【作者】 蔡丽艳；

【导师】 石凤翎；

【作者基本信息】 内蒙古农业大学 ， 草业科学， 2010， 博士

【摘要】 为了解苜蓿杂种优势形成的机理,促进优良杂交苜蓿的选育,本试验以8个苜蓿雄性不育系和4个具有优良性状的苜蓿品种(或种)为亲本,采用不完全双列杂交设计(NCⅡ),配置32个杂交组合。研究了苜蓿杂种优势形成的农艺学和生理学的性状表现;在基因调控水平上,探讨了基因差异表达模式与杂种优势表现的关系,进一步分析了杂种产量优势形成的机理。主要研究结果如下:(1)对各亲本牧草产量配合力效应的研究发现,亲本一般配合力基因型方差所占比重为71.18%,说明基因型加性效应对杂种产量性状的形成起主导作用。不育系一般配合力对杂种牧草产量优势形成的影响大于特殊配合力,其中2号、10号和12号不育系一般配合力较大,具有较高的利用价值。在各杂交组合中,竞争优势大于40%的组合有2×Ⅱ、2×Ⅲ、4×Ⅰ和12×Ⅰ。(2)据牧草产量及其杂种优势效应,将32个杂交组合分为强优势组、弱优势组和中间优势组3类。强优势组二年生第一茬的牧草产量(43.02g/株)及其杂种优势(41.88%)均显著高于弱优势组合(P<0.01)。在9个产量性状中株高、分枝数、主茎粗和节间数与牧草产量杂种优势呈极显著正相关(P<0.01)。(3)影响牧草产量杂种优势形成的主要光合生理指标为水分利用效率,其次为净光合速率。水分利用效率和净光合速率高,干物质合成量大,则有利于产量杂种优势的形成。蒸腾速率和叶绿素含量对杂种优势形成的影响不明显。(4)利用cDNA-AFLP技术,对不同物候期叶片的基因差异表达进行了分析。14对引物共检测出8577条稳定的谱带,差异表达基因占14.77%。现蕾期的差异表达基因较多,占总差异表达基因的20.27%,分枝期较少,仅占8.31%。共有6种基因差异表达类型,其中杂种特异表达类型(UNF1)和母本表达沉默类型(UNP1)对牧草产量杂种优势的形成起主要作用。在返青、分枝和现蕾期,UNF1与牧草产量优势显著正相关(r=0.8726)。(5)随机克隆了12个杂种与亲本差异表达的基因片段,这些基因在GenBank中均有相似性大于75%的同源性核酸序列,其中有6条基因片段与编码的蛋白质序列具有较高的同源性(相似性≥42%),由同源蛋白质的功能进一步推测苜蓿产量优势的形成涉及基础代谢、物质运输、转录调控、信号转导等代谢途径,其中以基础代谢途径为主。更多还原

【Abstract】 Study the formation mechanism of heterosis in alfalfa was important for the breeding of hybrid alfalfa. This study configured 32 hybridized combinations using incomplete diallel cross design (NCⅡ), and 8 alfalfa male sterile lines as female parents and 4 alfalfa varieties (or species) with superior characters as male parents. The research studied the character performance of alfalfa heterosis in agronomy and physiology, and investigated the relationship between heterosis and gene differential expression in gene regulation level, and further analyzed the formation mechanism of yield heterosis. The main results were as follows:(1) Combining ability effect of forage yield showed that the genotypic variance proportion of general combining ability of all parents was 71.18%,therefore,additive effect of genotype played a leading role on the formation of hybrid yield characters. General combining ability of cytoplasmic male sterility(CMS) had a significant impact on the formation of forage yield advantage of hybrid than specific combining ability. CMS 2, 10 and 12 had a higher general combining ability and utilization value. Strong heterotic combinations were 2×Ⅱ, 2×Ⅲ, 4×I and 12×I respectively,and all of their competitive advantage were more than 40%.(2) 32 hybrid combinations were divided into three kind of combination based on forage production and heterosis analysis, which were strong heterotic crosses, weak heterotic crosses and dominant heterotic crosses. The forage yield (43.02g/strain) and heterosis (41.88%) of strong heterotic crosses were significantly higher than the weak heterotic crosses (P<0.01). Correlation analysis showed that there was a remarkable positive correlation between plant height, branch number, main stem diameter and node number of 8 yield traits and yield heterosis respectively (P<0.01).(3) Water use efficiency was the main indices of photosynthetic physiology that affected forage yield heterosis formation, and followed by net photosynthetic rate. High water use efficiency and net photosynthetic rate leading to higher dry matter synthesis was to facilitate the formation of yield heterosis. But transpiration rate and chlorophyll content had no significant effect on heterosis.(4) Gene differential expression of leaves under different phenophase were analyzed using cDNA-AFLP technology. 8577 stable bands were detected using 14 primers, and proportion of differentially expressed genes was 14.77%. Differentially expressed genes in the squaring period were more than branching period, respectively 20.27% and 8.31%. There were 6 differential gene expression patterns between hybrids and their parents, bands observed only in hybrids (UNF1) and bands observed only in female (UNP1) played a major role on the formation of the yield heterosis. UNF1 was significant positive correlation with forage yield advantage at returning green, branching and squaring period (r=0.8726).(5) 12 gene fragments were randomly cloned that showed differentially expressed between hybrids and parents had homologous nucleotide sequence in the GenBank database, and their similarities were greater than 75%. 6 gene fragments had high homologous sequence with encoded protein sequences (similarity≥42%). The function of homologous proteins was further speculated and the results showed that alfalfa yield advantage had a relationship with a variety of metabolic pathway. They included basic metabolism, biological transport, transcription regulation, signal transduction, in which the basic metabolism was the main.更多还原