean reads were obtained, of which 78.95–82.92% were localized to the reference genome, compared with the initial material (CK sample), there were 5594 specific genes in the material of SBF type and 6142 specific genes in the MBF type. The DEGs from the SBF type material were mainly concentrated in the biological processes of GO terms such as phytohormones, substance transport, cell differentiation, and redox reaction. The KEGG enrichment analysis revealed these DEGs were more active in ubiquinone and other terpenoid-quinone biosynthesis, fatty acid elongation, steroid biosynthesis, and glycosphingolipid biosynthesis-globo and isoglobo series. In contrast, the DEGs induced by the MBF type material were mainly associated with the biological processes such as phytohormones, phosphorylation, photosynthesis and signal transduction. According to KEGG analysis, these DEGs of MBF type were significantly enriched in the porphyrin and chlorophyll metabolism, brassinosteroid biosynthesis, carotenoid biosynthesis, and peroxisome. Furthermore, the results from the phytohormone pathways analysis showed that the auxin-responsive factor SAUR and the cell wall modifying enzyme gene XTH were upregulated for expression but the protein phosphatase gene PP2C was downregulated for expression in SBF type; the higher expression of the ethylene receptor ETR, the ethylene transduction genes EBF1/2, the transcription factor EIN3, and the ethylene-responsive transcription factor ERF1/2 were induced by MBF type.ConclusionsAccording to the GO and KEGG analysis, it indicated the DEGs between two different regenerated materials from somatic embryos were significantly different which might be causing morphological differences. That was somatic embryos from Rosa hybrida ‘John F. Kennedy’ could regenerate plantlet via both classic somatic embryogenesis (seed-like germination) and organogenesis, cotyledonary somatic embryos should be considered as one kind of intermediate materials similiar to callus, rather than the indicator materials for somatic embryogenesis.

Relationship between nutrient status and density of Tetranychus urticae Koch in rose cut (Rosa hybrida)

La araña roja, Tetranychus urticae Koch, es la principal plaga del cultivo de rosas para corte (Rosa hybrida). Observaciones preliminares indican que plantas con alta densidad de araña roja presentan deficiencias nutrimentales, pero no existe información cuantitativa al respecto. El objetivo fue determinar la relación que existe entre la densidad de araña roja y el estado nutrimental de rosal 'Polo'. En cuatro muestreos, se seleccionaron 60 plantas libres de araña roja y 60 plantas con más de 60 ácaros por hoja (infestación alta). En ambos casos se determinó, mediante análisis químico foliar, la cantidad de macro y micronutrimentos, así como el índice de desbalance nutricional (IDN). Las plantas con presencia de araña roja muestran desequilibrio nutrimental debido a la reducción en la concentración foliar de nitrógeno, fósforo, potasio, calcio, manganeso y cobre. El porcentaje de reducción de la concentración de dichos elementos osciló entre 0.3 y 29 % respecto al testigo.

Studies on Effect of IBA Concentrations and Planting Times on Propagation of Different Varieties of Rose (Rosa hybrida Vill.)

The conventional method of rose propagation involves budding on one year old field established rootstock plants. For multiplication of plants, cutting is the simplest way of propagation of desirable rose varieties. There are relatively few varieties that develop roots, so exogenous application of growth promoters is essential. In order to study the effects of different concentrations of IBA (0, 500, 1000 and 1500 ppm) on rooting of different varieties (English Holiday, Eiffel Tower, Don Don, Confetti and Iceberg) of rose, during planting times viz., February, July, October and December, It was found that 500 ppm IBA resulted in maximum number of roots (15.66), number of leaves (22.33), the percentage of survival (50%), shoot length (13.23 cm), fresh weight of roots (4.80 g) and stem (5.93 g), dry weight of roots (4.36 g) and stem (4.33 g) and took minimum days (13.00) for leaf bud initiation, whereas,the maximum root length (7.80 cm) was found in 1000 ppm IBA in Eiffel Tower variety and control treatment had the lowest effect on the different traits of rooting in rose cutting . Among different varieties, Eiffel Tower was found to be best in terms of different traits, whereas English Holiday and Confetti didn't respond to any of the planting times and treatments. Cuttings planted in February showed the highest effect on their evaluated traits with a significant difference with those planted in July and October, whereas in December planting time, zero survival rates was observed.

