水稻籼粳杂种雌性不育的细胞学初步观察(简报)

普通栽培稻籼粳亚种间杂种结实率低是开展亚种间杂交育种和杂种优势利用的主要障碍。这一障碍是杂种花粉和胚囊的不育性引起的。不育性曾经认为是两者染色体在结构上存在微小的差异所致,但F_1植株减数分     

水稻杂种优势的理论探讨

杂种优势是生物界的普遍现象,其遗传机 理比较复杂,迄今还没有比较完善的解释,对其 实质和规律还有很多不清楚的地方。对于杂种 优势产生的原因以及不育胞质在杂种优势中的 效应问题,有着不同的看法。为了探讨水稻三 系杂种一代产生优势的原因,分析核质之间的 关系以及不育胞质对杂种优势的效应问题,为 生产上选配优良的三系组合,利用杂种优势提 供理论依据,我们进行了本试验。     

水稻广亲和性遗传的主基因一多基因混合模型分析

籼、粳亚种间的F1一般表现为半不育,这限制了籼、粳杂种优势的利用。广亲和基因的发现及其遗传研究有助于揭示这种半不育现象的遗传本质,使克服籼、粳亚种间F1的半不育成为可能。本研究采用主基因－多基因混合遗传模型,分析了籼、粳杂交组合3037/02428的P1、P2、F1、B1、B2和F2六世代材料。研究结果显示：广亲和性的遗传除受单个主基因控制外还受多基因的影响。在利用广亲和基因克服亚种间的半不育性时不仅要考虑主基因对育性的作用,也不能忽视多基因对育性的影响。     

中国科学家在杂种F1克隆繁殖研究领域取得突破性进展

杂种优势在提高作物产量和适应性方面已得到广泛应用。然而, 由于杂交种后代不能稳定遗传, 每年均需利用不育系和恢复系亲本配置杂交种子, 不仅制种成本高, 而且存在制种纯度问题, 限制了杂种优势利用的推广范围。近期, 中国科学家通过对减数分裂和受精过程关键基因进行编辑, 获得了杂种F₁的克隆种子, 为进一步固定杂种优势、实现“一系法”水稻杂种优势利用带来了曙光。     

水稻广亲和性遗传的再研究

水稻广亲和基因的利用是克服亚种间杂种不育性的重要途径。但在广亲和性的遗传上不同研究者的结论不尽一致。以3种有广亲和品种参加的三交组合为研究材料,研究了品种Ketan Nangka的广亲和性遗传。结果表明水稻亚种杂交F1同时存在着雄性不育和雌性不育,但雄性不育对小穗育性的作用大小因组合而异;无论是在雄性不育位点还是雄性不育位点上,Ketan Nangka均具有相对应的中性基因（广亲和基因）;广亲和性的遗传特点与所用的籼粳测验品种间的杂种不育性密切相关;S－5位点的广亲和基因遗传符合单位点孢子体－配子体互作模型。     

中国水稻遗传育种历程与展望

我国的水稻育种经历了矮化育种、杂种优势利用和绿色超级稻培育3次飞跃,其间伴随矮化育种(第一次绿色革命)、三系杂交稻培育、二系杂交稻培育、亚种间杂种优势利用、理想株型育种和绿色超级稻培育等6个重要历程。育种目标从唯产量是举到高抗、优质和高产并重,育种理念从高产优质逐步提升为“少投入,多产出,保护环境”。水稻功能基因组研究为第二次绿色革命准备了大量的有重要利用价值的基因,水稻育种正迈向设计育种的新时代。基因组选择技术和转基因技术将为培育“少打农药,少施化肥,节水抗旱,优质高产” 绿色超级稻保驾护航。本文对我国水稻遗传育种的发展历程进行了概括,指出了各种育种方法和育种技术的优缺点,系统介绍了水稻细胞质雄性不育和光温敏雄性核不育以及籼粳杂种不育的分子机制的研究进展,综述了水稻株型、穗型、粒形和养分高效利用相关的重要功能基因,阐明了产量与开花期联动的关系,凸显了我国水稻基础研究在国际上的重要地位。特别指出,近年来,我国水稻生产方式发生了或正在发生巨大变革,育种理念也要与时俱进。未来,杂交育种技术要与现代育种技术紧密结合,选育水稻品种不仅要满足市场需求,而且更要具备绿色健康的特点,同时还要适应新耕作制度和新耕作方法。     

