Young Plantlets Research Articles

Physiological Response of Dendrobium Udomsri Beauty under Low-temperature Treatment

Denphal-type Dendrobium is the famous cut and potted flower in the world, and most cultivated in tropical and subtropical regions. However, it often suffers from cold in winter in subtropical regions. To verify the physiological response of Denphal-type Dendrobium under low temperature in this study, the mature and young plantlets of Dendrobium Udomsri Beauty were treated under 15, 10, and 5 °C, respectively. And then the electrical conductivity (EC), soluble protein, soluble sugar, free proline, malondialdehyde (MDA), chlorophyll content, and the rate of defoliation after regrowth were measured. The results showed that both mature plant and young seedlings of Dendrobium Udomsri Beauty, the EC, soluble protein, soluble sugar, free proline, MDA content, and defoliation rate were increased with the decrease of treatment temperature and the extension of treatment times. The content of chlorophyll decreased gradually with the decrease of treatment temperature and the extension of treatment times. The correlation analysis showed that soluble sugar, free proline, MDA, chlorophyll content, and defoliation rate were significantly correlated with the semi-lethal temperature. It is indicated that the content of free proline, MDA, chlorophyll, and defoliation rate could be used as the effective indexes for the comprehensive assessment of cold tolerance of Dendrobium Udomsri Beauty.

Soil fertility and plant nutrition in an organic olive orchard after 5 years of amendment with compost, biochar or their blend

The agronomic use of compost and biochar as soil amendments may exhibit contrasting results in terms of soil fertility and plant nutrition. The effects of the biennial application of biochar, compost and a blend of compost:biochar (90:10; % dw:dw) on the agronomical performance of an organically managed and well established 25-year-old olive orchard was assessed 5 years after the initial application. The agronomical evaluation was based on the assessment of the soil physical, chemical, and biological characteristics, and the assessment of the soil fertility by both crop production and nutritional status of the orchard, and the bioassay with olive plantlets. Biochar mainly benefited the physical properties (bulk density, total porosity, aeration, water retention capacity) of soil, especially in the top 0–5 cm. Compost and its blend with biochar improved microbial activity, soil nutritional status (increasing the content of soluble organic C, N, and P) and favoured the formation of aggregates in soil. The bioassay conducted with young plantlets confirmed the enhanced soil fertility status in the three amended treatments, particularly in the case of biochar and its blend with compost. However, this effect was not significantly observed in the adult plants after 5 years of application, reflecting the slow response of adult olive trees to changes in fertilization. Based on these results, alongside the desirable long-residence time of biochar in soil and the ready availability of compost, the blend of biochar with compost assayed in this study is defined as a valid strategy for preparing high quality soil organic amendments.

A Cotyledon-based Virus-Induced Gene Silencing (Cotyledon-VIGS) approach to study specialized metabolism in medicinal plants

BackgroundVirus-induced gene silencing (VIGS) is widely used in plant functional genomics. However, the efficiency of VIGS in young plantlets varies across plant species. Additionally, VIGS is not optimized for many plant species, especially medicinal plants that produce valuable specialized metabolites.ResultsWe evaluated the efficacy of five-day-old, etiolated seedlings of Catharanthus roseus (periwinkle) for VIGS. The seedlings were vacuum-infiltrated with Agrobacterium tumefaciens GV3101 cells carrying the tobacco rattle virus (TRV) vectors. The protoporphyrin IX magnesium chelatase subunit H (ChlH) gene, a key gene in chlorophyll biosynthesis, was used as the target for VIGS, and we observed yellow cotyledons 6 days after infiltration. As expected, the expression of CrChlH and the chlorophyll contents of the cotyledons were significantly decreased after VIGS. To validate the cotyledon based-VIGS method, we silenced the genes encoding several transcriptional regulators of the terpenoid indole alkaloid (TIA) biosynthesis in C. roseus, including two activators (CrGATA1 and CrMYC2) and two repressors (CrGBF1 and CrGBF2). Silencing CrGATA1 led to downregulation of the vindoline pathway genes (T3O, T3R, and DAT) and decreased vindoline contents in cotyledons. Silencing CrMYC2, followed by elicitation with methyl jasmonate (MeJA), resulted in the downregulation of ORCA2 and ORCA3. We also co-infiltrated C. roseus seedlings with TRV vectors that silence both CrGBF1 and CrGBF2 and overexpress CrMYC2, aiming to simultaneous silencing two repressors while overexpressing an activator. The simultaneous manipulation of repressors and activator resulted in significant upregulation of the TIA pathway genes. To demonstrate the broad application of the cotyledon-based VIGS method, we optimized the method for two other valuable medicinal plants, Glycyrrhiza inflata (licorice) and Artemisia annua (sweet wormwood). When TRV vectors carrying the fragments of the ChlH genes were infiltrated into the seedlings of these plants, we observed yellow cotyledons with decreased chlorophyll contents.ConclusionsThe widely applicable cotyledon-based VIGS method is faster, more efficient, and easily accessible to additional treatments than the traditional VIGS method. It can be combined with transient gene overexpression to achieve simultaneous up- and down-regulation of desired genes in non-model plants. This method provides a powerful tool for functional genomics of medicinal plants, facilitating the discovery and production of valuable therapeutic compounds.