Resistance of rose varieties to black spot

Goal. To evaluate the resistance of tea-hybrid and floribunda roses to black spot caused by the fungus Diplocarpon rosae F.A. Wolf. (Marssonina rosae (Lib.) Died.).
 Methods. Laboratory — for diagnosis of the disease and identification of its causative agent. Field — visual assessment of the distribution and degree of development of black spot (on a 6-point scale) on rose varieties under conditions of a natural infectious background. Mathematical and statistical — to assess the reliability of experimental results.
 Results. The conducted studies show that during the growing seasons of 2022—2023, black spotting was widespread on all varieties of hybrid tea roses. The intensity of disease development ranged from 30 to 70%. The average lesion score was 1.5—3.5. Ascot, Fiesta and Charming Piano varieties were noted to have the lowest degree of damage (30%). Among roses of the floribunda group, the spread of the disease was in the range of 25—100%, and its development was from 5 to 70%. The average damage score of different varieties was in the range of 0.25—3.5. The least amount of black spotting was seen on plants of the Blu fo Y variety. At the same time, its intensity of damage was 5%. There were no immune groups among rose varieties of two garden groups. Of the 12 varieties of tea-hybrid roses, highly resistant ones were also not found. 3 varieties were resistant, 6 were moderately resistant, and 3 were susceptible. Of the 11 floribunda rose varieties examined, one variety was characterized by high resistance, 3 were resistant, 5 were moderately resistant, and 2 were susceptible.
 Conclusions. According to the results of screening for resistance to black spot, 23 varieties of garden roses did not find immune roses among them. All studied varieties were affected by the causative agent of the disease D. rosae against a natural infectious background. Among the hybrid tea roses, Ascot, Fiesta and Charming Piano varieties are classified as resistant. The Blue Pho Yu variety (floribunda roses) was characterized by high resistance. Floribunda roses Sim Salabim, Bernstein and Four Elis were resistant to the disease. These varieties can be recommended for use in urban landscaping.

The transcription factor RhMYB17 regulates the homeotic transformation of floral organs in rose (Rosa hybrida) under cold stress.

Low temperatures affect flower development in rose (Rosa hybrida), increasing petaloid stamen number and reducing normal stamen number. We identified the low-temperature-responsive R2R3-MYB transcription factor RhMYB17, which is homologous to Arabidopsis MYB17 by similarity of protein sequences. RhMYB17 was up-regulated at low temperatures, and RhMYB17 transcripts accumulated in floral buds. Transient silencing of RhMYB17 by virus-induced gene silencing decreased petaloid stamen number and increased normal stamen number. According to the ABCDE model of floral organ identity, class A genes APETALA 1 (AP1) and AP2 contribute to sepal and petal formation. Transcription factor binding analysis identified RhMYB17 binding sites in the promoters of rose APETALA 2 (RhAP2) and APETALA 2-LIKE (RhAP2L). Yeast one-hybrid assays, dual-luciferase reporter assays, and electrophoretic mobility shift assays confirmed that RhMYB17 directly binds to the promoters of RhAP2 and RhAP2L, thereby activating their expression. RNA sequencing further demonstrated that RhMYB17 plays a pivotal role in regulating the expression of class A genes, and indirectly influences the expression of the class C gene. This study reveals a novel mechanism for the homeotic transformation of floral organs in response to low temperatures.

Multi-omics analysis reveals key regulatory defense pathways and genes involved in salt tolerance of rose plants

Abstract Salinity stress causes serious damage to crops worldwide, limiting plant production. However, the metabolic and molecular mechanisms underlying the response to salt stress in rose (Rosa spp.) remain poorly studied. We therefore performed a multi-omics investigation of Rosa hybrida cv. Jardin de Granville (JDG) and Rosa damascena Mill. (DMS) under salt stress to determine the mechanisms underlying rose adaptability to salinity stress. Salt treatment of both JDG and DMS led to the buildup of reactive oxygen species (H2O2). Palisade tissue was more severely damaged in DMS than in JDG, while the relative electrolyte permeability was lower and the soluble protein content was higher in JDG than in DMS. Metabolome profiling revealed significant alterations in phenolic acid, lipids, and flavonoid metabolite levels in JDG and DMS under salt stress. Proteome analysis identified enrichment of flavone and flavonol pathways in JDG under salt stress. RNA sequencing showed that salt stress influenced primary metabolism in DMS, whereas it substantially affected secondary metabolism in JDG. Integrating these datasets revealed that the phenylpropane pathway, especially the flavonoid pathway, is strongly enhanced in rose under salt stress. Consistent with this, weighted gene coexpression network analysis (WGCNA) identified the key regulatory gene chalcone synthase 1 (CHS1), which is important in the phenylpropane pathway. Moreover, luciferase assays indicated that the bHLH74 transcription factor binds to the CHS1 promoter to block its transcription. These results clarify the role of the phenylpropane pathway, especially flavonoid and flavonol metabolism, in the response to salt stress in rose.

