The whole subject of male sterility in plants, a phenomenon first observed by Klreuter in 1763, is comprehensively treated in this volume, which is divided into 2 parts. Part I covers principles, generalizations and fundamental concepts, chemical induction and environmental influence, critical discussions and specific conclusions on the nature, type, inheritance, biochemistry, molecular basis,...

Two major types of male sterility, Mendelian sterility (MST) and cytoplasmic male sterility (CMS) can be distinguished according to their genetic control. Molecular advances concerning MST arose initially from the isolation and the characterization of genes expressed specifically in anther and pollen. These genes were manipulated to induce pollen failure. MST was induced by tapetal-specific expression of different genes such as an RNase gene, a modified glucanase gene, the Agrobacterium rhizogenes rolC gene or an unedited atp9 mitochondrial gene in tobacco transformants, and by antisense inhibition of flavonoid biosynthesis in anthers of petunia transformants. Other recent data on MST molecular genetics were obtained from the analysis of three categories of mutants

Abstract To feed the several billion people living on this planet, the production of high-quality food must increase with reduced inputs, but this accomplishment will be particularly challenging in the face of global environmental change. Plant breeders need to focus on traits with the greatest potential to increase yield. Hence, new technologies must be developed to accelerate breeding through improving genotyping and phenotyping methods and by increasing the available genetic diversity in breeding germplasm. The most gain will come from delivering these technologies in developing countries, but the technologies will have to be economically accessible and readily disseminated. Crop improvement through breeding brings immense value relative to investment and offers an effective approach to improving food security.

Abstract 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 genic male sterility (GMS). There are three major types of CMS (HL, BT and WA) and two types of GMS (photoperiod-sensitive (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 mitochondrial rearrangement. Rf3 for CMS-WA is located on chromosome 1, while Rf1, Rf4, Rf5 and Rf6 correspond to CMS-BT, CMS-WA and CMS-HL, located on chromosome 10. The Rf1 gene for BT-CMS has been cloned recently, and encodes a mitochondria-targeted 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.

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.

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.

An account is given of hybrid maize seed production as it is commercially practised in the USA in the late 1980s. The structure of the industry, the production methods used, quality assurance and storage and distribution are described in detail.

Cytoplasmic male sterility can be thought of as the product of a genetic conflict between two genomes that have different modes of inheritance. Male sterilizing factors, generally encoded by chimaeric mitochondrial genes, can be downregulated by specific nuclear restorer genes. The recent cloning of a restorer gene in rice and its comparison with restorer genes cloned in petunia [Petunia sp.] and radish could be regarded as the beginning of a general molecular scenario in this peculiar arms race.

Since plants retain genomes of an extremely large size in mitochondria (200-2,400 kb), and mitochondrial protein complexes are comprised of chimeric structures of nuclear- and mitochondrial-encoded subunits, coordination of gene expression between the nuclei and mitochondria is indispensable for sound plant development. It has been well documented that the nucleus regulates organelle gene expression. This regulation is called anterograde regulation. On the other hand, recent studies have demonstrated that signals emitted from organelles regulate nuclear gene expression. This process is known as retrograde signaling. Incompatibility caused by genome barriers between a nucleus and foreign mitochondria destines the fate of pollen to be dead in cytoplasmic male sterility (CMS), and studies of CMS confirm that pollen fertility is associated with anterograde/retrograde signaling. This review summarizes the current perspectives in CMS and fertility restoration, mainly from the viewpoint of anterograde/retrograde signaling.

Cytoplasmic male sterility (CMS) is a common feature encountered in plant species. It is the result of a genomic conflict between the mitochondrial and the nuclear genomes. CMS is caused by mitochondrial encoded factors which can be counteracted by nuclear encoded factors restoring male fertility. Despite extensive work, the molecular mechanism of male sterility still remains unknown. Several studies have suggested the involvement of respiration on the disruption of pollen production through an energy deficiency. By comparing recent works on CMS and respiratory mutants, we suggest that the “ATP hypothesis” might not be as obvious as previously suggested.

The studies reviewed date from 1925 to 1972 and contain extensive anatomical and cytological information all too often incomplete or vague. The terminology for microsporogenesis used is also often sketchy or inaccurate. An attempt therefore has been made to establish some consistency in microsporogenesis terminology via Fig. 1 and the tables. We have given, in convenient tabular form, CMS taxa, investigators, and the morphological and cytological events reported. By referring to a few keys, the reader can gain further insight into specific CMS taxa and can easily compare studiesThe work of Laser (1972) is only part of a more extensive investigation of the anatomy, cytology, and histochemistry of N and CMS Sorghum bicolor (Laser, unpub.). To date, only a small part is published (Christensen, Horner & Lersten, 1972), but when completed it probably will be the most complete study to date of these aspects of CMS. Hoefert (1969a, 1969b, 1971) has investigated only normal microsporogenesis so far, but her intention also is to make a detailed descriptive comparison of N and CMS development. Such comparative electron microscope studies will be needed to help answer questions raised in the Introduction of this review. Concerning the events within microspores at the beginning of abortion, for example, there is complete ignorance of what organelle shows the first sign of disintegration or whether there is a definite sequence or simply a simultaneous collapse. The answer to this question could yield valuable clues to the direct cause of abortionLooking at the existing published studies and taking into account numerous examples of questionable technique and interpretation, we conclude that abortion has been shown to occur at almost every point in development, and that probably more than one mechanism is involved...