Transcriptome Analysis of the Salt-Treated Actinidia deliciosa (A. Chev.) C. F. Liang and A. R. Ferguson Plantlets

The area of saline land in the world is quite large, and there is broad room for its development and usage. 'Xuxiang' is an Actinidia deliciosa variety that is tolerant to salt and can be planted in an area of light-saline land, and has good comprehensive characteristics and high economic value. However, the molecular mechanism of salt tolerance is unknown at present. To understand the molecular mechanism of salt tolerance, the leaves of A. deliciosa 'Xuxiang' were used as explants to establish a sterile tissue culture system, and plantlets were obtained using this system. One percent concentration (w/v) of sodium chloride (NaCl) was employed to treat the young plantlets cultured in Murashige and Skoog (MS) medium, then RNA-seq was used for transcriptome analysis. The results showed that the genes related to salt stress in the phenylpropanoid biosynthesis pathway and the anabolism of trehalose and maltose pathways were up-regulated; however, those genes in the plant hormone signal transduction and metabolic pathways of starch, sucrose, glucose, and fructose were down-regulated after salt treatment. The expression levels of ten genes that were up-regulated and down-regulated in these pathways were confirmed by real-time quantitative polymerase chain reaction (RT-qPCR) analysis. The salt tolerance of A. deliciosa might be related to the expression level changes in the genes in the pathways of plant hormone signal transduction, phenylpropanoid biosynthesis, and starch, sucrose, glucose, and fructose metabolism. The increased expression levels of the genes encoding alpha-trehalose-phosphate synthase, trehalose-phosphatase, alpha-amylase, beta-amylase, feruloyl-CoA 6-hydroxylase, ferulate 5-hydroxylase, and coniferyl-alcohol glucosyl transferase might be vital to the salt stress response of the young A. deliciosa plants.

Overexpressing an Arabidopsis SEIPIN1 reduces rubber particle size in guayule

A conventional source of natural rubber (NR) is from Hevea (Hevea brasiliensis). NR production from Hevea is limited by its narrow growth region and susceptibility to leaf blight disease. In response to these limitations, and to address NR supply and security, guayule (Parthenium argentatum Gray) has been developed as an alternative crop. NR consists mainly of cis-1,4-polyisoprene synthesized in/on rubber particles (RPs). RPs resemble lipid droplets (LDs) in that both are generated from endoplasmic reticulum (ER) and consist of hydrophobic cores and phospholipid monolayers. A prominent ER-related protein seipin plays an essential role in controlling LD biogenesis from the ER surface. Prior expression of AtSEIPIN1 in Arabidopsis increased LD size and consequently increased its core constituent triacylglycerol content in seed. To investigate if AtSEIPIN1 can similarly impact RPs and production of cis-1,4-polyisoprene, we generated three independent transgenic guayule lines overexpressing AtSEIPIN1 (SEIoe). Compared with wild-type, fewer RPs were observed, and RP size was significantly reduced in all SEIoe lines. Although not always statistically significant, NR quantity and quality were also reduced in SEIoe lines. Resin contents were reduced in mature stems, but not in young plantlets of SEIoe lines. The mechanisms of how AtSEIPIN1 influences RP biogenesis and NR production in guayule are discussed.

