摘要：
[Objective] The under-ear internode length determines maize seedling height and ear height,which are two agronomic traits associated with yield and lodging resistance.Heterosis,a wild-spread genetic phenomenon,is widely applied in crop yield and quality improvement.In a previous study,the lengths of the 7th,8th and 9th internodes were found to have a decisive effect on ear height and showed a high degree of heterosis.The aim of this study is to resolve the molecular mechanism of heterosis for comprehensive understanding and utilization ofheterosis.[Method] In this study,the chromosome single segment substitution lines (Single segment substitution lines,SSSLs) derived from continually cross of lx9801 and Chang7-2 were used as the basic materials.Test-crossing populations were constructed by crossing the SSSLs with inbred lines Zheng58 and Xun9058,respectively.The HL(Heterosis loci) of the 7th,8th,and 9th interuode length were detected through two-year and two-point tests.[Result] By using the SSSL×Zheng58 test-cross group and SSSL× Xun9058 test-cross group,the heterosis loci (HL) of the 7th,8th,and 9th internode length were detected through two-year and two-point tests.In 2012,the mid parent heterosis values of the 7th,8th,and 9th internode length in Xunxian were 57.25％ and 78.16％,68.30％ and 75.04％,59.48％ and 62.85％,respectively,and that in Changge were 48.27％ and 63.02％,43.36％ and 54.80％,37.26％ and 42.62％,respectively.In 2013,the mid parent heterosis values of the 7th,8th,and 9th internode length in Xunxian were 23.01％ and 37％,22.69％ and 35.65％,22.20％ and 34.74％,respectively,and that in Changge were 21.86％ and 33.19％,20.99％ and 35.57％,27.55％ and 42.19％,respectively.A total of 18 and 18 length heterosis loci were obtained from the 7th internode,20 and 23 were obtained from the 8th internode,17 and 19 were obtained from the 9th intemode.Compared the same HL of the two test-crossing groups,there are 3,3 and 1 same HL of 7th,8th,9th internode length,respectively.These same HL occupied 12.7％ and 11.6％ of the total HL numbers,respectively.[Conclusion] There were only 7 (6％) same HL sites had same location between SSSL×Zheng58 group and SSSL×Xun9058 group of the 7th,8th,and 9th intemode length,which indicated that the heterotic loci among different groups may be different.It was speculated that under different genetic backgrounds there are different genes controlling the same heterosis traits.The performance of heterotic loci at single gene level should be crossing group (genetic background) specific.%[目的]穗下节间长决定着玉米的株高和穗位高2个重要的农艺性状,并与产量、抗倒性等性状密切相关.前期研究发现玉米穗下第7、8、9节间长对穗位高具有决定作用,并表现出较强的杂种优势.文章拟解析玉米穗下节间长,尤其是穗下第7、8、9节间长杂种优势的决定因子,为全面了解和应用杂种优势奠定基础.[方法]利用以1x9801为遗传背景的昌7-2染色体单片段代换系(single segment substitution lines,SSSL)为基础材料,分别与优良自交系郑58和浚9058构建了两套测交群体,通过两年两点试验对玉米第7、8、9节间长进行杂种优势位点分析.[结果]利用SSSL x郑58测交群体和SSSL×浚9058测交群体通过两年两点试验发现,2 01 2年在浚县的第7、8、9节间长的中亲优势值分别为57.25％和78.16％、68.30％和75.04％、59.48％和62.85％;2012年在长葛的第7、8、9节间长的中亲优势值分别为48.27％和63.02％、43.36％和54.80％、37.26％和42.62％;201 3年在浚县的第7、8、9节间长的中亲优势值分别为23.01％和37.00％、22.69％和35.65％、22.20％和34.74％;201 3年在长葛的第7、8、9节间长的中亲优势值分别为21.86％和33.19％、20.99％和35.57％、27.55％和42.19％;共定位了18个和18个第7节间长杂种优势位点,20个和2 3个第8节间长杂种优势位点,17个和1 9个第9节间长杂种优势位点.2个测交群体第7、8、9节间长相同的HL分别有3个、3个和1个,共有7个HL相同,分别占2个总测交群体中HL数的12.7％和11.6％.[结论]在SSSL×郑58群体定位的第7、8、9节间长HL与SSSL×浚9058群体的定位结果相比仅有7个(6％)相同位点,说明不同群体之间的杂种优势位点差别较大,几乎没有相同的杂种优势位点,推测在不同遗传背景下控制同一性状的杂种优势位点并不相同,据此推论,在单基因水平上,杂种优势位点表现出杂交组合(遗传背景)特异的特征.
