Akram Amiri; Mahmood Shoor; Mina Taghizadeh; Seyyed Hossein Nemati; Ali Tehranifar
Abstract
Introduction: The genus of African violet is the most common genus known among the plants of Gesneriaceae family. This genus has beautiful leaves and flowers that are zygomorph. African violet (Saintpaulia ionantha) is a famous ornamental plant due to its various colors and shapes that an excellent model ...
Read More
Introduction: The genus of African violet is the most common genus known among the plants of Gesneriaceae family. This genus has beautiful leaves and flowers that are zygomorph. African violet (Saintpaulia ionantha) is a famous ornamental plant due to its various colors and shapes that an excellent model system for in vitro regeneration studies because of its tissue culture amenability.Besides the importance of this plant in plant production industry and increasing need for new plant varieties with desired traits, more studies for creating African violet with new features by increasing the ploidy level under the in vitro conditions were not done until now. Polyploidy is a widespread phenomenon in the evolution of flowering plant and a key in plant speciation and diversification. Polyploid plants have been used in plant breeding programs for developing superior varieties and restoring the fertility of interspecific or intergeneric hybrids. Polyploidy in ornamental crops were successfully obtained under in vitro conditions. The chemical colchicine can be used as the most effective substance to obtain polyploid plants. In vitropolyploidization has number of advantages such as treatment of more plants with less material, control of test conditions, lower toxicity of chemicals and high success rate. This study with the aim of polyploid induction was carried out by different concentrations of colchicine at various periods under in vitro conditions.Materials and Methods: The best treatment for the shoot regeneration and proliferation was MS medium with 2 mg/l BA after optimizing the tissue culture process. The study performed as follows: plantlets grown under in vitro in proliferation stage were treated with colchicine. The experiment was carried out in a 2-factorial manner based on a completely randomized design and factors were colchicine concentration at 0.02, 0.05, 0.1% and treatment duration for 18, 24, 48 hours. Evaluated characters of regenerated plants were as follows: plantlets survival percentage (the first month, the second month and the third month), morphological traits (include leaf number, petiole length, leaf length, leaf width, petiole diameter, leaf thickness and variation in form, vein, tip and margins leaf), reproductive traits (flower diameter (mm), number of petal, number of flower in inflorescence, height of inflorescence (mm)), microscopic epidermal cells in samples of diploid and tetraploid and ploidy levels. Assessment of flow cytometery was also used for all of the treated plants with colchicine and some diploid control plants and were expressed in the form of the percentage of diploid, mixoploid and tetraploid plants of African violet.Results and Discussion: Results indicated that tetraploidy induction successfully was changed different morphological and cytological characteristics. Plantlets of treated with 0.02% colchicine in all three times only survived after three months, and with increasing treatment time, plantlets survival percentage was reduced. Thus 0.02% colchicine treatment for 24 hour found effective in inducing in vitro culture polyploidy of African violet. Comparison of the leaves of tetraploid with diploid plants indicated that the leaves of tetraploid plants in length and width were bigger than the diploid ones. The selected tetraploid plants showed a more compact shape than the control plants. Other results revealed that the treated plants with colchicine showed delayed growth. The assessment of microscopic indicated that the epidermal cells of tetraploid were larger than diploid. The results of flow cytometery evaluation showed that with increasing duration of colchicine, the number of diploid plants reduced and were added to mixoploid and tetraploid plants. Most plants were mixoploid.Conclusion: The results of this study showed that the diploid and tetraploid plants indicated significant differences in term of morphological traits like leaf number, petiole length, leaf length, leaf width, petiole diameter, leaf thickness and variation in form, vein, tip and margins leaf, reproductive traits like flower diameter, number of petal, number of flower in inflorescence and also size of epidermal cells and flow cytometery evaluation. These differences can be suitable criterion for separating diploid and polyploid plants from each other. Generally, the combination of tissue culture methods and tetraploidy induction can be used as a rapid strategy for achieving new forms and properties of regenerates in vitro on African violet.
Amir Hossein Keshtkar; Noshin Fallahi; Mohammad Reza Abdollahi; Hassan Sarikhani; Hooshmand Safari; Zhaleh Mohseni Araghi
Abstract
Introduction: Polyploidy plays an important role in creation of genetic variability. Polyploidy induction by mutagenic chemicals such as colchicine is considered to enhance the potential of secondary metabolites production in herbs breeding. Colchicine is the most effective chemicals used in the polyploidy ...