Environmental factors influencing the growth and pathogenicity of microgreens bound for the market: a review

Abstract The world is experiencing a global push toward smart agriculture to help feed the burgeoning population by increasing food security while reducing the carbon footprint of food production. The guidelines for healthy eating have increased globally from five to seven servings of vegetables a day and this had led to the quest for a sustainable form of vegetable production that will reduce the carbon footprint and still provide consumers with the required nutrients. Microgreens contain more nutrients than some mature vegetables and can be cultivated on vertical farms, offering a different approach with the potential to resolve environmental and health challenges. Microgreens are young plantlets grown from the seeds of edible leafy vegetables and are usually eaten raw. They contain high levels of bioactive compounds and can be processed into oils to create valuable cosmetic products. Microgreens have become well-known to chefs and are gaining popularity in upmarket grocery outlets. Consequently, growing microgreens are presenting huge market opportunities worldwide. Their nutritional benefits, easy production methods and short production cycle are some of the reasons they are attractive to growers. The most important factors affecting the growth of microgreens are micro and macro-climates. One challenge to producing microgreens is that the growing environment is ideal for microbial organisms to thrive. As such, microgreens are prone to foodborne pathogens such as E. coli, Listeria and Salmonella. Consequently, the microgreens industry is facing various setbacks including product recalls from Salmonella and Listeria food poisoning outbreaks. In addition, the short shelf-life of microgreens is a serious challenge for getting microgreens to market, this is driving studies in several post-harvest treatments. This review examines the nutrient content and health benefits of microgreens and factors affecting microgreens' growth: temperature, humidity, photoperiod, fertilization, etc. and post-harvest treatments, all of which can potentially impact microbial growth, the phytochemical content and the physical appearance of microgreens bound for the market.

Development of an efficient in vitro regeneration system in Costus speciosus - an important herbal insulin plant

Costus speciosus is being rapidly eliminated in its natural habitats in India and driven to a nearly threatened degree of extinction because of non-selective collection and over-exploitation. The commercial cultivation of C. speciosus is impeded owing to its poor seed viability, reduced germination rate, and weak rooting potential of vegetative cuttings. As costus could not be multiplied rapidly by conventional propagation methods, in-vitro regeneration technology was experimented with to standardize explants in addition to the combinations of plant growth regulators (PGRs) to fortify the growing media that helps to produce the enormous number of plants in a shorter duration. Several kinds of explants viz., leaves and nodes were cultured into the Murashige and Skoog (MS) medium reinforced with different combinations and doses of PGRs. A higher frequency (51.67 ± 1.7%) of the regenerated adventitious shoot was obtained from nodal segments cultured onto MS medium fortified with 0.5 mg/l Thidiazuron (TDZ) and 2.0 mg/l of 6-benzyl amino purine (BAP). TDZ in combination with BAP and Indole-3-acetic acid (IAA) exhibited a remarkable effect on shoot multiplication and elongation. Further, MS medium with 0.5 mg/l TDZ, 1.0 mg/l 2, 4-dichlorophenoxyacetic acid, and 0.5 mg/l IAA yielded a great range of callus initiation (86.66 ± 1.6%) from leaf explants. Leaf-derived callus results in the greatest shoot regeneration (56.66 ± 1.7%) response on TDZ (0.5 mg/l) and BAP (1.0 mg/l) reinforced MS medium. Elongated shoots from node and callus cultures when inoculated with the MS medium reinforced along with 1.0 mg/l of IAA and 0.5 mg/l of Indole-3-butyric acid (IBA) produced optimum rooting (88.33 ± 1.66%). The rooted young plantlets were effectively acclimatized to the environmental climate and their greenhouse survival rate was 85%.

