【作者】 李芦江；

【导师】 杨克诚；

【作者基本信息】 四川农业大学 ， 作物遗传育种， 2010， 博士

【摘要】 我国是世界玉米生产第二大国和玉米育种较先进的国家,但也是种质资源较贫乏的国家之一。玉米种质资源的贫乏,造成了种质基础狭窄的局面,种质基础狭窄已成为限制我国玉米育种水平进一步提高的主要制约因素,这就客观地要求我们把研究重点放在种质扩增、改良和创新以及杂种优势群和杂种优势模式的研究和构建上。轮回选择是玉米种质扩增与改良的基本方法,能有效地打破基因间的连锁关系,增加优良基因重组的机会,使群体中优良基因频率不断提高,达到改善群体表现的目的,从而为选育优良自交系提供基本素材,进而提高选育自交系及杂交种的效率。本研究以两个玉米窄基群体P3C0和P4C0及其分别经过5轮控制双亲混合选择的改良后代P3MSC1、P3MSC2、P3MSC3、P3MSC4、P3MSC5、P4MSC1、P4MSC2、P4MSC3、P4MSC4和P4MSC5,共12个群体为材料,通过多点田间表型鉴定和配合力测定,研究控制双亲混合选择对不同玉米窄基群体的改良效果；以基础群体P4C0及其经过5轮控制双亲混合选择的改良后代P4MSC1、P4MSC2、P4MSC3、P4MSC4和P4MSC5,P4C0经过1轮半同胞-S2：3(HS-S2：3)轮回选择的改良后代P4HSC1,P4HSC1经过3轮控制双亲混合选择的改良后代P4HSC1-MSC1、P4HSC1-MSC2和P4HSC1-MSC3以及将两个自交系加入到P4HSC1中进行1轮动态改良的群体P4HSC1-AP,共11个群体为材料,通过多点田间表型鉴定和配合力测定,研究不同轮回选择方法对玉米窄基群体的改良效果,并利用SSR分子标记分析不同轮回选择方法对群体遗传多样性的影响,为玉米窄基群体改良方案的完善提供参考；以从2个基础群体P4C0和P5C0及其经过2轮控制双亲混合选择的改良群体P4MSC2、P5MSC2和经过1轮HS-S2：3选择的改良群体P4HSC1、P5HSC1的单株自交后代中,分别选取来自不同基本株的3个田间表现优良的株系(基础群体为S6株系,改良群体为S5株系),共计18个高代选系为材料,通过田间表型鉴定、多点配合力测定和SSR分子标记分析,对这些群体高代选系的育种潜势进行研究,为这些选系的利用及选系策略的制定提供依据。主要研究结果如下：1.控制双亲混合选择对基础群体P3C0和P4C0单株产量和主要构成性状及其一般配合力(GCA)改良效果明显,但对群体与测验种的特殊配合力(SCA)却没有明显的改良效果。经过5轮控制双亲混合选择改良后,两个基础群体P3C0和P4C0改良群体的株高和穗位高及其GCA效应值都随改良轮次增加而显著增加。基础群体P3C0及其改良后代,粒深和穗行数均以P3C0为最小,P3MSC5为最大,其GCA效应值分别以P3MSC2■和P3MSC5为最大；单株产量及其GCA效应值都以P3C0为最小,分别以P3MSC4和P3MSC2为最大。基础群体P4C0及其改良群体,粒深和穗行数均以P4C0为最小,分别以P4MSC5和P4MSC4为最大,其GCA效应值都以P4MSC4为最大；单株产量及其GCA效应值都以P4C0为最小,分别以P4MSC2和P4MSC4为最大。改良群体其余多数性状及其GCA效应值也都大于各自的基础群体,但不同群体的同一性状及同一群体的不同性状,在不同的改良轮次,其改良效果不尽相同。总体趋势表现为,控制双亲混合选择进行到一定世代后,群体一些性状及其GCA能得到同步有效改良,有些性状自身及其GCA的改良效果却不同步。当选择响应到达最大以后,持续的控制双亲混合选择会导致窄基群体的选择增益下降,甚至出现负增益。2.不同轮回选择方法对基础群体P4C0主要性状及其GCA改良效果不尽相同。P4C0经5轮控制双亲混合选择后,群体株高和穗位高及其GCA效应值持续增加,群体主要性状及其GCA都得到较好的改良,单株产量遗传增益主要集中在前2轮,3轮改良以后群体单株产量均值有下降的趋势。P4C0经过1轮HS-S2：3选择后,改良群体P4HSC1产量及其主要构成性状都得到了较好的改良。P4HSC1经3轮控制双亲混合选择后,群体主要性状及其GCA得到进一步改良。将两个与P4HSC1属同一杂优类群的优良自交系加入到群体P4HSC1中,进行1轮动态改良后,群体产量和主要构成性状及其GCA在P4HSC1的基础上得到了进一步改良。以时间计算,控制双亲混合选择对群体P4C0产量和主要构成性状及其GCA改良效果优于HS-S2：3轮回选择,但在植株性状改良上HS-S2：3选择效果较好。以轮次计算,动态改良对群体P4HSC1产量和主要构成性状及其GCA的改良效果优于控制双亲混合选择,但动态改良后,群体株高、穗位高及其GCA效应值有较大幅度的增加。3.经过改良后,群体内优良个体出现频率(粒深大于1.100cm,穗行数大于或等于16行,单株产量大于160g的个体百分比)发生了变化。经过5轮控制双亲混合选择后,基础群体P3C0和P4C0及其改良后代优良个体出现频率随选择轮回增加呈波动增加趋势。P4C0经过1轮HS-S2：3选择后,群体优良个体出现频率较P4C0有较大的提高。P4HSC1经过1轮动态改良后,群体优良个体出现频率较P4C0和P4HSC1均有较大的提高。P4HSC1经过3轮控制双亲混合选择改良后,群体优良个体出现频率随改良轮次增加呈增加趋势,但有一定的波动。4.不同轮回选择方法对基础群体P4C0遗传多样性的影响存在差异。P4C0经过5轮控制双亲混合选择后,在改良的前2轮,多数表征遗传多样性的参数下降不明显,基因杂合度和遗传多样性指数还有小幅度增加。经3轮改良以后,群体杂合度遗传多样性开始下降,虽然衡量群体遗传多样性的参数虽然变化规律不尽相同,但其反映的整体趋势是基本一致的,即在群体改良的低代,群体遗传多样性得到了较好的保持,而多代的改良则会导致群体遗传多样性的下降。P4C0经过1轮HS-S2：3选择后,6个表征群体遗传多样性的参数比P4C0均有较大幅度的下降。P4HSC1经过1轮动态改良后,6个表征群体遗传多样性的参数均有较大幅度的增加。P4HSC1经过3轮控制双亲混合选择改良后,6个表征群体遗传多样性的参数均呈增大的趋势,但每轮增加的幅度均较小5.本地选择和异地选择对基础群体P4C0遗传多样性存在不同影响。P4C0经过5轮控制双亲混合选择后,群体基因型数虽然总体上是减小的趋势,但表现出减少与增加交替出现的现象。在四川改良形成的群体,其基因型数较其上一轮改良群体少,在云南改良形成的群体,其基因型数较其上一代增加。6.不同轮回选择方法创造了不同的遗传变异。将P4C0经过不同轮回选择方法改良的11个群体按来源分为5个类型,第一类包括P4C0,第二类包括P4MSC1、P4MSC2、P4MSC3、P4MSC4(?)(?)P4MSC5,第三类包括P4HSC1,第四类包括P4HSC1-AP,第五类包括P4HSC1-MSC1、P4HSC1-MSC2和P4HSC1-MSC3。分子方差分析结果表明,不同类型间、群体间和群体内的变异分别为6%、5%和89%,说明经过不同的轮回选择方法改良后,群体遗传变异虽然发生了不同的变化,但不同改良群体间的遗传变异仍远远小于群体内的遗传变异。从主坐标分析结果可以看出,基础群体及控制双亲混合选择的早代,群体内个体间的分布相对分散,而高代群体和P4HSC1及以P4HSC1为起始群体的两类改良群体,分布相对集中,随着改良轮次的增加,群体内个体的分布发生了定向变化,且不同选择方法改良后,群体内个体偏移的方向和程度不一致。7.改良群体高代选系在自交代数少1代的情况下,其纯合的位点比例与基础群体高代选系相当,说明用改良群体高代选系纯合速度较快。与基础群体高代选系相比,改良群体高代选系间遗传差异虽有减小的趋势,但仍有较大的遗传差异。8.不同群体高代选系之间,表型及配合力差异较大,来自同一群体不同基本株的选系之间差异也较大,群体高代选系的表型和配合力差异来源于不同群体及基本株的差异。总体而言,改良群体高代选系产量和主要构成性状及其GCA表现优于基础群体高代选系,但值得注意的是多数改良群体高代选系株高、穗位高及其GCA都较各自的基础群体高代选系有所增加。9.改良群体高代选系P4MSC2-1、P4MSC2-2、P5MSC2-2和P5MSC2-3以及基础群体高代选系P5C0-3,自身产量和主要性状及其GCA表现较好,与测验种所配组合产量较高,有较大的育种利用价值。更多还原