Comparative transcriptome and metabolome analysis revealed diversity in the response of resistant and susceptible rose (Rosa hybrida) varieties to Marssonina rosae.

Rose black spot disease caused by Marssonina rosae is among the most destructive diseases that affects the outdoor cultivation and production of roses; however, the molecular mechanisms underlying the defensive response of roses to M. rosae have not been clarified. To investigate the diversity of response to M. rosae in resistant and susceptible rose varieties, we performed transcriptome and metabolome analyses of resistant (KT) and susceptible (FG) rose varieties and identified differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) in response to M. rosae at different time points. In response to M. rosae, DEGs and DAMs were mainly upregulated compared to the control and transcription factors were concentrated in the WRKY and AP2/ERF families. Gene Ontology analysis showed that the DEGs of FG were mainly enriched in biological processes, such as the abscisic acid-activated signaling pathway, cell wall, and defense response, whereas the DEGs of KT were mainly enriched in Golgi-mediated vesicle transport processes. Kyoto Encyclopedia of Genes and Genomes analysis showed that the DEGs of both varieties were concentrated in plant-pathogen interactions, plant hormone signal transduction, and mitogen-activated protein kinase signaling pathways, with the greatest number of DEGs associated with brassinosteroid (BR) in the plant hormone signal transduction pathway. The reliability of the transcriptome results was verified by qRT-PCR. DAMs of KT were significantly enriched in the butanoate metabolism pathway, whereas DAMs of FG were significantly enriched in BR biosynthesis, glucosinolate biosynthesis, and tryptophan metabolism. Moreover, the DAMs in these pathways were significantly positively correlated with the DEGs. Disease symptoms were aggravated when FG leaves were inoculated with M. rosae after 24-epibrassinolide treatment, indicating that the response of FG to M. rosae involves the BR signaling pathway. Our results provide new insights into the molecular mechanisms underlying rose response to M. rosae and lay a theoretical foundation for formulating rose black spot prevention and control strategies and cultivating resistant varieties.

TSPO-induced degradation of the ethylene receptor RhETR3 promotes salt tolerance in rose (Rosa hybrida).

The gaseous plant hormone ethylene regulates plant development, growth, and responses to stress. In particular, ethylene affects tolerance to salinity; however, the underlying mechanisms of ethylene signaling and salt tolerance are not fully understood. Here, we demonstrate that salt stress induces the degradation of the ethylene receptor ETHYLENE RESPONSE 3 (RhETR3) in rose (Rosa hybrid). Furthermore, the TspO/MBR (Tryptophan-rich sensory protein/mitochondrial benzodiazepine receptor) domain-containing membrane protein RhTSPO interacted with RhETR3 to promote its degradation in response to salt stress. Salt tolerance is enhanced in RhETR3-silenced rose plants but decreased in RhTSPO-silenced plants. The improved salt tolerance of RhETR3-silenced rose plants is partly due to the increased expression of ACC SYNTHASE1 (ACS1) and ACS2, which results in an increase in ethylene production, leading to the activation of ETHYLENE RESPONSE FACTOR98 (RhERF98) expression and, ultimately accelerating H2O2 scavenging under salinity conditions. Additionally, overexpression of RhETR3 increased the salt sensitivity of rose plants. Co-overexpression with RhTSPO alleviated this sensitivity. Together, our findings suggest that RhETR3 degradation is a key intersection hub for the ethylene signalling-mediated regulation of salt stress.

The F-box protein RhSAF destabilizes the gibberellic acid receptor RhGID1 to mediate ethylene-induced petal senescence in rose.