The cytoplasmic male sterility (CMS) phenotype in plants can be reversed by the action of nuclear-encoded fertility restorer (Rf) genes. The molecular mechanism involved in Rf gene-mediated processing of CMS-associated transcripts is unclear, as are the identities of other proteins that may be involved in the CMS-Rf interaction. In this study, we cloned the restorer gene Rf5 for Hong-Lian CMS in rice and studied its fertility restoration mechanism with respect to the processing of the CMS-associated transcript atp6-orfH79. RF5, a pentatricopeptide repeat (PPR) protein, was unable to bind to this CMS-associated transcript; however, a partner protein of RF5 (GRP162, a Gly-rich protein encoding 162 amino acids) was identified to bind to atp6-orfH79. GRP162 was found to physically interact with RF5 and to bind to atp6-orfH79 via an RNA recognition motif. Furthermore, we found that RF5 and GRP162 are both components of a restoration of fertility complex (RFC) that is 400 to 500 kD in size and can cleave CMS-associated transcripts in vitro. Evidence that a PPR protein interacts directly with a Gly-rich protein to form a subunit of the RFC provides a new perspective on the molecular mechanisms underlying fertility restoration.

Abstract In plants, male sterility can be caused either by mitochondrial genes with coupled nuclear genes or by nuclear genes alone; the resulting conditions are known as cytoplasmic male sterility (CMS) and genic male sterility (GMS), respectively. CMS and GMS facilitate hybrid seed production for many crops and thus allow breeders to harness yield gains associated with hybrid vigor (heterosis). In CMS, layers of interaction between mitochondrial and nuclear genes control its male specificity, occurrence, and restoration of fertility. Environment-sensitive GMS (EGMS) mutants may involve epigenetic control by noncoding RNAs and can revert to fertility under different growth conditions, making them useful breeding materials in the hybrid seed industry. Here, we review recent research on CMS and EGMS systems in crops, summarize general models of male sterility and fertility restoration, and discuss the evolutionary significance of these reproductive systems.

雄性不育作为生殖生物学的重要性状,在植物界普遍存在,对于作物杂种优势的利用具有重要意义,在作物育种中具有重要地位。禾本科(Gramineae)植物是人类粮食和牲畜饲料的主要来源,是具有重要经济价值的大科。文章综述了禾本科植物雄性不育的类型、遗传机制、雄性不育的相关基因及其应用,总结了这方面的研究进展,重点归纳了雄性不育的相关基因,展现了雄性不育理论研究及应用的广阔前景。

雄性不育作为生殖生物学的重要性状,在植物界普遍存在,对于作物杂种优势的利用具有重要意义,在作物育种中具有重要地位。禾本科(Gramineae)植物是人类粮食和牲畜饲料的主要来源,是具有重要经济价值的大科。文章综述了禾本科植物雄性不育的类型、遗传机制、雄性不育的相关基因及其应用,总结了这方面的研究进展,重点归纳了雄性不育的相关基因,展现了雄性不育理论研究及应用的广阔前景。

The exploitation of male sterility systems has enabled the commercialization of heterosis in rice, with greatly increased yield and total production of this major staple food crop. Hybrid rice, which was adopted in the 1970s, now covers nearly 13.6 million hectares each year in China alone. Various types of cytoplasmic male sterility (CMS) and environment-conditioned genic male sterility (EGMS) systems have been applied in hybrid rice production. In this paper, recent advances in genetics, biochemistry, and molecular biology are reviewed with an emphasis on major male sterility systems in rice: five CMS systems, i.e., BT-, HL-, WA-, LD- and CW- CMS, and two EGMS systems, i.e., photoperiod- and temperature-sensitive genic male sterility (P/TGMS). The interaction of chimeric mitochondrial genes with nuclear genes causes CMS, which may be restored by restorer of fertility ( Rf ) genes. The PGMS, on the other hand, is conditioned by a non-coding RNA gene. A survey of the various CMS and EGMS lines used in hybrid rice production over the past three decades shows that the two-line system utilizing EGMS lines is playing a steadily larger role and TGMS lines predominate the current two-line system for hybrid rice production. The findings and experience gained during development and application of, and research on male sterility in rice not only advanced our understanding but also shed light on applications to other crops.

Numerous inbreds have been crossed with the cytoplasmically male sterile line Tx 203Ms at the Texas Agricultural Experiment Station. Most of the resulting single crosses were completely sterile; a few showed partial fertility; three were completely fertile. Sterility has also been investigated in double crosses whose single-cross seed parents each involved a male sterile line. When one inbred c...

S-type cytoplasmic male sterility (CMS-S) is the largest group among the three major types of CMS in maize. CMS-S exhibits fertility instability as a partial fertility restoration in a specific nuclear genetic background, which impedes its commercial application in hybrid breeding programs. The fertility instability phenomenon of CMS-S is controlled by several minor quantitative trait locus (QTLs), but not the major nuclear fertility restorer (Rf3). However, the gene mapping of these minor QTLs and the molecular mechanism of the genetic modifications are still unclear. Using completely sterile and partially rescued plants of fertility instable line (FIL)-B, we performed bulk segregant RNA-Seq and identified six potential associated genes in minor effect QTLs contributing to fertility instability. Analyses demonstrate that these potential associated genes may be involved in biological processes, such as floral organ differentiation and development regulation, energy metabolism and carbohydrates biosynthesis, which results in a partial anther exsertion and pollen fertility restoration in the partially rescued plants. The single nucleotide polymorphisms (SNPs) identified in two potential associated genes were validated to be related to the fertility restoration phenotype by KASP marker assays. This novel knowledge contributes to the understanding of the molecular mechanism of the partial fertility restoration of CMS-S in maize and thus helps to guide the breeding programs.

