Re-evaluation of alien wild genes in rice

考虑到遗传侵蚀在世界范围内正在加速发生，评估和利用外来基因是当务之急。为了克服与外来物种基因转移相关的困难，我们必须了解更多关于作物基因组醇的基本知识。在这里，我们研究了在育种中利用野生稻亲缘关系的限制条件。当从野生稻中导入一段6号染色体到栽培品种中时，检测到单向杂交不亲和性。当用粳型授粉时，含有切段的植株结实率降低，反之则表现为正常结实率。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，该片段上存在一个控制母本不亲和性的基因和一个控制父本亲和性的基因(S)。此外，与籼型和野生稻相比，粳型的结实率有降低的趋势。将7号染色体的一段引入普通野生稻的栽培形式后，也对其进行了检测。由于杂草类型在渗入后仍经常显示红色的果皮，因此该节段上的遗传差异还有待研究，这表明该节段在自然条件下的适应意义。分离到两个显性基因，位于该片段上。其中一种只对营养阶段的矮小有影响。另一个基因负责光敏性。检测到扭曲的片段，随着植株变得类似于栽培类型，引入的片段似乎很快就被消除了。因此，为了有效利用外来基因，需要研究不同类群之间的内部约束。

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.