Endophytic bacteria from Euphorbia antiquorum L. protect Solanum lycopersicum L. against bacterial wilt caused by Ralstonia solanacearum

BackgroundBacterial wilt caused by Ralstonia solanacearum (syn. Pseudomonas solanacearum) is the most devastating bacterial disease of tomato (Solanum lycopersicum L.) occurring in tropical zones with consequential substantial yield losses in production fields. Currently, microbial technology in cropping systems has directed investigations toward biological control agents (BCAs), emphasizing the use of plant endophytes, including bacteria. The present work aimed to evaluate the potential of endophytic bacteria from Euphorbia antiquorum L. to suppress bacterial wilt incited by R. solanacearum in plants.ResultsOf the 10 endophytic species screened in vitro for their antagonistic activity, 6 exhibited promising potency with minimum inhibitory concentration (MIC) values ranging from 62.50 to 7.81 µg/ml. These species also produced cell wall-degrading enzymes (amylase, protease and cellulase), ammonia, siderophores, indole acetic acid and salicylic acid. The 3 most potent species (B. amyloliquefaciens CBa_RA37, B. velezensis CBv_BE1 and B. amyloliquefaciens CBa_BFL2) enhanced the germination of tomato seeds and protected young tomato plantlets from the devastating effects caused by R. solanacearum infection.ConclusionsThis investigation demonstrated that these endophytic bacteria from E. antiquorum L. endowed with the ability to improve the growth and protection of tomato plants could be further developed as potential biopesticides to help mitigating the effect of bacterial wilt in tomato farms. Further investigation will set the baseline for formulation and evaluation of their efficacy in the open field.

Optimization of in vitro propagation protocol of Dendrobium heterocarpum Wall. ex. Lindl. and clonal genetic fidelity assessment of the regenerates: An orchid of horticultural and medicinal importance

Dendrobium heterocarpum Wall. ex Lindl. (Orchidaceae) is an orchid having medicinal as well as ornamental values. The natural population of the species is downsized due to different anthropogenic activities. The present study was undertaken to standardize in vitro propagation technique of the species through immature embryo culture and optimizing different factors. Further, the study demonstrates the use of low cost substrata for hardening of in vitro regenerates. Immature embryos of 5–8 months after pollination (MAP) were cultured on three different media enriched with different organic carbon sources and four plant growth regulators at varied concentrations. The embryos of 8 MAP registered ∼95% germination on MS medium fortified with sucrose (3%, w/v), kinetin (3 μM/L). The resultant PLBs differentiated to young plantlets on the same initiation medium. Subsequently, the young plantlets proliferated and as many as ∼18 shoots were produced on MS medium containing sucrose and kinetin and α-naphthalene acetic acid (3 + 12 μmol/L) in combination. The regenerates were primary hardened by culturing on low cost substrata (coconut husk + wood bark at 1:1 ratio) fortified with 1/4th MS salt solution for one wk, subsequently maintaining to normal room temperature under 75% diffused light for ∼3–4 wk before transferring to potting mix. About 87% transplants survived post transfer. Clonal fidelity of the regenerants was also evaluated using RAPD, DAMD and SCoT markers. High degree of monomorphic percentage (96.89%) and low polymorphism (3.11%) was recorded between the mother plant and in vitro regenerates; thus, showing genetic homogeneity of the in vitro raised plants.

Impact of the potato inoculation date on potato virus Y load and viral distribution in daughter tubers at harvest

AbstractAged plants are more difficult to infect than young plantlets. This modification of susceptibility is described as mature plant resistance (MPR). For potato virus Y (PVY), MPR is known to lead to low infection rates of plants inoculated at the postflowering stage and a decrease in the number of infected daughter tubers. However, the impact of inoculation date on the capacity of PVY to accumulate in daughter tubers has not been studied so far. Field and greenhouse experiments were carried out to better understand PVY epidemiology and to help potato growers to evaluate consequences of early/late infections on the quality of their crops. In field trials, potato plants (cv. Bintje) were covered by insectproof nets from planting to harvest except for a 14‐day period to expose plants to natural PVY infections. Under controlled conditions, potato plants were mechanically inoculated with PVY at different dates from preflowering stages (early inoculations) to postflowering stage (late inoculations). At harvest, daughter tubers were individually collected and analysed to define proportions and viral load of infected tubers according to the time between virus inoculation and harvest. Our results showed that although the age of plants at the time of inoculation can modify their susceptibility to PVY infection, in return, early and late PVY inoculations lead to similar rates of infected tubers at the plant scale and equivalent viral accumulation in infected tubers. All together, these data revealed that both early/late infections are high risks for the sanitary quality of potato tubers.

