【作者】 徐保钦；

【导师】 陆作楣；

【作者基本信息】 南京农业大学 ， 作物遗传育种， 2009， 博士

【摘要】 杂交稻制种田发生穗发芽是一种自然灾害,几十年来一直是杂交稻种业生产上亟待解决的难题。在我国杂交稻制种大省四川,冈优系列、D优系列、Ⅱ优系列杂交制种经常受到穗发芽的威胁,严重年份甚至会影响到种子外调数量。在另一个制种外销大省江苏省,汕优、协优、冈优、特优、Ⅱ优系列制种生产上穗发芽也十分普遍。2007年9月底至10月初的“罗莎”台风使江苏省北部地区的数万亩杂交稻制种田发生不同程度倒伏,伴随着数天阴雨,穗发芽现象严重发生。据盐都、建湖、阜宁、金湖等地反映,许多田块杂交稻种子的穗发芽率超过40%。有些制种农户生产的种子经过筛选、漂选,合格种子产量仅有750kg／hm2左右,经济损失惨重。据粗略估计,全国每年有13.3万公顷左右的杂交稻制种田,年平均穗发芽率在10%左右,由此每年造成的种子损失在3500万kg左右,价值达7亿元人民币,至于重灾年份,损失更加严重。水稻是自花授粉作物,利用不育系制种时,类似于异花授粉作物,不育系开颖角度大,部分种子稃壳闭合不全,形成裂颖种子。杂交稻制种时为了解决不育系包颈问题,在抽穗期喷施“九二零”已经成为一项常规措施,而“九二零”具有促进种子发芽的作用。我国杂交稻主要制种地区在收获前常会遇到阴雨和台风等灾害性天气的影响,这些都是造成杂交稻种子穗发芽较重的原因。但是,从根本上说种子休眠性强弱是影响种子穗发芽发生程度的主要原因。赵明等(2004)研究发现生产上常见的籼稻不育系和保持系休眠性相当弱或者无休眠性,恢复系的休眠性大部分较差,少部分具有一定的休眠性,生产上还没有抗穗发芽的杂交稻组合。因此,现在迫切需要改良杂交稻亲本种子的休眠性,培育休眠性较强的杂交稻组合,以经济有效地预防水稻杂交稻制种田穗发芽危害。为此目的,本论文进行了以下5个部分的研究：(1)、水稻不同品种种子休眠性的形成和解除时间的研究；(2)、水稻不同品种稃壳和种皮对种子休眠性影响的研究；(3)、籼稻IR112-12及其衍生系Ⅱ112B种子休眠性遗传特点的研究；(4)、在杂交稻制种条件下F1的休眠性与亲本的相关以及休眠性的配合力研究；(5)、新选育的强休眠不育系Ⅱ112A的育性研究及产量等农艺性状的配合力研究。1利用新选育的和生产上常用的共35个水稻品种为材料,检测了各品种抽穗后15d-35d具有潜在发芽能力种子的休眠指数,研究种子休眠性的形成时间及其变化。从中选择了6个休眠性不同的品种,收获后用自然室温和低温(0℃)两种方式贮藏,分期测定种子休眠指数,还对刚收获的种子在高温(50℃)条件下处理不同天数,再测定种子休眠指数,研究种子休眠性在自然室温、0℃和50℃情况下的解除时间。结果表明：(1)水稻种子的休眠性,在种子发育中期(抽穗后15d-20d)即已形成,也就是说种子刚有潜在发芽能力就受到休眠性的保护。随着种子成熟度的提高休眠性逐渐下降。根据休眠性下降速度快慢,水稻品种可以分为三类：一类休眠性下降速度很慢,即使到种子成熟时(抽穗后35d)仍能保持很强的休眠性(称为强休眠品种)；一类休眠性在种子成熟过程中迅速下降,到收获时种子休眠性接近于零(称为无休眠或者弱休眠品种)；还有一类是介于以上两者之间(称为中等休眠品种)。(2)种子休眠性的解除速度是由内外因素共同决定的。从内因来看,种子本身休眠性强的品种休眠解除慢,弱休眠品种休眠解除快。强休眠品种收获后在自然室温条件下贮藏,种子休眠性仍然继续下降,种子休眠性可以持续50d左右,直到最终休眠解除。因此,水稻种子休眠性的强弱实际上是由休眠性下降速度的快慢所决定的。而不同品种成熟后期休眠性的强弱,决定了该品种的穗发芽抗性的大小。从外因看,种子在低温条件下贮藏,种子休眠解除较慢,高温条件下贮藏,种子休眠解除加快。强休眠品种种子在50℃条件下处理2d,即可解除种子休眠。所以,在南繁加代、杂交水稻种子生产和贮藏过程中,可根据种子休眠特点采取必要措施打破或者维持种子的休眠性,以适应生产的要求。2利用5个休眠性不同的水稻品种和无休眠的油菜种子为材料,测定了手工剥去稃壳和完整种子的休眠指数,研究剥壳前后种子休眠性的变化；测定了剥壳后糙米和剥壳后再划破种皮(包括果皮)的糙米的休眠指数,研究稃壳、种皮对种子休眠性的影响；利用不同水稻品种稃壳的水浸出液浸泡无休眠的油菜种子和剥壳Ⅱ-32B糙米,测定了种子发芽率、芽长和根长,研究稃壳是否含有发芽抑制物质。结果表明：(1)无休眠品种种子剥壳或不剥壳情况下休眠指数均为0,稃壳、种皮对休眠已起不到控制作用。强休眠品种休眠指数在剥壳后会出现两种情况：一种情况是强休眠品种N22剥壳前后种子休眠指数分别为100%和99%,N22剥壳后休眠指数降低很少,结果表明非稃壳因素影响种子的休眠。Ⅱ112B、IRll2-12、IR64不剥壳种子的平均休眠指数分别为95.3%、99.7%、98.5%,剥壳后糙米的休眠指数分别为15.7%、81.3%、80%,表明稃壳对种子休眠性具有很大的影响,但是不同品种间影响的程度不同。如果在去除稃壳的同时,又划破种皮(连带果皮和一些胚乳),种子的休眠性基本消失,这表明种皮对种子的休眠性也有一定影响,但其影响机制尚不明了。(2)用IRll2-12、Ⅱ112B、N22、IR64、Ⅱ-32B稃壳蒸馏水浸出液分别处理油菜种子和Ⅱ-32B糙米。结果显示,对油菜种子的发芽率抑制率分别为16.5%、16%、14%、12%、0；对芽长的抑制率分别为97.4%、92.21%、79.22%、29.87%、12.99%；对根长的抑制率分别为89.12%、78.29%、61.68%、41.97%、9.49%。对Ⅱ-32B糙米的发芽率抑制率分别为18%、15%、15%、11%、0；芽长抑制率分别为9.94%、9.42%、7.45%、6.21%、3.11%；根长抑制率分别为42.98%、40.35%、38.6%、21.05%、8.77%。上述结果表明强休眠水稻品种稃壳水浸出液对油菜种子和Ⅱ-32B糙米发芽率具有明显的抑制作用,但是抑制程度不同。可以推测水稻稃壳中含有发芽抑制物质,不同品种稃壳所含发芽抑制物质的数量有差异,强休眠品种稃壳可能含有更多的发芽抑制物质。无休眠水稻品种的稃壳水浸出液对无休眠油菜种子和无休眠Ⅱ-32B糙米发芽率影响未被发现,对芽长根长影响很小,说明其稃壳中不含发芽抑制物质,或者含量极少。(3)休眠种子IR112-12、Ⅱ112B、N22、IR64的稃壳在50℃烘箱里处理2d,稃壳的水浸出液即丧失抑制种子发芽作用,由此可以推测水稻稃壳中含有的发芽抑制物质可能对高温敏感,在50℃条件下处理2d,发芽抑制物质即消失。3利用2个杂交组合Ⅱ-32B／IRll2-12、Ⅱ-32B/Ⅱ112B的6世代群体(P1、P2、B1、B2、F1、F2)以及2个组合IR64／龙特浦B、抗85／IR64的4世代群体(P1、P2、F,、F2)为试验材料,研究了水稻种子休眠性的遗传特点。