Rhododendron Flower Research Articles

Cardiovascular effects of poisoning following ingestion of dried Rhododendron flower in a middle-aged woman: a case report

Rhododendron toxicity can be life-threatening or fatal when manifested with cardiovascular and neurological adverse effects. A 56-year-old woman presented with dizziness, chest tightness, shortness of breath, and a tingling sensation in her face and limbs after ingestion of dried flowers of Rhododendron. On examination, she had sinus bradycardia and hypotension. She was admitted for monitoring and observation. She was managed with intravenous crystalloids, noradrenaline infusion, and atropine. Her vital parameters were normalised and was discharged after 24 hours. These symptoms were most likely due to grayanotoxin found in the Rhododendron species. This case highlights the need to raise awareness on the risks of plant poisoning due to rhododendrons and to seek timely medical care in case of symptoms. Clinicians are recommended to take context-specific history to identify potential aetiologies of poisoning.

Mass spectrometry and Nuclear magnetic resonance spectroscopy profiles of red and pink Rhododendron flower petals establish them as rich sources of bioactive secondary metabolites

AbstractRhododendron petals are considered high‐value owing to their commercial utility, national/state flower status in certain countries, and bioactive potential from recent studies. Profiling and quantitative analysis of the bioactive metabolites would evaluate if they can be natural sources. This study is focused on the comprehensive profiling of secondary metabolites in the hot aqueous petal extracts of Red and Pink Rhododendron flowers (Rhododendron arboreum and Rhododendron campanulatum) using separation and fragmentation patterns from mass spectrometry (MS) (gas chromatography‐MS and liquid chromatography‐tandem MS) and chemical shifts from proton‐nuclear magnetic resonance spectroscopy. The complementary analytical platforms highlighted the petals to be rich in promising bioactive molecules such as quinic acid, chlorogenic acid (caffeoyl quinic acid), protocatechuic acid, coumaroyl quinic acids, catechin, epigallocatechin, and shikimic acid. The analysis also reflected the activity of shikimic acid, phenolic acid, and flavonoid biosynthetic pathways in Rhododendron flowers. These metabolites are well reported for their bioactive potential as anti‐oxidative, anti‐viral, anti‐cancerous, anti‐diabetic, anti‐inflammatory, etc. While the quantitative and multivariate analysis showed variations in the levels of phenolic acids and flavonoids, it is established that red and pink Rhododendron flower petals are a rich source of bioactive phytochemicals of interest to the phytochemical Industry.

High toxin concentration in pollen may deter collection by bees in butterfly-pollinated Rhododendron molle.

The hypothesis that plants evolve features that protect accessible pollen from consumption by flower visitors remains poorly understood. To explore potential chemical defenses against pollen consumption, we examined the pollinator assemblage, foraging behaviour, visitation frequency and pollen transfer efficiency in Rhododendron molle, a highly toxic shrub containing Rhodojaponin III. Nutrient (protein and lipid) and toxic components in pollen and other tissues were measured. Overall in the five populations, floral visits by butterflies and bumblebees were relatively more frequent than visits by honeybees. All foraged for nectar but not pollen. Butterflies did not differ from bumblebees in the amount of pollen removed per visit, but deposited more pollen per visit. Pollination experiments indicated that R. molle was self-compatible, but both fruit and seed production were pollen limited. Our analysis indicated that the pollen was not protein-poor and had a higher concentration of the toxic compound Rhodojaponin III than petals and leaves, which compound was undetectable in nectar. Pollen toxicity in Rhododendron flowers may discourage pollen robbers (bees) from taking the freely accessible pollen grains, while the toxin-free nectar rewards effective pollinators, promoting pollen transfer. This preliminary study supports the hypothesis that chemical defense in pollen would be likely to evolve in species without physical protection from pollinivores.

A Clean-Label Formulation of Fortified Yogurt Based on Rhododendron Flower Powder as a Functional Ingredient.

