Development of an Efficient In vitro Regeneration Protocol for Chrysanthemum (Chrysanthemum morifolium Ramat)

An efficient and rapid in vitro regeneration protocol was developed for chrysanthemum (Chrysanthemum morifolium Ramat) using two local varieties of Bangladesh namely, BARI Chrysanthemum-2 (BARI Chry-2) and local yellow (Y). MS medium supplemented with nine different concentrations and combinations of BAP and IAA was employed to optimize regeneration protocol using young in vitro derived leaf explants. Direct organogenesis was observed from the leaf explants on MS medium supplemented with 0.5 mg/l BAP and 2.0 mg/l IAA (T6) for both the varieties. This treatment (T6) induced shoot buds directly on the adaxial surface of the leaf providing the highest regeneration percentage (90% for BARI Chry-2 and 94.73% for Y), the highest number of shoot/explant (7.6 for BARI Chry-2 and 8.6 for Y) and maximum length of the shoot after six weeks (3 cm for BARI Chry-2 and 2.9 cm for Y) of culture. Explants with initially regenerated shoots were subculture on hormone free MS medium for shoot elongation after 4 weeks of their inoculation. During elongation of shoots, 90-95% of the regenerated shoots produced roots spontaneously in hormone free MS medium within 7-8 weeks of their inoculation. Rooted plantlets were transplanted to the field following hardening where 100% plantlets were survived and produced flower without any variation. Plant Tissue Cult. & Biotech. 31(2): 161-171, 2021 (December)

Highly divergent isolates of chrysanthemum virus B and chrysanthemum virus R infecting chrysanthemum in Russia

Background Chrysanthemum is a popular ornamental and medicinal plant that suffers from many viruses and viroids. Among them, chrysanthemum virus B (CVB, genus Carlavirus, family Betaflexiviridae) is widespread in all chrysanthemum-growing regions. Another carlavirus, chrysanthemum virus R (CVR), has been recently discovered in China. Information about chrysanthemum viruses in Russia is very scarce. The objective of this work was to study the prevalence and genetic diversity of CVB and CVR in Russia. Methods We surveyed the chrysanthemum (Chrysanthemum morifolium Ramat.) germplasm collection in the Nikita Botanical Gardens, Yalta, Russia. To detect CVB and CVR, we used RT-PCR with virus-specific primers. To reveal the complete genome sequences of CVB and CVR isolates, metatransciptomic analysis of the cultivars Ribonette, Fiji Yellow, and Golden Standard plants, naturally co-infected with CVB and CVR, was performed using Illumina high-throughput sequencing. The recombination detection tool (RDP4) was employed to search for recombination in assembled genomes. Results A total of 90 plants of 23 local and introduced chrysanthemum cultivars were surveyed. From these, 58 and 43% plants tested positive for CVB and CVR, respectively. RNA-Seq analysis confirmed the presence of CVB and CVR, and revealed tomato aspermy virus in each of the three transcriptomes. Six near complete genomes of CVB and CVR were assembled from the RNA-Seq reads. The CVR isolate X21 from the cultivar Golden Standard was 92% identical to the Chinese isolate BJ. In contrast, genomes of the CVR isolates X6 and X13 (from the cultivars Ribonette and Fiji Yellow, respectively), were only 76% to 77% identical to the X21 and BJ, and shared 95% identity to one another and appear to represent a divergent group of the CVR. Two distantly related CVB isolates, GS1 and GS2, were found in a plant of the cultivar Golden Standard. Their genomes shared from 82% to 87% identity to each other and the CVB genome from the cultivar Fiji Yellow (isolate FY), as well as to CVB isolates from Japan and China. A recombination event of 3,720 nucleotides long was predicted in the replicase gene of the FY genome. It was supported by seven algorithms implemented in RDP4 with statistically significant P-values. The inferred major parent was the Indian isolate Uttar Pradesh (AM765837), and minor parent was unknown. Conclusion We found a wide distribution of CVB and CVR in the chrysanthemum germplasm collection of the Nikita Botanical Gardens, which is the largest in Russia. Six near complete genomes of CVR and CVB isolates from Russia were assembled and characterized for the first time. This is the first report of CVR in Russia and outside of China thus expanding the information on the geographical distribution of the virus. Highly divergent CVB and CVR isolates have been identified that contributes the better understanding the genetic diversity of these viruses.

Cytotoxicity Effect and Morphological Changes of Chrysanthemum Morifolium Methanolic Extract against Chronic Myeloid Leukaemia K-562 Cell Line

