Showing papers on "Mutation breeding published in 2007"

Molecular breeding of a novel herbicide‐tolerant rice by gene targeting

Abstract: Summary We have previously reported the production of a rice cell line tolerant to the acetolactate synthase (ALS)-inhibiting herbicide bispyribac (BS), and demonstrated that the BS-tolerant phenotype was due to a double mutation in the rice ALS gene. We further indicated that while changing either of the two amino acids (W548 L or S627I) individually resulted in a BS-tolerant phenotype, conversion of both amino acids simultaneously conferred increased tolerance to BS. As the BS-tolerant cell line had lost the ability to regenerate during two years of tissue culture selection, we attempted to introduce these two point mutations into the rice ALS gene via gene targeting (GT). Using our highly efficient Agrobacterium-mediated transformation system in rice, we were able to regenerate 66 independent GT rice plants from 1500 calli. Furthermore, two-thirds of these plants harbored the two point mutations exclusively, without any insertion of foreign DNA such as border sequences of T-DNA. The GT plants obtained in the present study are therefore equivalent to non-GM herbicide-tolerant rice plants generated by conventional breeding approaches that depend on spontaneous mutations. Surprisingly, GT rice homozygous for the modified ALS locus showed hyper-tolerance to BS when compared to BS-tolerant plants produced by a conventional transgenic system; ALS enzymatic activity in plants homozygous for the mutated ALS gene was inhibited only by extremely high concentrations of BS. These results indicate that our GT method has successfully created novel herbicide-tolerant rice plants that are superior to those produced by conventional mutation breeding protocols or transgenic technology.

Haploid and Doubled Haploid Technology

Abstract: The microspore culture technique has its wide applications in plant genetic research and breeding programmes in oilseed Brassicas due to its relative simplicity, efficiency in haploid and doubled haploid production, mutation and germplasm generation, and gene transformation. Various factors could influence microspore embryogenesis and haploid production including donor plant genotype, donor plant physiology, microspore developmental stage, culture conditions, culture environment and pretreatments. Stress is also an essential component during embryogenesis induction in microspore culture. Efficient plant regeneration from microspores mostly occurs through direct embryogenesis ensuring minimal occurrence of cytogenetic abnormalities. Appropriate stress conditions such as chilling, partial desiccation, cotyledon excision, and successive subculture of microspore-derived embryos could promote plant development in oilseed rape. Medium renovation, phytohormones and plant growth regulators, and chromosome doubling agents such as colchicine treatment also affect plant regeneration in Brassica species. Compared to colchicine treatments of microspore-derived embryos and plants, immediate colchicine treatment of isolated microspores results in high embryogenesis and diploidisation and low chimeric percentages. The ploidy level of microspore-derived plants of Brassica species could be estimated by different methods at various stages. Mutation breeding techniques are widely used in plant breeding for producing useful mutants and variants. Microspore culture also provides an ideal method for mutation because the mutated traits can be fixed in homozygous condition by chromosome doubling, which can enforce to obtain target mutation traits efficiently. Ultraviolet irradiation, mutagenic agents ethyl methane sulphonate and sodium azide could be applied to isolated microspores and the derived embryos of rapeseed. Utilization of microspore-derived embryos for production of desired traits such as the altered fatty acids, disease resistance and glucosinolate compositions through mutagenesis and selection is advancing and also discussed.

Study of genetic variability in sugarcane induced through mutation breeding

Abstract: Three sugarcane clones viz., NI-98, NIA-2004 and BL4 were tested for induced somatic mutation using irradiation doses of 0, 10, 20, 30, and 40Gy. The treatments 30Gy and 40Gy exhibited negative impact on the agronomic traits under study. The dose 20Gy showed stimulating and enhancing effect on plant height and cane yield (kg/plot). The analysis of variance (mean square) for all the characters under study revealed that all the radiation doses were significantly different (P ≤ 0.5). Genetic advance at 2% selection intensity was about two fold higher than that at 30% selection intensity and intermediate at 10% selection intensity. High heritability percentage in broad sense was recorded. Variability obtained from mutation breeding was also examined through molecular marker techniques (RAPD), most similar sugarcane mutants (20 Gy) were P1 and P4 (85%) while most dissimilar mutants were P3 and Parent (38%).

