为探讨我国北方不同年代玉米产量杂种优势的演变规律，能够为玉米品种的改良提供理论依据。选用我国北方1970s、1980s、1990s、2000s 4个年代在生产中大面积推广应用的玉米单交种及其亲本为试材，在三个种植密度下比较分析了品种更替过程中产量杂种优势的演变特征。结果表明，我国北方单交种更替过程中绝对杂种优势随年代的推进逐渐增加，低密度、中密度、高密度下绝对杂种优势平均增加比率分别为3.9%、7.9%和18.8%，而相对杂种优势、中亲优势及杂种优势指数在低密度、中密度下略有降低趋势，在高密度下略有增加趋势；超高亲优势年代间变化较为平缓，1980S-1990S品种超低亲优势显著低于1970S。通过以上分析表明，低密度下杂种优势对产量的贡献率较大，随着密度的增加杂种优势越来越小，说明非杂种优势因素对产量的贡献率越来越大。
英文摘要:
In order to study the evolution law of yield heterosis of different era maize variety in north China and provide theoretical basis for the improvement of maize varieties, the evolution characteristics of yield heterosis in the process of maize variety replacement in north China were compared and analyzed under the three planting density using the large-area popularization single-cross maize variety and their parents of 1970s, 1980s, 1990s and 2000s in north China were used as experimental materials. The results showed that the absolute heterosis in the process of single-cross variety replacement in north China gradually increased with the advancement of the era and the average increase rates of absolute heterosis were3.9%, 7.9% and 18.8% respectively under the low density, medium density and high density. However, the relative heterosis, mid-parent heterosis and heterosis index all took on the decreasing trends slightly under the low density and medium density while those of the high density slightly increased; the over high-parent heterosis of different era maize variety changed more gently and the over low-parent heterosis of 1980s and 1990s maize varieties were obviously lower than that of the 1970s. The analysis above shows that the contribution rate of heterosis for yield is larger under the low density while it is lower with the increase of density, which shows that the contribution of the other factors for yield is bigger.
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