Roses are among the most popular ornamental plants cultivated worldwide for their great economic, symbolic, and cultural importance. Nevertheless, rapid petal senescence markedly reduces rose (Rosa hybrida) flower quality and value. Petal senescence is a developmental process tightly regulated by various phytohormones. Ethylene accelerates petal senescence, while gibberellic acid (GA) delays this process. However, the molecular mechanisms underlying the crosstalk between these phytohormones in the regulation of petal senescence remain largely unclear. Here, we identified SENESCENCE-ASSOCIATED F-BOX (RhSAF), an ethylene-induced F-box protein gene encoding a recognition subunit of the SCF-type E3 ligase. We demonstrated that RhSAF promotes degradation of the GA receptor GIBBERELLIN INSENSITIVE DWARF1 (RhGID1) to accelerate petal senescence. Silencing RhSAF expression delays petal senescence, while suppressing RhGID1 expression accelerates petal senescence. RhSAF physically interacts with RhGID1s and targets them for ubiquitin/26S proteasome-mediated degradation. Accordingly, ethylene-induced RhGID1C degradation and RhDELLA3 accumulation are compromised in RhSAF-RNAi lines. Our results demonstrate that ethylene antagonizes GA activity through RhGID1 degradation mediated by the E3 ligase RhSAF. These findings enhance our understanding of the phytohormone crosstalk regulating petal senescence and provide insights for improving flower longevity.

Comparison of Vitamin C Levels in Rose Kombucha (Rosa hybrida) during Storage

Kombucha is a drink made from tea and sugar fermented by SCOBY. One of the ingredients in kombucha that is good for the body is vitamin C. Vitamin C can increase immunity and prevent the body from free radicals. Vitamin C in kombucha is formed through a fermentation process by remodeling glucose. This research aimed to determine the comparison of vitamin C levels in kombucha with 3 and 6 days shelf life. Measurement of vitamin C levels using the UV-Vis spectrophotometry method by measuring absorbance at a maximum wavelength of 248 nm which is then calculated using a linear regression equation and measuring the pH of the preparation. Sampling by pipetting as much as 10 ml kombucha then put into a 100 ml measuring flask and add aquadest up to the mark. The results of the research showed that vitamin C levels in rose kombucha after being stored for 3 days decreased 5.05% and after being stored for 6 days, vitamin C increased by 5.32%. Therefore, the pH of rose flower kombucha also decreased after 7 days of fermentation but stays constant after being stored for 3 and 6 days (pH 4).

Mediator Subunit RhMED15a Regulates Drought Tolerance in Rose

Mediator is a multiprotein complex integral to the transcription machinery, mediated by RNA polymerase II. Some Mediator subunits have been found to have critical functions in plants’ responses to abiotic stresses. However, the role of plant Mediator subunits in drought responses remains largely enigmatic. Here, we identified a Mediator subunit, RhMED15a, in roses (Rosa hybrida). Its expression was greatly and swiftly induced by dehydration treatment in the root. The promoter sequence of RhMED15a contains cis-acting elements that respond to abscisic acid (ABA) and methyl jasmonate (MeJA). In addition, the expression of RhMED15a was significantly up-regulated with ABA treatment and inversely down-regulated with MeJA treatment. Silencing RhMED15a using virus-induced gene silencing (VIGS) in roses significantly reduced drought tolerance in rose plants. This resulted in a significant increase in the malondialdehyde (MDA) level and a decreased survival rate in comparison to TRV controls. Moreover, we found that the expression of five drought-related genes, including dehydration responsive element binding factor 1B (DREB1B), responsive to desiccation stress 29A (RD29A), responsive to desiccation stress 29B (RD29B), early response to dehydration 14 (ERD14), and 9-cis-epoxycarotenoid dioxygenase 1 (NCED1), was considerably suppressed in RhMED15a-silenced plants during drought stress. Taken together, our results present that the Mediator tail module subunit RhMED15a serves as an enhancer of drought tolerance in rose, probably through the modulation of the expression of some drought-related genes.

Effect of variety and different levels of nitrogen and potassium on flowering, quality and yield on rose (Rosa hybrida L.) through fertigation cv. gladiator and divine

Effect of variety and different levels of nitrogen and potassium on flowering, quality and yield on rose (Rosa hybrida L.) through fertigation cv. gladiator and divine

Aplicação de ácido húmico via solo atenua os impactos adversos da alcalinidade na rosa

Abstract Alkaline stress is a major environmental factor that limits the growth and productivity of rose plants. Humic acid (HA) is a natural substance that has been shown to have various beneficial effects on plant growth and stress tolerance. Roses (Rosa hybrida L.) are among the world's most important and popular cut flowers, dominating the cut flower export market. This study investigated the effects of HA application on the physiological and biochemical properties of rose plants grown under alkaline conditions. A randomized complete design with three replicates was used. Each replicate consisted of two pots containing a single rose plant. Humic acid was applied at 0, 500, 1,000, and 2,000 mg L-1 through drenching at 15-day intervals for two months. Plants treated with 1,000 mg L-1 HA exhibited significantly higher levels of total protein, proline, catalase activity, guaiacol peroxidase activity, and antioxidant capacity. Control plants (receiving no HA) showed the highest levels of malondialdehyde and electrolyte leakage, indicating greater cellular damage. Plants treated with 500 mg L-1 HA displayed the highest sugar content and ascorbate peroxidase activity. Overall, the results of this study suggest that HA application can be an effective strategy to improve the tolerance of rose plants to alkaline stress and enhance their growth and productivity in alkaline soils.