A new cytoplasmic male-sterile (CMS) system for hybrid wheat breeding, YA-type CMS line with the cytoplasmic mutant from the common wheat variety 'CA8057', was developed by the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. The pollen sterility of YA-type CMS line was easily maintained but difficult to restore. Some sterile lines with desirable agronomic performance, such as msYA-'CA8057' (BC 17 ), msYA-'Yuandong 6' (BC 9 ), msYA-'Jin 411' (BC 9 ), msYA-'WL1' (BC 10 ), msYA-'Yanshi 9' (BC 10 ), msYA-'BPm16' (BC 9 ), msYA-'Jindong 8' (BC 9 ) and msYA-'Jinmai 33' (BC 9 ), were bred and a restorer line GR1 was screened with 26 new restorer lines being developed by transferring restorer genes from GR1. It was found that abnormal phenomena occurred at the uninucleate-pollen stage and the abortive pollen was poor in starch content and other components. The variance analysis of agronomic traits in eight sterile lines indicated that there was no general negative effect of cytoplasm. The genetic analysis for fertility restoration showed that two pairs of independent major genes (designated YA Rf 1 YA Rf 1 YAr f 2 YAr f 2 ) and some minor genes could be involved in the fertility restoration in restorer line GR1, and YA Rf 1 was epistatic over YA Rf 2 for the genetic effect of fertility restoration. As a new CMS system, the YA-type CMS line was of potential value for hybrid wheat breeding and should be further studied.

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Brassicaceae crops display strong hybrid vigor, and have long been subject to F1 hybrid breeding. Because the most reliable system of F1 seed production is based on cytoplasmic male sterility (CMS), various types of CMS have been developed and adopted in practice to breed Brassicaceae oil seed and vegetable crops. CMS is a maternally inherited trait encoded in the mitochondrial genome, and the male sterile phenotype arises as a result of interaction of a mitochondrial CMS gene and a nuclear fertility restoring (Rf) gene. Therefore, CMS has been intensively investigated for gaining basic insights into molecular aspects of nuclear-mitochondrial genome interactions and for practical applications in plant breeding. Several CMS genes have been identified by molecular genetic studies, including Ogura CMS from Japanese radish, which is the most extensively studied and most widely used. In this review, we discuss Ogura CMS, and other CMS systems, and the causal mitochondrial genes for CMS. Studies on nuclear Rf genes and the cytoplasmic effects of alien cytoplasm on general crop performance are also reviewed. Finally, some of the unresolved questions about CMS are highlighted.

Two wheat– Thinopyrum substitution lines X479 and X482 selected from the progenies of wheat “Mianyang26 (MY26)”02×02wheat– Thinopyrum intermedium ssp. trichophorum partial amphiploid were characterized by seed storage protein electrophoresis, genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), and PCR-based molecular markers. Seed storage protein analysis showed that X479 expressed some of Th. intermedium ssp. trichophorum -specific gliadin and glutenin bands. Chromosome counting and GISH probed by Pseudoroegneria spicata genomic DNA indicated that two pairs of Thinopyrum -derived chromosomes (St genome and St–J S translocated chromosomes) substituted for two pairs of wheat chromosomes in both X479 and X482. FISH using pAs1 and pHvG38 as probes showed that chromosomes 1B and 4B, and 4D and 6D were absent in X479 and X482, respectively. Using the newly isolated J S chromosome-specific repetitive sequence pDb12H as a probe, the FISH signals revealed that the translocation of St–J S chromosomes in X479 and X482 occurred in repetitive sequence regions of the short arm. The molecular markers based on wheat–rice colinearity confirmed that the chromosome constitutions of X479 and X482 were 1St (1B)02+024St–4J S (4B) and 4St–J S (4D)02+026St (6D), respectively. The substitution lines were both fully fertile which suggests that the Th. intermedium chromosomes in X479 and X482 substitute well for the corresponding wheat chromosomes. The rust resistance and novel agronomic traits revealed that the substitution lines will be potentially useful for genetic improvement of wheat.

The inheritance of a previously identified dominant Rf gene in the confection sunflower line RHA 280 has been determined and designated as Rf 3 . This study reports the mapping of the Rf 3 locus using an F2 population of 227 individuals derived from CMS HA 89-314902×02RHA 280. Bulked segregant analysis with 624 pairs of simple sequence repeat (SSR) primers and sequence tagged site (STS) primers identified two polymorphic SSR markers each of linkage groups (LGs) 7 and 11 from a previous map. Results on 90 F2 individuals with 42 polymorphic markers of LGs 7 and 11 indicated that the Rf 3 gene was linked with eight markers on LG 7, including five SSR markers (ORS328, ORS331, ORS928, ORS966, and ORS1092) and three expressed sequence tag (EST)-SSR markers (HT619-1, HT619-2, and HT1013). Further analysis of the total F2 population of 227 individuals identified a co-dominant marker, ORS328, linked to Rf 3 at a genetic distance of 0.702cM on one side, and a female-dominant marker HT1013 at 12.602cM proximal to Rf 3 on the other side; a genetic distance of 47.102cM for LG 7 was covered. This is the first report of an Rf gene from the confection sunflower. The closely linked marker to Rf 3 will facilitate marker-assisted selection, and provide a basis for cloning of this gene.

Fertility restoration in three diverse CMS sources of sunflower was studied using fifty inbreds (testers). While 22 inbreds maintained sterility of CMS PET 1 and CMS ARG 1, 28 inbreds restored their fertility. The third CMS line GIG 1, was maintained by all the inbreds indicating involvement of different gene(s). Most of the commercial sunflower hybrids are been produced using CMS PET 1. Now with the identification of restorers for CMS ARG 1, new more productive commercial hybrids can be produced. Efforts should be made to locate restorers for CMS GIG 1 for its utilization in production of sunflower hybrids.