The world-wide-dispersed Rhododendron is a tiny, evergreen plant with vivid red or pale pink blossoms that is a member of the Ericaceae family and is well-known for its stunning flowers. To improve yogurt's nutritional profile and sensory qualities, this study investigates an innovative application of Rhododendron flower powder (RFP). The potential health benefits of Rhododendron flowers, which are a rich source of bioactive compounds such as polyphenols and antioxidants, have attracted attention. Consequently, the physicochemical, phytochemical, and sensory qualities of fortifying yogurt with RFP at various concentrations were studied. The results showed that the texture and color of the yogurt were highly influenced by the addition of RFP. The addition of this functional ingredient also resulted in a significant increase in the yogurt's polyphenol content and antioxidant capacity. These findings demonstrate the suitability of RFP in yogurt formulations as a functional food ingredient, being a good source of phenolics.

Transcriptome sequencing reveals the senescence mechanism of ethylene-insensitive cut Rhododendron flowers

Cut rhododendron flowers have high ornamental value and are loved by consumers. It is important to clarify the senescence mechanism of cut rhododendron flowers to prolong their vase life. Transcriptome sequencing was used to investigate flower senescence in four stages of Rhododendron ‘Hong Shanhu.’ Using RNA sequencing, we generated approximately 100.17 Gb clean data and 173,502 annotated unigenes. Ethylene biosynthesis genes, ACOs , had different expression trends, and most ethylene signaling genes had low expression levels. The ethylene release rate and the activities of ACS and ACO were on the rise during cut flower development. The effects of 200 mg/L ethephon and 0.1 mM/L spermidine on vase life and fresh weight were limited. Most of the LEA and Dehydrin were upregulated with cut flower development and the fresh weight was decreased during fully flowering stage. Based on the different expression trends, differentially expressed genes were classified into 10 clusters. Cluster 2 showed significant upregulation between Z4 and Z3, suggesting that the genes in this cluster were upregulated, probably due to the senescence of cut flowers. The overall trend of Cluster 7 was positively correlated with the opening process of cut flowers. Cluster 9 had a peak at Z3, which indicated that the unigenes started the senescence process. bZIP53, RAP2.4, UIF1, HAT5, ILR3, DEAR3, SCL8, TZF10, MYB70, ERF5, ERF9, and CBF1 had higher expression levels than the other transcription factors in these clusters, indicating that they are probably the key transcription factors involved in petal senescence. Our results indicated that ‘Hong Shanhu’ cut flowers were ethylene-insensitive, and their senescence was probably related to water stress. These results contribute to understanding the mechanism of senescence in cut rhododendron flowers.

Effect of pre-treatments and drying on the quality attributes of dried rhododendron flowers

Rhododendron is a highly perishable and nutritious flower abundant in phytocompounds. However, due to its availability for a short span, it is not much exploited by food researchers. Therefore, the aim of the current study was to optimize the pre-treatments for drying of Rhododendron with maximum phytochemical retention. The effect of different variables was evaluated on the physico-chemical parameters (such as moisture, ash, protein, total sugars and reducing sugars) and phytocompounds (such as ascorbic acid, carotenoids, anthocyanin, total phenols, flavonoids, antioxidant activity and tannins). All the quality attributes were significantly (p ≤ 0.05) affected by blanching treatment and dipping time. Among the chemical pre-treatments, KMS had a significant (p ≤ 0.05) effect on the retention of all phytochemicals, whereas, citric acid could not possess a significant (p ≤ 0.05) effect on the phytochemicals. The optimum process conditions for Rhododendron flowers were found to be 3 min blanching time, 2000 ppm KMS, 0% citric acid, and 26.28 min dipping time along with 0.917 desirability. In the nutshell, it is concluded that KMS in combination with blanching, prior to drying has been proven beneficial in the preservation of the phytocompounds and has the potential to utilize as a new ingredient in various food products.

