Fertility Segregation Research Articles

A germline PAF1 paralog complex ensures cell type-specific gene expression.

Animal germline development and fertility rely on paralogs of general transcription factors that recruit RNA polymerase II to ensure cell type-specific gene expression. It remains unclear whether gene expression processes downstream from such paralog-based transcription is distinct from that of canonical RNA polymerase II genes. In Drosophila, the testis-specific TBP-associated factors (tTAFs) activate over a thousand spermatocyte-specific gene promoters to enable meiosis and germ cell differentiation. Here, we show that efficient termination of tTAF-activated transcription relies on testis-specific paralogs of canonical polymerase-associated factor 1 complex (PAF1C) proteins, which form a testis-specific PAF1C (tPAF). Consequently, tPAF mutants show aberrant expression of hundreds of downstream genes due to read-in transcription. Furthermore, tPAF facilitates expression of Y-linked male fertility factor genes and thus serves to maintain spermatocyte-specific gene expression. Consistently, tPAF is required for the segregation of meiotic chromosomes and male fertility. Supported by comparative in vivo protein interaction assays, we provide a mechanistic model for the functional divergence of tPAF and the PAF1C and identify transcription termination as a developmentally regulated process required for germline-specific gene expression.

Processing and Visualization of Protec-Seq Data for the Generation of Calibrated, Genome-Wide Double Double-Strand Break(dDSB) Maps.

This chapter describes the computational pipeline for the processing and visualization of Protec-Seq data, a method for purification and genome-wide mapping of double-stranded DNA protected by a specific protein at both ends. In the published case, the protein of choice was Saccharomyces cerevisiae Spo11, a conserved topoisomerase-like enzyme that makes meiotic double-strand breaks (DSBs) to initiate homologous recombination, ensuring proper segregation of homologous chromosomes and fertility. The isolated DNA molecules were thus termed double DSB (dDSB) fragments and were found to represent 34 to several hundred base-pair long segments that are generated by Spo11 and are enriched at DSB hotspots, which are sites of topological stress. In order to allow quantitative comparisons between dDSB profiles across experiments, we implemented calibrated chromatin immunoprecipitation sequencing (ChIP-Seq) using the meiosis-competent yeast species Saccharomyces kudriavzevii as calibration strain. Here, we provide a detailed description of the computational methods for processing, analyzing, and visualizing Protec-Seq data, comprising the download of the raw data, the calibrated genome-wide alignments, and the scripted creation of either arc plots or Hi-C-style heatmaps for the illustration of chromosomal regions of interest. The workflow is based on Linux shell scripts (including wrappers for publicly available, open-source software) as well as R scripts and is highly customizable through its modular structure.

A note on intraspecific cytomorphological comparison in two cytotypes (4x, 12x) of Potentilla atrosanguinea Lodd. from Cold Deserts of Ladakh, NW Himalayas, India

The present communication reports the record of intraspecific polyploids (4x, 12x) in Potentilla atrosanguinea from the cold deserts of Ladakh, India. The individuals of the specie showed morphogenetic variations in the studied area and two variants have been recoginized on the basis of flower colour and chromosome count. The study included the male meiosis, microsporogenesis, pollen fertility and morphometric parameters in the populations of 4 × and 12 × cytotypes. Both the polyploids exhibited normal meiotic behaviour characterized by normal chromosome pairing, regular segregation of chromosomes and high pollen fertility. The two cytotypes could be differentiated on the basis of size of stomata and pollen grains also, which are significantly larger in the 12 × compared to the 4x.

QRf8-1, a Novel QTL for the Fertility Restoration of Maize CMS-C Identified by QTL-seq.