其中，Ⅱ112B是利用IRll2-12和Ⅱ-32B杂交、与Ⅱ-32B回交并经过选择的强休眠保持系,也就是IRll2-12的衍生系。结果表明：(1)水稻种子休眠性为数量性状,且具有不同的遗传模式,有的品种的休眠性具有主基因的效应,有的品种多为多基因的效应,而且基因作用也有显性和隐性的区别。(2)IRll2-12种子休眠性在由多基因控制的同时,也有显性主基因的作用；品种Ⅱ112B与Ⅱ-32B所配组合Ⅱ-32B/Ⅱ112B的F1比IRll2-12与Ⅱ-32B所配组合Ⅱ-32B／IR112-12的F1休眠性的显性程度有所下降,表明Ⅱ112B控制休眠性的基因在杂交回交选择过程中部分丢失。IR64种子休眠性是由多基因控制的,且以隐性基因为主；抗85与IR112-12休眠性遗传特点相似,由多基因控制,且表现出显性主基因的作用。但是抗85与IR112-12相比,休眠性基因作用总效应和F,的显性程度变得较低。(3)每个品种休眠性在南京、海南的测定结果比较一致,年度间差异小,表明休眠性具有很高的遗传力。由各世代方差计算得出广义遗传力为96%-99%,狭义遗传力为62%-65%。(4)此外,水稻种子休眠指数与产量等农艺性状的相关分析表明,种子休眠指数与播抽历期呈极显著的线性正相关关系,决定系数达到0.5765,回归方程为Y=0.0278X-2.2384。这可能是因为决定种子休眠指数与决定播抽历期的基因具有连锁关系。种子休眠指数与播抽历期以外的产量等农艺性状的线性相关性均不显著。4利用19个核质互作型不育系和9个恢复系,配制了109个杂交组合,抽穗后35d收获种子,分别检测了每个杂交组合F,及其亲本种子在不剥壳和剥壳情况下的休眠指数。采用5×5 NCⅡ遗传交配设计配制了25个组合,利用其种子的休眠指数分析了配合力。结果表明：(1)在不剥壳情况下,杂种F1种子的休眠指数与双亲种子的休眠指数以及中亲值呈极显著正相关。109个组合中,82个组合种子休眠性超过中亲值,43个组合种子休眠性超过高亲值,具有明显的中亲优势和超亲优势。(2)去除稃壳的双亲及杂种F1种子的休眠指数均大幅度下降,显示稃壳对种子休眠性具有重要作用,但剥壳后双亲种子和F1种子休眠性之间的关系,仍然存在与不剥壳时相似的趋势。(3)杂交稻种子休眠性是由F1的基因型决定的,因而同时受到杂交双亲休眠性的影响,所以水稻种子休眠性不存在简单的母体效应。母本植株上收获的杂交种子即稃壳是母本开花授粉前形成的,所以是母体的一部分,但其抑制发芽能力却是在开花授粉后种子发育成熟过程中形成的,而且受到杂种胚基因调控。(4)5×5双列杂交试验结果表明,不同杂交稻亲本种子休眠性具有极显著的一般配合力效应。不育系、恢复系休眠性的一般配合力方差和组合的特殊配合力方差占总遗传方差的比例分别为59.2%、31.1%和9.7%,三者均达到极显著水平,说明基因的加性作用占主导地位。不育系Ⅱ112A种子休眠性的一般配合力效应最高,D62A次之；恢复系以IRll2一般配合力效应最高,2786次之。它们是选配强休眠杂交种的优良亲本材料。5利用不育系Ⅱ112A、Ⅱ-32A为材料,比较了其育性、开花习性以及部分农艺性状的表现；利用5个籼稻不育系和5个籼稻恢复系为亲本,采用NCⅡ设计,对产量等14个农艺性状的配合力进行了分析。结果表明：(1)Ⅱ112A休眠指数多年稳定在90%以上,不育株率达100%,花粉不育度大于99.9%,典、圆败率高,开花习性好,保持了来自于Ⅱ-32A的优良不育性和异交习性。(2)NCⅡ设计试验结果表明,14个农艺性状的一般配合力方差均达到极显著水平。Ⅱ112A在单株产量性状上,一般配合力效应高,得利于单株有效穗和结实率一般配合力效应较高；Ⅱ112A后代比Ⅱ-32A后代早熟,并可能降低植株高度,但是增加籽粒长度的作用不大。Ⅱ112A／05-7、Ⅱ112AA／抗85是单株产量较高、综合性状较优的组合。(3)25个组合F,的单株产量与休眠指数的相关系数为-0.0161,不显著。这表明对种子休眠性的改良不会影响单株产量的提高。更多还原

【Abstract】 Pre-harvest sprouting in hybrid rice seed production fields has become a natural disaster for decades, and is an urgent problem that needs to be solved at all times. In Sichuan, a major province of hybrid rice seed production, Gang You Series, D You Series and II You Series are often threatened and challenged by pre-harvest sprouting. When it goes severe, amount of seeds produced and transferred to other localities would be affected. In Jiangsu, another major province of seed production and export sales, pre-harvest sprouting is also common in ShanYou, XieYou, Gang You andⅡYou series hybrid rice. In 2007, from the end of September till the beginning of October, typhoon "Krosa" struck the north of Jiangsu Province, went with the long spell of rainy weather, thousands hectares of hybrid rice lodged in different degrees, and pre-harvest sprouting occurred badly. Pre-harvest sprouting rates of hybrid rice seeds were over 40% in a lot of fields, especially in Yan Du、Jian Hun、Fu Ning、Jin Hu Counties. After screening and winnowing, qualified seeds that produced by some farmers were only 750 