【Abstract】 China is the second largest country in maize production all over the world. The maize breeding was relatively advanced, but also the germplasm resources were relatively poor in china. The lack of maize germplasm result in the narrow basis, it was the main factor that block the development of maize breeding. This fact requires us to focus on the expansion and improvement and innovation of germplasm. The recurrent selection is the basic method for the improvement and expansion of maize germplasm. It could break the chain linkage between genes effectively and increase the superior gene frequency continuously. These populations with the performance improved then can serve as a potential source of superior inbred lines and can inhabit development of a possible genetic ceiling for further hybrid improvement. In this study, two synthetic narrow-base maize populations P3 and P4 were improved by 5 cycles of biparental mass selection method to obtain 12 populations. In different ecological environment, the phenotypes of the populations per se were analysis and the combing ability was tested according to an incomplete diallel model to study the effect of MS on different populations. The narrow base population P4 was improved by different recurrent selection method to obtain 11 populations. In different ecological environment, the phenotypes of the populations per se were analysis and the combing ability was tested according to an incomplete diallel model to study the effect of different recurrent selection method on a same population, also the effect of different recurrent selection methods on genetic diversity of populations were analysis by SSR markers with the objective to make suggestions on how to raise the efficiency of improvement and utilization of synthetic populations. Three inbred lines derived from each of the 6 populations, including P4C0, P4MS2, P4HSC1, P5C0, P5MSC2 and P5HSC1, to make a total of 18 lines. The phenotypes of the lines per se were analysis, and the combing ability was tested according to an incomplete diallel model, the genetic diversity of the lines were analysis by SSR markers with the objective to make suggestions on the usage of these lines and generating strategies for deriving lines from a improved population. The main results were summarized as follows: 1. After 5 cycles of biparental mass selection (MS), for both of the base population P3C0 and P4C0, most traits of the populations per se and the GCA were improved significantly, whereas the SCA of most traits showed no significant increase. The mean of plant height and ear height per se and their GCA increased with the advance of selection for the both base populations. For P3C0 and its improved descendants, the mean of kernel depth and rows per ear