通过60Co衰变产生的r射线辐照籼稻品种“双科早”，获得小粒密穗突变体sep1，该突变体与野生型双科早相比表现为籽粒变小，穗轴变短，着粒密度增加。主茎切片观察结果显示，突变体维管束数和单位面积细胞数均比野生型多。遗传分析和等位性分析结果表明，该突变体为隐性突变，与已克隆的直立密穗基因不等位。利用InDel分子标记将小粒密穗基因sep1定位在第5染色体着丝粒附近的两个标记XP2628与XP2631之间，物理距离约为3.896 Mb。此外，还利用该突变体开展了相应的育种利用研究，已获得高代稳定的不育系材料。
By 60Co rray radiation, a small grain and dense panicle mutant sep1 was obtained from the indica variety Shuangkezao. Compared to the wild type Shuangkezao, it was a mutant with smaller grain, shorter spikestalk but more grain number per panicle. The histological slice observation of the main stem showed that the mutant had more vascular bundle number in one cycle and more cell number per unit area than the wild type. Genetic and allelism analysis results showed that the small grain and dense panicle mutant was controlled by a recessive gene, and it was different to the dense panicle genes which had been already cloned. Then by constructing the genetic segregated population and using the InDel markers, the small grain and dense panicle gene was mapped on the centromeric region of chromosome 5 between marker XP2628 and XP2631. In addition, the breeding application of the mutant was carried out on CMS lines and the stabile lines of high generations had finally been obtained.
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