Cytoplasmic-genetic Male Sterility Research Articles

Male sterility in plants: an overview of advancements from natural CMS to genetically manipulated systems for hybrid seed production.

The male sterility system in plants has traditionally been utilized for hybrid seed production. In last three decades, genetic manipulation for male sterility has revolutionized this area of research related to hybrid seed production technology. Here, we have surveyed some of the natural cytoplasmic male sterility (CMS) systems that existed/ were developed in different crop plants for developing male sterility-fertility restoration systems used in hybrid seed production and highlighted some of the recent biotechnological advancements in the development of genetically engineered systems that occurred in this area. We have indicated the possible future directions toward the development of engineered male sterility systems. Cytoplasmic male sterility (CMS) is an important trait that is naturally prevalent in many plant species, which has been used in the development of hybrid varieties. This is associated with the use of appropriate genes for fertility restoration provided by the restorer line that restores fertility on the corresponding CMS line. The development of hybrids based on a CMS system has been demonstrated in several different crops. However, there are examples of species, which do not have usable cytoplasmic male sterility and fertility restoration systems (Cytoplasmic Genetic Male Sterility Systems-CGMS) for hybrid variety development. In such plants, it is necessary to develop usable male sterile lines through genetic engineering with the use of heterologous expression of suitable genes that control the development of male gametophyte and fertile male gamete formation. They can also be developed through gene editing using the recently developed CRISPR-Cas technology to knock out suitable genes that are responsible for the development of male gametes. The present review aims at providing an insight into the development of various technologies for successful production of hybrid varieties and is intended to provide only essential information on male sterility systems starting from naturally occurring ones to the genetically engineered systems obtained through different means.

Heterosis and combining ability studies under artificial epiphytotic condition for yield and its related traits in Indian mustard

The performance of Indian mustard genotypes for eleven morpho-physiological traits was assessed. Genotypes (lines) having white rust resistance viz., BioYSR, Donskaja, Heera and Basanti, were crossed with genotypes (testers) having high per se performance for yield viz., Varuna, Kranti, RH749 and Giriraj in the line × tester fashion. The analysis of variance revealed significant mean sum of squares due to crosses for all traits. All traits, except area under disease progression curve and daysto 50% flowering, showed both, additive and a predominance of non-additive gene action. Results suggested that heterosis breeding would lead to good result. All traits had lower levels of narrow sense heritability, as well. Predominance of non-additive gene action coupled with low heritability suggested that, selection should be practised once plant reach sufficient levels of homozygosity. Single seed descent method with large F2 and diallel selective mating design would be preferable for obtaining superior pure lines. Additionally, all lines showed significant desirable general combining ability for disease resistance. Varuna × BioYSR was the only cross that showed significant heterosis for yield over national check, Kranti. It also revealed significant heterobeltiosis for: seeds per siliqua, number of primary branches, days to 50% flowering, AUDPC and days to maturity. This potential hybrid can be deployed with the help of cytoplasmic-genetic male sterility, or it can be utilised to obtain superior purelines through conventional breeding methods.

Genetic analysis for fertility restoration for the a1 and a4 cytoplasmic genetic male sterility system in pearl millet Ppennisetum glaucum L.).

Genetic analysis for fertility restoration for the a1 and a4 cytoplasmic genetic male sterility system in pearl millet Ppennisetum glaucum L.).

Genetics of fertility restoration in A2‐based cytoplasmic genetic male sterility system in pigeonpea (Cajanus cajan)

AbstractThe three short duration cytoplasmic genetic male sterility (CGMS) hybrids developed using A2 (Cajanus scarabeoides) cytoplasm‐based male sterile lines (CORG 990047A, CORG 990052A and CORG 7A) and the restorer inbred AK 261322 and their segregating populations (F2 and BC1F1) were subjected to the study of inheritance of fertility restoration in pigeonpea. The fertility restoration was studied based on three different criteria, namely, anther colour, pollen grain fertility and pollen grain morphology and staining. The F2 and BC1F1 populations of the three crosses, namely, CORG 990047A × AK 261322, CORG 990052A × AK 261322 and CORG 7A × AK 261322, segregated in the ratio of 3:1 and 1:1, for anther colour (yellow:pale yellow), pollen grain fertility (fertile:sterile) and for pollen grain morphology and staining. The above study confirmed that the trait fertility restoration was controlled by single dominant gene. This finding can be utilized for the identification of potential restorers, which can be further used in the development of CGMS‐based hybrids in pigeonpea.