Systemin modulates defense responses in roots of tomato plants (Solanum lycopersicum L.) during the pre-colonization stage of the mycorrhizal symbiosis

Aim of study: The symbiotic association with arbuscular mycorrhizal fungi (AMF) enhances the uptake of soil minerals by the plant, predominantly phosphorus, in return for plant photosynthates. This study was performed to support the premise that the suppression of root defense responses during the pre-colonization stage is required for the subsequent colonization of tomato roots by AMF. Area of study: This study was performed in the Plant Defense Laboratory of Cinvestav, at Irapuato, Guanajuato, Mexico. Material and methods: Systemin (SYS) was added, together with spore suspensions of three different AMF species, to young tomato plantlets. The roots were subsequently sampled, 0.5 to 12 h post-application, in order to quantify degree of mycorrhizal colonization, in vitro β-glucanase (GLN) and chitinase (CHI) enzyme activity and wound-responsive gene expression levels. Main results: The sole application of exogenous SYS induced the rapid expression of a battery of early wound-responsive genes, together with a swift and transient activation of CHI, but not GLN. However, when added together with AMF spores, SYS differentially modulated the activity of these enzymes in an AMF species-dependent manner. Modified lytic activity was preceded or accompanied by the rapid and sustained induction of the RbohD, LOXD and PLA2 genes shortly after contact with AMF spores. Research highlights: The findings of this study suggest a role for oxylipins and reactive oxygen species in the initial AMF recognition process. They also indicate that exogenous SYS is perceived by the roots, where it modulates the local root defense response to facilitate AMF colonization.

Isolation, Identification and Molecular Characterization of Endophytic Fungi from the leaves of Coelogyne species, and their role as an Antimicrobial agent

Endophytic fungi from Orchids believed to have an essential symbiotic relationship with the plant for both the germination of seeds and the development of young plantlets. Endophytes are microorganisms which live in the intercellular spaces of healthy host tissues without causing apparent symptoms. Endophytic fungi isolated from the medicinal plants are used for the development of drugs as they act as the source of bioactive compounds. This study has been designed to isolate the fungal endophytes from the leaves of three epiphytic orchid species (Coelogyne nervosa, A. Rich., Coelogyne mossiae, Rolf and Coelogyne cristata, Lindl) from the same genus Coelogyne, collected from Ooty flora, Coonoor. About five different endophytes were identified and their morphological characters were studied. Coelogyne cristata showed maximum colonization frequency. Among the five species, Fusarium species showed antibacterial activity against the gram-positive bacteria Bacillus Subtilis, a pathogen found in soil, water and food. Fungal genomic DNA isolated for molecular identification from the four fungal species.

Root Growth and Carbohydrate Content of <i>Phalaenopsis</i> ‘KS Little Gem’ Young Plantlets as Influenced by Temperature and Fertilizer Application

Root Growth and Carbohydrate Content of <i>Phalaenopsis</i> ‘KS Little Gem’ Young Plantlets as Influenced by Temperature and Fertilizer Application

Characterization of putative salinity-responsive biomarkers in olive (Olea europaea L.)

AbstractLow-quality water and soil salinization are increasingly becoming limiting factors for food production, including olive – a major fruit crop in several parts of the world. Identifying putative salinity-stress tolerance in olive would be helpful in the future development of new tolerant varieties. In this study, novel salinity-responsive biomarkers (SRBs) were characterized in the species, namely, monooxygenase 1 (OeMO1), cation calcium exchanger 1 (OeCCX1), salt tolerance protein (OeSTO), proteolipid membrane potential modulator (OePMP3), universal stress protein (OeUSP2), adaptor protein complex 4 medium mu4 subunit (OeAP-4), WRKY1 transcription factor (OeWRKY1) and potassium transporter 2 (OeKT2). Unique structural features were highlighted for encoded proteins as compared with other plant homologues. The expression of olive SRBs was investigated in leaves of young plantlets of two cultivars, ‘Nabali’ (moderately tolerant) and ‘Picual’ (tolerant). At 60 mM NaCl stress level, OeMO1, OeSTO, OePMP3, OeUSP2, OeAP-4 and OeWRKY1 were up-regulated in ‘Nabali’ as compared with ‘Picual’. On the other hand, OeCCX1 and OeKT2 were up-regulated at three stress levels (30, 60 and 90 mM NaCl) in ‘Picual’ as compared to ‘Nabali’. Salinity tolerance in olive presumably engages multiple sets of responsive genes triggered by different stress levels.

