湛水条件下においてダイズの胚軸に形成される二次通気組織量の品種間差異

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湛水ストレスに対して適応性の高いダイズ品種を検索する目的で，ダイズ30品種を供試し，胚軸における二次通気組織の形成量と畑および湛水条件下での生育を調査した．水田土壌を充填したポットに播種し，初生葉展開時から適宜灌水して栽培する畑区および土壌表面まで湛水する湛水区の2処理区を設定し，処理開始後18日目に材料の採取を行った．その結果，湛水区における30品種平均の全乾物重および地上部，地下部別乾物重は畑区に比べていずれも小さく，湛水ストレスによって生育が抑制されたことが明らかであった．T／R比は湛水区で大きく，特に低酸素の影響を直接受ける地下部の抑制程度が大きかった．耐湿性程度（乾物重比＝湛水区全乾物重／畑区全乾物重×100）は，最大はアソアオガリの101.26％，最小はトヨムスメの76.93％であったが，5％水準で品種間には有意差が認められず，品種間差異を検出するためには処理期間を長期に設定し，比較集団を大きくするなどの必要があると考えられた．一方，胚軸における二次通気組織の形成量はいずれの品種においても畑区に比べて湛水区で著しく大きく，品種間に有意差が認められたことから，育種的手法により二次通気組織の形成量の大きい品種育成の可能性が示唆された．また，本実験に供試した品種の中で，耐湿性程度が最も高かったアソアオガリは二次通気組織の形成量も極めて大きいことから，耐湿性の強いダイズを育成する上で有望な品種であると考えられた．To select soybean cultivars with morphological and anatomical adaptations to flooding stress, the relationships between amount of secondary aerenchyma in hypocotyls and plant growth were examined by using the seedlings of 30 Japanese cultivars grown under flooded as well as under non-flooded conditions. The seeds were sown in paddy soil in plastic pots. When primary leaves were fully expanded, half of the pots were flooded and the water surface was kept as same as the soil level, and the rest was observed under non-flooded conditions. Plants were treated for 18 days. The total, top and root dry matter averages over 30 cultivars grown under flooding were lower than those grown under nonflooding. T/R ratio of flooded plants was higher than that of non-flooded ones. It seems that low 0_2 environments in the rooting zone inhibited their root growth. Flood tolerance rating (dry matter ratio = dry matter under floodingdry matter under non-flooding × 100) was the highest in cv."Aso aogari"(101.26%) and the lowest in cv."Toyomusume"(76.93%). But varietal difference in this rating was not significant at the 5% levels. It is suggested that identification of flood tolerant soybean cultivars may require selection for continued growth under flooding or using many comparative varieties. On the other hand, the amount of secondary aerenchyma in hypocotyl of 30 cultivars grown under flooded conditions was greater than that of non-flooding. Varietal difference of the ratio of secondary aerenchyma area to stele area under flooding was significantly different in cultivars. From these finding, it seems possible to breed the cultivar with high amount of secondary aerenchyma formation. Furthermore, cv."Aso aogari" was the highest in flood tolerance rating and the amount of secondary aerenchyma, so that this cultivar may be available for the breeding of flood tolerance.
九州大学農学部附属農場,University Farm, Kyushu Universityの論文
2001-09-03

湛水条件下においてダイズの胚軸に形成される二次通気組織量の品種間差異

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