Genome-Wide Analysis of the Rhododendron AP2/ERF Gene Family: Identification and Expression Profiles in Response to Cold, Salt and Drought Stress.

The AP2/ERF gene family is one of the most conserved and important transcription factor families mainly occurring in plants with various functions in regulating plant biological and physiological processes. However, little comprehensive research has been conducted on the AP2/ERF gene family in Rhododendron (specifically, Rhododendron simsii), an important ornamental plant. The existing whole-genome sequence of Rhododendron provided data to investigate the AP2/ERF genes in Rhododendron on a genome-wide scale. A total of 120 Rhododendron AP2/ERF genes were identified. The phylogenetic analysis showed that RsAP2 genes were classified into five main subfamilies, AP2, ERF, DREB, RAV and soloist. Cis-acting elements involving plant growth regulators, response to abiotic stress and MYB binding sites were detected in the upstream sequences of RsAP2 genes. A heatmap of RsAP2 gene expression levels showed that these genes had different expression patterns in the five developmental stages of Rhododendron flowers. Twenty RsAP2 genes were selected for quantitative RT-PCR experiments to clarify the expression level changes under cold, salt and drought stress treatments, and the results showed that most of the RsAP2 genes responded to these abiotic stresses. This study generated comprehensive information on the RsAP2 gene family and provides a theoretical basis for future genetic improvement.

Identification of terpene synthase gene family members in Rhododendron and its relationship with terpenoid metabolism

Terpene synthase (TPS) plays important roles in the synthesis of terpenoids which are the main fragrances in Rhododendron flowers. To understand the function of TPS genes in terpenoid metabolism in relation to flower aroma formation, we identified all TPS gene family members in Rhododendron by analyzing its genome database. We then used a transcriptomic approach to analyze the differential gene expression patterns of TPS gene family members in the scented flower Rhododendron fortunei compared to the non-scented flower Rhododendron 'Nova Zembla'. The contents of terpenoid compounds in petals of the above two Rhododendron species at different developmental stages were also measured by using qRT-PCR and head space-solid phase micro-extraction combined with gas chromatography-mass spectrometry. Our results showed that a total of 47 RsTPS members, with individual lengths ranged from 591 to 2 634 bp, were identified in the Rhododendron genome. The number of exons in RsTPS gene ranged from 3 to 12, while the length of each protein encoded ranged from 196 to 877 amino acids. Members of the RsTPS family are mainly distributed in the chloroplast and cytoplasm. Phylogenetic analysis showed that RsTPS genes can be clustered into 5 subgroups. Seven gene family members can be functionally annotated as TPS gene family since they were temporally and spatially expressed as shown in the transcriptome data. Notably, TPS1, TPS10, TPS12 and TPS13 in Rhododendron fortunei were expressed highly in flower buds reached the peak in the full blossoming. Correlation analysis between gene expression levels and terpenoid content indicates that the expression levels of TPS1, TPS4, TPS9, TPS10, TPS12 and TPS13 were positively correlated with the content of terpenoids in the petals of R. fortunei at all flower developmental stages, suggesting that these six genes might be involved in the aroma formation in R. fortunei.

Identification and Characterization of Circular RNAs Involved in the Flower Development and Senescence of Rhododendron delavayi Franch

