Exploitation of a New Breeding System by the Use of Mutator in Rice

从伽玛辐照的水稻品种金伯祖种子中同时诱导出一个突变基因和一个隐性的细长颖片基因。该突变体由一个细长颖片基因的反向突变激活，在许多位点上诱导各种突变。本研究的目的是探索将突变体引入实际育种计划的方法。1. 对细长颖片系中出现的具有该突变体的非细长颖片植株（M_1） M_3后代的农艺性状进行了测定。结果表明，所诱导的农艺性状遗传变异较大，且往往具有突变体特有的方向。注意到高产突变体是相当容易获得的。2. 将该突变体诱导的若干个抽穗时间突变体与γ射线诱导的抽穗时间突变体进行了若干农艺性状的比较。突变体和伽马射线不仅可以诱导单性状突变，还可以诱导多性状突变。3. 突变基因与标记基因之间的等位基因测试表明，突变子至少在1、2、3、4、5、9和11.4条不同染色体上的位点上诱导突变。用一个细长颖片系与三个品种杂交得到的F_3细长颖片系，测定了非细长颖片植株的出现频率，以此作为诱变活性的判据。因此。除原品种金伯祖外，在不同的遗传背景下，突变体活性也保持不变。综上所述，该突变体是一种具有可与伽马射线相媲美的威力的新型诱变剂。

A mutator and a recessive slender-glume genes were simultaneously induced from gamma-irradiated seeds of a rice variety Gimbozu. The mutator is activated by a reverse mutation of a slender-glume gene, inducing various kinds of mutations at many loci. The objective of this study is to exploit the way of introducing the mutator into practical breeding program. 1. A number of M_3 Progenies of non-slender-glume plants (M_1) which had appeared in slender-glume lines, possessing the mutator, were examined for their agronomic characteristics. The results showed that the genetic variations induced in agronomic characters were quite large and often had the directions peculiar to the mutator. It was noted that high-yielding mutants were rather easily obtainable. 2. A number of heading-time mutants induced by the mutator were compared with gamma-ray induced heading-time mutants for several agronomic characters. The mutator as well as gamma-ray proved to induce not only single-character mutation but also plural-character mutation. 3. Allelism tests between the mutant genes and marker genes revealed that the mutator induced mutations at least at the loci on seven different chromosomes 1, 2, 3, 4, 5, 9 and 11.4. A number of F_3 slender-glume lines derived from the crosses between a slender-glume line and three varieties were examined for the appearance frequency of nonslender-glume plants as a criterion of mutator activity. As a result. mutator activity is kept also in various kinds of genetic backgrounds other than that of the original variety Gimbozu. 5. From the above findings, it was concluded that the mutator is a new mutagen having the power comparable with that of gamma-ray.