Abstract: Using 7 maintainer lines and 9 restorer lines as the materials, the genetic difference of hybrid rice parents and its relation to F₁ heterosis were studied through principal component analysis and cluster analysis of 11 major agronomic characters. The results showed that among all of the 120 genetic distances of the 16 parents, morethan 80% was below 2; the average genetic distances among the 9 restorers and among the 7 maintainers except Xiangxiang 2B were 0. 4793 and 0. 7723, respectively, which indicates that the genetic difference is comparatively small in the existing hybrid rice parents, especially within restorer lines or within maintainer lines. The analysis of Correlation between the genetic distance of both parents and heterosis of their F₁ hybrids showed that there was not correlation between them among the existing hybrid rice parents. However, it was found that the grain yield of F₁ hybrids was closely related to that of both parents, especially to the mean grain yield of both parents, indicating thatparental improvement is of great importance to increase hybrid rice yield. Furthermore, the relation between parental improvement and heterosis, the approaches to the improvement of parents and the principle of choice of pareals for developing hybrids were also discussed.

Key words: correlation, genetic distance, heterosis, hybrid rice, parent

摘要： 以目前生产上大面积应用和新育成的16个籼型三系杂交水稻亲本为材料，根据11个主要农艺和经济性状进行主成分分析和聚类分析，以马氏距离为指标，研究了杂交水稻亲本间遗传差异的状况及其与杂种优势的关系。在16个亲本的120个遗传距离中，80%以上小于2；9个恢复系间的平均遗传距离仅为0.4793， 7个保持系间，除湘香2号B外，平均遗传距离为0.7723。说明现有杂交稻亲本间遗传差异较小，尤其是保持系内和恢复系内遗传差异更小。对亲本间遗传距离与杂种优势的相关分析表明，现有籼型三系杂交稻亲本间遗传差异与杂种优势关系不密切，而杂交稻产量的高低与双亲产量尤其是双亲产量平均值的高低密切相关。说明亲本改良在提高杂交稻产量中极为重要。此外，还对亲本改良与杂种优势的关系、杂交稻亲本改良的方法和途径以及杂交稻组合亲本选配原则进行了讨论。

关键词: 杂交水稻, 亲本, 遗传差异, 杂种优势, 相关关系