were smallest at P3C0 and largest at P3MSC5. The GCA effects of them were smallest at P3C0, and largest at P3MSC2 and P3MSC5, respectively. The yield per plant of populations per se and its GCA effects were both smallest at P3C0, and largest at P3MSC4 and P3MSC2, respectively. For P4C0 and its improved descendants, the mean of kernel depth and rows per ear were smallest at P4C0, and largest at P4MSC5 and P4MSC4, respectively. The GCA effects of them were both smallest at P4C0, and largest at P4MSC4. The yield per plant of the populations per se and its GCA effects were both smallest at P4C0, and largest at P4MSC2 and P4MSC4, respectively. For most of the other traits per se and their GCA effects, the improved descendants were larger than their respective CO. There were different effects of improvement on different populations and traits at different cycles. The general trend showed that after cycles of biparental mass selection, some traits of populations per se and their GCA were improved simultaneously, while the improvement of population per se and the GCA did not display a synchronicity for some others. After the largest selection response to biparental mass selection was obtained, a sustained biparental mass selection would lead to a decrease in genetic gain or even a negative genetic gain.2. The effect of different recurrent selection method on the main traits and their GCA were different. After 5 cycles of MS, the mean of plant height and ear height per se and their GCA increased with the advance of selection for P4C0,most traits of the populations per se and the GCA were improved significantly, and the genetic gain were obtain in first 2 cycles, the genetic gain decrease from the 3rd cycle. After 1 cycles of HS-S2:3 selection, most traits of the populations per se and the GCA were improved significantly. After 3 cycles of MS, most traits of the population P4HSC1 per se and the GCA were improved further. After add the inbred lines to the population P4HSC1, most traits per se and their GCA display a significant increase over P4HSC1.In time, the effect on yield and the yield component and their GCA were better than HS-S2:3 selection, but the HS-S2:3 selection was more beneficial to maintain the plant and ear height of population. In turn, adding lines to the population were more effective on the improvement of yield and the yield component and their GCA than MS, but also the plant and ear height increase more.3. After five cycles of MS, the excellent individual frequency increase with the advance of selection with a wave phenomenon for both P3C0 and P4C0.After 1 cycle of HS-S2:3 selection, the excellent individual frequency increase over P4C0. After add the inbred lines to the population P4HSC1, the he excellent individual frequency increase. After 3 cycles of bi-parents mass selection, the excellent individual frequency increase with the advance of selection with a wave phenomenon.4. The effects of different recurrent selection methods on the genetic diversity were different. After 5 cycles of MS on P4C0, the number and the percentage of polymorphic loci displayed a descending trend with the advance of