Article

Mutation Breeding Using Gamma Irradiation in the Development of Ornamental Plants: A Review

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Abstract

Gamma irradiation has been used in several ornamental plant species to obtain the desired genetic variability. Commercially, ornamental plants with a rich variety of flower colors and uniform shapes are prized and in high demand. Irradiation technology is widely utilized to generate a high number of mutations, which helps introduce new, improved variants in comparison to the control plant. The main purpose is to promote well-adjusted species by customizing some specific features to expand on the desired parameter. Exposure to an optimum dose of gamma irradiation is crucial to ensure the most beneficial mutation density. The effects of dose rates are species-dependent, thereby affecting the probability of inducing favorable attributes, such that they are either not clearly exhibited or are disoriented during the gradual physical development of the plants. To obtain high-quality species within a very limited period, gamma irradiation may present an alternative method to selective screening with its combined application of molecular-based analysis to contribute to mutational changes in plant physiology. Here we review current literature that focuses on the effect of appropriate doses of gamma irradiation and the morphological, functional, and molecular objectives of such irradiation in ornamental plants.

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... The use of random mutagenesis has been widely accepted; besides that, it has no regulatory restrictions. Induced mutations can be generated by the use of physical mutagens such as X-rays, gamma rays (cobalt-60 being the most common source of radiation), and neutrons [121][122][123][124][125][126][127]. Moreover, to induce mutagenesis, chemical mutagens, including alkylating agents such as ethyl methanesulfonate (EMS), intercalating agents (such as ethidium bromide), and base analogs (such as bromouracil), can be used [121,128,129]. ...
... Mutation induction is a powerful tool for creating new and novel plant germplasm [132]. Radiation-induced mutation, also known as plant mutation breeding, is the most widely used method to improve direct mutant varieties in a faster way in comparison with the laborious and time-consuming traditional plant breeding [125,127,133]. ...
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Chapter
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The advent of complete genetic linkage maps consisting of codominant DNA markers [typically restriction fragment length polymorphisms (RFLPs)] has stimulated interest in the systematic genetic dissection of discrete Mendelian factors underlying quantitative traits in experimental organisms. We describe here a set of analytical methods that modify and extend the classical theory for mapping such quantitative trait loci (QTLs). These include: (i) a method of identifying promising crosses for QTL mapping by exploiting a classical formula of SEWALL WRIGHT; (ii) a method (interval mapping) for exploiting the full power of RFLP linkage maps by adapting the approach of LOD score analysis used in human genetics, to obtain accurate estimates of the genetic location and phenotypic effect of QTLs; and (iii) a method (selective genotyping) that allows a substantial reduction in the number of progeny that need to be scored with the DNA markers. In addition to the exposition of the methods, explicit graphs are provided that allow experimental geneticists to estimate, in any particular case, the number of progeny required to map QTLs underlying a quantitative trait.
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This comprehensive book covers the underlying scientific principles, state-of-the-art technologies and methodologies of plant mutagenesis. It covers historical development and commonly used terminologies, chemical and physical mutagenesis, mutation induction, mutation breeding and mutations in functional genomics research. Suitable both as a manual for professionals and a resource for students in plant breeding and research, the book includes exemplary cases of practical applications and an appendix of recommended doses of gamma and fast neutron irradiation for almost 200 plant species.
Chapter
Somaclonal variation in the major crop plants, rice, wheat, maize, barley, triticale, sugarcane, potato and a few forage grasses is reviewed. Reported somaclonal variants include chlorophyll-deficient plants, and those with changed morphology, single-gene mutations, polyploidy, aneuploidy, chromosomal re-arrangements, modified yield, quality and disease resistance, and occasionally novel variants not present in the natural gene pools. Somaclonal variation results from both dominant and recessive mutations. The type and frequency of variants suggests that somaclonal variation is akin to non-directed, random mutagenesis which generates a large amount of unwanted variation. Consequently, most of somaclonal variation is either useless or of limited use in direct varietal upgrading. However, somaclonal variants are easier to detect than those in conventional mutagenesis. It is concluded that the development of in-vitro selection procedures is essential to sieve out useful from useless variation to overcome the constraints of somaclonal variation in breeding programs.