1990年发现两个杂交组合的F1表现不育。随即对这两个组合的后代进行追踪观察，确认了这种不育性是可以遗传的。1992年有目的的选用6个品种（系）进行了双列式完全杂交，获得６个不育组合和相应的3个反应组合，从正反交的结果看，是双亲基因工作的结果，估计可能是质核基因互作引起的不育，且表现为显性。造成不育的母本效应来源于同一个母本家系，而父本效应来源复杂且广泛。

1990年发现两个杂交组合的F1表现不育。随即对这两个组合的后代进行追踪观察，确认了这种不育性是可以遗传的。1992年有目的的选用6个品种（系）进行了双列式完全杂交，获得６个不育组合和相应的3个反应组合，从正反交的结果看，是双亲基因工作的结果，估计可能是质核基因互作引起的不育，且表现为显性。造成不育的母本效应来源于同一个母本家系，而父本效应来源复杂且广泛。

THE first cytoplasmic male sterile soybean line was reported by Davis in a U.S. Patent, but no further information has been released since then. Sun et al. developed a cytoplasmic-nuclear male sterile soy-

It is very important for both of the investigation of cytoplasmic male sterile soybean and the hybrid soybean production to develop and search for the male sterile cytoplasm with diversified sources. The data from test crosses of this study verified the existence of male sterile cytoplasm in soybean line ZD8319.Based on the cytoplasm of ZD8319 a CMS soybean line, its maintainer and restorers were developed. Another soybean line carrying male sterile cytoplasm was also discovered.

Hybrids, which exploit the phenomenon termed hybrid vigor or heterosis, have proven to be a practical method of crop improvement. Hybrid autogamous legumes for commercialization have received limited attention. Soybean is an autogamous legume species. Manual cross-pollination to provide large quantities of hybrid seed is difficult and time consuming. This method is acceptable to plant breeding studies but is not acceptable for commercialization. Our goal was to review soybean flower morphology, pollination mechanisms within the genus Glycine, and present sources of male-sterile genes and cytoplasms, and to give examples of their use in plant breeding. The last section will cover heterosis in soybean and the potential for commercial production of hybrid soybean. The soybean flower has all the features that are in agreement with entomophilous characteristics of plants. In the United States, honeybees and alfalfa leafcutter bees, while certain native thrip species in China, may be the most effective in soybean cross-pollinations. Both nuclear and cytoplasmic-nuclear sterility systems are known. With appropriate selectable markers, nuclear systems may be successful. With appropriate restorer genes, nuclear-cytoplasmic systems could be successful. Both systems are under development for commercialization. The heterosis of various soybean parental combinations has not been adequately evaluated. Ten percent or more heterosis, when combined with "gene stacking", seems to be the preferred method for the first generation of commercially available soybean hybrids. The most formidable problem to commercial production is the difficulty in producing large quantities of hybrid seed.

At present, no report on inheritance of male fertility restoration has been released, yet more than 10 cytoplasmic-nuclear male-sterile soybean lines as well as their maintainers and restorers have been developed. Based on our previous work, 25 restorers for the male-sterile line NJCMS1A were identified and the inheritance of male fertility restoration for these restorers was studied. The results showed that F 1 s between NJCMS1A and its restorers were completely male-fertile. The numbers of fertile and sterile plants in the F 2 population of Cross I (NJCMS1A N23601) and Cross II (NJCMS1A N23683) corresponded to a segregation ratio of 15:1, and the numbers of non-segregation lines, 3:1 segregation lines and 15:1 segregation lines in F 2:3 of the same two crosses fitted a 7:4:4 genotypic segregation ratio. The testcross BC 1 F 1 s between the F 1 s of the above two crosses and NJCMS1A, NJCMS1B showed a 3:1 segregation ratio. Accordingly, it was inferred that two pairs of duplicate dominant genes controlled the male fertility restoration of NJCMS1A in both crosses. Meanwhile, F 2 of other 23 crosses between NJCMS1A and its 23 restorers showed a fertility segregation ratio of 3:1 or 15:1. The F 1 s of the five testcrosses between NJCMS1A and the F 1 s of five crosses selected from the above 23 crosses showed that fertility segregation was 3:1 in BC 1 F 1 s between NJCMS1A and F 1 s of the crosses of which fertility segregation fitted 15:1 in F 2 population, while fertility segregation in BC 1 F 1 s was 1:1 for those fertility segregation fitted 3:1 in F 2 population. Allelism tests showed that restore genes of all restorers in the experiment were allelic to two pairs of dominant genes. All results showed that some restorers bore one pair of dominant restore gene and the others bore two pairs of duplicate dominant gene. The mechanism of F 1 male sterility of the cross N8855 N2899 was discussed.

Most of the cytoplasmic-nuclear male-sterile (CMS) lines of soybean were developed only from a limited cytoplasm sources and performed not as good as required in hybrid seed production, therefore, to explore new male-sterile cytoplasm sources should be one of the effective ways to improve the pollination and hybridization for a better pod-set in utilization of heterosis of soybeans. In the present study, total 80 crosses between 70 cultivated and annual wild soybean accessions and three maintainers (N2899, N21249, and N23998) of NJCMS1A were made for detecting potential new sources with male-sterile cytoplasm. The results showed that in addition to the crosses with N8855.1 (the cytoplasm donor parent of NJCMS1A) and its derived line NG99-893 as cytoplasm parent, there appeared three crosses, including N2156602×02N21249 and N2316802×02N21249, with male-sterile plants in their progenies. According to the male fertility performance of backcrosses and reciprocal crosses with the tester N21249, the landrace N21566 and annual wild soybean accession N23168 were further confirmed to have male-sterile cytoplasm. Accordingly, it was understood that the source with male-sterile cytoplasm in soybean gene pool might be not occasional. The results also showed that the genetic system of male sterility of the newly found cytoplasm source N21566 was different from the old cytoplasm source N8855.1, while N23168 was to be further studied. Based on the above results, the derived male-sterile plants from [(N2156602× N21249) F 102 × 02 N21249] BC 1 F 1 were back-crossed with the recurrent parent N21249 for five successive times, and a new CMS line and its maintainer line, designated as NJCMS3A and NJCMS3B, respectively, were obtained. NJCMS3A had normal female fertility and stable male sterility. Its microspore abortion was mainly at middle uninucleate stage, earlier than that of NJCMS1A and NJCMS2A. The male fertility of F 1 s between NJCMS3A and 20 pollen parents showed that 7 accessions could restore its male fertility and other 13 could maintain its male sterility. The male sterility of NJCMS3A and its restoration were controlled by one pair of gametophyte male-sterile gene according to male fertility segregation of crosses between NJCMS3A and three restorers. The nuclear gene(s) of male sterility in NJCMS3A appeared different from the previously reported CMS lines, NJCMS1A and NJCMS2A. The development of NJCMS3A demonstrated the feasibility to discover new CMS system through choosing maintainers with suitable nuclear background.