Efficacy of mutagenic treatments in producing useful mutants in finger millet (Eleusine coracana Gaertn.)

Abstract: A mutation breeding project was initiated with finger millet varieties, VR 708 and GPU 26 using three doses each of gamma rays (150, 300 and 450 Gy), ethyl methane sulphonate (0.15, 0.30 and 0.45%) and nitroso guanidine (0.015, 0.030 and 0.045%) coupled with combination treatments of 300 Gy gamma rays with 0.30% EMS or 0.030% NG. Fifteen selected M2 plant progenies from each of the eleven mutagenic treatments along with the parental variety were evaluated in M3 generation. Four high yielding M3 progenies from each treatment along with the parental variety were evaluated for yield and eight component traits in M4 generation. In M3 generation, of the 165 progenies, 61 in VR 708 and 65 in GPU 26 produced significantly higher yield than the parent and EMS treatments produced more of such high yielding progenies. In M4, out of 44 progenies in each of VR 708 and GPU 26, 8 and 9 progenies showed superiority over the parental variety in one or more traits, respectively. High frequency of positive mutations was observed for 1000-grain weight, finger length and fingers/ear in case of VR 708 and fingers/ear and finger length in case of GPU 26. Moreover, EMS treatments produced more superior mutants (28.93% in VR 708 and 39.13% in GPU 26) in different traits than the other mutagenic treatments. Among the mutagenic treatments, the frequency of high yielding progenies in M3and M4 generations were higher in 0.30% and 0.45% EMS, 0.030% NG and combination treatment of 300 Gy gamma rays + 0.30% EMS.