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The study on the effect of gamma irradiation on in-vitro shoot growth of chrysanthemum cv. Yellow Puma has been carried out. The aim of the study was to observe genetic variability of shoot growth caused by gamma irradiation. Shoot explants with four leaves were irradiated by gamma with dose of 10, 15 and 20 Gy with 3 replications at each of dose. The irradiated shoot explants were then transferred into fresh MS solid medium and placed in a growth room. Observation was performed on number of leaves and branches on M1V0 generation, while plantlets height and number of branches were observed a M1V1 generation. Number of survival plantlets and multiplication rate on three subsequent subcultures were observed as well. Results showed that gamma rays with dose of 20 Gy inhibited growth of leaves as much as 50% compared to control (shoots without irradiation), and branches 73.7% in three weeks. Observation on multiplication rate at M1V1 generation showed that gamma irradiation with dose of 10 Gy promoted multiplication rate as much as 10% higher than control. It can be concluded that in vitro mutagenesis using gamma iradiation with dose of 10 to 15 Gy can be used for inducing genetic variability of chrysanthemum cv. Yellow Puma.
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Lately, radiation technology is widely used to produce changes in the product characteristics leading to the development of new products. Gamma irradiation is capable of hydrolyzing chemical bonds, thereby cleaving large molecules of starch into smaller fragments of dextrin that may be either electrically charged or uncharged as free radicals. These changes may affect the physical and rheological properties of irradiated foods, resulting in increased solubility of starch, decreased swelling power, and decreased viscosity of starch paste. Irradiation of gamma rays on bud wood can produce higher frequencies of mutation, leading to the creation of new variants compared to the control. Macronutrients (carbohydrates, proteins and lipids) content are relatively stable against irradiation doses up to 10 kGy, on the other hand, gamma irradiation affects proteins by causing conformational changes, oxidation of amino acids, rupturing of covalent bonds and formation of protein free radicals. Radiation mediated morphological, structural and functional changes in a plant are governed by the intensity and duration of the gamma irradiation.
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The purple color clone of spray type chrysanthemum available as pot plant in the market was used to study the effect of gamma radiation on in vitro culture of chrysanthemum (Chrysanthemum morifolium). Ray-florets were cultured on the MS medium containing 10 mg/l BA. Multiple shoots produced were irradiated with gamma rays at 0, 10, 30, 50, 70, 90 and 110 Gy. Subculturing was carried out three times from M 1 V 1 to M 1 V 4 after which M 1 V 4 shoots were rooted and transplanted to the greenhouse. M 1 V 4 shoots irradiated at 50 Gy and over died within 25-30 days. LD 50 for this purple clone of chrysanthemum was 14 Gy. Only the controls and treated plants at 10 Gy were able to survive and gave rise to the full grown plants. After transplanting into the greenhouse for 60 days, control plants and treated ones were found to be different in four traits which were average height, average number of leaves, average number of nodes and % flowering. Plants were trimmed twice at three month intervals and allowed to produce flowers. Changes in flower characters were found in both controls and treated plants. However, the treated plants had much more variation than the controls and new flower color (yellow tinge) was only obtained from the treated ones.
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To determine the effects of gamma radiation on the photosynthetic pigments, sugar content and total carbon gain, seeds of Cullen corylifolium (L.) Medik. were irradiated with variable doses (0, 2.5, 5, 10, 15, and 20 kGy) at the rate of 1.65 kGy h(-1) from Co-60 gamma source. Cullen corylifolium represents an important Chinese medicine with adequate levels of secondary metabolites, thus we hypothesized that gamma irradiation could modulate primary metabolites which could supplement secondary metabolite levels. The seeds were then transferred to field for biochemical analysis at different developmental stages; pre-flowering, flowering and post-flowering. Gamma dosage at 10 kGy resulted in a significant increase in concentration of chlorophyll a (61.17%), chlorophyll b (93.18%) and total chlorophyll (71.66%), suggesting that low doses of radiation could activate photosynthetic pigment system while at 15 and 20 kGy dose resulted in depletion of such parameters. Sugar and total C analysis of plants irradiated at 10 kGy demonstrated significantly maximum (216.01%) sugar content in leaves at all developmental stages and significantly minimum (46.13%) and (57.81%) in plants raised from seeds irradiated at 15 and 20 kGy respectively. Effective stimulatory dose for C. corylifolium '11062' is 10 kGy. In contrast, the carotenoid content of the plants exposed to 15 and 20 kGy was maximum than control. Significance of such stimulation correlated with increasing C mass of the plant concerned is discussed in the light of newer aspects in research.