Peach palm plantlet growth in different culture media in a temporary immersion system

ABSTRACT: Peach palm is a domesticated palm commercially important for the production of fruits and hearts of palm. Somatic embryogenesis, an effective technique for mass propagation, was successfully established for this species. Furthermore, a temporary immersion system improved plant regeneration. However, production can be further improved by understanding the peach palm’s growth dynamic and modifications of culture media. The aims of this study were to evaluate the growth of plantlets cultured in different culture media in a temporary immersion system and to correlate the results with nutrient uptake during the growth period. Somatic embryo-derived young plantlets approximately 1 cm in length were cultivated for 12 weeks in a twin flask system containing MS, Y3 or N6 salts, Morel and Wetmore vitamins and 3% sucrose, with a monthly medium refreshment. Growth was measured and mineral analysis of the plantlets was carried out after 12 weeks of culture. The Y3 and MS salts were the most appropriate for the plant growth. Number of roots was 52.52% higher and the root size was 40.42% between the N6 and MS medium and the root number in Y3 medium was 37.74% greater than in MS medium, which is important for post acclimatization survival. K and Na are important elements for peach palm. N is not required at such a high concentration as in Murashige and Skoog formulation. The Chu (N6) medium did not generate high quality plantlets, possibly due to the absence of some micronutrients, like Mo, Cu and Co.

English

Canola is a moderately salt tolerant plant, high salinity inhibits germination of seeds, vegetative growth of young plantlets, and reduces biomass production. This study investigated the effects of priming with 1 mM S-methylmethionine (SMM) on germination, leaf gas exchange, induced chlorophyll fluorescence, photosynthetic pigment content and membrane damage through lipid peroxidation by exposing canola (Brassica napus L. cv. Cindi) plants to moderate and severe salt stress (induced by 60 mM and 120 mM NaCl) for different periods. Priming with SMM alleviated the reduction of net photosynthetic rate, the effective quantum efficiency and efficiency of excitation energy capture by open photosystem II reaction centers, chlorophylls to carotenoids ratio, enhanced water use efficiency and contributed to reduction of oxidative membrane damage in fully developed young leaves. Delay and inhibition of seed germination by salt stress were significantly reduced by SMM, as well as the non-photochemical quenching of the singlet excited state of chlorophyll a, suggesting a more efficient protection against hyperosmotic stress, ionic toxicity and associated oxidative stress in primed plants exposed to high salinity. This first assay of SMM as a priming agent for canola plants under high salinity contributes to a better understanding of the mode of action of this natural, plant-derived bioactive compound and the optimization of canola cultivation under the adverse growth conditions caused by salt stress. © 2021 Friends Science Publishers

Nuclear DNA content as an indicator of inflorescence colour stability of in vitro propagated solid and chimera mutants of chrysanthemum

In chrysanthemum, breeders seek for desirable characteristics of the inflorescence, which can first be established once the plant is mature. The present study aims to determine whether measurement of DNA content can be useful in the detection of somaclonal variants and/or separation of chimera components in chrysanthemum at the early in vitro multiplication stage. Eleven Chrysanthemum × morifolium (Ramat.) Hemsl. cultivars of the Lady group (a mother cultivar and ten of its radiomutants obtained by X-ray- or γ-irradiation; solid and periclinal chimeras) were propagated in vitro. Single-node explants were cultured in Murashige and Skoog (MS) medium, either without plant growth regulators (PGRs) or supplemented with 6-benzyladenine (BA) and indole-3-acetic acid (IAA). The nuclear DNA content was measured by flow cytometry (FCM) in the shoots produced in vitro. After acclimatization and growth of the plants in a glasshouse, inflorescence colour was recorded. The addition of PGRs to the medium almost doubled the mean number of shoots produced in vitro per explant, but caused a change in inflorescence colour of all (‘Lady Apricot’; periclinal chimera) or part of the plants (‘Lady Amber’; solid mutant and ‘Lady Salmon’; periclinal chimera). All radiomutants contained less DNA than the mother cultivar ‘Richmond’. There were significant differences in DNA content between plants of the same cultivar grown in media with or without PGRs for ‘Lady Apricot’ and ‘Lady Salmon’, but no phenotype alternation occurred in chrysanthemums produced in PGR-free medium compared to the original cultivars. Conversely, in medium with PGRs, chimeras produced flowers different from the original colour. In all except one cultivar (‘Lady Amber’; solid mutant) a lack of differences in genome size between plants grown in either medium coincided with a stable inflorescence colour. The occurrence of some plants of ‘Lady Amber’ with different inflorescence colour may be due to small DNA changes, undetectable by FCM. It can be concluded that FCM analysis of DNA content in young plantlets can be indicative of the stability of inflorescence colour in chrysanthemum, especially chimeric cultivars, and for mutant detection.