Are Mutations in Genetically Modified Plants Dangerous

Abstract: Latham et al. [1] and Wilson et al. [2] reviewed the long known phenomenon that plant transformation may cause mutations. Mutations can occur at any position in the genome, due to the tissue culture phase or other factors. Furthermore, insertion mutations may be induced by Agrobacterium-mediated transformation or particle bombardment. The authors focus in particular on mutations and chromosomal rearrangements flanking the insertion of the T-DNA. In their view, these mutations pose a risk regarding biosafety. The transgenic plant should in their opinion be as identical to its parent as possible. Therefore, they recommend extended backcrossing for elimination of genome-wide mutations, and sequencing of flanking DNA of 50 kbp at each side of the insertion, and discarding of plants that show any mutation in the flanking DNA compared to the parent plant. These and other precautions should ensure that transformation-induced mutations will not impact on biosafety. Apparently, the authors suggest that in addition to the inserted transgene, mutations have their own contribution to uncertainties regarding biosafety. If the transgenic plant was to be released in the environment, genotypes with mutations should be discarded. The authors do not mention mutation breeding of plants. Since the discovery of X-ray induced mutations in barley nearly 80 years ago (Stadler [3]), plant breeders and geneticists have realized how DNA mutations can be induced for widening the genetic variation in their germplasm. During the past seventy years, mutation breeding led to more than 2250 plant varieties (Maluszynski et al. [4]; Ahloowalia et al. [5]). 70% of these varieties were released as directly induced mutants, and the other 30% from crosses with induced mutants. The use of chemical treatments was relatively infrequent, but gamma rays were frequently used (64%), followed by X-rays (22%) (Ahloowalia et al. [5]). The freely accessible FAO/IAEA website contains a database of plant varieties derived from induced mutations (http://www-infocris.iaea.org/MVD/default.htm). This list has been composed on the basis of official information from plant breeders and authorities. The composers of the database mention that the list is far from complete, as frequently it is not published how new varieties have been obtained. In spite of that, the list contains now (August 2007) already 2543 released plant varieties. In reality, the number of induced mutant varieties is much larger. If spontaneous mutants would also be included, the list would further expand strongly. The induced mutant varieties have been developed in 175 plant species, including rice, wheat, barley, cotton, rapeseed, sunflower, grapefruit, apple, banana, and many other species. They are released in Europe, Asia, North America, South America, and Australia. Dozens of these varieties are grown at large scales (Ahloowalia et al. [5]). Many millions of people eat and use products of these varieties. The authors also do not mention the experiences in wheat breeding with gene transfer from wild species using induced translocations. In this approach, a resistance gene was introgressed by means of an interspecific cross followed by repeated backcrosses. This led to addition of an alien chromosome, containing the resistance gene. For adoption of the resistance gene into the wheat chromosomes, the addition lines were irradiated for mutation induction. During repair of the breakages of the wheat chromosomes, sometimes a part of the alien chromosome was incorporated, leading to normal Mendelian inheritance of the resistance gene in the wheat genome (Friebe et al. [6]; Mukai et al. [7]). Many wheat varieties have been released that contain one or more of these kinds of induced translocations. The authors did not mention that in conventional breeding, traits from wild germplasm are introduced into cultivars by means of crosses and backcrosses with an elite cultivar. During this process, chromosomal parts from the wild germplasm are introduced. These chromosomal parts may harbour hundreds of unknown “wild” alleles and thousands of deviations in the DNA sequence compared to the original elite cultivar. These thousands of natural deviations can be regarded as thousands of mutations. We all use and eat such cultivars for many decades. The mutant varieties and those originating from translocation events or backcrosses usually are not molecularly characterized by DNA sequencing, nor compared with their parents at the DNA sequence level. Sometimes cytogenetic or genetic marker studies are performed to locate introduced chromosomal parts in the recipient genome. However, the plant breeders of mutant varieties usually do not know the number of mutations or changes, the kinds of mutations, nor the number of rearrangements in their varieties. Neither they know whether new open reading frames or fused genes have been created by the mutations, nor whether expression levels of genes have changed due to mutation, or due to introgression of DNA from wild germplasm. However, the cultivars generally have been phenotyped thoroughly by the breeders and compared phenotypically to their parents and contemporary cultivars in view of their commercial value. In spite of the absence of molecular characterization, the cultivars, either from induced mutation, spontaneous mutation, or introgression breeding, have been widely accepted, grown, and used. The precautionary measures proposed by Latham et al. [1] and Wilson et al. [2] for genetically engineered plants regarding detection of mutations are not in balance at all with common practice in conventional plant breeding as described above. It is unscientific to propose screening flanking DNA of 50 kbp at each side of the insertion, requiring discarding of plants that show any changes there, but simultaneously accepting plants with tens or hundreds or thousands of unknown but probably more dramatic DNA changes after irradiation or introgression. One could react with a proposal to put also plants from induced mutations under strict safety regulations. This would make sense only if the mentioned 2543 varieties would have induced more frequently biosafety problems then varieties from cross breeding. However, we are not aware of any biosafety problem caused by an induced mutation of a released variety or by an induced translocation. Apparently, the common thorough evaluation of induced mutants at the phenotypic level by the breeders suffices. Proposing a ban on mutations caused by gene transformation for the sake of biosafety indicates a blind spot for the safety of numerous mutations induced by conventional breeders for more than 70 years, and introgression of unknown chromosomal parts from wild germplasm since centuries.

Effects of ion beam irradiation on mutation induction in rice.

Abstract: Heavy- ion beam irradiation is an effective technique for mutation breeding to produce new cultivars. We evaluated the conditions of heavy-ion beam irradiation on mutation induction in rice (Oryza sativa L.). Rice seeds were irradiated by C or Ne ions accelerated to 135MeV/u within a dose range of 10 to 400 Gy. The LET (linear energy transfer) range of the C-ion beam was 23 to 100keV/μm and that of the Ne-ion beam was 60 to 100keV/μm. To evaluate the effect of irradiation, survival rate and the seed fertility were examined in M1 plants and the frequency of chlorophyll deficient mutants (CDM) was examined in M2 plants. The conditions of C-ion and Ne-ion irradiation to maintain high survival rate were up to 20Gy with 23-40keV/μm, and up to 10Gy with 60-80 keV/μm, respectively. Seed fertility tended to be unaffected by LET values of 23-70 keV/μm with the same dose of irradiation. The highest frequency of CDM was observed in 10Gy at C or Ne ion irradiation with 60-70 keV/μm. In this study, we isolated several mutant lines such as salt-tolerant, bronzing, crinkled-dwarf, necrosis and chlorosis. These mutants could be important as genetic resources for research in plant functional genomics.

