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。     

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.     

Characterization and Use of Male Sterility in Hybrid Rice Breeding

The hybrid rice （Oryza sativa L.） breeding that was Initiated In China in the 1970s led to a great improvement in rice productivity. In general, It increases the grain yield by over 20% to the inbred rice varieties, and now hybrid rice has been widely introduced into Africa, Southern Asia and America. These hybrid varieties are generated through either three-line hybrid and two-line hybrid systems; the former is derived from cytoplasmic male sterility （CMS） and the latter derived from genlc male sterility （GMS）. There are three major types of CMS （HL, BT and WA） and two types of GMS （photoperlod-sensitlve （PGMS） and temperature-sensitive （TGMS））. The BT- and HL-type CMS genes are characterized as orf79 and orfH79, which are chimeric toxic genes derived from mltochondrial rearrangement. Rf3 for CMS-WA Is located on chromosome 1, while Rf1, Rf4, Rf5 and Rf6 correspond to CMS-BT, CMSoWA and CMS- HL, located on chromosome 10. The Rfl gene for BT-CMS has been cloned recently, and encodes a mltochondriatargeted PPR protein. PGMS Is thought to be controlled by two recessive loci on chromosomes 7 and 12, whereas nine recessive alleles have been identified for TGMS and mapped on different chromosomes. Attention Is still urgently needed to resolve the molecular complexity of male sterility to assist rice breeding.     

远缘杂交和异源多倍体化技术在水稻育种中的应用

从野生稻遗传资源在育种中的作用出发,概述了栽培稻与野生稻远缘杂交和多倍体化在水稻育种中的应用。对远缘杂交中的杂交不亲和性以及杂种不育等问题采用激素处理、胚挽救等途径解决,对所获杂种从形态学、细胞学、生物化学以及分子生物学等多方面鉴定,对栽野杂种存在的野生性状通过选择与改造相结合的方法而淘汰,对其有利基因则加以选择和聚合以获得稳定优良品种。这些从理论上和实践上证明远缘杂交和多倍体化相结合的异源多倍体化是获得高产优质水稻新品种的一条新途径。     

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...     

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.     

Cybrids and tetrad sterility for developing true potato seed hybrids

Potato cybrids result from the fusion between cytoplasm and nuclear gene donors. Such genetic materials are an alternative means to broaden the breeding pool by non‐sexual gene transfer. Tetrad pollen sterility provides also another source of male sterility with some potential for true potato seed breeding. The objective of this research was to investigate cybrid‐derived offspring for both agronomic and reproductive characteristics in two contrasting Peruvian locations, and to examine new exotic germplasm for tetrad sterility, with the aim of broadening the breeding pool available at the Centro Internacional de la Papa (CIP). The cybrids were derived from fusions between Y‐245.7, a clone with tetrad sterility, and Atzimba. These cybrids were crossed with selected male parents from the CIP breeding population, and their hybrid offspring were tested in La Molina (coastal desert) and Huancayo (cool highlands). In addition, other clones with tetrad sterility were also crossed with selected testers to determine their breeding value. There were significant differences for tuber yield, style length, and berry number among the hybrid offspring, and the genotype by environment interaction was significant for tuber yield and berry number. The top 25% highest yielding cybrid‐derived offspring across both locations showed the same tuber yield although they were significantly different for some of the reproductive characteristics. With the exception of one cybrid, the others did not exhibit segregation for tetrad sterility in their hybrid offspring, which were male fertile. However, the offspring derived from crosses between other sources of tetrad sterility and the same testers all showed tetrad sterility, and some of them had outstanding tuber yield at La Molina. The lack of segregation for tetrad sterility in these new crosses suggests that the non‐cybrid, male sterile, female parents are triplex or quadriplex for the Tr nuclear locus, which interacts with a sensitive cytoplasm (e.g. Trs from S. verrucosum or S. stoloniferum) to produce tetrad sterility in potato.     

Towards molecular breeding of reproductive traits in cereal crops

The transition from vegetative to reproductive phase, flowering per se , floral organ development, panicle structure and morphology, meiosis, pollination and fertilization, cytoplasmic male sterility (CMS) and fertility restoration, and grain development are the main reproductive traits. Unlocking their genetic insights will enable plant breeders to manipulate these traits in cereal germplasm enhancement. Multiple genes or quantitative trait loci (QTLs) affecting flowering (phase transition, photoperiod and vernalization, flowering per se ), panicle morphology and grain development have been cloned, and gene expression research has provided new information about the nature of complex genetic networks involved in the expression of these traits. Molecular biology is also facilitating the identification of diverse CMS sources in hybrid breeding. Few Rf (fertility restorer) genes have been cloned in maize, rice and sorghum. DNA markers are now used to assess the genetic purity of hybrids and their parental lines, and to pyramid Rf or tms (thermosensitive male sterility) genes in rice. Transgene(s) can be used to create de novo CMS trait in cereals. The understanding of reproductive biology facilitated by functional genomics will allow a better manipulation of genes by crop breeders and their potential use across species through genetic transformation.     