Floral development and senescence are a crucial determinant for economic and ornamental value. CircRNAs play an essential role in regulating plant growth and development; however, there is no systematic identification of circRNAs during the lifespan of flowers. This study aims to explore the expression profile and functional role of circRNAs in the full flowering stages of Rhododendron delavayi Franch. We carried out transcriptome sequencing of the six stages of Rhododendron delavayi Franch flowers to identify the circular RNA expression profile. In addition, using bioinformatics methods, we explored the functions of circRNAs, including analysis of the circRNA-miRNA-mRNA network, short time-series expression miner (STEM), and so on. We identified 146 circRNAs, of which 79 were differentially expressed from the budding to fading stages. Furthermore, using STEM analysis, one of the 42 circRNA expression model profiles was significantly upregulated during the senescence stage, including 16 circRNAs. Additionally, 7 circRNA-miRNA-mRNA networks were constructed with 10 differentially expressed circRNAs, in which some target mRNA may regulate the development and senescence of the Rhododendron flowers. Finally, by analyzing the correlation between circRNAs and mRNA, combined with existing reports, we proposed that circRNAs play a regulatory role during flower development and senescence by mediating the jasmonate signaling pathway. Overall, these results provide new clues to the potential mechanism of circRNAs acting as novel post-transcriptional regulators in the development and senescence process of flowers.

Dried rhododendron flower ingestion presenting with bradycardia and hypotension: a case report

BackgroundRhododendron toxicity can be a life-threatening situation when manifested; it results in bradycardia and hypotension. Treatment remains challenging when it is complicated with refractory hypotension involving the multiorgan system if not treated early.Case presentationA 33-year-old Magar male presented with history of ingestion of two handfuls of white rhododendron flower. He had ingested the flowers believing that it would help relieve the pain and remove the materials stuck in his food pipe. Symptoms presented included muscular discomfort, dizziness, nausea, palpitation, tingling sensation around the face and lips, difficulty breathing, chest tightness, and difficulty swallowing within 4–5 hours after the ingestion of the dried flower. High-flow oxygen, intravenous fluids, atropine, and other supportive measures were used during the emergency, followed later by transfer to the intensive care unit for further observation.ConclusionThe patient was discharged with complete recovery after 2 days of hospital stay. Intentional or accidental ingestion of toxic plants can be severe or even life-threatening. Thus, clinicians should be familiar with local toxic plants with grayanotoxin action.

Evaluation of the antioxidant potential of the mad honey collected from the black sea region in Turkey

Objective: Mad honey (Rhododendron honey) is produced by honeybees from Rhododendron flowers and contains grayanotoxins, antioxidants, flavonoid and phenolic properties. The mad honey samples are collected from Turkey's Black Sea region by local residents and are sold as mad honey in free market conditions. This study was planned to evaluate the total phenolic content, total flavonoid content and total antioxidant capacity and protein profiles with SDS-Page electrophoresis determined the mad honey samples collected from seven different locations from Black Sea region by local residents.
 Material and Method: Total phenolic content was determined by the modified Folin-Ciocalteu method. Total flavonoid content was determined by colorimetric method using aluminum chloride (AlCl3). Total antioxidant activity was calculated according to the free radical scavenging effect of 1,1-diphenyl-2-picryl hydrazyl (DPPH). Protein profiles evaluated with SDS-Page electrophoresis.
 Results and Conclusions: In Turkey, in the Black Sea Region, antioxidant potential of the honey samples known as mad honey, collected from seven different locations by local people, were evaluated. The mean total phenolic contents of the mad honey samples were found as 285,44±118,43 (125.85 to 471.18) mg GAE/kg honey, the mean total antioxidant activities were found as 29,68±7,2 (21.71 to 35.03) mg AAE/kg honey and the mean total flavonoid contents were found as 27,26±4,79 (19.93 to 39.18) mg QE/kg honey.
 The results revealed that the mad honey samples examined in this study were a good source of antioxidant, flavonoid and phenolic content at varying levels depending on the characteristics of the region where they were collected.

Explore the unexplored: Potential anti-tumor properties of Rhododendron against bladder cancer.

Explore the unexplored: Potential anti-tumor properties of Rhododendron against bladder cancer.

Transcriptomic and metabolomic analyses reveal the altitude adaptability and evolution of different-colored flowers in alpine Rhododendron species.