kg/hm2, economic loss was serious. According to a rough estimation, all over the country, there were about 133,000 hectares of hybrid rice seed production fields, of which rice pre-harvest sprouting rate was about 10%. Thus, the output loss of seeds was about 35 million kilograms, which cost 700 million Yuan (RMB)and even more when disasters hit badly.Rice is a self pollinated crop, like cross pollinated crop when CMS lines were used to hybrid seed production. The phenomenon of glume-opened seeds of hybrid rice was serious, because the glumes opening angle of CMS lines was wide, and some glumes could not closed completely. Spraying Gibberellic acid at heading stage, which had the effect on promoting germination, was often used as a conventionality, for solving the panicle enclosure of CMS lines in hybrid rice seed production. In the main areas of hybrid rice seed production, rainy weather and typhoon disasters often occurred at pre-harvest stage, which cause serious pre-harvest sprouting of hybrid rice seed production. Fundamentally, rice seed dormancy was the determinants of pre-harvest sprouting.Researches showed that seed dormancy of CMS lines and maintainer lines of indica rice used commonly was quite weak or absented in seed dormancy, and seed dormancy of the most of the restorer lines were low, of the small part of the restorer lines had certain seed dormancy (Zhao Ming, et. al.,2004). There was not hybrid rice combination that could resist to pre-harvest sprouting in hybrid rice seed production now yet. So that, improving seed dormancy of the parents of hybrid rice and breeding hybrid rice combination with high seed dormancy were urgent tasks, for preventing pre-harvest sprouting economically and effectively.Research contents of this paper mainly include 5 parts:1. Forming and releasing time of seed dormancy of different rice cultivars; 2. Influence on seed dormancy of hulls and seed coat of different rice cultivars; 3. Genetic characteristics of seed dormancy of IR112-12 and its derived lineⅡ112B; 4. Correlation between parents and F1 and combining ability of parents in seed dormancy for indica hybrid rice; 5. Studies on pollen fertility, flowering habits and agronomic traits ofⅡ112A and the combining ability for 14 agronomic traits.1. The forming and changing trend of seed dormancy were studied in 35 indica rice cultivars (Oryza sativa L.), which were cultivated recently or used commonly in hybrid rice seed production, by detecting the seed dormancy index of every cultivar at 15-40 days after heading. Seed dormancy disappearing time were studied by using 6 cultivars selected from those 35 cultivars after harvesting, and seed dormancy indexes were detected in different days in three conditions as stored at in-door natural conditions, stored at ice box (0℃) and treated in dry oven (50℃) for different days. The results