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     

利用生物技术创建主要作物雄性不育杂交育种和制种的技术体系

雄性不育技术在作物杂种优势利用和杂交种生产中发挥着重要作用。基于核质互作雄性不育的“三系法”与光温敏核不育的“两系法”已经在水稻等主要作物的杂交制种中获得了广泛应用,但是存在着资源利用效率低、育性不稳定、易受外界环境影响等诸多问题。近三十年来,利用生物技术创建不同类型的植物雄性不育系取得了一系列突破性进展。主要针对玉米、水稻、小麦三大作物的基因工程雄性不育技术的最新进展进行总结,特别详细地描述了本实验室最近研究创制的玉米多控不育技术体系,以期为相关研究和产业化应用提供技术参考。     

Genetic bases of instability of male sterility and fertility reversibility in photoperiod-sensitive genic male-sterile rice

Photoperiod-sensitive genetic male-sterile (PSGMS) rice, with its male fertility regulated by photoperiod length, is very useful for hybrid rice development. However, breeding for new PSGMS lines has faced two major difficulties – the stability of male sterility and the reversibility of male fertility. In this study we assessed the genetic bases of stability of sterility and fertility reversibility using a molecular marker-based approach. A cross was made between two newly bred PSGMS lines: Peiai 64S, which has a stable sterility but is difficult to reverse to fertility, and 8902S, which has a unstable sterility but is easy to reverse to fertility. The fertility of the parents and of the F₁ and F₂ populations was repeatedly examined under 11 different long-day and short-day conditions. The genetic effects were assayed by interval mapping and two-way analyses of variance using the F₂ data of 128 polymorphic loci representing all the 12 rice chromosomes. The analyses resolved a number of single-locus QTLs and two-locus interactions under both long-day and short day conditions. The interactions involved a large number of loci, most of which were not detectable on a single-locus basis. The results showed that the genetic bases of both stability of sterility and reversibility of fertility are the joint effects of the additive effects of the QTLs and additive-by-additive components of two-locus interactions. The implications of these findings in hybrid rice development are also discussed. Received: 11 January 1999 / Accepted: 19 January 1999     

The molecular mechanisms of male reproductive organogenesis in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Stamen is the male reproductive organ of rice (Oryza sativa L.), and the development is a considerably significant stage during the sexual reproduction. It is very important to reveal what is the molecular mechanisms which controlling the development of stamen, and will be helpful in producing hybrid seeds by manipulating the male sterility. This article reviews the progress on the molecular mechanisms of male reproductive organogenesis in rice, which would facilitate the further studies on male sterile genes in rice.     

Reproductive isolation in Saccharomyces

Although speciation is one of the most interesting processes in evolution, the underlying causes of reproductive isolation are only partially understood in a few species. This review summarizes the results of many experiments on the reproductive isolation between yeast species of the Saccharomyces sensu stricto group. Hybrids between these species form quite readily in the laboratory, but, if given a choice of species to mate with, some are able to avoid hybridization. F1 hybrids are viable but sterile: the gametes they produce are inviable. For one pair of species, hybrid sterility is probably caused by chromosomal rearrangements, but for all the other species, the major cause of hybrid sterility is antirecombination-the inability of diverged chromosomes to form crossovers during F1 hybrid meiosis. Surprisingly, incompatibility between the genes expressed from different species' genomes is not a major cause of F1 hybrid sterility, although it may contribute to reproductive isolation at other stages of the yeast life cycle.     

