大麦網斑病抵抗性の選抜効果

Selection effectiveness for the resistance to net blotch was estimated by using two sets of F2 and F3 populations derived from the crosses between resistant and susceptible parents. In every F2 and F3 population, disease ratings showed a continuous distribution. As many F3 lines with intermediate resistance had a smaller variance and homozygous genotype, the resistance might be controlled by a few genes. The heritabilities of the disease rating were estimated　by correlation coefficients and regression coefficients between each F2 plant and the descended F3 lines. Another estimate for heritability was calculated by the selection differential in the F2 plants and genetic gain in the F3 lines. Despite the different level of resistance in the resistant parents of the two crosses, the three kinds of heritabilities estimated were similar and ranged from 0.6 to 0.8. Because of the fewer number of genes controlling the disease resistance and the higher heritabilities, selection in a early generation may be effective for net blotch resistance in barlcy.抵抗性と罹病性の両親間の交雑に由来する2組のF2集団とその後代のF3系統を用いて、大麦網斑病における抵抗性の選抜効果を推定した。F3系統の平均値と分散から、病斑指数の分散が小さく、すでに固定した系統が多数存在したので、抵抗性は少数の遺伝子に支配されているとみられた。F2個体とF3系統間の親子相関、親子回帰およびF2の選抜差とF3系統の遺伝獲得量から遺伝率を推定したところ、2組の交雑組合せで抵抗性親の病斑指数は異なっていたにもかかわらず、3種類の遺伝率の推定値はいずれも0.6～0.8の値を示した。遺伝率が高く、しかも関与する遺伝子数であるため、雑種集団で連続変異を示す場合の大麦網斑病抵抗性の選抜はF2からでも効果的とみられた

日本とカナダの春播オオムギから採取した大麦網斑病菌株の病原性の変異

Twenty-two isolates of Pyrenophora teres Drechs. collected from Japanese and Canadian spring barleys were inoculated to 38 barley varieties having various genetic backgrounds. The analysis of variance for the discase ratings showed that there were significant differences both in the virulence of isolates and the resistance of varieties. However, the interaction among isolates and varieties was not statistically significant. Both Finlay-Wilkinson regression analysis and principal component analysis by Additive Main effects and Multiplicative Interaction effects(AMMI)model classified the isolates into three groups,which were different in origins and sympton types. A spot tyte isolate was distinguished from net type isolates by its generally high virulence. A slight pathogenic differentiation was suggested between Japanese and Canadian net type isolates.北海道およびカナダの春播オオムギがら採取した22の大麦網斑病菌株（Pyrenophora teres Drechs.）を世界各地のオオムギ38品種に幼苗接種し、病斑指数によって病原性の変異を検討した。分散分析の結果、菌株の病原力ならびに品種の抵抗性には有意差が認められたが、菌株と品種の交互作用は統計的には有意でなかった。各菌株の反応をFinlay-Wilkinson（1963）の回帰分析によって解析したところ、北海道とカナダの菌株で病原性反応に差が認められた。この傾向はカナダの菌株のうち、通常のNet typeの菌株よりも斑点状病斑を示すSpot typeの菌株で顕著であった（Fig.1）。さらに、菌株と品種の交互作用を詳細に解析するために相互作用と相乗交互作用モデル（AMMIモデル）を適用して交互作用に関する主成分分析を行った結果、各菌株は日本のNet type、カナダのNet type、カナダのSpot typeの3群に分けられた（Fig.1）。各菌株について群間ならびに群内の相関係数を算出したところ（Table5）、Net typeの菌株相互の相関係数は0.601～0.969と相対的に高かったが、一部の菌株と品種の組合わせでは抵抗性反応の逆転がみられた（Fig.4）。一方、Spot typeの菌株とNet typeの菌株の相関係数は0.302～0.538と低く、両者の病原性は多少異なることが示された。このような一部の菌株と品種の間に認められる弱い交互作用は、抵抗性を支配する主働遺伝子の特異的な反応が、いわゆる圃場抵抗性を支配する微働遺伝子の作用によって修飾された結果と考えられる

