配合力和杂种优势的评价是有利于确定育种目标和方向。当前还缺乏对美国南部长粒水稻的配合力和杂种优势的评价。我们为评估如产量、株高、穗数、穗长、稳重及第一次枝梗数等参数，１９８９年我们完成了两个４×４双列杂交试验，１９９０年在Ａｒｋａｎｓａｓ（阿肯萨斯）位于Ｓｔｕｔｔｇａｒｔ附近的水稻研究推广中心和Ｍａｒｉａｎｎａ的棉花试验站两个地点，对３２个杂交种Ｆ１和１６个亲本进行了研究。这１６个亲本是美国南部对育种者有效的长粒水稻种质资源中最优秀的代表。小区试验为单本插植，株、行距６１ｃｍ，一般配合力（ＧＣＡ）比特殊配合力（ＳＣＡ）更重要，即占产量变异的７０％，株高变异的８９％，穗数的８４％，穗长的６０％，穗重的６９％，第一次枝梗的８５％，除了穗数之外，其他性状的特殊配合力也是很明显的，这表明非加性基因的效应是很重要的。在确定杂交组合时，仅用中亲值不能充分地预测后代的平均特性。高值亲本的杂种产量优势变化范围为－１６％～１８％，产量的杂种优势基本上是穗重大于穗数。通过应用杂交水稻品种将可能提高美国南部长粒水稻的产量。 Combining ability and heterosis evaluation is conducive to determine the breeding goal and direction. There is still a lack of evaluation of the combining ability and heterosis of long-grain rice in southern United States. In order to assess parameters such as yield, plant height, spike number, spike length, robustness and number of first branches, we completed two 4 × 4 diallel cross tests in 1989, two in 1990 in Arkansas, 32 hybrid F1 and 16 parents were studied at two sites, the Rice Research and Extension Center near Stuttgart and the Cotton Experiment Station at Marianna. The 16 parents are the best representatives of breeder-use long-grain rice germplasm in the southern United States. The cell-plot test was single-planted with the plant spacing of 61 cm. GCA was more important than SCA, accounting for 70% of yield variation, 89% of plant height variation, 84% of panicle number, The spikelet length is 60%, the spike weight is 69%, and the first branch stem is 85%. Besides the number of spikes, the special combining ability of other traits is also obvious, which shows that the effect of non-additive genes is very important . When determining crossover combinations, only median progeny can not adequately predict the average characteristics of offspring. The heterosis of high-yielding parents varied from -16% to 18%, and the heterosis of yield was basically greater than panicle weight. The use of hybrid rice varieties will likely increase the yield of long-grain rice in the southern United States.