【作者】 李小军；

【导师】 李立会；

【作者基本信息】 中国农业科学院 ， 作物种质资源， 2009， 博士

【摘要】 在我国小麦育种和生产中,骨干亲本(Founder Parent或Foundation Genotypes)发挥了至关重要的作用。利用骨干亲本不仅直接培育了众多大面积推广品种,而且还由其衍生出许多具有广泛应用价值的亲本育种材料。但是,在育种过程中发挥重要作用的所有农作物骨干亲本均是根据利用以后的系谱分析总结出来的,而对于骨干亲本是如何从众多的种质资源中衍生出来的?利用骨干亲本能够培育出大量主栽品种的内在本质是什么?这两个事关骨干亲本研究和利用的核心问题,却缺乏系统的理论基础研究。本研究以小麦骨干亲本碧蚂4号及其衍生品种、衍生品种的其他亲本、碧蚂4号的6个姊妹系及其亲本共105个品种(系)为材料,通过表型和基因组扫描分析,试图阐明碧蚂4号之所以成为骨干亲本的内在本质,为探讨小麦骨干亲本形成与演变规律、创造候选骨干亲本提供理论指导。1、碧蚂4号之所以成为骨干亲本的表型特征。通过在陕西杨凌、山东泰安、河北石家庄、四川成都和江苏扬州等5个试验点(分别代表了我国小麦生产的主要生态区,每点3次重复)连续两年的田间种植,并对相关产量性状统计分析,发现碧蚂4号在株高、小穗数、穗粒数、千粒重和有效分蘖等主要产量性状上均优于主栽品种;骨干亲本在千粒重等主要产量因子上对其衍生后代品种具有突出的贡献,而且随着世代的增加,这些产量因子可以通过基因/QTL间的互作表现出超亲遗传。2、碧蚂4号之所以成为骨干亲本的特异位点。利用分布于小麦18对染色体(除了2A、1B和1D)的434对SSR引物(根据Somers遗传图谱,引物间平均距离为5.92 cM),对碧蚂4号、衍生品种及中间亲本进行扫描,发现368(84.8%)对引物在供试品种间表现多态。多态引物在碧蚂4号中共扩增出448个等位变异,其中12个在80个后代品种的分布频率为100%,7个未遗传给后代,其余等位变异的遗传频率变异范围为0.0125~0.9875。其中由157对引物产生的180个等位变异在碧蚂4号后代的遗传频率等于或高于60%。另外,分别与不同子代品种涉及的中间亲本相比较,发现43个碧蚂4号特异等位变异(中间亲本没有该等位变异)遗传了3代。如果以每杂交一次后代保留亲本50%的遗传信息为标准,发现在10个SSR位点碧蚂4号特异等位变异遗传了3代,且在每一代的分布频率均高于它们的理论比例。表明在以上位点碧蚂4号在衍生品种的遗传均受到了不同程度的选择作用。3、碧蚂4号之所以成为骨干亲本的特异基因组区段。在157对碧蚂4号等位变异高频率遗传(在80个后代的遗传频率等于或高于60%)的引物中,以相邻引物间遗传距离小于11 cM为标准,有56对引物在小麦15对染色体(除了3B、4D和7A)上形成20个重要的基因组区段,其中多数区段位于着丝粒附近。每个染色体区段的长度从0~16 cM,其中3D染色体上的Xgwm456和Xgwm341之间距离为0 cM,3A染色体上的Xgwm5~Xbarc67~Xcfa2234~Xwmc264为最长区段,达到16 cM。另外,比较43个产生碧蚂4号特异等位变异(中间亲本没有该等位变异)且3代遗传的引物在染色体上的分布,发现其中6对引物在2B、5B和3D染色体上分别形成Xgwm120~Xgwm47、Xgwm371~Xgwm499和Xgwm645~Xcfd49重要区段,相隔分别为4、2和1 cM。4、碧蚂4号之所以成为骨干亲本的特异位点、特异基因组区段与农艺性状的关联分析。利用228对引物与五个环境所获得的穗长、小穗数、穗粒数、千粒重、有效分蘖、产量和株高等7个重要农艺性状进行关联分析,在q<0.20,发现93对引物与性状相关联,标记对性状的贡献率变异范围为0.0125~0.2672,平均值为0.1219。有38对碧蚂4号等位变异高频率遗传引物与性状相关,等位变异效应比较发现,在其中13对引物碧蚂4号等位变异类型的性状值均不低于或明显高于其他等位变异类型,表现“增产效应”。另外,11对产生碧蚂4号特异等位变异(中间亲本没有该等位变异)且3代遗传的引物与性状相关,其中在Xbarc18位点,碧蚂4号特异等位变异与高的千粒重密切相关。此外,19对与农艺性状相关引物位于碧蚂4号等位变异高频率遗传所形成的重要染色体区段,其中5个区段上的引物与多种性状相关。对于不同位点之间或同一位点不同性状之间,碧蚂4号等位变异既存在正效应也表现负效应,可能与为了达到产量因素的协调发展,不同位点或性状之间存在一定的互作有关。5、碧蚂4号与其他5个骨干亲本的特异位点、特异基因组区段比较分析。碧蚂4号衍生系谱涉及了其他的5个骨干亲本(北京8号、欧柔、阿勃、早洋麦和洛夫林10号),发现它们具有40个共同的等位变异,其中38个在碧蚂4号衍生品种的分布频率大于86%,这些位点都包含于以上的157对碧蚂4号等位变异高频率遗传引物中。6、碧蚂4号与其他5个姊妹系的特异位点、特异基因组区段比较分析。对碧蚂1~6号SSR位点多态性比较分析发现,碧蚂4号具有13个特异位点,碧蚂1和碧蚂4号具有5个相同但与其他姊妹系不同的特异位点,其中2A染色体上的Xgwm425~Xgwm95和6D染色体上的Xcfd42~Xgwm469相隔均为1 cM。用产生碧蚂4号特异等位变异的18对引物对其衍生品种进行系谱追踪,发现在7对引物碧蚂4号特异等位变异在后代的遗传频率高于0.60。进一步的关联分析发现,10个特异染色体位点与株高、穗长、小穗数、穗粒数、千粒重和产量等重要性状相关。7、碧蚂4号之所以成为骨干亲本的遗传特征。综上所述,在主要产量因子上碧蚂4号对其衍生后代品种具有突出的贡献,而且随着世代的增加,产量因子可以通过基因/QTL间的互作表现出超亲遗传;同时,碧蚂4号中存在与重要农艺性状相关的特异染色体位点和区段。这可能是碧蚂4号成为骨干亲本的主要遗传特征。更多还原

【Abstract】 Founder parents have played an important role for the development of wheat in China, which have produced many large-grown varieties or important breeding lines. But all founder parents in different crops were found as a result of summation of the pedigrees. How are founder parents produced from various germplasm? Why can many important varieties be bred through using them? The answers for the two questions are not clear.In order to understand the formation of founder parent Bima 4, explore the evolution law of founder parents and find new founder parents in future, the founder parent Bima 4, its 80 progeny, 17 intermediate parents in the pedigree derived from Bima 4, its 5 sister varieties and the parents (total 105 accessions) were analyzed in this study using agronomic traits and SSR markers.1. Phenotypic trait of founder parent Bima 4. Total accessions were grown in five ecological areas including Yangling in Shaanxi, Taian in Shandong, Shijiazhuang