C-type cytoplasmic male sterility (CMS-C), one of the three major CMS types in maize, has a promising application prospect in hybrid seed production. However, the complex genetic mechanism underlying the fertility restoration of CMS-C remains poorly understood. The maize inbred line A619 is one of the rare strong restorer lines carrying the restorer gene Rf4, but different fertility segregation ratios are found in several F2 populations derived from crosses between isocytoplasmic allonucleus CMS-C lines and A619. In the present study, the segregation ratios of fertile to sterile plants in the (CHuangzaosi × A619) F2 and BC1F1 populations (36.77:1 and 2.36:1, respectively) did not follow a typical monogenic model of inheritance, which suggested that some F2 and BC1F1 plants displayed restored fertility even without Rf4. To determine the hidden locus affecting fertility restoration, next-generation sequencing-based QTL-seq was performed with two specific extreme bulks consisting of 30 fertile and 30 sterile rf4rf4 individuals from the F2 population. A major QTL related to fertility restoration, designated qRf8-1, was detected on the long arm of chromosome 8 in A619. Subsequently, qRf8-1 was further validated and narrowed down to a 17.93-Mb genomic interval by insertion and deletion (InDel) and simple sequence repeat (SSR) marker-based traditional QTL mapping, explaining 12.59% (LOD = 25.06) of the phenotypic variation. Thus, using genetic analyses and molecular markers, we revealed another fertility restoration system acting in parallel with Rf4 in A619 that could rescue the male sterility of CHuangzaosi. This study not only expands the original fertility restoration system but also provides valuable insights into the complex genetic mechanisms underlying the fertility restoration of CMS-C.

Unique fertility restoration suppressor genes for male-sterile CMS ANN2 and CMS ANN3 cytoplasms in sunflower (Helianthus annuus L.)

Single dominant fertility restoration (Rf) genes for cytoplasmic male-sterile (CMS) sunflower lines CMS ANN2 and CMS ANN3 were previously identified in three and five sources, respectively. However, expressions of the dominant Rf genes were suppressed when crossing restoration lines with three inbred lines. Preliminary results indicated that segregation of fertility in most testcross progeny families from crosses of half-diallel F1’s of restoration lines with the two CMS lines, respectively, did not agree with those of the F2 generation of the half-diallel crosses. In this study, using selected CMS ANN2 and CMS ANN3 plants without the silencing suppressor (S) genes, we confirmed the existence of S genes in the nuclear genomes of the CMS lines used for crossing of the two CMS cytoplasms. Inheritance study suggested that Rf gene suppression was controlled by a single dominant gene in specific backgrounds, whereas two to three complementary S genes could exist in certain backgrounds. Using testcross population Rf ANN2-P21/RHA 274//Rf ANN2-P21, a single S gene from RHA 274, designated S1, was mapped to a recombination suppressed region on the sunflower linkage group (LG) 3, co-segregating with 16 SSR or single nucleotide polymorphism (SNP) markers, flanked by NSA_003339 and ORS124 at a distance of 1.4 and 0.7 cM, respectively. These molecular markers will potentially assist in identifying lines without suppressor genes, including CMS lines. Unique suppression of Rf genes confirmed existence of suppressor (S1) gene in CMS lines that mapped to a recombination suppressed region on linkage group 3, which will enhance understanding of cytoplasm-nuclear interactions.

Exploring differentially expressed genes associated with fertility instability of S-type cytoplasmic male-sterility in maize by RNA-seq

AbstractThe germplasm resources for the S-type male sterility is rich in maize and it is resistant to Bipolaris maydis race T and CI, but the commercial application of S-type cytoplasmic male sterility (CMS-S) in maize hybrid industry is greatly compromised because of its common fertility instability. Currently, the existence of multiple minor effect loci in specific nuclear genetic backgrounds was considered as the molecular mechanism for this phenomenon. In the present study, we evaluated the fertility segregation of the different populations with the fertility instable material FIL-H in two environments of Beijing and Hainan, China. Our results indicated that the fertility instability of FIL-H was regulated by multiple genes, and the expression of these genes was sensitive to environmental factors. Using RNA sequencing (RNA-seq) technology, transcriptomes of the sterile plants and partially fertile plants resulted from the backcross of FIL-H×Jing 724 in Hainan were analyzed and 2 108 genes with different expression were identified, including 1 951 up-regulated and 157 down-regulated genes. The cluster analysis indicated that these differentially expressed genes (DEGs) might play roles in many biological processes, such as the energy production and conversion, carbohydrate metabolism and signal transduction. In addition, the pathway of the starch and sucrose metabolism was emphatically investigated to reveal the DEGs during the process of starch biosynthesis between sterile and partially fertile plants, which were related to the key catalytic enzymes, such as ADP-G pyrophosphorylase, starch synthase and starch branching enzyme. The up-regulation of these genes in the partially fertile plant may promote the starch accumulation in its pollen. Our data provide the important theoretical basis for the further exploration of the molecular mechanism for the fertility instability in CMS-S maize.

