Abstract：Space mutation breeding with the characteristics of high efficiency, large variation rang and short breeding period , is an important way of improving germplasm, broadening germplasm foundation and enriching germplasm resources. In order to understand the mutagenic effect on the combining ability for different inbred lines after spaceflight, three maize(Zea mays L.) inbred lines 08-641, RP125 and 18-599 were used as basic materials for space mutation, some mutation lines obtained from these three inbred lines were used as female parent for three sets of diallel cross design with Mo17, 478, Huangzaosi and so on as male parent according to NCⅡdesign. The combinations were evaluated at two different locations both in Sichuan and Yunnan，and the general combining ability (GCA) for plant yield was analysed . The results showed that GCA of yield per plant in these mutant lines from 08-641 and RP125 decreased compared with their original materials but GCA of yield per plant in the mutant line Y2709 and Y3235 from 18-599 increased significantly. Space mutation had an effect on the combining ability of plant yield traits in three maize inbred lines with different degrees, the overall performance showed that the variation range in the RP125 mutant line was the biggest, the 18-599 mutation line was the second, and the 08-641 mutation line was the smallest. Hybrid heterosis in mutant lines S1449, Y2803, Y3165, and Y3235 performed significantly higher compared with their original material and might have great potential in breeding. These results not only enrich the material basis of corn breeding, but enrich the theoretical content for mutation breeding.