Abstract With 2 figures and 2 tables Abstract In this study, we report the mapping of the Rf locus in soybean by microsatellite simple sequence repeat (SSR) genetic markers. A cross was made between cytoplasmic male sterility (CMS) line JLCMS82A and restorer line JIHUI 1 based on the DNA polymorphisms revealed by 109 SSR markers. A F 2 population derived from a single F 1 plant containing 103 individuals was used for mapping the Rf locus. The Rf gene of JIHUI 1 gametophytically restores male fertility to JLCMS82A. Fertile and semi-fertile DNA bulks and parental DNAs were screened with 219 SSR markers, and Satt215 which was previously mapped to soybean LG J, was found linked to the Rf gene. Five additional polymorphic SSR markers from LG J were used for analysis and a regional linkage map around the Rf locus was established. SSR markers, Sctt011 and Satt547, flanked the Rf locus at 3.6cM and 5.4cM, respectively. The availability of these SSR markers will facilitate the selection of restorer lines in hybrid soybean breeding.

Observations on the reproductive biology of a male-sterile mutant (ms4) of soybean, Glycine max (L.) Merr., demonstrated that male sterility was the result of a syndrome of abnormalities that influenced the function of the postmeiotic microspore mother cells (MMCs). Cytokinesis following telophase II was absent, incomplete, or disoriented, resulting in cells with different numbers of nuclei. Postmeiotic cells demonstrated various abnormalities in the formation of pollen walls. The nature of the exine ranged from absence through amorphous accumulations of sporopollenin to stratified layers. Infrequently, anther locules functioned properly, and normal pollen was differentiated. The extent and frequency of cytokinesis varied both between and within locules of single anthers. Temperature influenced the frequency of cytokinesis. At temperatures of 35 C day/32 C night, cytokinesis did not occur. Male sterility was concluded to result from the cumulative effects of various abnormalities, all of which involve functions of the postmeiotic MMCs' plasmalemmas.

Essentially all sorghum, (L.) Moench, hybrids are made with a single cytoplasmic-genic sterility system. In an attempt to derive new cytoplasmic-genic male-sterility systems in sorghum, recently introduced lines of diverse types from widespread geographic locations were intercrossed and backcrossed. Three male sterile from this program were tested to determine their cytoplasmic diversity for induction of male sterility. Fertility of the Fhybrids from crosses of each sterile line with a series of tester lines was compared with fertility of hybrids from crosses of a currently used sterile (‘A Tx3197’) with the same testers. Differential sterility responses indicated that each of these cytoplasms probably differ from milo cytoplasm of A Tx3197. Of these, the line with IS 12662C cytoplasm is the most desirable sterile and has been released as ‘A2 Tx2753’. Differential sterility responses among the three steriles also indicated possible cytoplasmic differences among them. Because each of these steriles was in an early generation and differed in nuclear genes, definitive conclusions must await the testing of more nearly isocytoplasmic lines developed by incorporating a common nuclear genotype into each cytoplasmic source.

Cytoplasmic-nuclear male steriles are used as female parents in the production of hybrid seed of sorghum, Sorghum bicolor (L.) Moench. A single male-sterility inducing cytoplasm is most often used in the female parents, resulting in uniformity of cytoplasm in hybrids and also a restriction on nuclear diversity. The purpose of the present study was to identify diverse malesterility inducing cytoplasms. Seed set and other characteristics of hybrids of sorghum were studied to determine differences in fertility response and related characteristics among the cytoplasms of male-sterile female parents. Thirteen near-isonuclear female parents with cytoplasms from diverse introduced sources were crossed by eight male parents, and the progeny were grown at eight locations. From seed-set, anther, and pollen characteristics five groups were identified. Cytoplasms from IS6271C, IS2266C, IS3579C, IS7502C, and IS6705C were not distinguished from milo cytoplasm. Cytoplasm from IS12662C differed from milo in degree of fertility restoration in hybrids and was somewhat similar to IS3063C, IS1056C, and IS2801C. Another group, composed of IS1112C and IS12565C, was distinct in that most male parents produced highly sterile hybrids when crossed with these male steriles. Another cytoplasm, from IS7920C, differed from all the other cytoplasmstudied in its effects on seed-set, anther, and pollen characteristics. It is concluded that among these cytoplasms there are at least four distinct groups in their effects on fertility characteristics. They have potential for providing diversity among parents and hybrids in sorghum, but their utility for such purposes remains to be tested.

Research Agronomist, Cereal Crops Division, ARS, USDA, University of Nebraska

Research Division, Agricultural Research Service, US Department of Agriculture, in 1971 releasedseven grain sorghum Registered by the Crop Science Society of America. REGISTRATION OFD6647, D6654, D6659, AND D6660 DURUM WHEAT GERMPLASM ~ (Reg. No.