Segregation for fertility and meiotic stability in novel Brassica allohexaploids.

Allohexaploid Brassica populations reveal ongoing segregation for fertility, while genotype influences fertility and meiotic stability. Creation of a new Brassica allohexaploid species is of interest for the development of a crop type with increased heterosis and adaptability. At present, no naturally occurring, meiotically stable Brassica allohexaploid exists, with little data available on chromosome behaviour and meiotic control in allohexaploid germplasm. In this study, 100 plants from the cross B. carinata × B. rapa (A2 allohexaploid population) and 69 plants from the cross (B. napus × B. carinata) × B. juncea (H2 allohexaploid population) were assessed for fertility and meiotic behaviour. Estimated pollen viability, self-pollinated seed set, number of seeds on the main shoot, number of pods on the main shoot, seeds per ten pods and plant height were measured for both the A2 and H2 populations and for a set of reference control cultivars. The H2 population had high segregation for pollen viability and meiotic stability, while the A2 population was characterised by low pollen fertility and a high level of chromosome loss. Both populations were taller, but had lower average fertility trait values than the control cultivar samples. The study also characterises fertility and meiotic chromosome behaviour in genotypes and progeny sets in heterozygous allotetraploid Brassica derived lines, and indicates that genotypes of the parents and H1 hybrids are affecting chromosome pairing and fertility phenotypes in the H2 population. The identification and characterisation of factors influencing stability in novel allohexaploid Brassica populations will assist in the development of this as a new crop species for food and agricultural benefit.

Novel genetic male sterility developed in (Capsicum annuum x C. chinense) x C. pubescens and induced by HNO2 showing Mendelian inheritance and aborted at telophase of microspore mother cell stage.

A novel genetic male sterile germplasm was developed by successively crossing of (C. annuum x C. chinense) x C. pubescens and by chemical mutagenesis in pepper. The sterile anthers showed morphological abnormalities, but pistils developed normally with fine pollination capability. We investigated fertility segregation through sib-crossing of the same strains and test crossing by male sterile plants with 6 advanced inbred lines. The results showed that male fertility in the pepper was dominant in the F1 generation and segregated at a rate of 3:1 in the F2 generation, suggesting that monogenic male sterility was recessive and conformed to Mendelian inheritance. Cyto-anatomy analysis revealed that microspore abortion of sterile anthers occurred during telophase in the microspore mother cell stage when tapetal cells showed excessive vacuolation, resulting in occupation of the loculi. The microspore mother cells self-destructed and autolyzed with the tapetum so that meiosis in pollen mother cells could not proceed past the tetrad stage.

Development of a candidate gene marker for Rf 1 based on a PPR gene in cytoplasmic male sterile CMS-D2 Upland cotton

The cytoplasmic male sterility (CMS) system is convenient and efficient for hybrid seed production in Upland cotton (Gossypium hirsutum L.). However, it has not been widely used because of limited restorer lines carrying the restorer gene Rf1 in the CMS-D2 system. In this study, the fertility segregation in a backcross (BC8F1) population of 409 individuals and an F2 population of 695 plants confirmed that the fertility restoration was determined by one dominant restorer gene (Rf1). A sequence alignment showed that 13 Rf1-linked simple sequence repeat marker sequences were distributed on nine scaffolds of chromosome 9 in the sequenced D5 genome of G. raimondii Ulbrich. Ten pentotricopeptide repeat (PPR)-like genes were identified on two scaffolds, including Scaffold 333 where nine PPR-like genes were clustered in a region of about 160 kb. Among them, PPR-like gene Cotton_D_gene_10013437 was identified as the candidate for the Rf1 gene through a comparative sequence analysis of the homologous gene among sterile (A), maintainer (B) and restorer (R) lines, and co-segregation analysis. Compared with the non-restoring lines, the restorer had a 9-nucleotide (nt) insertion and a single nucleotide polymorphism (SNP) 8 nt upstream of the insertion at the 3′ untranslated regions (3′ UTRs) in this gene. A cleaved amplified polymorphic sequence (CAPS) marker named CAPS-R was developed from the SNP site using the restriction enzyme DraI, and was further used to track the restorer gene and its homozygous or heterozygous status in molecular breeding for restorer lines. A marker-assisted selection system using the Rf1-specific CAPS-R marker and a CMS-D2 cytoplasm-specific SCAR marker was established to distinguish the three-line hybrids from other genotypes.

