Institute of Radiation Breeding

Tsuchiura, Japan

Institute of Radiation Breeding

Tsuchiura, Japan
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Shirasawa K.,Tohoku University | Shirasawa K.,Kazusa DNA Research Institute | Sekii T.,Tohoku University | Ogihara Y.,Tohoku University | And 7 more authors.
Molecular Breeding | Year: 2013

An unusually high temperature during the grain-filling period, such as that caused by global warming, impairs the quality of rice (Oryza sativa L.) grains. This sensitivity to high-temperature stress is different among cultivars, suggesting the possibility of developing a high-temperature-tolerant cultivar. Since marker-assisted selection would reduce time and labor in breeding for such a quantitative trait, we determined the chromosomal region responsible for high-temperature tolerance during the grain-filling period. A high-temperature-sensitive japonica cultivar Tohoku 168 and a tolerant japonica cultivar Kokoromachi were selected as the parental lines of recombinant inbred lines (RILs) by high-temperature stress treatment from 5 to 10 days after anthesis, which was found to be the period most critical for grain quality. Using the RILs, whose genotypes were determined by analysis with 131 DNA markers which were selected as polymorphic markers between these two cultivars from 2,648 DNA markers tested, the quantitative trait locus (QTL) for the percentage of white-back grains was mapped on chromosome 6. The Kokoromachi allele of the QTL, which had a positive additive effect on the high-temperature tolerance, was introduced into the Tohoku 168 genome by repeated backcrossings with marker-assisted selection. Using high-temperature stress treatment of the near isogenic lines developed, the QTL on chromosome 6 was localized within a 1.9-Mb region between two DNA markers, ktIndel001 and RFT1. These DNA markers would be useful not only for breeding high-temperature-tolerant cultivars but also for map-based cloning of the QTL. © 2013 Springer Science+Business Media Dordrecht.


Muramatsu N.,Institute of Radiation Breeding | Yamamoto M.,Kagoshima University | Nakano H.,Kagoshima University | Yamanouchi H.,Institute of Radiation Breeding
Scientia Horticulturae | Year: 2011

We compared hydraulic traits of 18 tropical/subtropical fruit-producing species plants and a further 18 from temperate zone. Plants were classified into four categories by height: tall tree (>10m), small tree (4-9m), shrub (1-4m) and vine. We measured ratios [(cross-section area of xylem)/(cross-section area of twig)], and the diameters and numbers of xylem vessels in microscopic images. We calculated the water flow index (WFI: Σr4S-1×xylem ratio, where, r is the vessel radius, and S is the xylem cross-section area) according to Hagen-Poiseuille's law. Vine had thick vessels and remarkably higher WFI than free-standing trees in both temperate and tropical fruit species. Vessel diameter increased as trees being taller in both in latitudinal groups. Xylem vessel number decreased with height in temperate fruit trees but not in tropical species. WFI increased with tree height of both latitudinal groups. There were no significant effects of latitude on WFI. © 2011 Elsevier B.V.


Ukai Y.,Institute of Radiation Breeding | Yamashita A.,Institute of Radiation Breeding
Breeding Science | Year: 2010

We recently presented a method for simultaneous estimation of relative biological effectiveness (RBE) of alpha particles and protons. Here, we evaluate RBE for chlorophyll mutation rate and four M1 effects in thermal neutron exposure of barley (Hordeum vulgare L.) seeds. RBEs of both alpha particles and protons were low for germination rate, seedling height, and number of spikes, and high for seed fertility and mutation rate. Thus, M1 effects are not necessarily accurate as a proxy for mutation rate in comparisons of different types of radiation. RBE of alpha particles for mutation rate was 130.3, much higher than values so far reported in plant materials. RBE of protons for mutation rate was 106.4; as far as we are aware, this is the first value reported for thermal neutron exposure of plant materials. RBEs of alpha particles and protons were significantly correlated (r = 0.939, P < 0.05).


Ukai Y.,Institute of Radiation Breeding
Breeding Science | Year: 2010

The "Crossing-within-Spike-Progeny (CSP) method" is a method to efficiently screen for mutants in allogamous (cross-fertilizing) plants. This paper presents a theoretical analysis of how to minimize the total number of plants in the screening generation (T) and the total cost (Tc) required to detect one or more mutants with a given probability when using the CSP method. Tc depends on the number of plants per line in the screening generation (n), the number of plants per hill plot in the M2 generation (h), the ratio of the cost needed in non-screening generations to that in the screening generation (W), and the mutation rate per cell (p1). T was lowest when n = 1 (T = 47.93 × p1 -1), irrespectively of h. On the other hand, the value of n which gave minimum Tc (designated n*) was not constant, but varied with h. n* was 6 when h = 2, increased as h increased, and was 15 when h = 48, when W= 10. Unlike in the case of autogamous species, the presence of chimeras in the M1 inflorescences greatly increased both T and Tc. A method for estimating the mutation rate per cell is also presented.