Planting ratio and plant growth regulators affecting seed quality in CGMS based chilli (Capsicum annuum) hybrid

In the present study, the seed production was carried out during 2016 and 2017 in the newly released cytoplasmic genetic male sterility (CGMS) based chilli (Capsicum annuum) hybrid. The objective of this study was to enhance the seed quality for newly released hybrid using given treatments in the field. The experiment was conducted at the Department of Seed Science and Technology, University of Agricultural Sciences, Raichur, Karnataka in the laboratory and field conditions. Plant growth regulators (PGRs) target specific receptor molecules in the plant tissue that can certainly transform plant metabolism. Similarly adapting a specific ratio of female and male while planting can check yield and quality constraints in fruit and seed production. Henceforth treatments were decided keeping in view these points. It was found that planting ratio (2:1 was best) and PGR spray (NAA @40 ppm best) significantly promoted the seed quality parameters, viz. germination (%), seedling dry weight (mg), shoot length (cm), seedling vigour index, dehydrogenase enzyme activity and lowered the electrical conductivity (dS/cm) as compared to other treatments. Also, the treatment combination P2S4 (2:1 + NAA @40 ppm) proved to be the best for these seed quality parameters. Thus, the parental lines in 2:1 ratio proved to be best for natural crossing followed by spraying at flower initiation stage with NAA @40 ppm as PGR to obtain higher seed quality in CGMS based chilli hybrid UARChH42 (JCH42). Hence it may be recommended in seed production technology of this hybrid.

Genetics of fertility restoration in A1 Cytoplasmic Genetic Male Sterility (CGMS) systems in Sorghum (Sorghum bicolor L. Moench)

The cause of Cytoplasmic Genetic Male Sterility (CGMS) is specific nuclear and mitochondrial interactions. Almost all commercial sorghum hybrids were developed using the A1 cytoplasmic genetic male sterility system. Understanding the inheritance of fertility restoration in sorghum for A1 cytoplasm, for example, can improve the selection efficiency of restorer lines for increased seed production. In a cross of male sterile line 296A with A1 cytoplasm and restorer lines comprised of a set of Recombinant Inbred Lines (RILs), the inheritance pattern of fertility restoration of sorghum was studied. The F1 hybrid was completely fertile, revealing the dominant nature of fertility restoration, which is controlled by one or two major genes with modifiers. In this study, the genetics of fertility restoration of the A1 cytoplasmic nuclear male sterility system (CGMS) in sorghum were investigated in segregating F2 and BC1 populations of A1 cytoplasm crosses. Fertility restoration was governed by a monogenic inheritance (3F:1S) mechanism represented by a single dominant gene responsible for fertility restoration in all of the crosses studied.

Identification of SNP markers linked to Rf locus in carrot using GBS

Commercial carrot production is based on the use of hybrid seed varieties worldwide. Cytoplasmic genetic male sterility (CGMS) mechanism has been widely used as the main method for hybrid carrot seed production. There is a significant demand for a rapid method for identification of fertility restorer gene (Rf) carrying individual plants in a carrot breeding population. The objective of this research was to identify SNP markers linked to Rf locus and develop a genetic map of Rf gene in carrot. For this purpose, a carrot F2 population segregating for male sterility was produced and segregating 10,425 SNP markers were discovered by using genotyping by sequencing (GBS). Association mapping analysis demonstrated that Rf was located on chromosome 9 in the carrot genome. A genetic map of chromosome 9 was constructed by using GBS based SNP markers. In order to confirm GBS-generated SNP markers, three markers closely linked to Rf locus were converted to simple probe markers (DcSNP-ch9_3342931, DcSNP-ch9_4822988 and DcSNP-ch9_6233708). Simple probe assay was able to distinguish the individuals of F2 population as homozygous male fertile (RfRf), heterozygous male fertile (Rfrf) and male sterile (rfrf). Simple probe assay confirmed the phenotypic observation in the population and a genetic map of Rf was constructed by using these markers. In conclusion, mapping of Rf in this work would be an efficient tool for future fine mapping and cloning studies of Rf gene in carrot. Thus, this research can help to accelerate the identification of maintainer lines for the development the new hybrid carrot varieties.