A STUDY IN AN AREA OF TRANSITION BETWEEN SEASONALLY DRY TROPICAL FOREST AND MESOTROPHIC CERRADÃO, IN MATO GROSSO DO SUL, SOUTHWESTERN BRAZIL

This study describes the tree vegetation and soils occurring in a seasonally dry tropical forest (SDTF) and mesotrophic cerradão transition in southwestern Brazil. All trees ≥ 5 cm diameter were measured in 20 plots of 20 × 25 m, 10 in SDTF, and 10 in mesotrophic cerradão. Ten soil samples of 0−20 cm depth were made per plot and mixed in plot groups to produce two composite samples. A total of 71 species was recorded. Anadenanthera colubrina had the highest importance values in both formations. Differences in soil fertility were found between SDTFs (eutrophic soils) and mesotrophic cerradão (mesotrophic soils). A non-metric multidimensional scaling and cluster analysis confirmed the soil fertility segregation, and also showed an agreement between soil fertility and variance in species composition gradients. The mesotrophic cerradão showed higher species richness since it also includes many species typical of more dystrophic and open forms of Cerrado.

Genetically Characterizing a New Indica Cytoplasmic Male Sterility with Oryza glaberrima Cytoplasm for Its Potential Use in Hybrid Rice Production

Cytoplasmic diversification is of vital importance to avoid the genetic vulnerability of hybrid rice (Oryza sativa L.). A new indica cytoplasmic male sterility (CMS), designated African rice (AF) CMS, has been derived from interspecific crosses using African rice (Oryza glaberrima Steud.) as the cytoplasmic donor and genetically characterized for its potential use. The AF CMS lines were completely sterile whereas the fertility of its F1 hybrids was readily restored. The restoration–maintenance relationship of AF CMS was consistent with that of sporophytic wild abortive (WA) and Indonesian paddy (ID) CMS but different from the gametophytic Honglian (HL) CMS. Specific banding patterns for AF CMS were identified by amplified fragment length polymorphism (AFLP). The AFLP markers can be used to detect genetic purity of seed stocks of AF CMS lines and their hybrids. Fertility segregation in F2 populations of crosses between AF CMS lines and an introgression restorer line corresponded to a 3:1 fertile:sterile ratio, indicating a single major dominant restorer gene was involved. The fertility‐restoring gene was located on chromosome 10 between simple sequence repeat (SSR) markers RM304 and RM6100 at a genetic distance of 1.25 cM from RM6100. Molecular assays confirmed the introgression of a major restorer gene from O. glaberrima into the O. sativa genome. We conclude the new AF CMS system should be of great potential use in hybrid rice production.

Studies on Inheritance of Geneic Male Sterility (GMS) and Hybrid Seed Production in Okra [Abelmoschus esculentus (L.) Moench.

Inheritance of geneic male sterility in GMS line MS-1 of okra [Abelmoschus esculentus (L.) Moench.] was studied using F1, F2 and test-cross generations of crosses between GMS line MS-1 and normal fertile genotypes, and the varieties Arka Anamika, Parbhani Kranti, Arka Abhay, IIHR-108-1-31, IIHR-109-20-6, IIHR-116-23-6, IIHR- 180-6-3, IIHR-161-10-1 and IIHR-130-2-10. All the F1 were found fertile. Segregation of pollen fertility in F2 and test - cross generations involving ms1 was segregated in the ratio 1 fertile: 1 sterile, respectively. This indicated that GMS trait in the line is controlled by a single recessive gene (ms1ms1). Large-scale F1 hybrid seed production in okra becomes rather slow due to the tedious hand-emasculation, followed by hand-pollination, incurring additional labour and cost of F1 seed production. In comparison to fertile lines, this saves approximately 70% time and manual labour. Use of Geneic Male Sterile (GMS) line MS-1 can make F1 hybrid seed production in okra easy and more economical compared to hand-emasculation.