in Hebei, Chengdou in Sichuan and Yangzhou in Jiangsu in 2006-2007 and 2007-2008 seasons with 3 repeats per site and analyzed for seven important agronomic traits. The result indicated that the founder parent Bima 4 was attractive for plant height, spikelet number, grain number, 1000-grain weight and spike number per plant, and had produced prominent contribution to its progeny in main agronomic traits. With the increasing of the generations, there was an enhancement trend for 1000-grain weight. When comparing the change among Bima 4, intermediate parents and the accessions in different generations, transgressive inheritance was found for the agronomic traits, which might result from the interaction among different genes of QTL.2. Important chromosomal loci in founder parent Bima 4. Total ninety-eight varieties in the pedigree derived from Bima 4 were analyzed using 434 SSR markers which are distributed across eighteen chromosomes with the exception of 2A, 1B and 1D with average genetic distances of 5.92 cM among adjacent markers according to the reported literature by Somers et al., of which, 368 (84.2%) were polymorphic. Total 448 alleles were amplified in Bima 4 using the polymorphic markers, of which, 12 alleles could be found in its total progeny, 7 alleles could not be detected in any of them, and the remaining alleles were transmitted to the progeny with the frequencies of 0.0125 to 0.9875. One hundred and eighty alleles were amplified at 157 SSR loci in Bima 4 and could be found in equal or over 60% of the progeny. On the other hand, when compared with intermediate parents in different generations of the pedigree respectively, 43 alleles which were amplified in Bima 4 but absent in 16 intermediate parents could be tracked in the accessions from the first to third generation. If expected parental contribution with Mendelian inheritance is 0.5 for a F2 -derived inbred, the unique alleles of Bima 4 at 10 SSR loci could be tracked from the first to third generation with higher frequencies than theoretical varlues in each generation. This indicated that the chromosomal loci in Bima 4 underwent certain selection pressure during the breeding.3. Important chromosomal regions in founder parent Bima 4. Of 157 SSR markers, where the alleles of Bima 4 were inherited in equal or over 60% of the progeny, 56 markers which distribute 15 chromosomes with the exception of 3B, 4D and 7A formed 20 important chromosomal regions, whose genetic distance was less than 11 cM between adjacent markers, and most of them were round the centromere. The range of genetic distance in the chromosomal regions were from 0 to 16 cM, of which, the distance between Xgwm456 and Xgwm341 on the chromosome 3D is 0 cM, and Xgwm5~Xbarc67~Xcfa2234~Xwmc264 on the chromosome 3A had the longest genetic distance. On the other hand, of 43 markers which amplified unique alleles in Bima 4 and they could be tracked from the first to third generation, 6 markers formed three important chromosomal regions, namely Xgwm120~Xgwm47 on chromosome 2B, Xgwm371~Xgwm499 on chromosome 5B and Xgwm645~Xcfd49 on chromosome 3D with 4, 2 and 1 cM, respectively.4. Association between important chromosomal loci, regions and agronomic traits. Association were tested betweem 228 SSR markers and important agronomic traits (including spike length, spikelet number, grain number, 1000-grain weight, spike number per plant, yield and plant height). At q<0.20, 93 markers