栽培稻种间杂种不育基因S1的图位克隆

水稻种间杂种不育限制了其杂种优势的有效利用,S1是其中一个最重要的杂种不育基因座。为探讨S1对杂种的雌雄配子选择性杀灭作用,本研究首先采用图位克隆法,对粳稻IRAT216及其包含非洲栽培稻S1座位的近等基因系IRAT216S1构建的BC_9F_2分离群体,进行了S1精细定位与克隆。首先在定位区间内筛选了所有网上公开的SSR标记,并结合自行测序比较,开发出了31对有多态性的分子标记,把S1锁定在P0535G04克隆上标记2180与2198之间18 kb的精细定位区段,内有ORF11、ORF12两个候选基因。对两基因基因组测序、RT-PCR、基因芯片分析,排除了ORF11,确定了ORF12是唯一候选基因,同时也排除了此座外存在辅助因子的可能性。本研究分子标记的开发将为水稻的分子标记辅助育种提供帮助,而S1基因的克隆将为杂交育种中克服杂种不育提供了可能,也为进一步杂种优势的利用打下基础。     

水稻台中65与其花粉不育近等基因系的杂种F1的裂药性研究

以台中65及其7个F1花粉不育近等基因系为材料,对水稻亚种间杂种F1裂药性及其与小穗育性的关系进行了研究。结果表明,杂种F1的裂药性受花粉不育基因互作控制。不同杂合座位内等位花粉不育基因互作导致杂种F1花药不开裂的程度不同,S-b座位导致杂种F1部分花药不开裂;不同杂合座位问非等位花粉不育基因互作明显降低杂种F1的裂药程度;杂种F1中含杂合花粉不育基因座位数越多,其裂药指数越小,裂药程度越低,含三个杂合花粉不育基因座位的杂种F1裂药指数为2．27,35．3％的花药不开裂。杂种F1花药不开裂的原因随其所含的杂合花粉不育基因座位种类和数目不同而异。杂种F1裂药程度的下降显著减少落在其柱头上的花粉总数和萌发的花粉数。杂种F1裂药指数和结实率呈极显著的正相关关系。     

水稻亚种间杂种F1半不育小孢子发生的细胞学观察

利用石蜡切片和染色体压片法对水稻亚种间半不育杂种F1及其亲本的小孢子母细胞减数分裂过程进行细胞学观察.结果显示:亲本及杂种F1的花药壁发育正常,但部分F1的小孢子母细胞减数分裂异常,形成不均等的二分体和异常的四分体;其染色体在中期Ⅰ分散在赤道板两旁或远离赤道板,形成单价体;在后期Ⅰ和后期Ⅱ产生大量落后染色体或染色体桥.研究表明,部分花粉母细胞减数分裂中期和后期染色体行为异常可能是造成杂种F1花粉半不育的主要原因.     

大豆细胞核雄性不育基因研究进展

雄性不育是指植物雄蕊不能正常生长和产生有活力花粉粒的现象。利用雄性不育突变体开展杂交育种工作,是快速提高作物单产的有效途径。目前,通过杂种制种已大幅度提高了水稻(Oryza sativa L.)、玉米(Zea mays L.)和小麦(Triticum aestivum L.)等作物的产量。大豆(Glycinemax(L.)Merr.)作为自花授粉作物,通过人工去雄生产杂交种子不仅困难而且经济上不可行。由于适用于杂交种生产的不育系资源短缺,目前大豆还没有实现大规模杂种优势利用。因此,快速实现大豆杂种优势利用迫切需要鉴定稳定的大豆雄性不育系统。本文总结了大豆细胞核雄性不育(genic male sterility, GMS)突变体及不育基因研究进展,同时结合拟南芥(Arabidopsis thaliana)、水稻和玉米中已报道的细胞核雄性不育基因,从反向遗传学的角度,为大豆核雄性不育基因的鉴定提供依据。     

Understanding the genetic and molecular constitutions of heterosis for developing hybrid rice

The wide adoption of hybrid rice has greatly increased rice yield in the last several decades. The utilization of heterosis facilitated by male sterility has been a common strategy for hybrid rice development. Here, we summarize our efforts in the genetic and molecular understanding of heterosis and male sterility together with the related progress from other research groups. Analyses of F1 diallel crosses show that strong heterosis widely exists in hybrids of diverse germplasms, and inter-subsp...     