Genetics and mapping of the R 11 gene conferring resistance to recently emerged rust races, tightly linked to male fertility restoration, in sunflower (Helianthus annuus L.)

Sunflower oil is one of the major sources of edible oil. As the second largest hybrid crop in the world, hybrid sunflowers are developed by using the PET1 cytoplasmic male sterility system that contributes to a 20 % yield advantage over the open-pollinated varieties. However, sunflower production in North America has recently been threatened by the evolution of new virulent pathotypes of sunflower rust caused by the fungus Puccinia helianthi Schwein. Rf ANN-1742, an 'HA 89' backcross restorer line derived from wild annual sunflower (Helianthus annuus L.), was identified as resistant to the newly emerged rust races. The aim of this study was to elucidate the inheritance of rust resistance and male fertility restoration and identify the chromosome location of the underlying genes in Rf ANN-1742. Chi-squared analysis of the segregation of rust response and male fertility in F(2) and F(3) populations revealed that both traits are controlled by single dominant genes, and that the rust resistance gene is closely linked to the restorer gene in the coupling phase. The two genes were designated as R ( 11 ) and Rf5, respectively. A set of 723 mapped SSR markers of sunflower was used to screen the polymorphism between HA 89 and the resistant plant. Bulked segregant analysis subsequently located R ( 11 ) on linkage group (LG) 13 of sunflower. Based on the SSR analyses of 192 F(2) individuals, R ( 11 ) and Rf5 both mapped to the lower end of LG13 at a genetic distance of 1.6 cM, and shared a common marker, ORS728, which was mapped 1.3 cM proximal to Rf5 and 0.3 cM distal to R ( 11 ) (Rf5/ORS728/R ( 11 )). Two additional SSRs were linked to Rf5 and R ( 11 ): ORS995 was 4.5 cM distal to Rf5 and ORS45 was 1.0 cM proximal to R ( 11 ). The advantage of such an introduced alien segment harboring two genes is its large phenotypic effect and simple inheritance, thereby facilitating their rapid deployment in sunflower breeding programs. Suppressed recombination was observed in LGs 2, 9, and 11 as it was evident that no recombination occurred in the introgressed regions of LGs 2, 9, and 11 detected by 5, 9, and 22 SSR markers, respectively. R ( 11 ) is genetically independent from the rust R-genes R ( 1 ), R ( 2 ), and R ( 5 ), but may be closely linked to the rust R-gene R ( adv ) derived from wild Helianthus argophyllus, forming a large rust R-gene cluster of R ( adv )/R ( 11 )/R ( 4 ) in the lower end of LG13. The relationship of Rf5 with Rf1 is discussed based on the marker association analysis.

Characteristics of a novel male–female sterile watermelon (Citrullus lanatus) mutant

A novel male–female sterile (MFS) watermelon mutant was discovered as a progeny of the F1-hybrid cultivar Chunlei, which was irradiated twice with gamma rays. The present study aimed to characterise the primary mechanism responsible for the sterility of the MFS watermelons. Morphological characteristics of male and female gametophyte development were investigated using acetocarmine staining, pollen germination, and paraffin methods. Genetic analyses were conducted using heterozygote fertility reciprocal crossing with one normal line, M134. The most meiotic pollen mother cells (PMCs) showed variable chromosome behaviours such as incomplete synapsis, chromosome lagging, univalents, and bridges, which led to the formation of multiple nuclei and non-viable male gametes with only 0.58% stainability and zero germination rate. Embryo-sac mother cells (EMCs) were also shown to be abnormal. As a result, 0.31% of the ovules had complete embryo sacs and 99.8% of the seeds per fruit were empty. Fertility segregation was observed in the heterozygote, with a fertile-to-sterile plant ratio of 3:1. Findings of this study indicate that the male–female sterility of the watermelons, which was controlled by a single recessive gene, can be attributed to abnormal meiosis in PMCs and EMCs.