showed as follows:(1) Rice seed dormancy formed in the middle stage of seed development (15d-20 d after heading), which means the seeds were protected by seed dormancy as soon as the seeds have potential germination ability. According to the seed dormancy decreasing, speed, 35 rice cultivars could be classified into three groups. The first groups were strong seed dormancy cultivars, seed dormancy of which decreased slowly, keeping strong seed dormancy even at the mature period (35 d after heading). The second groups were no seed dormancy or weak seed dormancy cultivars, seed dormancy of which decreased so fast that the seed dormancy would be closed to zero at the mature period (35 d after heading). The third groups were moderate seed dormancy cultivars, seed dormancy of which didn’t decrease slow or fast, keeping middle level at the mature period (35 d after heading). (2) Seed dormancy decreasing speed was determined by both internal and external factors. Viewing from internal factors, seed dormancy of strong seed dormancy cultivars decreased slowly, while seed dormancy of weak seed dormancy cultivars decreased fast. When strong seed dormancy cultivars were stored at natural in-door conditions, seed dormancy went on decreasing, and could keep about 50 days until the seed dormancy was relieved finally. Strong or weak of seed dormancy of different rice cultivars was determined by decreasing speed of seed dormancy, while the resistance to pre-harvest sprouting of different rice cultivars was determined by seed dormancy at the late maturing phase. Viewing from external factors, seed dormancy of cultivars decreased slowly when stored at low temperature conditions, and decreased fast when stored at high temperature conditions. Seed dormancy of strong seed dormancy cultivars could be relieved by treating in dry oven for 2 days (50℃). In the process of seed reproduction in Hainan, hybrid rice seed production and storage, to meet the requirements of the practical production, seed dormancy should be broken or maintained by some measures.2. The effect of hull of rice on seed dormancy was studied by detecting the seed dormancy indexes of hull intact and de-hulled seeds of 5 rice cultivars, which had different seed dormancy indexes. The effect of seed capsule (include pericarp) was studied by detecting the seed dormancy indexes of de-hulled seeds and seed capsule destroyed seeds of 5 rice cultivars. Inhibitor on seed germination in hull of rice were studied by detecting the seed germination rate, sprout length and root length of rape seed (no seed dormancy) andⅡ-32B de-hulled seeds (no seed dormancy), which were treated by soaked-solution of hull of different rice cultivars. The results showed that:(1) Seed dormancy indexes of weak dormancy cultivars were zero at hull intact and de-hulled conditions. It showed that hull, seed