Understanding the molecular mechanisms and evolutionary process of plant adaptation to the heterogeneous environment caused by altitude gradients in plateau mountain ecosystems can provide novel insight into species' responses to global changes. Flower color is the most conspicuous and highly diverse trait in nature. Herein, the gene expression patterns, evolutionary adaptation and metabolites changes of different-colored flowers of alpine Rhododendron L. species along altitude gradients were investigated based on a combined analysis of transcriptomics and metabolomics. Differentially expressed genes were found to be related to the biosynthesis of carbohydrates, fatty acids, amino acids and flavonoids, suggesting their important roles in the altitude adaptability of Rhododendron species. The evolution rate of high-altitude species was faster than that of low-altitude species. Genes related to DNA repair, mitogen-activated protein kinase and ABA signal transduction, and lipoic acid and propanoate metabolism were positively selected in the flowers of high-altitude Rhododendron species and those associated with carotenoid biosynthesis pathway, ABA signal transduction and ethylene signal transduction were positively selected in low-altitude species. These results indicated that the genes with differentiated expressions or functions exhibit varying evolution during the adaptive divergence of heterogeneous environment caused by altitude gradients. Flower-color variation might be attributed to the significant differences in gene expression or metabolites related to sucrose, flavonoids and carotenoids at the transcription or metabolism levels of Rhododendron species. This work suggests that Rhododendron species have multiple molecular mechanisms in their adaptation to changing environments caused by altitude gradients.

Gibberellin and spermidine synergistically regulate polyamine metabolism during the development of Rhododendron flowers

Polyamines (PAs) are involved in various developmental processes, especially plant flowering. Their significant influences have been established; however, the exact mechanism by which PAs regulate flowering remains unclear. To explore PA metabolism in plant flowering, gibberellic acid (GA3, 0~2400 mg L−1) and spermidine (Spd, 0~1 mM) were applied alone or in combination during the early stage of flower bud formation in Rhododendron simsii. The application of GA3 alone advanced initial flowering, while that of Spd alone delayed initial flowering. Interestingly, GA3 and Spd applied in combination advanced initial flowering by 2 days. Furthermore, from stage 1 to 2, endogenous PA levels and the soluble conjugated and insoluble bound fractions of PAs and key enzymes (e.g., diamine oxidase, arginine decarboxylase, ornithine decarboxylase and S-adenosylmethionine decarboxylase) increased, and the level of PA oxidase decreased. These findings revealed that exogenous GA3 and Spd delay flower senescence by improving PA biosynthesis and preventing PA degradation. Moreover, exogenous GA3 and Spd enhanced the levels of endogenous PA and GA3, while the conversion of free PAs to soluble conjugated and insoluble bound forms delayed Rhododendron senescence. Overall, our findings reveal a potential positive feedback mechanism by which higher endogenous PA contents and the combined effects of exogenous GA3 and Spd synergistically delay Rhododendron senescence by enhancing PA biosynthesis and converting free PA to soluble conjugated and insoluble bound forms, thus reducing PA degradation during flower senescence.

Gene Duplication and Differential Expression of Flower Symmetry Genes in Rhododendron (Ericaceae).

Bilaterally symmetric flowers have evolved over a hundred times in angiosperms, yet orthologs of the transcription factors CYCLOIDEA (CYC), RADIALIS (RAD), and DIVARICATA (DIV) are repeatedly implicated in floral symmetry changes. We examined these candidate genes to elucidate the genetic underpinnings of floral symmetry changes in florally diverse Rhododendron, reconstructing gene trees and comparing gene expression across floral organs in representative species with radial and bilateral flower symmetries. Radially symmetric R. taxifolium Merr. and bilaterally symmetric R. beyerinckianum Koord. had four and five CYC orthologs, respectively, from shared tandem duplications. CYC orthologs were expressed in the longer dorsal petals and stamens and highly expressed in R. beyerinckianum pistils, whereas they were either ubiquitously expressed, lost from the genome, or weakly expressed in R. taxifolium. Both species had two RAD and DIV orthologs uniformly expressed across all floral organs. Differences in gene structure and expression of Rhododendron RAD compared to other asterids suggest that these genes may not be regulated by CYC orthologs. Our evidence supports CYC orthologs as the primary regulators of differential organ growth in Rhododendron flowers, while also suggesting certain deviations from the typical asterid gene regulatory network for flower symmetry.

