Mutation breeding

About: Mutation breeding is a research topic. Over the lifetime, 531 publications have been published within this topic receiving 6730 citations. The topic is also known as: variation breeding.

Lethal and mutagenic effects of ion beams and γ-rays in Aspergillus oryzae.

Abstract: Aspergillus oryzae is a fungus that is used widely in traditional Japanese fermentation industries. In this study, the lethal and mutagenic effects of different linear energy transfer (LET) radiation in freeze-dried conidia of A. oryzae were investigated. The lethal effect, which was evaluated by a 90% lethal dose, was dependent on the LET value of the ionizing radiation. The most lethal ionizing radiation among that tested was (12)C(5+) ion beams with an LET of 121keV/μm. The (12)C(5+) ion beams had a 3.6-times higher lethal effect than low-LET (0.2keV/μm) γ-rays. The mutagenic effect was evaluated by the frequency of selenate resistant mutants. (12)C(6+) ion beams with an LET of 86keV/μm were the most effective in inducing selenate resistance. The mutant frequency following exposure to (12)C(6+) ion beams increased with an increase in dose and reached 3.47×10(-3) at 700Gy. In the dose range from 0 to 700Gy, (12)C(5+) ion beams were the second most effective in inducing selenate resistance, the mutant frequency of which reached a maximum peak (1.67×10(-3)) at 400Gy. To elucidate the characteristics of mutation induced by ionizing radiation, mutations in the sulphate permease gene (sB) and ATP sulfurylase gene (sC) loci, the loss of function of which results in a selenate resistant phenotype, were compared between (12)C(5+) ion beams and γ-rays. We detected all types of transversions and transitions. For frameshifts, the frequency of a +1 frameshift was the highest in all cases. Although the incidence of deletions >2bp was generally low, deletions >20bp were characteristic for (12)C(5+) ion beams. γ-rays had a tendency to generate mutants carrying a multitude of mutations in the same locus. Both forms of radiation also induced genome-wide large-scale mutations including chromosome rearrangements and large deletions. These results provide new basic insights into the mutation breeding of A. oryzae using ionizing radiation.

Mutation breeding, evolution, and the law of recurrent variation.

Abstract: In the present paper the history of the rise and fall of mutation breeding as an autonomous branch of breeding research is documented as well as its positive side effects for plant breeding and biology in general. Perhaps the most important generalization on the basis of the total outcome of mutation breeding will be termed “the law of recurrent variation”. It states that “treating homozygous lines with mutagenic agents generates large, but clearly finite, spectra of mutants. This consistently occurs when the experiments are carried out on a scale adequate to isolate the potential of alleles causing phenotypic and functional Correspondence/Reprint request: Dr. Wolf-Ekkehard Lönnig, Max-Planck-Institut for Plant Breeding Research Carl-von-Linné-weg 10, 50829 Cologne, Federal Republic of Germany. E-mail: loennig@mpiz-koeln.mpg.de deviations (saturation mutagenesis).However, due to almost Wolf-Ekkehard Lönnig 46 invisible residual effects of changes in redundant sequences and/or of further chromosome rearrangements, the corresponding saturation curve is asymptotically approaching its limit for the micro-quantitative part of variation.” Also, reasons are given why the law is relevant for heterozygotes and allogamous species as well, and the genetical basis of the law is briefly defined. In addition, arguments are presented why the overoptimism and euphoria at the beginnings of the period of mutation breeding are to be evaluated in connection with the basic assumptions of the synthetic theory of evolution − i.e. the assurance that mutations and selection constitute the entirely sufficient explanation of the origin of all species and higher systematic categories of the plant and animal kingdoms alike. This point established, the question is discussed whether the finite nature of the mutant spectra found in plant breeding research might also have repercussions on the present theory of the origin of species. Providing an affirmative answer of the applicability of the law of recurrent variation not only to cultivated plant and animal lines but also to species in the wild, the statements and assertions of the synthetic theory as quoted below will have to be revised.

Mutation breeding for rice improvement in Tanzania.