Interspecific crosses involving Rf3 gene carriers as potential sources of R lines for D2 type cytoplasm based hybrid wheat system

The exploitation of heterosis, which is associated with the development of hybrid wheat varieties, has a great potential for increasing global wheat grain yields. Nevertheless, common wheat hybrids now account for less than 1% of global wheat production. In practice, two general approaches in hybrid wheat seeds production are being used. The first is based on the application of a chemical hybridizing agent, while the second is based on the use of cytoplasmic-genetic male sterility derived from Triticum timopheevii Zhuk. (G type cytoplasm). In this study, we present the development of R (restorer) lines for an alternative hybrid wheat system based on the cytoplasm of Aegilops crassa Boiss. (D2 type cytoplasm). Considering the cytoplasm types, it was found that different types of experimental F1 crosses required different sources of fertility restorer genes. CMS materials with T. timopheevii cytoplasm achieved the highest productivity in combination with Rf3 gene carriers. On the other hand, CMS materials with D2 cytoplasm in combination with interspecific crosses of synthetic hexaploid wheat accessions and SBEII mutants led to highly heterotic F1 hybrids. D2 cytoplasm based male sterility induction system represents a promising tool for hybrid wheat development.

A Study on Sources of Cytoplasmic Genetic Male Sterility, Heterosis, and Combining Ability in Pearl Millet

A Study on Sources of Cytoplasmic Genetic Male Sterility, Heterosis, and Combining Ability in Pearl Millet

Exploitation of heterosis in hybrids developed using cytoplasmic genetic male sterility (CGMS) system in pigeonpea [Cajanus cajan (L.) Millspaugh

To ascertain heterosis forty hybrids were developed from fourteen parents in a line x tester mating design during kharif, 2017-18 and tested in a Randomized Block Design with three replications during kharif, 2018-19. The analysis of variance revealed that the mean sum of squares due to lines were significant for all characters except number of seed per pod and 100 seed weight, whereas the mean sum of squares due to testers were significant for all characters except number of seed per pod and seed yield per plant. This indicates the presence of sufficient amount of variability in parents utilized for hybridization. The mean sum of squares due to lines vs testers was significant for all characters except days to flowering, days to maturity, plant height, number of seed per pod and 100 seed weight. The mean sum of squares due to parents vs hybrids as well as due to hybrids were significant for all characters. The analysis of variance further revealed that the significant difference was found among lines, tester and hybrids for all the characters. This indicates that there is good chance of exploit the heterosis from present investigation. The estimates of heterosis showed that the five hybrids CMS GT 1603 A x GTR 23, CMS GT 288 A x GTR 55, CMS GT 1603 A x GTR 97, CMS GT 1616 A x GTR 55 and CMS GT 1616 A x GTR 97 were found the most promising on the basis of per se performance, standard heterosis, mid parent heterosis and better parent heterosis. Therefore, it needs to be exploited in future breeding programme.

Developing rice hybrids for temperate conditions using three line approach

Exploitation of heterosis in the form of hybrid rice is yet to be exploited at commercial level in the temperate regions of India. The present study is attempted to develop rice hybrids for the temperate conditions of Kashmir valley by utilizing the cytoplasmic genetic male sterility system (CGMS). Among the four CMS lines evaluated, the genotype SKUA-7A and SKUA-11A had desirable performances. The 24 test crosses developed involving these CMS lines were evaluated for spikelet fertility and pollen fertility. Moreover, the highest standard heterosis for grain yield and other yield attributes over the check varieties (Jehlum and Shalimar Rice-3) was recorded in the cross combination K15-34 followed by K15-31 and K15-40. Pollen parents of all the three test crosses on screening with RM-6100, DDRMRf3-10 and DRCG-Rf4-14 markers revealed presence of both Rf3 and Rf4 genes responsible for fertility restoration. Besides, 39 genotypes were screened for fertility restoration and the lines RL-2, RL-5, RL-6, RL-7, RL-10, Pusa Sugandh3 and Kohsar were identified to carry homozygous alleles at both Rf3 and Rf4 loci. These genotypes can thus be used as promising restores for the development of temperate rice hybrids.

English

One of the main barriers to the production of hybrid maize seeds consists of needing detasseling of female parent in order to avoid contamination with unwanted pollen. This activity is a laborious practice, which makes the production more expensive and promotes productive losses. Thus, the use of cytoplasmic genetic male sterility can facilitate the hybridization process, and consequently, the production of hybrid seeds. The objective of this study was compare grain yield in maize hybrids produced from the combination of two testers with five distinct lines of cytoplasm C “Charrua” versus the isogenic of fertile cytoplasm. Twenty common hybrids were evaluated in relation to grain crops and resistance to leaf diseases, white spot and gray leaf spot. The experiments were carried out during summer season of 2015/2016 and winter season of 2016. The use of lines with cytoplasm C was observed and it is promising since it did not affect the agronomic performance of hybrids, regardless of environment, crop season, parental and tester used. Therefore, cytoplasm C can be used as an excellent source of cytoplasmic genetic sterility in the production of hybrid seeds in seed companies that want to decrease the use of detasseling practice. Key words: Zea mays L, production of seeds, detasseling.