2:1 Atrioventricular Block and Severe Hypotension Due to Wild Honey Poisoning: A Case Report

Wild Honey poisoning is caused by ingestion of wild honey obtained from the nectar of some species of Rhododendron, consuming leaves and flowers of Rhododendron found in the higher altitudes of Nepal which has traditionally been used by indigenous people of Nepal especially Himalayan belt of Nepal for its medicinal properties. The cause of poisoning is the toxin called grayanotoxin which is a naturally occurring sodium channel toxin that leads to life threatening bradycardia, hypotension and altered mental status but sometime it may present with rare life threatening atrioventricular block and cardiovascular collapse. Wild honey intoxication has widely been reported from Turkey, regions around the Black sea, Austria, Korea and some cases from Nepal. Wild honey poisoning is not the uncommon presentation to emergency department of Chitwan Medical College as it is located to central part of Nepal. We report a case of wild honey poisoning who was referred to our hospital with arrhythmia and hypotension. Keywords: 2:1 Atrioventricular block, Grayanotoxin, Hypotension, Nepal, Wild honey.

Poisonous delicacy: Market-oriented surveys of the consumption of Rhododendron flowers in Yunnan, China

Ethnopharmacological relevancePlants from the family Ericaceae, and in particular those in the genus Rhododendron are frequently reported to contain grayanotoxins. Plant products such as honey and herbal medicines made from these plants occasionally contain grayanotoxins, and in turn may lead to intoxication. The balance between the benefits and risk of poisoning from Rhododendrons is of concerns. This study explores the ethnobotanical knowledge of the people in Yunnan, China as regards the consumption of Rhododendron flowers, and gives special focus to their assessment of the benefit-risk balance. Materials and methodsAn ethnobotanical survey was conducted across 14 county-level local markets in north and central Yunnan province, during which a total of 82 stalls selling Rhododendron flowers were visited and 204 people were interviewed. Voucher specimens were obtained under the guidance of collectors, and details about local practices and knowledge were recorded using semi-structured interviews and participatory observations. ResultsThe consumption of the corollas of Rhododendron decorum Franch. Flowers (RDf) or Rhododendron pachypodum Balf. f. & W.W. Sm. Flowers (RPf) as a seasonal delicacy is a long-standing tradition in the study area. RDf are widely consumed in northwest and northeast Yunnan, while RPf are more prevalent in the central regions of Yunnan, and there is a high consistency in the knowledge of the process for detoxification or palatability for each species. The main reasons for eating the flowers were listed as health benefits (mostly clear heat), wild collected, tradition and good flavor. All RPf consumers stated that the corolla from this species is not toxic, while 67.4% of the RDf consumers claim that the corolla from RDf is toxic. We compared the two species and analyzed their process intensities, poisoning cases and cautions, market trade forms and existing toxicity studies, which agreed well and consistently that the corolla of RDf deserve more toxicity attention than RPf. ConclusionOur study provides a window to look into the ways, beyond honey and herbal medicine, by which Rhododendron species have influenced human wellbeing. The local culture can justify eating Rhododendron flowers, and meanwhile, has developed a series of skills to avoid the side effects of eating them, and therefore the study also provides a good case to answer more general questions about the rationality of eating any plant products by assessing the trade-off between benefits and side effects.

