Elucidation of inheritance and physiology factors to decide root system structure in rice.

在大田条件下，对水稻品种冠根的生长方向进行了研究。印尼地方品种的冠根比孟加拉地区的地方品种和日本品种的冠根更粗，更接近土壤表面。各品种冠根的生长方向变化趋势与暗条件下发芽后的生长方向变化趋势基本一致。因此，在黑暗条件下萌发后冠根的生长方向可以作为田间根系结构的指标。在火烧地栽培的高地，其生长趋势与印尼本地品种相似。此外，我们还证实了在老挝北部火烧地栽培的高地的冠状根分布在土壤表层之下。接下来，我们研究了根的向重力性和向气性反应之间的相互作用。这些结果表明，印尼地方品种根的向重力性敏感性强于向氧性敏感性。与日本低地稻品种和孟加拉地区地方品种相比，我们用日本低地稻品种与印尼地方品种杂交的F_2和F_3植株研究了冠根生长方向的遗传背景。这些结果表明，冠根的生长方向可能受两个或两个以上的基因控制。此外，向气性敏感性比向重力性敏感性更上级的性状似乎是一个优势性状。这些结果将为根系结构的育种提供有用的信息。

We investigated the growth direction of the crown roots of rice cultivars in field. The crown roots of the native variety in Indonesia grew much coarse crown roots near to the soil surface compared with the native variety in the Bengal area and Japanese rice cultivar. The trend of the growth direction of crown roots in each cultivar was similar that which had been observed immediately after the germination in dark condition. Therefore, these results indicated that the growth direction of the crown root immediately after germinating in dark condition might be the index of the root system structure in field.We studied the growth direction of crown roots of the cultivated rice strains which had been collected in Thailand and Lao. The tendency of the upland rice which had been cultivated in the burnt field was similar to the native varieties of Indonesia. In addition, we confirmed that the crown roots of the upland rice cultivated to the burnt field in north Lao were distributed just under soil surface.Next, we investigated interactions between the gravitropic and the aerotropic response of the root. These results suggested that the sensitivity of the gravitropism in the root of the native variety of Indonesia was stronger than the sensitivity of the aerotropism Compared with that of Japanese lowland rice cultivars and the native cultivars in the Bengal area.we examined the genetic background concerning the growth direction of the crown roots by using F_2 and F_3 plants of hybrid between Japanese lowland cultivar and Indonesian native cultivar. Those results showed that the growth direction of crown roots might be under the control of two or more genes. In addition, the character which aerotropic sensitivity is more superior to the gravitropic one seems to be a dominant character. These results will give useful information for breeding of the root system structures.