Two non-allelic nuclear genes restore fertility in a gametophytic pattern and enhance abiotic stress tolerance in the hybrid rice plant

In indica rice, the HongLian (HL)-type combination of cytoplasmic male sterility (CMS) and fertility restoration (Rf) is widely used for the production of commercial hybrid seeds in China, Laos, Vietnam and other Southeast Asian countries. Generally, any member of the gametophytic fertility restoration system, 50% of the pollen in hybrid F(1) plants displays recovered sterility. In this study, however, a HL-type hybrid variety named HongLian You6 had approximately 75% normal (viable) pollen rather than the expected 50%. To resolve this discrepancy, several fertility segregation populations, including F(2) and BC(1)F(1) derived from the HL-CMS line Yuetai A crossed with the restorer line 9311, were constructed and subjected to genetic analysis. A gametophytic restoration model was discovered to involve two non-allelic nuclear restorer genes, Rf5 and Rf6. The Rf5 had been previously identified using a positional clone strategy. The Rf6 gene represents a new restorer gene locus, which was mapped to the short arm of chromosome 8. The hybrid F(1) plants containing one restorer gene, either Rf5 or Rf6, displayed 50% normal pollen grains with I(2)-KI solution; however, those with both Rf5 and Rf6 displayed 75% normal pollens. We also established that the hybrid F(1) plants including both non-allelic restorer genes exhibited an increased stable seed setting when subjected to stress versus the F(1) plants with only one restorer gene. Finally, we discuss the breeding scheme for the plant gametophytic CMS/Rf system.

Aanlysis of short photo-periodic sensitive genic male sterility and molecular mapping of rpms3(t) gene in rice (Oryza sativa L.) using SSR markers

A research was conducted on the pollen fertility of rice sterile lines D52S and D38S responsive to photoperiod during the sensitive stage under natural and controlled conditions. Bulk segregant analysis (BSA) and recessive class approach were applied to identify DNA markers that co-segregate with gene conferring male-sterility in D52S mutant rice. The results showed that in day-light higher or equal to 14.00 h, D52S and D38S rice pollen were fertile; however, they were sterile when day-length was less than 14.00 h. They were therefore considered to be short photo-periodic sensitive genic male sterile lines(Short PGMS lines). Under short day-light conditions, the pollen fertility segregation of F2 populations from crosses between D52S/Shuhui527 and D52S/Gui99showed 3:1 ratio of fertile to sterile plants suggestingthat male sterility in D52S was controlled by one recessive gene. Two markers RM244 and RM216 located on chromosome number 10 co-segregated completely with the rpms locus. The locus was mapped to the interval between SSR markers RM2571 (6.6 cM) and RM244 (4.6 cM).

English

Information on the genetics of fertility restoration facilitates breeding and/or selection of restorer lines used in hybrid breeding program in a cytoplasmic male sterility (CMS) system. Inheritance of fertility restoration of WA type CMS in rice, (Oryza sativa L.) was studied utilizing IR58025A, IR62829A and IR68899A CMS lines and three restorers viz., Amol-2, IR50 and Poya. The F1s showed pollen and spikelet fertility similar to the restorer parents, indicating that restoration ability were dominant and the cytoplasmic-genetic sterility system of CMS lines were sporophytic in nature. Evaluation of fertility in F2 populations and testcross progenies (BC1) revealed that fertility restoration in Amol-2 and IR50 were controlled by two major dominant genes whereas, it was controlled by one dominant gene in Poya. Segregation for spikelet fertility in F2 and backcross generation conformed to the results on pollen fertility. Analysis of line x tester indicated pre-dominance of non-additive genetic variance. It suggested greater importance of non-additive gene action in pollen and spikelet fertility expression and indicated very good prospect for the exploitation of non-additive genetic variation for pollen and spikelet fertility through hybrid breeding.   Key words: Rice, genetics, male fertility restoration, combining ability.