Chrysanthemum morifolium, also known as “Bunga kekwa” in Malaysia, has various benefits and widely used in Chinese herbal medicines. The plant extract was reported to have significant biological activities, such as anti-inflammation, anti-tumour, anti-oxidant, and anti-cancer. Nonetheless, its anti-cancer potential on chronic myeloid leukaemia has remained elusive. The main goal of this study is to evaluate the cytotoxic effect of C.morifolium buds and flowers in methanolic extracts on chronic myeloid leukaemia malignancy K-562 cell lines. The bud and flower of C.morifolium were macerated for 72 hours in 100% methanol then were concentrated under reduced pressure using a rotary evaporator and oven-dried to obtain crude extracts. K-562 cells were treated with six different concentrations 400, 200, 100, 50, 25, and 12.5 µg/ml and incubated for 24, 48 and 72 hours. The in vitro cytotoxic activity was measured using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) test and was quantified using a microplate reader at 570 nm. Acridine orange and propidium iodide (AO/PI) staining were used to assess morphological alterations. MTT assays results showed moderate toxicity of both extracts. The lowest maximal half inhibitory concentration (IC50) value were observed at 72 hours of incubation; 182 ± 4.04 ug/ml for BM and 161 ± 7.88 ug/ml for flower extract (FM). However, there was a significantly different IC50 value (p<0.05) between the incubation periods of both treatments where the IC50 value at 24 hours was 301.33 ± 8.51 ug/ml 301 µg/ml in BM, 216 ± 10.79 ug/ml 216 µg/ml in FM and at 48 hours was 227 ± 12.25 ug/ml 227 µg/ml in bud extract (BM), 174 ± 11.92 ug/ml 174 µg/ml in FM. The morphological changes evidence was shown in AO/PI staining by the appearance of a mixed population of cells; early apoptosis, late apoptosis and necrotic cells. These findings suggested that methanolic C.morifolium extracts showed moderate cytotoxic effect on chronic myeloid leukaemia K-562 cells. Further study needed to identify the mode and mechanism of cell death in K-562 cells treated with the C.morifolium extracts.

Aqueous extracts from Acalypha gaumeri and Bonellia flammea for leaf blight control in chrysanthemum (Chrysanthemum morifolium)

The chrysanthemum is the second most important cut flower in the world, however, its quality and commercial value is affected by the leaf blight produced by <em>Alternaria </em>spp. The objective of this work was to evaluate the causal agent of leaf blight in Chrysanthemum, and its control with aqueous extracts of <em>Acalypha gaumeri </em>and <em>Bonellia flammea</em>. The fungus was collected and identified from leaves and stems of chrysanthemum plants. Subsequently, molecular identification and pathogenicity tests were performed on chrysanthemum plants. In the field, treatments were evaluated with weekly applications of: T1: <em>B. flammea </em>bark extract, T2: <em>A. gaumeri </em>root extract, T3: negative control (water) and T4: Captan® fungicide. Prior to the application of the treatments, plants were inoculated with the isolated fungus (2.5 × 106 spores mL-1) and severity was evaluated. <em>Alternaria chrysanthemi </em>was identified as the causal agent. Based on the severity percentage, the lowest averages of the area under the disease progress curve, the lowest rates of apparent infection, the lowest intensity of the disease and the greater effectiveness in controlling the disease were observed for T2 (165, 0.017, 8 and 67%, respectively) followed by T1 (186, 0.022, 13 y 50 %, respectively) and T4 (179, 0.023, 14 y 45%, respectively), observing a significantly different than negative control T3 (369, 0.025, 25 and 0%, respectively). Plant extracts have potential to be used as an alternative in the management of <em>Alternaria </em>leaf blight in chrysanthemum.

Transcriptome Analysis Reveals Genes Respond to Chlorophyll Deficiency in Green and Yellow Leaves of Chrysanthemum morifolium Ramat

Chlorophyll is vital for photosynthesis to produce sugars and other useful biochemical products in green plants. However, the molecular effects of chlorophyll deficiency in Chrysanthemum are largely unknown. In this study, we identified a bud sport mutant chrysanthemum belonging to the variety ‘Nannong Binyun’, which has yellow branches. Plant physiological studies have shown that the yellow color is revealed due to chlorophyll loss. RNA extracts of yellow and green tissues were analyzed using high-throughput RNA-sequencing, and a total of 11,649 tissue enriched unigenes that respond to chlorophyll deficiency were identified, including 4803 unigenes upregulated in yellow tissues and 6846 unigenes in green tissues. GO analysis revealed that these tissue-enriched genes may involve in the physiological processes of chlorophyll accumulation and photosynthesis. In addition, many DEGs from the families of AP2-EREBP, bHLH, MYB, and FAR1 that are associated with plant development and stress response were detected. Our study found that most of the genes from the GRAS family were downregulated in yellow leaves, indicating their putative roles in stem cell maintenance and possible contribution to leaf size determination.

Sunlight Photocatalytic Performance of ZnO Nanoparticles Synthesized by Green Chemistry Using Different Botanical Extracts and Zinc Acetate as a Precursor

In this work, the assessment of Azadirachta indica, Tagetes erecta, Chrysanthemum morifolium, and Lentinula edodes extracts as catalysts for the green synthesis of zinc oxide nanoparticles (ZnO NPs) was performed. The photocatalytic properties of ZnO NPs were investigated by the photodegradation of methylene blue (MB) dye under sunlight irradiation. UV-visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Thermogravimetric (TGA), and Brunauer-Emmett-Teller analysis (BET) were used for the characterization of samples. The XRD results indicate that all synthesized nanoparticles have a hexagonal wurtzite crystalline structure, which was confirmed by TEM. Further, TEM analysis proved the formation of spherical and hemispherical nanoparticles of ZnO with a size in the range of 14–32 nm, which were found in aggregate shape; such a size was well below the size of the particles synthesized with no extract (~43 nm). ZnO NPs produced with Tagetes erecta and Lentinula edodes showed the best photocatalytic activity, matching with the maximum adsorbed MB molecules (45.41 and 58.73%, respectively). MB was completely degraded in 45 min using Tagetes erecta and 120 min using Lentinula edodes when subjected to solar irradiation.