PubMed | Institute of Radiation Breeding
Type: Journal Article | Journal: Plant cell reports | Year: 2013

A simple method of detecting polymorphism of S locus glycoprotein gene, SLG, in Chinese cabbage and cabbage was developed, and used for identification of breeding lines. DNA was amplified by the polymerase chain reaction (PCR) with a pair of primers having S 6 SLG sequences from inbred lines, and digested with restriction endonucleases which recognize tetranucleotide sequences. The cleaved DNA fragments were size-fractionated by polyacrylamide gel electrophoresis and detected by silver staining. PCR with S 6 SLG primers amplified a fragment of ca. 1.3kb in more than half of the inbred lines tested. After digestion, polyacrylamide gel electrophoresis revealed polymorphism between the amplified 1.3kb DNA fragments. These polymorphic bands were detected by Southern hybridization using a probe of S 6 SLG cDNA, suggesting that the amplified DNA was SLG. Primers having the SLG sequences of S 2 , a representative of recessive S alleles, were used for amplification of SLG in the lines which did not give the 1.3kb DNA fragment by the PCR with S 6 SLG primers. Polymorphism of amplified DNA was found in these lines. However these primers also appeared to amplify an invariant SLR-2 sequence of 1.3kb in addition to the polymorphic S 2 SLG related sequences. Although the used primer sequences still need improvement for the analysis of recessive S alleles, PCR-RFLP of SLG was considered to be useful for identification of breeding lines as well as for S allele identification in cruciferous vegetables. F1 hybrids exhibited the sum of the bands of both parents, and, therefore, this method is expected to be used for a purity test of F1 seeds.


PubMed | Institute of Radiation Breeding
Type: Journal Article | Journal: TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik | Year: 2013

Rice mutants containing low levels of the 16-kDa allergenic protein, which is the main allergen in the rice grain for patients of atopic dermatitis due to the intake of rice, were screened, and 4 independent mutant lines with small amounts of this protein were found by SDS gel electrophoresis and immunoblot analysis. These mutants were grouped into two types. Two mutant lines, 85KG-4 and 86RG-18, contained low levels of the 16k-Da and 26-kDa polypeptides and a high level of the 57-kDa polypeptide. The 16-kDa polypeptide content of these mutants was about half that of the original cultivars. Homozygous lines were developed, and these showed normal growth and seed set. The other 2 mutant lines, 87KG-970 and 89WPKE-149, showed traces of the 16-kDa and 26 kDa polypeptides and contained a high level of the 13 kDa polypeptide. The homozygous plants of this type were sterile. All of the mutant lines had floury endosperms. Genetic analysis suggested that low 16-kDa polypeptide content is controlled by a single recessive gene. Attempts to separate of the genes for low 16-kDa polypeptide content and floury endosperm by crossing with the original cultivar were unsuccessful, suggesting the tight linkage of these two genes or pleiotropism of a single mutated gene. The relationship between low 16-kDa polypeptide content and the floury character and the possible use of the mutant as a low allergen rice are discussed.


PubMed | Institute of Radiation Breeding
Type: Journal Article | Journal: TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik | Year: 2013

Among the mutant lines of rice that have been selected for morphological characters, one line, NM67, was found to have a low content of glutelin and a higher content of prolamine in its seed protein than other Japanese cultivars. This mutant is a semi-dwarf and partially sterile line, and its leaves turn yellow before heading. Genetic analysis after backcross to the original cultivar, Nihonmasari, revealed the following: (1) the character of low glutelin content was always accompanied by the character of high prolamine content; (2) the low glutelin (and high prolamine) character seemed to be manifested by a single dominant gene; and (3) semi-dwarfness, low fertility and early yellowing leaf of the mutant, which might also be pleiotropy, were controlled by a single recessive gene independent of the gene for protein content. The protein character of NM67 was genetically separated from semi-dwarfness and low fertility, and a new line having low glutelin content and high prolamine content with normal morphological characters comparable to those of the original cultivar was obtained from the progenies of the cross. The possible use of this line as a low protein rice cultivar is discussed.

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