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We investigated the effect of total irradiation dose and dose rate on flower color mutation and nuclear DNA content as an index of radiation damage in chrysanthemum. Chrysanthemum morifolium cv. 'Taihei' plants grown by in vitro culture were gamma-irradiated with a total dose of 15, 30 and 60 Gy at a rate of 0.5, 1, 2 and 5 Gy/h. Leaf explants cut from the irradiated plants were tissue cultured, and the regeneration rates and frequency of flower color mutation were investigated. Nuclear DNA content was measured by flow cytometric analysis. The regeneration rate decreased with increase in the total dose and dose rate of irradiation. Mutation frequency did not differ significantly among dose rates, indicating that mutation frequency was independent of dose rate and was dependent mainly on total dose. Comparison of the average of the nuclear DNA content with each treatment revealed that it was influenced by both dose rate and total dose, and that the reduction in nuclear DNA content was less at low dose rates, even when total doses were high. It appears that same mutation frequencies were obtained without large reduction in nuclear DNA content by 0.5 Gy/h, when compared with 2 Gy/h. Consequently, we conclude that gamma ray irradiations of high total doses at low dose rates efficiently induce mutations with less radiation damage in chrysanthemum.
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The present work describes radiation-induced effects on some morphological characters of a cereal and a pulse-producing crop in India. Co-60 gamma source is used for irradiating (from 50 to 350 Gy) the rice (Oryza sativa L., Cv-2233) and mung (Phaseolus mungo L.). Irradiation at lower doses of gamma rays effectively influences improving the morphological traits like seedling/plant height, tiller number, panicle number, panicle length, seed per particle, seed per pod, pod length, pod number, while exposure at higher doses results in depletion of such parameters, Effective stimulatory dose for Oryza sativa L. Cv-2233 is 50 Gy and that for Phaseolus mungo L. is 200 Gy. Significance of such stimulation correlated with yielding ability of the plant concerned is discussed in the light of newer aspects in agricultural research.
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In plants, there is evidence that different dose rate exposures to gamma (γ) rays can cause different biological effects. The dynamics of DNA damage accumulation and molecular mechanisms that regulate recovery from radiation injury as a function of dose rate are poorly explored. To highlight dose-rate dependent differences in DNA damage, single cell gel electrophoresis was carried out on regenerating Petunia x hybrida leaf discs exposed to LDR (total dose 50Gy, delivered at 0.33Gymin(-1)) and HDR (total doses 50 and 100Gy, delivered at 5.15Gymin(-1)) γ-ray in the 0-24h time period after treatments. Significant fluctuations of double strand breaks and different repair capacities were observed between treatments in the 0-4h time period following irradiation. Dose-rate-dependent changes in the expression of the PhMT2 and PhAPX genes encoding a type 2 metallothionein and the cytosolic isoform of ascorbate peroxidase, respectively, were detected by Quantitative RealTime-Polymerase Chain Reaction. The PhMT2 and PhAPX genes were significantly up-regulated (3.0- and 0.7-fold) in response to HDR. The results are discussed in light of the potential practical applications of LDR-based treatments in mutation breeding.
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Definitions of fundamental quantities, and their units, for ionizing radiation are given, which represent the recommendation of the International Commission on Radiation Units and Measurements (ICRU). © 2011 International Commission on Radiation Units and Measurements.