were found to connect with agronomic traits using association mapping, and the contribution rate of the markers for agronomic traits was from 0.0125 to 0.2672 with the average of 0.1219. Thirty-eitht markers which amplified the same alleles as Bima 4 in more than 60% of the progeny were connect with agronomic traits, and when comparing the means of agronomic traits among different alleles amplified by the same marker, we found that the values across total varieties which had the same alleles as Bima 4 were equeal or higher than those with other alleles at each of 13 SSR markers, that is to say, the alleles of Bima 4 increased the production of wheat. On the other hand, 11 markers, which amplified unique alleles in Bima 4 and the alleles could be tracked from the first to third generation, were connected with agronomic traits, of which, the allele of Bima 4 at the locus Xbarc18 was correlated with higher 1000-grain weight than other alleles amplified at the same locus. Nineteen markers which were connected with agronomic traits located on the important chromosomal regions mentioned above. The markers on 5 chromosomal regions were related with different traits. The alleles of Bima 4 presented positive or negative effects between different loci or on the same regions for different traits, which might result from certain interaction among different loci or traits in order to reach coordinated development in the breeding.5. Important chromosomal loci or regions in 6 founder parents. Six founder parents including Bima 4, Beijing 8, Orofen, Abbordanze, Early Piemium and Lovrin 10, which were in the pedigree from Bima 4, had 40 common alleles. Of them, the frequencies of 38 alleles were more than 86% in total progeny, and the markers were included in the 157 ones mentioned above.6. Important chromosomal loci or regions in Bima 4 compared with other 5 sister varieties. Through comparing the polymorphic patterns among the 6 sister varieties, we found that Bima 4 had 13 unique alleles, Bima 1 and Bima 4 had 5 common alleles which were different from the remaining 4 sister accessions. Moreover, the genetic distances between Xgwm425 and Xgwm95 on the chromosome 2A and between Xcfd42 and Xgwm469 on the chromosome 6D were 1 cM, respectively. The alleles, which were amplified only in Bima 4 or were common in Bima 4 and Bima 1 but absent in other sister varieties, were tracked in the progeny from Bima 4, and the result indicated that the alleles amplified in Bima 4 by 7 SSR markers accurred in over 60% progeny. What′s more, association test indicated that ten of these special SSR loci were connected with plant height, spike length, spikelet number, grain number, 1000-grain weight, spike number per plant or yield.7. Genetic features of Bima 4 as a founder parent. Through the analysis of this work, we found that Bima 4 had produced prominent contribution to its progeny in main agronomic traits. With the increasing of the generations, there was an enhancement trend for 1000-grain weight. When comparing the change among Bima 4, intermediate parents and the progeny in different generations, transgressive inheritance was found for the agronomic traits, which might result from the interaction among different genes of QTL; on the other hand, there existed important chromosomal loci and regions which were connected with important agronomic traits in Bima 4. This might be basic genetic features of Bima 4 as a founder parent.更多还原