Varietal Variation and Effects of Some Major Genes on Salt Tolerance in Barley Seedlins

In order to select the salt tolerant cultivars, and to evaluate the effects of some major genes on salt tolerance in barley, 5,182 varieties and 368 isogenic lines were tested by exposing to 1.0 and 0.5M sodium chloride at the seedling stage. The average rating of salt tolerance was higher in varieties from Korea and Japan , but lower in varieties from Nepal and Southwest Asia. When the varieties were grouped by several morphological characters, six-rowed, covered, E type of nonbrittle rachis and uzu type groups were more tolerant than two-rowed, naked, W type and non-uzu type counterparts, respectively. A comparison between the isogenic pairs revealed that the uzu type was more tolerant than non-uzu type, but other major gene pairs did not show any obvious differences. These findings indicate that the uz gene affects the salt tolerance, and diferences between varietal groups characterized by other major genes are due to the difference in the genetic background among these varieties.本研究では耐塩性品種を見出す目的で、世界各地のオオムギ5,182品種について幼植物の耐塩性の品種変異ならびにその地理的変異、および主要形質との関係を調査した。幼植物の耐塩性を地域別に比較すると、朝鮮半島および日本の品種が強く、ネパールと西南アジアの品種が弱い傾向にあった。次に、条性や皮裸性など、オオムギにおける主要形質と幼植物の耐塩性との関係を調べるために、5,182品種を主要形質に分けて耐塩性を比較した結果、六条品種は二条品種より、皮品種は裸品種より、小穂非脱落性のE型はW型より、日本と朝鮮半島に分布する六条の渦品種は、同地域の六条の並品種よりもそれぞれ耐塩性が有意に強かった。さらに、供試品種を条性、皮裸性および小穂非脱落性の3形質の組合せで8タイプに分類して幼植物耐塩性を比較したところ、皮裸性、小穂非脱落性が同じ場合、二条品種と六条品種の間では有意差がなく、また、皮裸性と小穂非脱落性の組合せによって耐塩性の強弱が逆転した。同質遺伝子系統を用いて幼植物の耐塩性を比較したところ、品種群でみられた条性、皮裸性の間における耐塩性の差異は、品種群の遺伝的背景の差異によるものとみられた、一方、並渦性でみられた耐塩性の差異は主働遺伝子の副次的効果によるものとみられた

オオムギの組換え型自殖系統、同質遺伝子系統、および倍加半数体系統を用いた発芽時における耐塩性の遺伝解析

To determine the relationship between morphological markers and salt tolerance at germination in barley (Hordeum vulgare L.), a total of 125 recombinant inbred (RI) lines of Russia 6×HES 4, a seriesof 70 isogenic (IG) lines for V/ν gene derived from Russia 6×HES 4, and 145 doubled haploid (DH) lines of Leger×CI 9831 were evaluated for their salt tolerance at germination. Comparison between each set of character pairs revealed that the six-rowed type was significantly more tolerant than the two-rowed type in the RI and IG lines of Russia 6×HES 4, annd the two-rowed type and the short haired rachilla type were significantly more tolerant than the six-rowed type and the long haired rachilla type in the DH lines of Leger×CI 9831. On the other hand, no significant difference was observed in salt tolerance such as the smoothness of awn, ear density, and lemma color, r (awn type), l (ear density), and Re-2 (lemma color) genes inherited independent of gene(s) for salt tolerance at germination.オオムギの発芽時みおける耐塩性と形態マーカーとの連鎖関係を調べるために、Russia 6×HES 4の交雑から養成した組換え型自殖系統125系統と同質遺伝子系統70系統、およびLeger×CI 9831の交雑から養成した倍加半数体145系統の種子を1.5％の塩化ナトリウム溶液を用いて20℃、12時間日長の条件で発芽させ、置床後10日後に調査してシュートを25mm以上抽出した種子の置床種子に対する割合をもって発芽時の耐塩性とした。各種主働遺伝子が発芽時の耐塩性に及ぼす影響を解析するために、組換え型自殖系統、同質遺伝子系統、および倍加半数体系統を親品種間の間で異なる形質によって群別し、発芽時の耐塩性を比較した。その結果、Russia 6×HES 4の組換え型自殖系統、および同質遺伝子系統においては六条型は二条型よりも耐塩性が有意に強く、また、Leger×CI 9831の倍加半数体系統においては二条型は六条型よりも、底刺の短毛は長毛よりもそれぞれ耐塩性が有意に強く、条性間の耐塩性の強弱は交雑組合せによって逆転した。一方、芒の粗滑、穂密度、および頴色の比較においては有意差が認められなかった。以上の結果から、条性を支配するν遺伝子、および底刺のタイプを支配するs遺伝子と発芽時の耐塩性を支配する遺伝子との関連性が推察された。また、芒の粗滑を支配するr遺伝子、穂密度を支配するl遺伝子、および頴色を支配するRe-2遺伝子と発芽時の耐塩性は独立であると考えられた