Induced mutants in common bean (Phaseolus vulgaris), and their potential use in nutrition quality breeding and gene discovery

Abstract: Common bean (Phaseolus vulgaris) is the most widely grown grain legume for human consumption and a major protein and mineral source in East Africa and Latin America. It is also a simple diploid species with a small genome (650 Mb). Despite its nutritional and economic importance and tractable genome, P. vulgaris has a paucity of mutant resources compared to other crops, making it difficult to perform genetic screening in the species. In this review we discuss recent studies on mutagenesis that aim to produce large-scale, mutagenized populations for generalized trait screening, as well as previous EMS (ethyl methane sulfonate) and gamma radiation mutants that were developed for biological nitrogen fixation or plant morphology traits. Mutant stocks in this crop will allow researchers to conduct both forward (systematic phenotypic screening) and reverse genetics (such as TILLING, or Targeting Induced Local Lesions In Genomes) experiments aimed at understanding the genes involved in various traits, including abiotic and biotic stress tolerance, grain quality, and nutritional value, as well as genes involved in symbiosis with Rhizobia. Thus, mutant stocks will be important for gene discovery and creating novel variability. In this review, we highlight applications of mutation breeding for nutritional quality improvement of common bean, giving examples of seed protein, mineral content, and tannin accumulation traits.

Mutagenesis: Generation and Evaluation of Induced Mutations

Abstract: Mutation breeding is one of the approaches to enhance the spectrum of beneficial alleles of agronomic and economic significance in crop improvement program. It has been demonstrated in oleiferous Brassica species too. Physical and chemical mutagens were used to isolate mutations for reduced plant height and yield‐contributing characters. Wide range of variability for flower morphology has been isolated. Yellow seed coat mutants and their use in crossbreeding program have resulted in the development of high oil content lines. Ethyl methane sulfonate (EMS) has played an important role to tailor fatty acid composition of rapeseed‐mustard. Mutations for reduced erucic acid and increased oleic acid have been achieved using EMS. Use of mutations for modified fatty acids in crossbreeding has improved oil quality and seed yield potential. The haploid system was found to be beneficial in Brassica napus for the induction of mutation for herbicide resistance, disease resistance, and oil and meal quality. Mutation breeding has been successfully employed to develop high‐yielding varieties. So far 31 high‐yielding varieties have been developed and released for cultivation all over the world. Compared to important cereal and oilseed crops, limited work on mutation breeding has been undertaken in rapeseed‐mustard. Therefore, efforts need to be strengthened to enhance the wide range of variability for agronomical, morphological, biochemical, and biotic and abiotic stress‐tolerant characters and to use them in breeding program to break the yield barriers in Brassica crop species. Analysis of mutant at molecular level would reinforce the understanding on mechanism of mutations in the era of genomics.

Genetic Improvement of Taro (Colocasia esculenta var esculenta) through in-vitro mutagenesis

Abstract: Mutation breeding has been applied for many years for the improvement of crops. According to the FAO/IAEA mutant variety database, there are at least 2300 mutant varieties released officially worldwide. Taro (Colocasia esculenta) is vegetatively propagated, hence induced mutations offer the best way to induce variability in breeding program. In-vitro culture technique has also been applied to recover mutated cells through repeated in- vitro multiplication and to accelerate the breeding time. In the in-vitro culture media test, Murashige and Skoog medium supplemented with Indole –3-acetic acid (10 mgL -1 ) was found optimum for initiation and growing of taro. Benzylaminopurine (2 mgL -1 ) or Thidiazuron (0.9 mgL -1 ) was found optimum for multiplication of taro. In the radiosensitivity test, shoot tips were irradiated from 0 to 60 grays of a 135 Co gamma irradiation source and cultured on MS Medium supplemented, with 10 mgl -1 Indole –3-acetic acid. The effective mutation dose (LD 30 ) that causes 30% reduction in growth was found to be 7.65 grays. 300 shoot tips were irradiated with 7.65 grays and multiplied for four generations. A population of more than 30,000 in-vitro plantlets of taro has been reached. A low-cost alternative substrate (60% composted scum + 40% fly ash) for hardening of tissue-cultured plantlets of taro was identified. 3500 plantlets were already hardened and used to optimize screening protocols for disease resistance against Phytophthora colocasiae. Key words : taro, mutation breeding, in-vitro culture, Phytophthora Leaf Blight resistance.

