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

在田间研究了不同水稻品种冠根的生长方向。与孟加拉地区的本地品种和日本水稻品种相比，印度尼西亚本地品种的冠根在接近土壤表面的地方生长得更粗。各品种冠根的生长方向趋势与在黑暗条件下萌发后立即观察到的趋势相似。因此，这些结果表明，在黑暗条件下萌发后冠根的生长方向可能是田间根系结构的指标。研究了在泰国和老挝采集的栽培水稻品种冠根的生长方向。烧地栽培的旱稻的生长趋势与印尼本土品种相似。此外，我们还证实了老挝北部旱地水稻的冠根分布在土壤表面以下。接下来，我们研究了根系向地性和向风性响应之间的相互作用。这些结果表明，与日本低地水稻品种和孟加拉地区本地品种相比，印尼本地品种根系向地性的敏感性要强于向气性的敏感性。以日本低地品种与印尼地方品种杂交的F_2和F_3植株为材料，对其冠根生长方向的遗传背景进行了研究。这些结果表明，冠根的生长方向可能受到两个或多个基因的控制。此外，向风性敏感性优于向地性敏感性的特征似乎是一个优势特征。这些结果将为根系结构的选育提供有用的信息。

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.