Sources of Resistance to Net Blotch in Barley Germplasm

Net blotch caused by a fungus Pyrenophora teres Drechs. is a common disease in barley. Its source of resistance has been screened by many researchers by field evaluations or seedling tests inoculating a single isolatc. Since the pathogcnic variation of isolates has been reported in net blotch, resistance of the varieties to the disease may be different among the isolates with different pathogenicities. In this study, the pathogenic variation was examined and the varietal variation of the resistance was evaluated by inoculating with four P. teres isolates collected from Japan and Canada to more than 2,200 barley varieties of the world collection preserved at the Barley Germplasm Center of Okayama University. A preliminary inoculation test showed that the disease rating was affected little by the inoculation seasons. Disease ratings of varieties showed a continuous variation with a single mode in the resistant range in each of the four isolates. However, the correlation coefficient between Japanese isolate K105 and Canadian isolate WRS102 was as low as 0.55, indicating a slight pathogenic differentiation between these isolates. Significant correlation coefficients (r=.55~.78) among the ratings of isolates indicated that the pathogenicity to the varieties was rather similar and that the pathogenic differentiation was small among the four isolates tested. In general, varieties from Ethiopia, North Africa and Korea were more resistant than those from other regions. Varieties from Turkey and Europe were susceptible to Japanese isolates, while Nepalese varieties were susceptible to Canadian isolates. Twenty of 25 varieties which were resistant to the isolate K105 but susceptible to the isolate WR102 were from Nepal and most of those were Oriental-type (Bt bt2) in brittleness of rachis. These findings revealed an example of regional concentration of resistant gene in net blotch.日本ならびにカナダで採取した大麦網斑病菌4菌株を、岡山大学資源生物科学研究所大麦系統保存施設の保有する2,200あまりの品種に接種して、各菌株に対する抵抗性遺伝子源を評価すると共に病原性の分化を検討した。結果の概要は以下の通りである。1）3回にわたって44品種に4菌株を接種した予備試験の結果、病斑指数の品種変異は極めて大きく、品種の抵抗性に対する接種時期の影響は小さかった。2）供試4菌株に対するオオムギ品種の抵抗性の頻度分布はいずれも連続的で、そのピークは抵抗性側であった。各菌株間の病斑指数は有意な正の相関関係にあり、菌株間の病原性の分化は小さかった。3）各菌株に対する抵抗性遺伝資源はエチオピア、北アフリカおよび朝鮮半島に多かった。一方、日本で採取した2菌株に対する罹病性の品種はトルコおよびヨーロッパに多いのに対して、カナダで採取した菌株に対する罹病性の品種はネパールに多かった。また、ネパールに由来する品種の病斑指数は、日本の2菌株に対しては抵抗性と罹病性の2群に分かれたが、カナダの2菌株に対しては連続的な分布を示した。特に、カナダの菌株WRS102に対するネパール由来の品種の反応は、強度の抵抗性を示す品種がなく、ピークが罹病性側に片寄っており、日本の菌株に対する反応とは大きく異なった。4）日本で採取したK105とカナダで採取したWRS102の病斑指数の菌株間相関係数は、4菌株の組合せの中で最も小さく、K105とWRS102の病原性は多少分化していた。なお、K105に抵抗性でWRS102に罹病性の品種は25品種であり、そのうち20品種がネパール由来で、かつ、そのほとんどが小穂脱落性東亜型を示した。従ってK105に抵抗性でWRS102に罹病性の遺伝子は、ネパールの東亜型品種に偏在しているとみられる

Lepton Universality in the ν\nuMSM

We consider the $\nu$MSM which is an extension of the Standard Model by three right-handed neutrinos with masses below the electroweak scale, in which the origins of neutrino masses, dark matter, and baryon asymmetry of the universe are simultaneously explained. Among three heavy neutral leptons, $N_2$ and $N_3$, which are responsible to the seesaw mechanism of active neutrino masses and the baryogenesis via flavor oscillation, can induce sizable contributions to various lepton universality in decays of charged mesons. It is then investigated the possible deviations of the universality in the $\nu$MSM. We find that the deviation in kaon decay can be large as ${\cal O}(10^{-3})$, which will be probed in near future experiments.Comment: 15 pages, 5 figures, version to appear Physics Letters

Germplasm evaluation for crop improvement: Analysis of grain quality and cadmium accumulation in barley

Evaluating genetic variation in barley (Hordeum vulgare) germplasm, combined with genome-wide genotyping, is vital for identifying genes controlling important grain-quality traits. For example, in addition to traditional grain quality properties such as starch and protein contents, grain safety parameters such as heavy metal content, are important in the use of barley for human food and animal feed. A number of genes affecting grain quality have been identified by map-based cloning strategies and functionally analyzed by genetic transformation experiments. Moreover, germplasm evaluation yielded information that enabled the introgression of a key gene controlling grain cadmium accumulation into an elite barley cultivar, reducing the content of this heavy metal in grain. Genotyping of molecular markers and resequencing of germplasm accessions may provide information about how grain quality–related loci evolved and how the current allelic diversity was established. In this review, we describe germplasm resources for barley grain quality–related traits and the methods used to analyze the functions of genes controlling these traits, illustrating cadmium accumulation as an example. We also discuss future directions for the efficient identification of grain quality–related genes.Evaluating genetic variation in barley (Hordeum vulgare) germplasm, combined with genome-wide genotyping, is vital for identifying genes controlling important grain-quality traits. For example, in addition..