capsule and pericarp had no control effect on seed dormancy in this condition. Seed dormancy indexes of cultivars with strong seed dormancy would appeare two cases:One case was that seed dormancy index of N22, a strong dormancy cultivar, was 100% at hull intact conditions, and 99% at de-hulled conditions. It showed that non-hull factors, including seed capsule, pericarp, embryo and endosperm had control effect on seed dormancy. Another case was that seed dormancy indexes ofⅡ112B, IR112-12 and IR64, which with strong dormancy, were 95.3%,99.7%, 98.5% at hull intact conditions, while seed dormancy indexes were 15.7%,81.3%,80% at de-hulled conditions respectively. The results showed that hull, seed capsule, pericarp, embryo and endosperm had strong control actions on seed dormancy, but the degrees of control action were different among different cultivars.Seed dormancy disappeared when destroyed the seed capsule, pericarp and partial of endosperm of de-hulled seed of IR112-12,Ⅱ112B, N22 and IR64. It showed that seed capsule and pericarp had some control actions on seed dormancy, but the influence mechanism of the seed capsule and pericarp remain unknown.(2) Rape seeds with no seed dormancy were soaked by soaked-solution of rice hull of IRl 12-12,Ⅱ112B, N22, IR64 andⅡ-32B. Risuts indicated that the inhibition rate to seed germination rate were 16.5%,16%,14%,12% and 0, respectively. The inhibition rate to sprout length were 97.4%,92.21%,79.22%,29.87%,12.99%, respectively. The inhibition rate to root length were 89.12%,78.29%,61.68%,41.97%,9.49%, respectively. De-hulled seeds ofⅡ-32B were soaked by soaked-solution of rice hull of IRl 12-12,Ⅱ112B, N22, IR64 andⅡ-32B. Risuts showed that the inhibition rate to seed germination rate were 18%,15%,15%,11%and 0, respectively. The inhibition rate to sprout length were 9.94%,9.42%,7.45%,6.21%,3.11%, respectively. The inhibition rate to root length were 42.98%,40.35%,38.6%,21.05%,8.77%, respectively. These results showed that, soaked-solution of rice hull of strong seed dormancy rice cultivars had control effects on rape seeds orⅡ-32B de-hulled seeds, but the control degree were different. It suggested that rice seed hull would hed inhibitor on germination, and the quantity of inhibitor of different rice cultivars were different. The hull of rice seeds with strong dormancy should be had more inhibitor than that of seeds with less strong dormancy. The inference of soaked-solution of rice hull of no dormancy rice cultivars on the germination rate of rape seeds orⅡ-32B de-hulled seeds were not found. It indicated that the hull had no inhibitor or the amount was very little.