Genome-Wide Identification and Expression Analysis of the Trehalose-6-phosphate Synthase and Trehalose-6-phosphate Phosphatase Gene Families in Rose (Rosa hybrida cv 'Carola') under Different Light Conditions.

Trehalose, trehalose-6-phosphate synthase (TPS),and trehalose-6-phosphatase (TPP) have been reported to play important roles in plant abiotic stress and growth development. However, their functions in the flowering process of Rosa hybrida have not been characterized. In this study we found that, under a short photoperiod or weak light intensity, the content of trehalose in the shoot apical meristem of Rosa hybrida cv 'Carola' significantly decreased, leading to delayed flowering time. A total of nine RhTPSs and seven RhTPPs genes were identified in the genome. Cis-element analysis suggested that RhTPS and RhTPP genes were involved in plant hormones and environmental stress responses. Transcriptome data analysis reveals significant differences in the expression levels of RhTPSs and RhTPPs family genes in different tissues and indicates that RhTPPF and RhTPPJ are potential key genes involved in rose flower bud development under different light environments. The results of quantitative real-time reverse transcription (qRT-PCR) further indicate that under short photoperiod and weak light intensity all RhTPP members were significantly down-regulated. Additionally, RhTPS1a, RhTPS10, and RhTPS11 were up-regulated under a short photoperiod and showed a negative correlation with flowering time and trehalose content decrease. Under weak light intensity, RhTPS11 was up-regulated and negatively regulated flowering, while RhTPS5, RhTPS6, RhTPS7b, RhTPS9, and RhTPS10 were down-regulated and positively regulated flowering. This work lays the foundation for revealing the functions of RhTPS and RhTPP gene families in the regulation of rose trehalose.

Transcription factors RhPIF4/8 and RhHY5 regulate autophagy-mediated petal senescence in rose (Rosa hybrida)

Petal senescence refers to the progressive loss of intracellular structures and functions within plant decorative organs, ultimately leading to cell death. Autophagy involves the degradation of damaged cellular components and nutrient recycling. Plant organ senescence and autophagy are highly coordinated; however, the mechanisms by which autophagy regulates petal senescence remain largely unknown. In this study, by using transmission electron microscopy, we observed that autophagic activity peaked early, at flower opening, without any senescence and other morphological symptoms in petals. We found that darkness positively regulated petal senescence and upregulated autophagy-related genes (ATGs). Dark treatment promoted the accumulation of Rosa hybrida phytochrome-interacting factor 4 (RhPIF4) in petals. RhPIF4 silencing delayed petal senescence and repressed the expression of ATGs. In contrast, silencing of the light-responsive gene Rosa hybridaelongated hypoctyl 5 (RhHY5) promoted petal senescence and ATG gene expression. RhPIF4/8 and RhHY5 could directly interact with RhWRKY40, and RhWRKY40 is directly bound to the promoters of RhATG7 and RhATG11. Silencing RhWRKY40 delayed petal senescence and suppressed RhATG7 and RhATG11 expression. Based on these results, we propose that RhPIF4/8 and RhHY5 transcription factors are involved in regulating petal senescence in response to dark or light conditions by modulating autophagic activity.

The role of supplemental lighting during late fall and winter on photosynthetic and non-photosynthetic pigments biosynthesis of cut rose flower (Rosa hybrida cv. ‘Dolce Vita’)