Molecularmarker diversity and hybrid sterility in indica-japonica rice crosses

 The partial sterility of hybrids between the indica and japonica rice subspecies of Asian cultivated rice is a serious constraint for utilizing inter-subspecific heterosis in hybrid rice breeding. In this study, we have investigated the relationship between molecular-marker polymorphism and indica-japonica hybrid fertility using a diallel set involving 20 rice accessions including 9 indica and 11 japonica varieties. Spikelet fertility of the resulting 190 F₁s and their parents was examined in a replicated field trial. Intra-subspecific hybrids showed much higher spikelet fertility than inter-subspecific hybrids except in crosses involving wide-compatibility varieties. The parents were surveyed for DNA polymorphism using 96 RFLP and ten SSR markers, which revealed extensive genetic differentiation between indica and japonica varieties. A large number of markers detected highly significant effects on hybrid fertility. The chromosomal locations for many of the positive markers coincided well with previously identified loci for hybrid sterility. The correlation between hybrid fertility and parental distance was low in both intra- and inter-subspecific crosses. The results suggest that the genetic basis of indica-japonica hybrid sterility is complex. It is the qualitative, rather than the quantitative, difference between the parents that determines the fertility of hybrids. Received: 3 January 1997/Accepted: 17 January 1997     

Suppression or knockout of SaF/SaM overcomes the Sa-mediated hybrid male sterility in rice

Hybrids between the indica and japonica subspecies of rice(Oryza sativa) are usually sterile, which hinders utilization of heterosis in the inter-subspecific hybrid breeding. The complex locus Sa comprises two adjacently located genes, SaF and SaM, which interact to cause abortion of pollen grains carrying the japonica allele in japonica-indica hybrids. Here we showed that silencing of SaF or SaM by RNA interference restored male fertility in indica-japonica hybrids with heterozygous Sa. We further used clustered regularly interspaced short palindromic repeats(CRISPR)/Cas9-based genome editing to knockout the SaF and SaM alleles, respectively, of an indica rice line to create hybrid-compatible lines. The resultant artificial neutral alleles did not affect pollen viability and other agricultural traits, but did break down the reproductive barrier in the hybrids. We found that some rice lines have natural neutral allele Sa-n, which was compatible with the typical japonica or indica Sa alleles in hybrids. Our results demonstrate that SaF and SaM are required for hybrid male sterility, but are not essential for pollen development. This study provides effective approaches for the generation of hybrid-compatible lines by knocking out the Sa locus or using the natural Sa-n allele to overcome hybrid male sterility in rice breeding.     

Identification and fine mapping of <Emphasis Type="Italic">S-d</Emphasis>, a new locus conferring the partial pollen sterility of intersubspecific F<Subscript>1</Subscript> hybrids in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

The partial pollen abortion of hybrids between the indica and japonica subspecies of Asian cultivated rice is one of the major barriers in utilizing intersubspecific heterosis in hybrid rice breeding. Although a single hybrid pollen sterility locus may have little impact on spikelet fertility, the cumulative effect of several loci usually leads to a serious decrease in spikelet fertility. Isolating of the genes conferring hybrid pollen sterility is necessary to understand this phenomenon and to overcome the resulting genetic barrier. In this study, a new locus for F₁ pollen sterility, S-d, was identified on the short arm of chromosome 1 by analyzing the genetic effect of substituted segments of the near-isogenic line E11-5 derived from the japonica variety Taichung 65 (recurrent parent) and the indica variety Dee-geo-woo-gen (donor parent). The S-d locus was first mapped to a 0.8 cM interval between SSR markers PSM46 and PSM80 using a F₂ population of 125 individuals. The flanking markers were then used to identify recombinants from a population of 2,160 plants derived from heterozygotes of the primary F₂ population. Simultaneously, additional markers were developed from genomic sequence divergence in this region. Analysis of the recombinants in the region resulted in the successful mapping of the S-d locus to a 67-kb fragment, containing 17 predicted genes. Positional cloning of this gene will contribute to our understanding of the molecular basis for partial pollen sterility of intersubspecific F₁ hybrids in rice.     