Mutation breeding for resistance to disease and other useful traits

Abstract: Particular aspects provide novel mutant plants and plant parts thereof, derived via mutagenesis, having disease resistance and other useful traits. Particular embodiments provide a wheat genotype 'RRR Scarlet' ('Scarlet-Rz1'), plants and seeds thereof, methods for producing a plant comprising crossing 'Scarlet-Rz1' plants with another wheat plant, hybrid wheat seeds and plants produced by crossing 'Scarlet-Rz1'plants with another line or plant, and creation of variants by mutagenesis or transformation of 'Scarlet-Rz1'. Additional aspects provide methods for producing other varieties or breeding lines derived from 'Scarlet-Rz1' and to varieties or breeding lines produced thereby. Further aspects provide for mutant plants and plant parts thereof that are resistant and/or tolerant to plant root fungal pathogens such as Rhizoctonia and Pythium. Additional embodiments provide mutant plants and plant parts thereof that exhibit stress tolerance and/or resistance. Yet further aspects provide mutant plants and plant parts thereof that are drought resistant or tolerant.

Plant breeding using the ion beam irradiation in riken

Abstract: Since 1986, RIBF has been the one of the biggest facilities capable of accelerating heavy ions world wide. Although nuclear physics is the primary theme investigated at the facility, plant scientists started our trials in plant breeding in 1993. Soon we found that the ion beam is highly effective for inducing mutagenesis of tobacco embryos during fertilization without damage to other plant tissue. We isolated many types of tobacco mutants including albino, periclinal chimera, sectorial chimera, herbicide-tolerant and salt-tolerant phenotypes. We have put 6 new flower cultivars on the market in Japan, USA, Canada and EU since 2002. The developmental period of these new cultivars was only three years. The ion beam irradiation technique induces a high mutation rate without severe growth inhibition at relatively low doses. Thus, we conclude that the ion beam is an excellent tool for mutation breeding to improve horticultural and agricultural crops with high efficiency.

Generation, characterization, and application of mutant genetic resources in soybean

Abstract: Efficient mutant production systems, through either physical or chemical mutagenesis, have been well established in soybean. A vast amount of genetic variability, of both quantitative and qualitative traits, has been generated through experimental mutagenesis in the past 30 years. Characterization of mutated traits has greatly advanced our understanding of the underlying mechanisms of a score of important traits, including the genetic and genomic basis of nodulation and synthesis of fatty acids and storage proteins. Mutation techniques have also been successfully used in breeding new soybean varieties. More than 100 mutant varieties were developed and released for commercial cultivation; among them are several groundbreaking varieties; i.e., the supernodulating variety Sakukei 4; the glycinin-rich variety Yumenori; the lipoxygenases-free variety Ichihime; and the low linolenic varieties IA3017 and IA2064. It is expected that more new varieties with novel traits will become available in the coming years, and a variety with a reduced phytate level may become available in the near future. Induced mutants will become a unique genetic resource in functional genomic studies, and the advance of functional genomics will increase the usefulness and use efficiency of induced mutations in soybean breeding.

Molecular genetics: Step by step implementation in maize breeding

Abstract: Efficiency in plant breeding is determined primarily by the ability to screen for genetic polymorphism, productivity and yield stability early in program. Dependent on the knowledge about the biochemical bases of the trait and nature of its genetic control, trait could be modified either through mutagenesis of genes controlling it or through the transfer of already existing mutant genes, controlling desired trait to different plant genotypes by classic crossing. Objective of this report is to present partly results on the investigation of the possibilities to apply ionizing radiations (fast neutrons, γ -rays) and chemical mutagens (EI, iPMS, EMS, ENU) to get maize and wheat mutants with increased amount and improved protein quality. Besides this approach in mutation breeding, results on the very early investigation of biochemical background of opaque -2 mutation including use of coupled cell - free RNA and protein synthesis containing components from both wild and opaque - 2 maize genotypes (chromatin, RNA polymerase, microsomall fraction, protein bodies) will be presented. Partial results on opaque - 2 gene incorporation in different genetic background are reviewed. Part of report is dealing with different classes of molecular markers (proteins, RFLP, AFLP, RAPD, and SSR) application in maize genome polymorphism investigation. Besides application of different molecular markers classes in the investigation of heterosis phenomena they are useful in biochemical pathway of important traits control determination as well. .