Commercial viability of three cytoplasmic-nuclear male sterility (CMS) systems (A 4 , A 5 and A v ) as potential alternatives to the most widely used A 1 system in pearl millet ( Pennisetum glaucum (L.) R.Br.) was evaluated in terms of stability of complete male sterility of four isonuclear A-lines (81A 1 , 81A 4 , 81A 5 and 81A v ) and the level and stability of male fertility restoration of their 44 single-cross hybrids. Lines 81A 4 and 81A 5 had no pollen shedders (PS), and there were very low frequency of non-PS plants of these A-lines that had a maximum of 1-5% selfed seedset (SSS). In 81A 1 and 81A v ,there were, albeit low frequency (<1%) of PS plants, and relatively higher frequency of the non-PS plants in these two lines, the more so in 81A v ,had 1-5% and even greater SSS. Some hybrids made on each of the three A-lines (81A 1 , 81A 4 and 81A v ) had high and stable male fertility, while others made on the same three A-lines displayed large variation in SSS across the environments, the more so in case of hybrids made on 81A v . These results indicate that the A 4 CMS system provides a better alternative to the A 1 CMS system, while the A v system does not. On the basis of highly stable male sterility and the highest frequency of pollinators behaving as maintainers, the A 5 CMS system appeared to be the best for A-line breeding. The commercial viability of this CMS system in breeding R-lines of grain hybrids, however, still remains to be ascertained as no hybrid on it was fully male fertile in any environment.

Abstract The A{sub 1} cytoplasm in pearl millet, Pennisetum glaucum (L.) R. Br., is widely used buy produces fertile revertants. The objectives of this study were to evaluate the stability of male sterility in a cytoplasm (A{sub m}) transferred from P. glaucum (L.) R. Br. subspecies monodii (Maire) Brunken and to determine if this cytoplasm differed from the A{sub 1}, A{sub 2}, and A{sub 3} cytoplasms. In 1983, seeds of male-sterile Tift 23A{sub 1} and Tift 23a{sub m} were stored at 24, 5, and {minus}5{degree}C. In 1984 to 1986, seeds of each line were planted in the field and observed daily at anthesis for fertile revertants. Male sterility of the line with A{sub m} cytoplasm is maintained by the maintainer lines of A{sub 1}, A{sub 2}, and A{sub 3} cytoplasma. Seven tester lines restored full or partial male fertility to hybrids with A{sub 1}, A{sub 2}, and A{sub 3} cytoplasms but only two of the testers restored male fertility to hybrids with A{sub m} cytoplasm. Plants with A{sub 1} cytoplasm are 2 or 3 earlier than plants with A{sub 1} cytoplasm and have darker red anthers than those with A{sub 1} cytoplasm. In 3 yr, male-sterile plants with A{sub 1} cytoplasm averaged 0.91 fertile revertant events per 1000 inflorescences, while no fertile revertants were observed for plants with A{sub m} cytoplasm. The number of fertile revertants for A{sub 1} cytoplasm increased with age of seed from 1 to 3 yr. Seeds stored at 24{degree}C produced plants with significantly more fertile revertants than seeds stored at 5 or {minus}5{degree}C. Differences in seed germination and vigor of seedlings with A{sub 1} and A{sub m} cytoplasms were nonsignificant or of little practical significance. The new cytoplasm, designated A{sub 4}, is different from A{sub 1}, A{sub 2}, and A{sub 3} cytoplasms based on fertility of hybrids, morphological characters, and stability.

Abstract Among the cytoplasmic-nuclear male sterility (CMS) systems reported in pearl millet, Pennisetum glaucum (L.) R. Br., the A m = A 4 system produces the highest frequency of male-sterile hybrids. A CMS source identified in a large-seeded gene pool (LSGP) was compared with the A 4 system. Seven diverse restorer lines of the A4 system produced hybrids with 81A4 that were all fertile (pollen-shedding score 4 and 68–89% selfed seedset). In contrast, all the hybrids of these inbreds made with the isonuclear line with the LSGP cytoplasm were sterile (pollen-shedding score 1 and 0–3% selfed seedset). Topcross hybrids of four diverse composites made with 81A4 had 10–35% plants that had good fertility (> 50% selfed seedset). In comparison, no plant of any topcross hybrid with the isonuclear line having LSGP cytoplasm exceeded 20% selfed seedset, and it was rare for a plant to exceed even 10% selfed seedset. These differential fertility restoration patterns of hybrids indicate that the LSGP cytoplasm represents a CMS system that is different from the A4 and, by implication, from all those reported to date. This new CMS system is designated A 5 .

This chapter discusses the efforts made in the study of male sterility systems and their application in the development of hybrid varieties of various food legume crops (adzuki bean, chickpea, common bean, cowpea, faba bean, mung bean, pigeon pea and soyabean).

Cultivated pigeonpea germplasm has a narrow genetic base due to the bottlenecks caused by domestication and breeding from a small number of genotypes. Pigeonpea genetic improvement has witnessed a slow pace due to low genetic diversity and to the scarce genomics resources. To address these challenges, wild relatives of pigeonpea which represent an unexploited resource of vast genetic variation can be incorporated in breeding programmes facilitating the broadening of genetic base. Although interspecific hybridization has not been commercially successful in pigeonpea, it has played an important role in the development of the cytoplasmic male sterility (CMS) system. Recent years however have witnessed the development of genomics resources at large scale in the crop which has remained untouched with genomics revolution in the past. These resources, together with advances in genomics platform such as high throughput genotyping assays and next generation sequencing technologies and modern genetics and breeding approaches will accelerate harnessing natural variation for pigeonpea improvement.

Abstract Top of page Abstract Genetic Male-Sterility (GMS) Systems in Pigeonpea Cytoplasmic-Nuclear Male-Sterility (CMS) Systems in Pigeonpea Blockages in Microsporogenesis of Male-Sterile Genotypes Inheritance of Male-Sterility and Fertility Restoration Systems Effect of Environment on Male-Sterility Systems Molecular Characterization of Male-Sterile Lines Utilization of Male-Sterility Systems in Pigeonpea Breeding Summary and Outlook Acknowledgements References With 1 figure and 4 tables Abstract Male-sterility has been successfully used for enhancing yield in a number of cereal and vegetable crops. In food legumes, this technology could never be used either due to non-availability of natural out-crossing system, or an efficient male-sterility system or both. Pigeonpea [ Cajanus cajan (L.) Millsp.] is a partially cross-pollinated food legume and recent success in breeding a stable male-sterility system has allowed breeders to exploit hybrid vigour for increasing yields. The cytoplasmic-nuclear male-sterility (CMS)-based hybrids have recorded 28.4% yield superiority over local checks in farmers' fields. This paper besides summarizing the reports of all the genetic and CMS systems, also discusses the prospects of utilizing these male-sterility systems in commercial hybrid breeding programmes.