水稻的杂种不育研究进展

水稻亚种间杂种优势利用曾使水稻单产有了很大的提高,但水稻种间与亚种间的杂种不育性仍然普遍存在,从而影响了杂种优势的进一步利用。本研究对水稻产生杂种不育的细胞学水平原因进行了分类分析,对产生杂种不育的遗传学机理进行了探讨,对各种杂种不育基因座位的定位以及已克隆获得的基因进行了全面总结,并对如何克服杂交不育与利用杂种优势提出了自己的观点。     

水稻雄性不育突变体ms102的鉴定和基因定位

水稻(Oryza sativa)隐性核雄性不育突变体是第三代杂交水稻技术的核心。为了挖掘优质雄性不育突变体, 该研究通过筛选优质籼稻黄华占(HHZ)的甲基磺酸乙酯(EMS)诱变突变体库, 获得1个雄性不育突变体ms102 (male sterility mutant 102)。该突变体营养生长正常, 但花药不开裂, 花粉败育。细胞学分析表明, 突变体花药绒毡层不能正常降解, 导致小孢子发育异常; 遗传分析表明, 该突变体的不育表型由1个已报道编码酰基转移酶的DPW2基因突变造成。研究获得了1个隐性核雄性不育突变体, 进一步证实了DPW2基因在水稻花药发育中的功能。     

Effect of nitrogen,phosphorus and potassium on spikelet sterility induced by low temperature at the reproductive stage of rice

Spikelet sterility induced by low temperature at the reproductive stage of rice increased further with the increase of nitrogen supply. Spikelet sterility in Fujisaka-5 did not increase due to low temperature when nitrogen supply was increased from 10 to 40 ppm and at 80 ppm nitrogen supply it was less affected than IR36. Total nitrogen content in the leaves increased with the increase of nitrogen supply and was forced to be associated with the spikelet sterility induced by low temperature. Based on auricle distance between the last two leaves, the most sensitive stage to low temperature damage differed in Fujisaka-5 and IR36. Spikelet sterility induced by low temperature for 10 days was very high in both the varieties and the effect of nitrogen was not clear.The effect of phosphorus on the spikelet sterility induced by low temperature at reproductive stage was not clear except that at the highest phosphorus (P) level (10 ppm) the spikelet sterility increased both in Fujisaka-5 and IR36.Spikelet sterility induced by low temperature at the reproductive stage of rice decreased with the increase of Potassium (K) supply in both Fujisaka-5 and IR36. With an increase of potassium supply, nitrogen (N) content decreased in the leaves and panicles and spikelet sterility induced by low temperature decreased with an increase of the K to N ratio in the leaves and panicles. The results suggest that potassium might play a major role to counteract the low temperature damage at the reproductive stage of rice.     

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.     

A genome-wide analysis of wide compatibility in rice and the precise location of the S5 locus in the molecular map

 The discovery of wide-compatibility varieties (WCVs) that are able to produce normal fertility hybrids when crossed both to indica and japonica rice has enabled the fertility barrier between indica and japonica subspecies to be broken and provided the possibility of developing inter-subspecific hybrids in rice breeding programs. However, a considerable variation in the fertility level of hybrids from the same WCV crossed to different varieties has often been observed. One hypothesis for this variable fertility is that additional genes are involved in hybrid fertility besides the wide-compatibility gene (WCG). To assess such a possibility, we performed a genome-wide analysis by assaying a large population from a three-way cross ‘02428’/‘Nanjing 11’//‘Balilla’ using a total of 171 RFLP probes detecting 191 polymorphic loci distributed throughout the entire rice linkage map. Our analysis recovered 3 loci conferring significant effects on hybrid fertility. The major locus on chromosome 6 coincided in chromosomal location with the previously identified S ₅ locus, and the 2 minor loci that mapped to chromosomes 2 and 12, respectively, were apparently distinct from all previously reported hybrid sterility genes. Interaction between the indica and japonica alleles at each of the loci caused a reduction in hybrid fertility. The joint effect of the 2 minor loci could lead to partial sterility even in the presence of the WCG. The location of the S ₅ locus on the molecular marker linkage map was determined to be approximately 1.0 cM from the RFLP locus R2349. This tight linkage will be useful for marker-aided transfer of the WCG in hybrid rice breeding and for map-based cloning. Received: 5 February 1997 / Accepted: 4 April 1997     

Developing disease‐resistant thermosensitive male sterile rice by multiplex gene editing

High-quality and disease-resistant male sterile lines have great potential for applications in hybrid rice breeding. We introduced specific mutations into the TMS5, Pi21, and Xa13 genes in Pinzhan intermediate breeding material using the CRISPR/Cas9 multiplex genome editing system. We found that the transgenefree homozygous triple tms5/pi21/xa13 mutants obtained in the T1 generation displayed characteristics of thermosensitive genic male sterility(TGMS) with enhancedresistance to rice blast and bacterial blight. Our study provides a convenient and effective way of converting breeding intermediate material into TGMS lines through multiplex gene editing, which could significantly accelerate the breeding of sterile lines.