Laser applications in seed germination, mutation breeding and gene engineering for forestry and horticulture

Abstract: Laser radiation has a very high power density so it has been used in accelerating seed germination and mutation breeding, and can be applied in new technical methods to improve the genes of trees and plants. We discuss the mechanism of the biological effects of laser radiation, then review the applications of lasers in accelerating seed germination, mutation breeding and gene engineering of forest trees and horticultural plants.

Irradiation-induced variations in M2 populations of Eksotika papaya

Abstract: Mutation breeding of papaya by gamma irradiation was started at MARDI in August, 2000 as a contract research project with the International Atomic Energy Agency (IAEA). Irradiation of seed of ‘Eksotika’ variety was carried out at MINT using 525 Gy for dry seed and 42.5 Gy for pre-soaked seed previously found to be the most suitable dosages for mass irradiation. A total of 200 M1 plants from each dosage treatment were subsequently raised. M2 seed were obtained by self-pollinating M1 hermaphrodite trees and a population of 1,000 M2 plants was established for studies on variation of 13 traits. Another 1,920 M2 seedlings were raised, inoculated and screened for resistance to papaya ringspot virus disease. In the M2 populations, wide variability was recorded for many traits. At the seedling stage, low irradiation of 42.5 Gy on pre-soaked seed produced a high number of M2 progenies that were shorter and more vigorous in leaf development than those irradiated at 525 Gy and the control seedlings. The distribution patterns of M2 progenies for nine quantitative traits showed great variation with ranges often exceeding the limits of the control population. There appears to be good prospects in improving Eksotika papaya using irradiation, especially in selecting for more dwarf trees, lower fruit bearing stature, higher total soluble solids in fruit and larger fruit. Several M2 mutants also showed very good resistance to malformed top disease caused by Cladosporium. However, no resistance to papaya ringspot virus disease was found in the 1,920 M2 seedlings that were inoculated and screened.

Mutation breeding of Termitomyces albuminosus producing anti-coagulation protein TA-P

Abstract: The fungus,Termitomyces albuminosus TA-SD could produce anti-coagulation protein TA-P.In order to screening the mutants with higher activities,the mutation breeding of the strain TA-SD was carried out by ultraviolet mutagenesis.When the time of ultraviolet radiation was 40 seconds,the most positive mutation rate and anti-coagulation activity were reached,and it was 33.3% and 104.7% respectively.Both the positive mutation rate and anti-coagulation activity in the N-type mutants and cycloheximide-resistant mutants were higher than it in the S-type mutants and non-cycloheximide-resistant mutants.After screening the mutant SD-A-8 was obtained and its anti-coagulation activity was 2.3 times higher than the initial strain.The mutant was stable after the transfer of culture.

Mutation breeding for resistance to fungal disease and for drought tolerance

Abstract: Particular aspects provide novel mutant plants and plant parts thereof, derived via mutagenesis, having disease resistance and other useful traits. Particular embodiments provide a wheat genotype ‘RRR Scarlet’ (‘Scarlet-Rz1’), plants and seeds thereof, methods for producing a plant comprising crossing ‘Scarlet-Rz1’ plants with another wheat plant, hybrid wheat seeds and plants produced by crossing ‘Scarlet-Rz1’ plants with another line or plant, and creation of variants by mutagenesis or transformation of ‘Scarlet-Rz1’. Additional aspects provide methods for producing other varieties or breeding lines derived from ‘Scarlet-Rz1’ and to varieties or breeding lines produced thereby. Further aspects provide for mutant plants and plant parts thereof that are resistant and/or tolerant to plant root fungal pathogens such as Rhizoctonia and Pythium. Additional embodiments provide mutant plants and plant parts thereof that exhibit stress tolerance and/or resistance. Yet further aspects provide mutant plants and plant parts thereof that are drought resistant or tolerant.