(3) Soaked-solution of rice hull of IRl 12-12、Ⅱ112B、N22 and IR64 would had no control effect on seed germination after treating in dry oven at 50℃conditions for 2 days. It suggested that inhibitor on seed germination in the hull would be sensitive to temperature. Inhibitor would be disappeared after treating in dry oven at 50℃conditions for 2 days. 3. Genetic characteristics of seed dormancy were studied by using P1, P2, F1, F2, B1, B2 generations ofⅡ-32B/IR112-12 andⅡ-32B/Ⅱ112B, and by using P1, P2, F1, F2 generations of IR64/LongtepuB and Kang85/IR64. Among them,Ⅱ112B was a maintainer line, and IR112-12 was a restorer line. Both of them had strong seed dormancy.Ⅱ-32B and Longtepu B were maintainer lines with low seed dormancy index, while IR64 and Kang85 were restorer lines. Results showed that as follows: (1) Rice seed dormancy was a quantitative characteristic, inherit patterns were different. Seed dormancy of some rice cultivars had major gene effect, while seed dormancy of some rice cultivars had polygene effect. Some had dominant gene effect, and some had recessive gene effect.(2) Seed dormancy of IR112-12 were controlled by polygene, meanwhile had dominant major gene effect. Seed dormancy ofⅡ112B, compared with IR112-12, dominant degree of seed dormancy of F1 generation had declined. It showed that the genes controlled seed dormancy was abandoned at the process of crossing and backcrossing. Seed dormancy of IR64 was controlled by polygene, and had recessive gene mainly. Genetic characteristic of seed dormancy of Kang85 was same as that of IR112-12, were controlled by polygene, and had dominant major gene effect. But Kang85 compared with IR112-12, total effect of genes controlled seed dormancy and dominant degree of seed dormancy of F1 generation were lower than that of IR112-12.(3) Seed dormancy of every cultivar at Nanjing was the same as that at Hainan, and stable for many years. It showed that the heritability of seed dormancy was very high. Broad-sense heritability of the dormancy was 96%-98%, while narrow-sense heritability was 62%-65%, calculated by using variance of every generation.(4) Furthermore, correlation relationship between seed dormancy and agronomic characters were analyzed by using every plant of F2 generations, results noticed that there were linear positive correlation between seed dormancy index and DSH, determine coefficient was 0.5765, the regressive equation was Y=0.0278X-2.2384. The reason would be that genes controlled seed dormancy and DSH were in linkage. Correlation relationship between seed dormancy and agronomic characters except DSH were not distinct.4. Dormancy indexes of hulled and dehulled seeds were investigated by using 109 F1 hybrids and their 19 sytoplasmic male sterile (CMS) lines and 9 restorer lines in indica hybrid rice. The seeds of each F1 and the parents were harvested at 35 days after heading. Meanwhile, combining ability was analyzed in 25 combinations made by 5 CMS lines and 5 restorer lines (NCⅡgenetic design). The results showed that as follows:(1) The seed dormancy index of F1 was positively and highly significantly correlated with those of their parents and mid-parent value. Out of the 109 combinations,82 combinations showed mid-parent heterosis, and 43 combinations heterobeltiosis.