Virus-Induced Gene Silencing in Rose Flowers.

Virus-induced gene silencing (VIGS) is a favorable method to study gene function by posttranscriptional gene silencing in plants. Here we describe a methodology of graft-accelerated VIGS in rose aimed at obtaining posttranscriptional gene silencing in the flower. The resulting phenotype can be observed within 5-6weeks post infiltration. By using this method, we successfully silenced the expression of several genes involved in processes such as scent production, petal coloration, or flower architecture. We showed that graft-accelerated VIGS was faster, more efficient, and more convenient than conventional methods previously developed in rose such as agroinfiltration of young plantlets and in vitro cultured tissues or seeds.

In Vitro Propagation and Acclimatization of Dragon Tree (Dracaena draco)

In this study, an efficient in vitro procedure was developed for bud induction, rooting of developing shoots and greenhouse acclimatization of young plantlets of dragon tree (Dracaena draco). Effects of media (S1 (1 mg/L KIN and 1 mg/L NAA), S2 (3 mg/L KIN and 1 mg/L IAA), S3 (1 mg/L BAP and 2 mg/L IBA) and S4 (1 mg/L BAP and 1 mg/L NAA)) on shoot induction and media (R1 (0 mg/L IBA), R2 (0.5 mg/L IBA), R3 (1 mg/L IBA), and R4 (2 mg/L IBA)) on root induction were examined in order to find optimal plant hormone concentrations for efficient Dracaena draco dormant bud development and subsequent rooting. The best shoot induction and rooting media were S1 and S2, and R3 and R4, respectively. Dormant buds from one-year-old Dracaena draco plants submitted to this in vitro procedure allowed successful recovery of up to 8 individuals per explant used. In vitro grown plants were successfully acclimated in the greenhouse. The potential of this in vitro procedure for multiplication of this endangered tree is discussed in this report.

MICROPROPAGATION AND EVALUATION OF GENETIC STABILITY OF FOXGLOVE TREE (Paulownia tomentosa)

This reasearch work aimed to fine-tune micropropagation of Paulownia tomentosa in addition to assessing the genetic stability of in vitro raised clones from it. Paulownia tomentosa explants were surface sterilized using clorox (commercial bleach 5.25% sodium hypochlorite) at 10, 20, 25 and 30% + 0.5 g/l mercuric chloride (HgCl2) at different duration times, i.e. 10, 15, 20 and 25 min. In the multiplication stage, shoots were transferred to MS medium at ¾ strength containing BAP and Kin each at (0, 0.5, 1, 2, and 4 mg/l). Whereas, the rooting medium was MS medium at ¾ strength with IBA and NAA treatments each at 0, 0.5, 1, 2, and 4 mg/l. Sterilized explant with 30% Clorox for 20 min recorded highest survival percentage. The treatment of Kin at 4 mg/l gave higher significant shoot length. Whereas BAP application at 2 and 4 mg/l gave highest significant value of both shoot number and leaf number. Both IBA and NAA at 0.5 or 1 mg/l gave highest significant root number/shoot. Whereas, auxin at 4 mg/l gave highest significant root lengths. Young plantlets resulted from in vitro were acclimitized successfully in a mixture of peat moss: perlit (2: 1) by volume that showed 85.93% survival. The genetic stability of in vitro raised Paulownia tomentosa clones was assessed by using intersimple sequence repeats (ISSRs) markers. All of the three ISSR primers screened, produced clear, reproducible and scorable bands. The molecular size of Polymerase Chain reaction (PCR) products generated 22 fragments by these ISSR ranged from ≈460 to18660 bp. All banding profiles from micropropagated plants were monomorphic and similar to those of the mother plant, indicating 100% similarity. This confirmed the true to type nature of the in vitro raised clones.