Thirteen nonallelic genetic-male sterile loci of maize (Zea mays L.) were investigated cytologically to determine the microsporogenesis breakdown characteristics for each mutant. These male-sterile mutants included ms1, ms2, ms5, ms6, ms7, ms8, ms9, ms10, ms11, ms12, ms13, ms14, and ms17 in A632 and 0h43 inbred backgrounds. Male-sterile mutants ms8 and ms9 resulted in abnormal microspore (pollen) mother cells that exhibited nearly normal nuclear development but abnormal cellular development. These mutants had the earliest effect on microsporogenesis. Male-sterile mutants ms5, ms11, and ms14 had the latest effect on microsporogenesis in that microspores developed until the microspore mitosis stage. Other male-sterile mutants seemed to have similar expressions when compared with each other. Mutants ms2 and ms7 both lacked significant microspore wall formation at the time of microspore collapse. Mutants ms10 and ms13 were similar in that the microspore wall developed to approximately one-half the normal thickness before microspore collapse. A unique feature of ms1 was the occurrence of an abnormally thickened microspore wall. Almost complete microspore wall development occurred in ms12 plants despite nuclear degradation. Mutant ms6 was cytologically and genetically similar to polymitotic (po). Mutant ms17 had variable expression that most notably affected spindle formation. These observations may be useful in utilizing genetic male sterility in maize hybrid seed production schemes.

We have developed a novel hybridization platform that utilizes nuclear male sterility to produce hybrids in maize and other cross‐pollinating crops. A key component of this platform is a process termed Seed Production Technology (SPT). This process incorporates a transgenic SPT maintainer line capable of propagating nontransgenic nuclear male‐sterile lines for use as female parents in hybrid production. The maize SPT maintainer line is a homozygous recessive male sterile transformed with a SPT construct containing (i) a complementary wild‐type male fertility gene to restore fertility, (ii) an α‐amylase gene to disrupt pollination and (iii) a seed colour marker gene. The sporophytic wild‐type allele complements the recessive mutation, enabling the development of pollen grains, all of which carry the recessive allele but with only half carrying the SPT transgenes. Pollen grains with the SPT transgenes exhibit starch depletion resulting from expression of α‐amylase and are unable to germinate. Pollen grains that do not carry the SPT transgenes are nontransgenic and are able to fertilize homozygous mutant plants, resulting in nontransgenic male‐sterile progeny for use as female parents. Because transgenic SPT maintainer seeds express a red fluorescent protein, they can be detected and efficiently separated from seeds that do not contain the SPT transgenes by mechanical colour sorting. The SPT process has the potential to replace current approaches to pollen control in commercial maize hybrid seed production. It also has important applications for other cross‐pollinating crops where it can unlock the potential for greater hybrid productivity through expanding the parental germplasm pool.

The breeding and large-scale adoption of hybrid seeds is an important achievement in agriculture. Rice hybrid seed production uses cytoplasmic male sterile lines or photoperiod/thermo-sensitive genic male sterile lines (PTGMS) as female parent. Cytoplasmic male sterile lines are propagated via cross-pollination by corresponding maintainer lines, whereas PTGMS lines are propagated...

In 1973, in the field of the single cropping late Geng-type rice(Oryza sativa L. subsP. japonica) var. cv. Nongken 58, the author found one spontaneous male-sterile plant, which shows male-sterile under long-day condition and fertile under short-day condition. In 1984, Dr. Deng Jingyang of the Chinese Academy of Agricultural Sciences made analysis of the data obtained in many years with the scientists of Hubei Province, and recognized this material as controlled by a pair of photosensitive recessive male-sterile key-genes not hitherto reported at home or abroad. So Dr. Deng named it as "Hubei photosensitive genic male-sterile rice", This sterile material can reproduce itself by selfing under short-day condition, and crosses can be made under long-day condition to produce F_1 hybrids. In crosses, all Geng-type rice varieties can be used as pollen-donors, the fertility of F_1 hybrids is normal, so it is advantageous for extensive screening of vigorous heterosis combinations, and besides, this material can be used as an efficient breeding tool in rice hybridization.

Annong S1 is the first indica TGMS line in rice discovered and developed inside and outside China, which opens up a new way to the utilization of heterosis in rice. The researches on its reaction to temperature and light in fertility expression, inheritance of its sterility and its physiologicalbiochemical characteristics were reviewed. The utilization of it in twoline hybrid rice breeding and its prospect were summarized and discussed.

Photoperiod-sensitive genic male-sterile (PSGMS) rice, in which pollen fertility is regulated by day-length, originally arose as a natural mutant in the rice cultivar Nongken 58 ( Oryza sativa ssp. japonica ). Previous studies identified pms3 on chromosome 12 as the locus of the original PSGMS mutation. In this study we have assigned the pms3 locus to a 28.4-kb DNA fragment by genetic and physical mapping. A cross between Nongken 58S (PSGMS line) and DH80 was used to produce an F 2 population of about 7000 plants, from which 892 highly sterile individuals were obtained for recombination analysis. By analyzing recombination events in the sterile individuals using a total of 157 RFLP probes from a BAC contig covering the pms3 region, the pms3 locus was localized to a sub-region of less than 1.7 cM. Further analysis of recombination events using 49 additional probes isolated from this sub-region identified markers flanking the pms3 region on each side; these markers are only 28.4-kb apart. Sequence analysis of this fragment predicted the presence of five ORFs, found high homology with two ESTs in public databases, and detected three SNPs between the mutant and the wild-type parents, which may be helpful for identifying a candidate gene for pms3 .