Read More
Introduction: Polyploidy plays an important role in creation of genetic variability. Polyploidy induction by mutagenic chemicals such as colchicine is considered to enhance the potential of secondary metabolites production in herbs breeding. Colchicine is the most effective chemicals used in the polyploidy induction studies. The effect of colchicine is to form cells with two or multiply number of chromosomes resulting in a lack of germination and death of a large number of plant samples. Flow cytometry analysis and cytogenetic studies were effectively used to assess the ploidy levels for fenugreek (Trigonella foenum-graecum) plants. In the beginning of 90 decade, a new type of adsorption technique called solid-phase micro extraction (SPME) has been developed by Pawliszyn and co-workers. This method compared to the traditional techniques, offers many advantages such as the high sensitivity and reproducibility, does not require solvent, and combines extraction and pre-concentration in a single step without pre-treatment of samples. Moreover, it is a fast and inexpensive method, requires low sample volume and it can be easily automated. Solid-phase micro extraction (SPME) uses a fine rod (fused silica or metal) with a polymeric coating to extract organic compounds from their matrix and it directly transfer them into the gas chromatograph injector for thermal desorption and analysis (Kaykhaii, 2008). The aim of this study was to investigate the effect of colchicine treatment on ploidy levels and compare some of the morphological, physiological, cytogenetical, flow cytometric analysis and biochemical characteristics in diploid and tetraploid fenugreek plants.
Materials and Methods: In order to investigate the effect of polyploidy induction by colchicine on Trigonella foenum-graecum medicinal species, an experiment was planned as a factorial completely randomized design with five concentrations of colchicine (0, 0.05, 0.1, 0.2, and 0.5%) for 12, 24, 48 and 72 hours. In this experiment the effect of colchicine was examined on the percentage of survival and tetraploidy of seed, root and terminal bud samples. Level of ploidy was identified in survival explants through root tip chromosome counting and flow cytometry of leaf samples. In addition to distinguish tetraploid from the diploids plants, morphological, physiological and biochemical characteristics were considered in treated plants. SAS and SPSS software programs were used to analysis of variance and comparison of means by Duncan's multiple test. Graphs were also drawn by EXCEL software.
Results and Discussion: The analysis of variance showed that all characteristic factors for survival percent and mixoploidy percentage were statistically significant. Survival percentage was decreased with increasing of colchicine concentration and increased exposure time of colchicine-treated seed. After the observation of morphological changes, the samples were considered to assess the ploidy levels by flow cytometry system. Results showed that 0.5% colchicine concentration had the highest survival rate after control treatment for the terminal bud. The highest percentage of mixoploidy was also observed in treated terminal buds with 0.1 and 0.2% of colchicine concentrations. Morphological, physiological, cytogenetic, flow cytometric analysis and biochemical studies confirmed that terminal bud treatment with 0.2% colchicine for 72 hours is the most effective treatment to induce tetraploidy in fenugreek plant. The results of GC/MS also indicated an increase in secondary metabolites content, but traits including growth rate and plant height of tetraploid reduced compared to the diploid plants. Result of this study showed a significant increase in chlorophyll a, b and total chlorophyll contents of tetraploid plants, which were higher than the levels of diploid plants.
Conclusion: Polyploidy induction using mutagenic chemicals is one of the methods to enhance the production of plant secondary metabolites. Colchicine is the most effective mutagenic chemical in inducing plant polyploidy. Although, flow cytometry is an expensive method, it is increasingly used for ploidy screening by analyzing of nuclear DNA content. In this study, both flow cytometry and chromosome microscopic examinations were used to test ploidy. The two methods were compared, and it was found that flow cytometry testing was fast and labor saving, especially in case of a large number of samples. Tetraploidy induction significantly affected different morphological, physiological, and biochemical characteristics of Trigonella foenum-graecum. These changes suggested that ploidy manipulation as a rapid and effective method for enhancing genetic diversity and metabolite production for this plant. SMPE method offers a number of practical advantages: smaller sample volume, simplicity of extraction and low cost, when compared to the other methods that are currently being used.