Utilization of Edible Rhododendron (Rhododendron arboreum Sm.) Flowers for Development of Spiced Beverage (Appetizer) and Its Shelf Life Evaluation during Storage

In India, various types of unexplored edible flowers are being utilized traditionally as food and medicine by the rural communities since ancient time only during their flowering time due to short post harvest life. These flowers are rich in phytochemical (e.g. polyphenolics, anthocyanins) which possess numerous health benefits. So, the present investigations were conducted to develop a spiced beverage/appetizer (spiced squash) from rhododendron flower petals and its quality evaluation during storage. Different combinations of petals extract and total soluble solids (TSS) were tried to standardize proper combination for spiced beverage. Appetizer recipe (T3) prepared with 35% extract, 40°B TSS and 1.20% acid was found to be best based on quality characteristics of the product. The best-selected appetizer recipe was packed in glass and PET bottles and stored for 6 months under ambient (15-25°C) and refrigerated temperature conditions (4-7°C). Overall effect of packaging and storage revealed that various quality characteristics like TSS, apparent viscosity, reducing and total sugars of appetizer increased slightly, whereas, other chemical characteristics like acidity, ascorbic acid, anthocyanins, total phenols and sensory characteristics scores of colour, body, taste, aroma, overall acceptability score decreased slightly during storage. The quality of beverage was retained better in glass bottles under refrigerated condition as compare to ambient storage condition.

Impact of agribusiness on food security and livelihood generation: A case study in Assam, India

In the present study, Rhododendron flowers were used for the preparation of biscuits to enhance the utility of this valuable flower. Dried Rhododendron petals powder was incorporated at different levels (0%, 5%, 10% and 15%) in biscuits and their sensory and physico- chemical properties were evaluated. The results revealed that, the length and thickness of biscuits decreased by increasing the proportion of Rhododendron powder in biscuits. Addition of Rhododendron powder to wheat flour significantly increased the content of moisture, ash (0.75 to 1.20 %), protein (3.06 to 4.96 %), fibre (0.07 to 0.67 %) and iron (3.90 to 4.19 mg/100g). The sensory results showed a significant decrease (7.70 to 7.10) in the overall acceptability by the addition of Rhododendron power to wheat flour but the product remained acceptable in terms of sensory acceptability up to the level 10 per cent. From the study it can be concluded that a maximum of 15% Rhododendron powder can be incorporated to prepare acceptable quality of biscuits.

De novo transcriptome analysis of Rhododendron molle G. Don flowers by Illumina sequencing

Rhododendron molle G. Don occupies an important phylogenetic node in the genus rhododendron with unique yellow flower and medicinal functions. However, only limited genetic resources and their genome information are available for the generation of rhododendron flowers. The next generation sequencing technologies enables generation of genomic resources in a short time and at a minimal cost, and therefore provide a turning point for rhododendron research. Our goal is to use the genetic information to facilitate the relevant research on flowering and flower color formation in R. molle. In total, 66,026 unigenes were identified, among which 31,298 were annotated in the NCBI non-redundant protein database and 22,410 were annotated in the Swiss-Prot database. Of these annotated unigenes, 9490 and 18,680 unigenes were assigned to clusters of orthologous groups and gene ontology categories, respectively. A total of 7177 genes were mapped to 118 pathways using the Kyoto Encyclopedia of Genes and Genomes Pathway database. In addition, 8266 simple sequence repeats (SSRs) were detected, and these SSRs will undoubtedly benefit rhododendron breeding work. Metabolic pathway analysis revealed that 32 unigenes were predicted to be involved in carotenoid biosynthesis. Our transcriptome revealed 32 engines that encode key enzymes in the carotenoid biosynthesis pathway, including PSY, PDS, LCYB, LCYE, etc. The content of β-carotene was much higher than the other carotenoids throughout the flower development. It was consistent with the key genes expression level in the carotenoid biosynthesis pathway by the Illumina expression profile analysis and the qRT-PCR analysis. Our study identified genes associated with carotenoid biosynthesis in R. molle and provides a valuable resource for understanding the flowering and flower color formation mechanisms in R. molle.