Re-evaluation of alien wild genes in rice

考虑到世界各地正在加速发生的遗传侵蚀，迫切需要评估和利用外来基因。为了克服外源基因转移的困难，我们必须了解更多关于作物基因库的基本知识。在这里，我们研究了在育种中使用野生稻近缘种的限制。单向杂交不亲和性检测时，从野生稻6号染色体的片段被引入到一个栽培品种。当以粳稻型授粉时，具有该片段的植株表现出降低的结实率，而相反的植株表现出正常的结实率。细胞组织学观察表明，胚乳发育迟缓导致种子败育。遗传实验表明，在母本中控制不亲和性的基因以及在父本中控制亲和性的基因位于该片段上。此外，与籼稻和野生稻相比，粳稻类型倾向于表现出降低的结实率。将第7号染色体的一个片段导入普通野生稻的栽培型后，也进行了检测。该片段的遗传多样性有待进一步研究，因为杂草型在渐渗后仍经常出现红色果皮，表明该片段在自然条件下具有适应性。在该片段上检测到2对显性基因。一个是负责身材矮小，只有在营养阶段。另一个基因负责光敏性。检测到扭曲的分离，并且随着植物变得与栽培类型相似，引入的片段似乎很快被消除。因此，需要研究不同类群之间的内部约束，以便有效地利用外来基因。

Considering that genetic erosion is occurring at an accelerating rate through the world, it is urgent to evaluate and use alien genes. To overcome difficulties associated with gene transfer from alien species, we must learn more about the basic knowledge on crop genepools. Here, we examined constraints in using wild rice relatives in breeding.Unidirectional cross-incompatibility was detected when a segment of chromosome 6 was introduced from wild rice into a cultivar. When pollinated by Japonica type, the plant with the segment showed reduced seed setting while the reciprocal showed normal seed setting. Cytohistological observations revealed that retardation of the endosperm caused abortion of seeds. Genetic experiments revealed that a gene controlling incompatibility in the female parent as well as a gene (s) controlling compatibility in the male parent was located on the segment. Furthermore, Japonica type tended to show reduced seed setting compared to Indica type and wild rice. A segment of chromosome 7 was also examined after introducing it into a cultivated form from a common wild rice. The genetic diver-gence on the segment is needed to be studied since weedy forms frequently show red pericarps even after introgression, suggesting the adaptive significances of the segment under natural conditions. Two dominant genes were detacted to be located on the segment. One was responsible for short stature only in the vegetative phase. The other gene was responsible for photosensitivity. Distorted segreations were detected and the introduced segment seemed to be quickly eliminated as the plants become similar to cultivated type. Thus, internal constraints between different taxa are needed to be studied for efficient uses of alien genes.