(2) Seed dormancy index of F1 and their parents declined dramatically in dehulled seeds compared with hulled seed, indicating that the hull played an important role in seed dormancy. However, the trend was similar in hulled and dehulled seeds in terms of relationship between F1 and their parents in seed dormancy.(3) The influence of hull on seed dormancy depended mainly on F1 genotype, not on hull itself of female parent.(4) Test results of 5×5 incomplete diallel cross (NCⅡ) design indicated that the general combing ability (GCA) of all the characters were significant at 1% level. The variance of general combining ability (GCA) in female and male parents occupied 59.2% and 31.1% of total variance, respectively. The variance of specific combining ability (SCA) in combinations occupied 9.7% of total variance, indicating that gene additive effects were principal. Among the 5 CMS lines,Ⅱ112A had the highest GCA effect for seed dormancy, flowed by D62A. Among the 5 restorer lines, IR112 had the highest GCA effect for seed dormancy followed by 2786. They were excellent materials as parents for breeding F1 hybrid rice with stronger seed dormancy.5. Pollen fertility, flowering habits and agronomic traits ofⅡ112A were compared with that ofⅡ-32A, and the combining ability of 14 agronomic traits were studied with 5 CMS lines and 5 restorer lines by the way of NCⅡdesign. The results showed as follows:(1) Seed dormancy indexes ofⅡ112A were more than 90% and stable for many years, the sterile plant rate and sterile degree ofⅡ112A, a CMS line, reached 100% and 99.9%, respectively. Irregularly shaped pollen abortion rate and round-shaped pollen abortion rate ofⅡ112A were high, and flowering habits was excellent. The sterility and out crossing habits coming fromⅡ-32A were maintained.(2) Test results of NCⅡdesign indicated that the general combining ability (GCA) of all the characters were significant at 1% level. Effect of the general combining ability (GCA) of grain weight per plant ofⅡ112A was strong, because effect of the general combining ability (GCA) for number of panicles per plant and seed setting rate were high. Maturity stage of descendant ofⅡ112A was earlier than that ofⅡ-32A, and could decrease the plant height, but could not increase the length of grains.Ⅱ112A/05-7 andⅡ112A/Kang85 were two excellent combinations, with high grain weight per plant and good comprehensive characters.(3) Correlation coefficient between grain weight per plant and seed dormancy index in 25 combinations was-0.0161, not significant at 5% level. It indicated that improving seed dormancy would not influence upon the grain weight per plant.更多还原