Genetic analysis of fertility restoration genes for WA-type cytoplasmic male sterility in Iranian restorer rice line DN-33-18.

Cytoplasmic genetic male sterility system can be used to exploit heterosis in grain crops only when the effective restorer lines are available. Crosses between an Iranian CMS line Neda A with three newly developed lines DN-33-1, DN-33-18 and DN-32-6 showed that only the cross of Neda-A/DN-33-18 had more than 80% pollen and grain fertility in F1 generation. The inheritance of fertility restoration in F 2 population of this cross was evaluated at flowering and grain filling stages. Pollen staining test with 1% I 2 KI solution showed segregation ratio of 15:1 (fertile: sterile), representing two nuclear independent dominant genes controlling the trait carried by fertile parent DN-33-18. Segregation for spikelet fertility in F 2 confirmed the results of pollen fertility test. Molecular tagging of fertility restorer genes with SSR markers showed that four markers RM258, RM171, RM591 and RM3148 produced polymorphic bands between two parents. Linkage analysis on F 2 recessive class showed that RM258 and RM171 (on chromosome 10) flanked to restorer gene Rf4 at the distances of 3.1 and 6.3 cm, respectively. In this study polymorphism was not detected for Rf3 gene using SSR markers RM1, RM443, RM315 and RM294 on chromosome 1 of rice but we found new SSR marker RM3148 linked with Rf locus at a genetic distance of 19.7 cm. Key words : Rice, cytoplasmic male sterility (CMS), inheritance, molecular tagging, simple sequence repeat (SSR) markers.

Characterization of a male sterile mutant from progeny of a transgenic plant containing a leaf senescence-inhibition gene in wheat

A male sterile plant of wheat (Triticum aestivum L.) segregated from progenies of a transgenic family containing the leaf senescence-inhibition gene PSAG12-IPT in the genetic background of ‘Xinong 1376’, a well adapted winter wheat cultivar. The male sterile plant (named TR1376A) showed no phenotypic changes, except for florets and male organs, compared to its male fertile sibling plants (named TR1376B). The glumes and florets of male sterile TR1376A plants widely opened whereas those of the fertile counterpart TR1376B were closed or opened only briefly at flowing. Anthers of TR1376A were slender and indehiscent, and failed to release pollen. Compared to TR1376B, TR1376A anthers contained greatly reduced amounts of pollen, which was inviable or weakly viable. Ultra-structure studies indicated that cells in the endothecium and middle layers of the anther wall were dissolved or poorly developed in the sterile anthers of TR1376A. Molecular studies showed that the male sterility of TR1376A was caused by a sequence deletion or mutation that occurred in the promoter region of the transgene. F1 hybrids of TR1376A and TR1376B gave 1:1 segregation of male fertility to sterility, indicating that the male sterility of TR1376A was heritable and controlled by a single dominant gene (named Ms1376). To date, only a few dominant nuclear male sterility genes have been characterized and one of them (Ms2) has been successfully used to improve wheat cultivars through recurrent breeding strategies. The discovery of the Ms1376 gene provides another dominant male sterile source for establishing recurrent breeding systems in wheat.

Inheritance of Fertility Restoration for Cytoplasmic Male Sterility in a New Gossypium barbadense Restorer

In order to clarify inheritance mechanism of fertility restoration for cytoplasmic male sterility (CMS) in a new Gossypium barbadense restorer line Hai R which was found in the fertility test crossing of G. hirsutum CMS lines with G. barbadense germplasms. 23 fertility segregation populations of F 2 and backcross were used to analyze the inheritance of fertility restoring gene(s) of Hai R. The result showed that Hai R had one major dominant gene ( Rf B) to control the CMS fertility restoration and this fertility restoration gene functioned at the sporophytic level. The sterile cytoplasm background might not only influence the transmission rate of male gamete but also that of female gamete when the restorer gene was recessive. It could be deduced that this fertility restoration gene might come from G. harknessii cotton, Hai R is of value in the application of cotton interspecific hybrid breeding.