Abstract: The heterosis and combining ability of root activity and its declined properties in indica hybrid rice were investigated by way of 4×4 incomplete diallel cross design with four sterile lines and four restorer lines. The results showed that h_B² in root activity and its declined value was higher than 85 percentage, suggesting that they may be used as the indexes of selecting excellent root in rice breeding. The estimates of both combing ability (GCA and SCA) variances were highly significant for two traits, showing root activity and declined value existed for both additive and non-additive effects, but the former was affected mainly by non-additive effect, while the latter mainly by additive effect. Longtefu A and Zhenhui 048 had higher GCA and larger variance values of SCA, which implies that they can be utilized as superior parents in rice breeding. The mean heterosis of root activity and declined value were positive (it was excellent for the negative mean heterosis of the latter), showing it was difficult to improve root physiological activity trait, but the quality hybrid might be obtained because of the difference among crosses.

Key words: hybrid rice, root activity, heterosis, combining ability

摘要： 利用籼型水稻4个不育系和4个恢复系配组的4 ×4 不完全双列杂交，对其根系活力及其衰退特性进行了杂种优势和配合力分析。结果表明，（1） 根系活力及其衰退值的广义遗传力均大于85％，说明两者可以作为育种指标。（2）两个性状的一般配合力及特殊配合力方差均极显著，说明基因加性效应和非加性效应均起重要作用，但根系活力以非加性效应为主，而其衰退值以加性效应为主。（3）龙特甫A和镇恢084具有较高的配合力和较大的特殊配合力方差，可作为优良亲本利用。（4）根系活力及其衰退值均表现正向优势（衰退值负向优势为好）,表明利用杂种优势改良根系生理活性这一性状比较困难，但通过亲本的适当选配仍能获得强优势组合。

关键词: 杂交水稻, 根系活力, 杂种优势