We have previously shown that cytoplasmic male sterility in sunflower is associated with the insertion into the mitochondrial DNA of a novel open reading frame (ORF) located 3' to the atpA gene. Here, we show that in mitochondria from the sterile line, this novel ORF (ORF522) is cotranscribed with atpA. We have identified the product of the ORF522 as being a 15 kDa protein previously observed in sterile plant mitochondria by in organello translation. Both Western blot analysis and in organello translation assays show reduced levels of the 15 kDa polypeptide upon restoration of fertility. Interestingly, this reduction is tissue specific since it is only observed in the male florets from restored hybrid plants. These results suggest that the 15 kDa novel polypeptide is probably responsible for the CMS phenotype. Northern blot analysis using RNA from both seedlings and male florets shows a flower-specific reduction in the level of the ORF522 transcript in the restored hybrid line. The reduction is not due to a reduced transcription rate as demonstrated by 'run-on' experiments using mitochondria isolated from male florets. This suggests that the product of the nuclear restorer gene acts at the post-transcriptional level to destabilize the novel mitochondrial transcript in a tissue-specific manner and restore male fertility.

Rice is a major staple food worldwide. Making hybrid rice has proved to be an effective strategy to significantly increase grain yield. Current hybrid rice technologies rely on male sterile lines and have been used predominantly in indica cultivars. However, intrinsic problems exist in the implementation of these technologies, such as limited germplasms and unpredictable conversions from sterility to fertility in the field. Here, we describe a photoperiod-controlled male sterile line, carbon starved anther (csa), which contains a mutation in an R2R3 MYB transcription regulator of pollen development. This mutation was introduced into indica and japonica rice, and it rendered male sterility under short-day conditions and male fertility under long-day conditions in both lines. Furthermore, F(1) plants of csa and a restorer line JP69 exhibited heterosis (hybrid vigor), suggesting the feasibility of using this mutation to create hybrid rice. The csa-based photoperiod-sensitive male sterile line allows the establishment of a stable two-line hybrid system, which promises to have a significant impact on agriculture.

An alloplasmic wheat line with the cytoplasm of Aegilops crassa expresses photoperiod-sensitive cytoplasmic male sterility (PCMS). Southern- and Northern-hybridization analyses showed that this line contains alterations in both the gene structure and transcription patterns of the mitochondrial gene orf25. In this study, the nucleotide sequence around the orf25 gene of Ae. crassa (CR-orf25) and common wheat (AE-orf25) was determined, and we found that the upstream region of CR-orf25 had been replaced by that of rps7 of common wheat (AE-rps7) through recombination. A novel open reading frame (orf48) is present upstream of CR-orf25. In these three genes, transcription was initiated from the consensus promoter motif of plant mitochondrial genes located in the upstream regions. Processing enzymes in Ae. crassa and common wheat cleave the respective precursor mRNAs, namely CR-orf25 and AE-rps7, at sites similar to that of the premature mitochondrial 26S rRNA. In contrast, the precursor mRNA is not effectively processed at the target sequence of CR-orf25 in the alloplasmic wheat line. Because major transcripts of the euplasmic CR-orf25 and AE-rps7 genes would result in a truncated orf48 product, one possibility is that the orf48 protein might disturb mitochondrial function at a specific stage and hence affect the expression of the PCMS trait.

The common wheat ( Triticum aestivum L.) is a poly(hexa)ploid, derived from an amphi-diploidization process involving the donor species Triticum urartu , Aegilops speltoides , Triticum turgidum , and Aegilops tauschii . The genetic diversity of the autogamous wheat is narrow, which is a major reason for lesser rate of yield gain in wheat, in contrast to rice and maize. It is desirable to encourage hybrid breeding, i.e., combining different lines into genetically divergent heterotic pools. Thus, hybrid plants are a unique combination of desired alleles produced by crossing between genetically different parental lines. Hybrid seed production in a crop requires male-sterile female parents along with a reliable outcrossing system. The male-sterile female parent prevents pollen shedding and self-fertilization, maintaining the purity of hybrid seeds. An outcrossing system enhances hybrid seed production. This article emphasizes the biological relevance of crossbreeding and self-pollination in wheat, and reviews different male sterility systems which could be utilized for the development of hybrid wheat. Several biotechnological approaches and their practical utility in generating cross-compatible male-sterile female parent lines have been discussed.

A comparison of two male sterility systems was carried out in wheat for hybrid seed production and hybrid performance. Seventeen hybrid combinations based on Triticum timopheevi cytoplasm were compared with their genetically equivalent CHA-facilitated combinations. The same set of restorer lines was used as parents in CMS- and CHA-based hybrids to maintain genetic equivalence. In the first experiment aimed at study of female line behavior and crossed seed production, the CHA treated lines showed significantly shorter heights whereas CMS lines were similar to the control. The two systems were equally effective in sterilizing rate. The outcrossing percentage of the CMS lines was almost twice that of the CHA treated lines. Thousand-grain weight of the crossed seeds on CMS lines was greater than on the CHA treated lines and control. On average, the germination percentage of seeds on CMS lines was double that of the CHA treated lines and the percentage of effective outcrossed seeds in CMS lines was 3 times more than that from CHA treated lines. The second experiment was conducted to examine the yield performance of the hybrids derived from the two systems of male sterility. A total of 40 entries including 20 hybrids and 20 parents were evaluated in the experiment. The mean grain yield of the CMS-based hybrids was greater than that of the CHA-based hybrids,the B and R lines. All the CMS-based hybrids showed significantly higher grain yields than their better parents whereas all the CHA-based hybrids, except two,showed no significant yield increases over their better parents. Possible reasons for differences in CMS- and CHA-based hybrid performance are discussed.