ABSTRACT Low levels of natural light within the late fall and winter periods are main restricting factors for greenhouse-cut rose flower production in northern countries. Here, the effects of supplemental lighting on photosynthetic and non-photosynthetic pigments and the morphological response of cut rose flower cv. ‘Dolce Vita’ were investigated. Four different supplemental lighting regimes, including 85, 170, 255, and 340 μmol·m−2·s−1 PPFD using a high-pressure sodium lamp for a six-hour day extension started at sunset were applied to rose plants during late fall and winter. With increasing light intensity to 255 μmol·m−2·s−1 PPFD, the content of chlorophyll a, total chlorophyll, carotenoid content, and the ratio of chlorophylls a/b as well as amount of anthocyanins greatly improved. The highest phenol content and total antioxidant capacity was observed in 170 μmol·m−2·s−1 PPFD. Moreover, extending of daylength by light intensity of 255 μmol·m−2·s−1 PPFD had a significant affirmative effect on traits of growth, including flower stem length (P < 0.01), leaf number (P < 0.05), renewal bud formation (P < 0.05), time of harvesting (P < 0.05), and vase life of cut flowers (P < 0.01). Considering physiological and morphological improvement, extending of daylength from 10-h to 16-h by supplemental light of 255 μmol·m−2·s−1 PPFD would be the best choice to cultivate cut rose flower cv. ‘Dolce Vita’.

FAMOUS HYBRID TEA ROSES FROM THE BOTANIC GARDEN “DIMITRIE BRANDZA” ROSARIUM IN BUCHAREST

Flowers have been a form of commemoration of the most important events or people in our lives since ancient times. Roses breeders have always had the idea of paying homage through their creations. In this paper we will try to highlight some hybrid tea roses that are famous by their name, the importance they represent for the collections of roses or their perfume that reminds us of the old gardens from childhood.

Impact of Rhizobium radiobacter Inoculation on Physiological Stresses and Nutrients of Grafted Rose (Rosa hybrida L.) Cultivars

Impact of Rhizobium radiobacter Inoculation on Physiological Stresses and Nutrients of Grafted Rose (Rosa hybrida L.) Cultivars

Transcription factor RhRAP2.4L orchestrates cell proliferation and expansion to control petal size in rose.

Maintaining proper flower size is vital for plant reproduction and adaption to the environment. Petal size is determined by spatiotemporally regulated cell proliferation and expansion. However, the mechanisms underlying the orchestration of cell proliferation and expansion during petal growth remains elusive. Here, we determined that the transition from cell proliferation to expansion involves a series of distinct and overlapping processes during rose (Rosa hybrida) petal growth. Changes in cytokinin content were associated with the transition from cell proliferation to expansion during petal growth. RNA sequencing identified the AP2/ERF transcription factor gene RELATED TO AP2 4-LIKE (RhRAP2.4L), whose expression pattern positively associated with cytokinin levels during rose petal development. Silencing RhRAP2.4L promoted the transition from cell proliferation to expansion and decreased petal size. RhRAP2.4L regulates cell proliferation by directly repressing the expression of KIP RELATED PROTEIN 2 (RhKRP2), encoding a cell cycle inhibitor. In addition, we also identified BIG PETALub (RhBPEub) as another direct target gene of RhRAP2.4L. Silencing RhBPEub decreased cell size, leading to reduced petal size. Furthermore, the cytokinin signaling protein ARABIDOPSIS RESPONSE REGULATOR 14 (RhARR14) activated RhRAP2.4L expression to inhibit the transition from cell proliferation to expansion, thereby regulating petal size. Our results demonstrate that RhRAP2.4L performs dual functions in orchestrating cell proliferation and expansion during petal growth.

Effect of Foliar Application of CPPU and Two Type of Mulching Soil Pots in Growth and Flowering of Rose Plant (Rosa Hybrida L.)

The study was conducted in the Lath house of the College of Agriculture / University of Kirkuk / Agricultural Research and Experiment Station, for the period from September 15/ 2021 to Until the end of April / 2022, The research included studying the effect of spraying with a growth regulator (CPPU) at concentrations of (C1 0, C2 30, C3 60) mg L−1 with two sprays, the first one a day after the seedling rotation process, and the second one a week later, The first spray, And the type of mulching soil pots (bark and wood of eucalyptus trees) on the growth and flowering of Rosa hybrid L, The factorial experiment was conducted according to the (R.C.B.D), with a split experiment. The effect of spraying with the growth regulator CPPU at a concentration of 30 mg.L−1 led to a significant increase in the number of leaves, 167.66 leaves.plant−1 and the flower diameter was 13.91 cm, Plants grown in pots covered with eucalyptus bark obtained the highest significant values for some of the studied traits, As an increase in the number of developing branches, 11.00 branch.plant−1 and flower diameter 14.38 cm, The interaction between CPPU spraying and the type of mulching soil pots had a significant effect.The spray increased with 30 mg.L−1 of CPPU and plants growing in pots covered with eucalyptus bark, The number of developing branches is 11.50 branches.Plant−1 and flower diameter is 14.80 cm.