selection, the mean genetic distance represent slightly fluctuate declining. The expected heterozygosity (He) and Shannon genetic diversity index (I) increased in the first two cycles while decreased from the 3rd cycle with the advance of selection. The number of genotype presented the trend of declining with the advance of selection and showed an alternative growth and descends phenomenon related to the location where the populations were developed. The 6 index of genetic diversity decreased after HS-S3, after 3 cycles MS were carried out on P4HSC1 or adding 2 inbred lines into P4HSC1, the genetic diversity of population increase in varying degrees.5. In our study, the number of genotype presented the trend of declined with the selection process. In additional, the number of genotype appears to be related to the location where the populations were developed. When the population was developed in Yunnan province, the number of genotype increased while decreased when the population was developed in Sichuan province.6. The 11 populations devlopeped from P4 by different recurrent selection method were classified into 5 types based on the method the population were improved. The 1st type included P4C0, the 2nd type included P4MSC1, P4MSC2, P4MSC3, P4MSC4 and P4MSC5, the 3rd type included P4HSC1, the 4th type included P4HSC1-AP, the 5th type included P4HSC1-MSC1, P4HSC1-MSC2 and P4HSC1-MSC3.The AMOVA showed that the genetic various among regions, among populations and within populations were 5%, 6% and 89%, respectively. The genetic diversity changed with the advance of selection, while the genetic diversity within populations was much more than that of among populations. The result of principle coordinates analysis showed that the individual distribute in a larger range in the P4C0 and early cycles of MS while the distribution range become smaller in the advance cycles of MS and the P4HSC1 and the populations developed from P4HSC1 by MS and. The directional changes occurred in the distribution of the individual with the advance of selection, but degrees and direction vary from method to method.7. The inbred lines derived from different population, and the inbred lines derived from different basic individual in a same population vary in the phenotype and combing ability.8. The inbred lines P4MSC2-1, P4MSC2-2, P5MSC2-2 and P5MSC2-3 derived from improved population were superior in yield and yield component and their GCA, the hybrid between these lines and the testers were high in yield. In summary, most of the inbred lines derived from the improved population were better than the inbred lines derived from the base population in yield and yield component and their GCA. However the inbred lines derived from the improved population were taller in the plant height and ear height.9. The number and percentage of homozygote of the lines derived from the improved populations were roughly equivalent to that of the lines derived from the basic populations with one inbred generation less. The genetic diversity of the lines derived from the improved population showed a decrease trend, but the genetic diversity was still rich relatively.更多还原