杂交水稻育种将迎来新时代

杂种优势是生物界一种普遍的现象,在许多作物中得到应用．杂交水稻自20世纪70年代开始在中国大规模种植,对于粮食生产具有举足轻重的作用．现有的“三系法”和“两系法”杂交育种技术对粮食增产贡献巨大,但它们的技术缺陷也非常明显．本文在总结已有杂交育种技术的操作流程及优缺点的基础上,阐述了利用智能不育杂交育种技术,实现隐性雄性核不育材料在杂交水稻中应用的技术流程．这种飞跃性技术的运用将推动杂交水稻的生产进入一个新的时代．     

Hybrid male sterility in rice is due to epistatic interactions with a pollen killer locus

In intraspecific crosses between cultivated rice (Oryza sativa) subspecies indica and japonica, the hybrid male sterility gene S24 causes the selective abortion of male gametes carrying the japonica allele (S24-j) via an allelic interaction in the heterozygous hybrids. In this study, we first examined whether male sterility is due solely to the single locus S24. An analysis of near-isogenic lines (NIL-F(1)) showed different phenotypes for S24 in different genetic backgrounds. The S24 heterozygote with the japonica genetic background showed male semisterility, but no sterility was found in heterozygotes with the indica background. This result indicates that S24 is regulated epistatically. A QTL analysis of a BC(2)F(1) population revealed a novel sterility locus that interacts with S24 and is found on rice chromosome 2. The locus was named Epistatic Factor for S24 (EFS). Further genetic analyses revealed that S24 causes male sterility when in combination with the homozygous japonica EFS allele (efs-j). The results suggest that efs-j is a recessive sporophytic allele, while the indica allele (EFS-i) can dominantly counteract the pollen sterility caused by S24 heterozygosity. In summary, our results demonstrate that an additional epistatic locus is an essential element in the hybrid sterility caused by allelic interaction at a single locus in rice. This finding provides a significant contribution to our understanding of the complex molecular mechanisms underlying hybrid sterility and microsporogenesis.     

Progress in research and development on hybrid rice: a super-domesticate in China

BACKGROUND: China has been successful in breeding hybrid rice strains, but is now facing challenges to develop new hybrids with high-yielding potential, better grain quality, and tolerance to biotic and abiotic stresses. This paper reviews the most significant advances in hybrid rice breeding in China, and presents a recent study on fine-mapping quantitative trait loci (QTLs) for yield traits. SCOPE: By exploiting new types of male sterility, hybrid rice production in China has become more diversified. The use of inter-subspecies crosses has made an additional contribution to broadening the genetic diversity of hybrid rice and played an important role in the breeding of super rice hybrids in China. With the development and application of indica-inclined and japonica-inclined parental lines, new rice hybrids with super high-yielding potential have been developed and are being grown on a large scale. DNA markers for subspecies differentiation have been identified and applied, and marker-assisted selection performed for the development of restorer lines carrying disease resistance genes. The genetic basis of heterosis in highly heterotic hybrids has been studied, but data from these studies are insufficient to draw sound conclusions. In a QTL study using stepwise residual heterozygous lines, two linked intervals harbouring QTLs for yield traits were resolved, one of which was delimited to a 125-kb region. CONCLUSIONS: Advances in rice genomic research have shed new light on the genetic study and germplasm utilization in rice. Molecular marker-assisted selection is a powerful tool to increase breeding efficiency, but much work remains to be done before this technique can be extended from major genes to QTLs.