Yuichiro Nakayama

Identification of Polyploid Groups in the Genus Echinochloa by Isozyme Analysis.

温帯東アジアのヒエ属 (Echinochloa) 植物の形態的特徴の変異は非常に大きく, ときに分類群の同定が困難である。そこで, 中国雲貴高原を中心とした外国産および日本産のヒエ属植物の16の分類群または型-E. obtusiflora (2倍体), E. crus-pavonis (2倍体), E. stagnina (4倍体と6倍体), タイヌビエの群 (4倍体: タイヌビエのC型とF型, 非脱粒性タイヌビエ, 栽培型タイヌビエおよび E. phyllopogon), イヌビエの群 (6倍体: イヌビエ, ヒメタイヌビエ, ヒメイヌビエ, ヒエ, リコウビエおよび E. oryzoides) およびコヒメビエの群 (6倍体: コヒメビエおよびインドビエ)-のアイソザイムの変異を分析した。酵素6PGD, AATおよびADHにおいて, 4倍体および6倍体の種は, それぞれの倍数性に応じたバンドの重複を示した。イヌビエの群 (6倍体) とコヒメビエの群 (6倍体) では, アイソザイムパターンは異なっていた。タイヌビエの群 (4倍体) とイヌビエの群 (6倍体) は, 小穂の形態では識別が困難であるが, 群内のアイソザイムの多型はわずかしかみられず, アイソザイムパターンによって倍数性の異なる2群が識別できた。数種の酵素を用いてアイソザイム分析すれば, ヒエ属植物の倍数性群が判別できるので, 分類群の同定が容易となる。

Ecophysiological Traits of Field-Grown Crotalaria incana and C. pallida as Green Manure

Abstract To evaluate the growth capacity and some chemical characteristics of two Crotalaria species, C. incana and C. pallida, used as green manure, we conducted a field experiment at Osaka, Japan. Both Crotalaria species exhibited vigorous vegetative growth, and leaf area was expanded in C. pallida and branching was promoted in C. incan. Top dry weight and nitrogen content of C. pallida were twice as high as those of C. incana at 87 and 120 days after transplanting (DAT), and the lower values in C. incana were attributed to drastic defoliation of lower leaves due to earlier anthesis from mid-July. Several indicators for rapid decomposition of the plants used as green manure, such as C/N ratio, lignin (L) content and L/N ratio at 56, 87 and 120 DAT, were significantly higher in C. pallida than in C. incana. However, these values might not be critical for nitrogen mineralization after incorporation of the materials into soil. To evaluate the qualitative traits of the two species as green manures, the materials were mixed with soil at a rate of 20 g fresh weight per pot, and seeds of wheat were sown at 10 and 30 days after mixing the green manure (DAM). The growth and nitrogen uptake of wheat grown on the soil mixed with C. pallida were inferior to those of wheat grown on the soil mixed with C. incana on both sowing dates, and the difference between the effectiveness of the two species as green manure was larger in the wheat sown on 10 DAM than on 30 DAM. The possible increase in nitrogen supply and growth inhibition by incorporation of these materials to wheat plants were discussed.

Tricalcium phosphate solubilization by root nodule bacteria of Sesbania cannabina and Crotalaria juncea

Genus Sesbania and Crotalaria have high ability to symbiotically fi x atmospheric nitrogen, and to sustain soil productivity when incorporated into soil (Shioya et al., 1990). In our previous studies, we evaluated the contribution of these two legumes used as green manure plants to growth of the succeeding crops (Daimon, 2006). These plant species have also been studied on P (phosphorus) acquisition ability under low P conditions. For instance, Tanaka et al. (1999) reported that S. rostrata exudes malonic and malic acids, having a role of solubilizing Al-P in the medium, in response to lower P level. Various bacteria and fungi in different soils have been reported to solubilize the sparingly soluble P (Barea et al., 2002). The solubilization of P by root nodule bacteria such as Rhizobium, Bradyrhizobium and Mesorhizobium, which solubilize rock phosphate, hydroxyapatite, and/or tricalcium phosphate has been reported (Halder and Chakrabartty, 1993; AbdAlla, 1994; Peix et al., 2001). However, little is known about the ability of rhizobia of Sesbania cannabina and Crotalaria juncea. In this study, we examined the possibility of releasing P from tricalcium phosphate, which is sparingly soluble P in arable land, by the root nodule bacteria with these two green manure legumes.

Variation in phenological and morphological traits of cultivated and wild populations of Arthraxon hispidus collected from Hachijo Island and Kinki district.

日本全土の野原, 畦畔などに生育する形態的変異の大きいイネ科の一年草であるコブナグサは, 東京都八丈島で絹織物「黄八丈」の染料用として栽培されている。栽培の影響による形質の変化を検討するために, 八丈島で栽培されているコブナグサ3系統と野生 (雑草) のコブナグサ11系統および近畿地方の野生のコブナグサ5系統を比較栽培し, 出穂の特徴と形態的変異を調査し, 主成分分析による総合的評価を行った。栽培コブナグサでは, 出穂期間が短く, 分げつ枝が高い同時生長性を示し, 植物体の成熟の均一性が高く, 種子の脱粒性が低く, 葉, 茎, 穂などの器官が大型化する傾向にあった。八丈島の野生コブナグサは多様であったが, いくつかの形質において栽培コブナグサに似る傾向を示した。一方, 近畿地方の野生コブナグサは出穂期間の著しく長い系統があり, 分げつ枝の生長や植物体の成熟がばらつき, 脱粒性も高く, 器官のサイズが全体に小さくなる傾向にあった。主成分分析による第1主成分と第2主成分のスコア散布図は栽培コブナグサと八丈島の野生コブナグサおよび近畿地方の野生コブナグサの変異の状態を良く示し, 栽培コブナグサと八丈島の野生コブナグサは部分的な重なりを示したが, 近畿地方の野生コブナグサは両者と重ならなかった。八丈島の栽培コブナグサでは, 出穂期間や分げつ枝の同時生長性などに栽培行為による無意識的な選択が働いており, さらに, 積極的な栽培によって器官の大型化が進んだと推定された。