Abstract: The mutation breeding program based at Sokoine University of Agriculture (SUA), Morogoro, Tanzania aims at reducing plant height and maturation period of popular indigenous cultivars while maintaining some of the good qualities of the parents. Dry seeds of the indigenous popular cultivars were irradiated with 170, 210, 240 and 250Gy Gamma-rays from 60 Co at IAEA Seibersdorf Laboratories in Vienna in 1987, 1994 and 2001. The irradiated seeds and controls were sown at SUA. M 1 panicles were harvested, and planted as M 2 panicle-to-row progenies. M 2 plants were selected and advanced to M 3 and subsequent generations using pedigree selection method using plant height, early maturity and grain type as selection criteria. In another procedure, Single Seed Descent (SSD) method was used, whereby one seed was randomly selected from each M 2 plant to raise the M 3 generation. Apart from this, some improved mutants have been used in the cross breeding program. The selected variants with improved plant type have been evaluated in multi-locational trials and on farmers’ fields. Mutants that were selected using single seed descent were found to be very early in maturity and were resistant to rice yellow mottle virus (RYMV). After several years of multilocation and on-farm trials, SSD 35 was released in 2005 as a new variety under the name of Mwangaza. On the other hand, the improved mutants originating from cultivar ‘Salama’ also combined high yield potential and resistance to RYMV. Semi-dwarf Supa mutant, M-100 was backcrossed to ‘Supa’ variety and one high-yielding line selected from this cross has been recommended for cultivation in Zanzibar. Other lines originating from crosses between mutants and other varieties have been found to be resistant to rice yellow mottle virus and also combine high yield potential and acceptable grain quality.

Mutagenic effects of carbon ion beam irradiations on dry Lotus japonicus seeds

Abstract: Carbon ion beam irradiation is a powerful method for creating mutants and has been used in crop breeding more and more. To investigate the effects of carbon ion beams on Lotus japonicus, dry seeds were irradiated by 80 MeV/u carbon ion beam at dosages of 0, 100, 200, 300, 400, 500 and 600 Gy. The germination rate, survival rate and root length of M1 populations were explored and the dose of 400 Gy was selected as the median lethal dose (LD50) for a large-scale mutant screening. Among 2472 M2 plants, 127 morphological mutants including leaf, stem, flower and fruit phenotypic variation were found, and the mutation frequency was approximately 5.14%. Inter simple sequence repeat (ISSR) assays were utilized to investigate the DNA polymorphism between seven mutants and eight plants without phenotypic variation from M2 populations. No remarkable differences were detected between these two groups, and the total polymorphic rate was 0.567%.

Identification of novel mutants through Electron beam and Gamma irradiation in chickpea (Cicer arietinum L.)

Abstract: Chickpea is an important food legume grown worldwide. There is an increasing concern on narrowing of genetic base in mos t of the gra in legumes including chickpe a. Mutagenesis using ionizing radiations is one of the many ways of increasing genetic variability. To explore the potential of electron beam irradiation for mutagenesis and to compare it to gamma rays, seeds of a popular chickpea variety ‘Vijay ’were irradiated with four doses (200–500 Grey) of either electron beam or gamma rays. The M1 plants were grown in the field, harvested individually, and sown in the subsequent year to raise M2 plant to row progenies. Chlorophyll and other morphological mutants were identified in the M2 generation. The mutation frequency was found to be more for electron beam irradiation as compared to gamma rays treatments of the same dose. The overall mutation frequency calculated as chlorophyll mutants per 1000 M2 plants was almost double in case of electron beam (17.82) as compared to gamma irradiation (8.64). The overall percent of M1 derived families segregating for chlorophyll mutations was 4.42% for gamma rays while it was 9.42% for electron beam. Mutagenic effectiveness and efficiency was also higher for electron beam irradiation as compared to gamma rays of same doses. Some morphological mutants like no serration mutant, missing leaflet mutant, round leaflets with open flower were observed. Other putative mutants with agronomical importance (large pod, more branches, green canopy at harvest, early flowering, early maturity etc) were also isolated. These mutants constitute an important repository and may find uses in basic studies as well as in chickpea improvement program.