Genetical Studies on Callus Growth and Plant Regeneration from Immature Embryos in Barley

Immature embryos of 99 varieties of barley were cultured to investigate the ability of callus growth and plant regeneration. These two in vitro traits showed wide and continuous variations among the barley varieties tested. Ability of callus growth, which were evaluated by callus diameter ranged from 3.9mm to 11.2mm, and ability of plant regeneration from the calli ranged from 0% to 100%. A set of complete diallel crosses was made using six cultivars as the parents which differed in ability of callus growth and plant regeneration. The Vr/Wr graphical analysis showed that there were epistasis, or interaction among nonallelic genes for callus growth. As to ability of plant regeneration, no epistasis existed in the subdiallel without P1 (J232) which showed high specific combining ability, and it was controlled by a simple additive dominance genetic system. The mean degree of dominance(0.42) was relatively low and the broad(0.86) and narrow(0.78) sense heritabilities were high.オオムギ培養細胞の再分化の制御や細胞選抜の実用化に寄与するために、植物体再分化能の遺伝様式を解析した。未熟胚培養系においては世界各地の99品種についてカルス生長量及び植物体再分化能の調査を行ったところ、両形質共に連続的な変異を示し、複数の遺伝子あるいは微動遺伝子が関与していることが推察された。カルス生長量及び植物体再分化能の遺伝様式を調べるために、6品種で正逆総当たり交雑を行い、ダイアレル分析を行った。カルス生長量については、非対立遺伝子間の相互作用（エピスタシス）があると推察された。一方、植物体再分化能については、特定組み合わせ能力が高かったP1（J232）を除いた副ダイアレルの分析によって、植物体再分化能の遺伝変異は主として遺伝子の相加効果によるものと推察され、その平均優性度は0.42であった。遺伝率の推定値は狭義で0.78、広義で0.86といずれも高かった

Asymmetric auxin distribution establishes a contrasting pattern of aerenchyma formation in the nodal roots of Zea nicaraguensis during gravistimulation

Auxin distribution is essential for determining root developmental patterns. The formation of lateral roots and constitutive aerenchyma, which is a gas space developed through cell death, is regulated by auxin in rice (Oryza sativa). However, it is unclear whether the involvement of auxin in constitutive aerenchyma formation is conserved in other species. In this study, we found that constitutive aerenchyma formation was regulated by auxin in the nodal roots of Zea nicaraguensis, a wild relative of maize (Zea mays ssp. mays) grown naturally on frequently flooded coastal plains. Subsequent gravistimulation (root rotation) experiments showed opposite patterns of aerenchyma and lateral root formation. Lateral root formation on the convex side of rotated roots is known to be stimulated by a transient increase in auxin level in the pericycle. We found that aerenchyma formation was accelerated in the cortex on the concave side of the rotated nodal roots of Z. nicaraguensis. A cortex-specific expression analysis of auxin-responsive genes suggested that the auxin level was higher on the concave side than on the convex side. These results suggest that asymmetric auxin distribution underlies the regulation of aerenchyma and lateral root formation in the nodal roots of Z. nicaraguensis. As aerenchyma reduces the respiratory cost of the roots, constitutive aerenchyma on the concave side of the nodal root may balance resource allocation, thereby contributing to the uptake of water and nutrients by newly formed lateral roots. Our study provides insights into auxin-dependent asymmetric root patterning such as that of gravistimulation and hydropatterning response

Identification of QTL Controlling Flooding Tolerance in Reducing Soil Conditions in Maize (Zea mays L.) Seedlings

We investigated the tolerance to flooding in reducing conditions of five maize inbred lines and identified a quantitative trait locus (QTL) for the trait. Flooding treatment with 0.1% to 0.4% starch solution for 14 d reduced soil redox potential to about – 200 mV, mimicking reducing conditions in soil. Treatment with 0.2% starch revealed wide varietal differences in dry matter production among the five maize inbred lines. We identified the QTL for flooding tolerance in reducing conditions in a population of 178 F2 plants derived from a cross of inbred lines F1649 (tolerant) and H84 (sensitive). Flooding tolerance, evaluated as the degree of leaf injury following treatment with 0.2% starch solution, revealed wide variation in the F2 population. Amplified fragment length polymorphism (AFLP) markers linked to flooding tolerance gene(s) were screened with 64 AFLP primer combinations using 15 of the 178 F2 plants from each extreme representing the ‘tolerant’ and ‘sensitive’ plants, and found 11 AFLP markers associated with flooding tolerance. Of these, 10 co-segregated and were assigned to chromosome 1. Six SSR primer pairs around these markers were used to construct a linkage map. Composite interval mapping analysis revealed that a single QTL for degree of leaf injury was located on chromosome 1 (bin 1.03-4). Another QTL for flooding tolerance, evaluated as dry matter production under flooding with 0.2% starch, was located at the same position. These results suggest the potential to increase productivity by transferring flooding tolerance genes from F1649 to elite maize inbred lines