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

从γ射线辐照水稻品种金宝津种子中同时诱导出一个突变基因和一个隐性的长颖基因。该增变因子由细长颖基因的回复突变激活，在许多位点诱导各种类型的突变。本研究的目的是探索将突变基因导入育种实践的途径。1.研究了在细长颖株系中出现的具有突变基因的非细长颖株（M_1）的M_3代的农艺性状。结果表明，诱变所引起的农艺性状遗传变异较大，且常具有突变体所特有的方向。据指出，高产突变体相当容易获得。2.用诱变剂诱导的抽穗期突变体与γ射线诱导的抽穗期突变体的农艺性状进行了比较。诱变剂和γ射线都能引起单性状的突变，也能引起多性状的突变。3.突变基因和标记基因之间的等位性测试显示，该致变因子至少在7条不同染色体1、2、3、4、5、9和11.4上的位点上诱导突变。以一个细长颖株系与三个品种杂交的F_3代的细长颖株系为材料，测定了非细长颖株的出现频率，以此作为突变体活性的指标。结果。除了原始品种Gimbozu的遗传背景之外，在各种遗传背景中也保持了突变体活性。5.从以上结果可以得出结论，该诱变剂是一种新的诱变剂，其诱变力可与γ射线相媲美。

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.