Development of CGMS system in ridge gourd [Luffa acutangula (Roxb.) L.] for production of F1 hybrids

Cytoplasmic male sterile system in ridge gourd has been converted to cytoplasmic genetic male sterile (CGMS) system through the development of analogues of male sterile (MS) line, maintainer line and fertility restorer line. These lines were developed by crossing the MS mutant, regenerated through in vitro culture, with monoecious pollen parents Deepthi, Haritham, LA 101, CO 2, IC 92761 and IC 92685. All hybrids and the BC1 generation developed by crossing with the recurring pollen parents Deepthi, Haritham and LA 101 were male sterile. Male sterile BC1 plants have been advanced to BC6 generation and the parental line LA 101 was proved to be a successful maintainer line, producing male sterile progeny in successive back cross generations. Analogue of cytoplasmic male sterile line, MS LA 101, was developed through back crossing and on crossing with fertility restorer lines Arka Sumeet and LA 102, this line excelled as female parent, resulting heterotic combinations. Mitochondrial marker rpS14 and SCAR Tm-53 were identified to yield male sterility specific markers whereas SSR marker 18956 has generated the male fertility specific marker. These primers are recommended for marker assisted selection of ridge gourd, for utilizing male sterility for hybrid seed production and for developing A, B and C lines in CGMS system.

Phenotypic Data from Inbred Parents Can Improve Genomic Prediction in Pearl Millet Hybrids.

Pearl millet is a non-model grain and fodder crop adapted to extremely hot and dry environments globally. In India, a great deal of public and private sectors’ investment has focused on developing pearl millet single cross hybrids based on the cytoplasmic-genetic male sterility (CMS) system, while in Africa most pearl millet production relies on open pollinated varieties. Pearl millet lines were phenotyped for both the inbred parents and hybrids stage. Many breeding efforts focus on phenotypic selection of inbred parents to generate improved parental lines and hybrids. This study evaluated two genotyping techniques and four genomic selection schemes in pearl millet. Despite the fact that 6× more sequencing data were generated per sample for RAD-seq than for tGBS, tGBS yielded more than 2× as many informative SNPs (defined as those having MAF > 0.05) than RAD-seq. A genomic prediction scheme utilizing only data from hybrids generated prediction accuracies (median) ranging from 0.73-0.74 (1000-grain weight), 0.87-0.89 (days to flowering time), 0.48-0.51 (grain yield) and 0.72-0.73 (plant height). For traits with little to no heterosis, hybrid only and hybrid/inbred prediction schemes performed almost equivalently. For traits with significant mid-parent heterosis, the direct inclusion of phenotypic data from inbred lines significantly (P < 0.05) reduced prediction accuracy when all lines were analyzed together. However, when inbreds and hybrid trait values were both scored relative to the mean trait values for the respective populations, the inclusion of inbred phenotypic datasets moderately improved genomic predictions of the hybrid genomic estimated breeding values. Here we show that modern approaches to genotyping by sequencing can enable genomic selection in pearl millet. While historical pearl millet breeding records include a wealth of phenotypic data from inbred lines, we demonstrate that the naive incorporation of this data into a hybrid breeding program can reduce prediction accuracy, while controlling for the effects of heterosis per se allowed inbred genotype and trait data to improve the accuracy of genomic estimated breeding values for pearl millet hybrids.

Identification of CMS maintainers and restorers for hybrid rice development in Ghana

ABSTRACTThe cytoplasmic-genetic male sterility is the most widely used system for hybrid rice (Oryza sativa) seed production. It requires three lines: the two hybrid parents (A and R lines) and a third line (maintainer (B line)), which maintains the sterility of the female parent during seed increase. Studies were undertaken to identify maintainers and restorers for introduced cytoplasmic male sterile (CMS) lines using simple sequence repeat (SSR) markers and testcrosses. Molecular screening with SSR marker RM6100 grouped the assembled inbred lines into 30 potential restorers and 55 potential maintainers. One maintainer (WAS 127 -12-1-6-3-1) and 16 restorers were confirmed by testcrosses. WAS 127-12-1-2-3 had higher grain yield per plant in crosses with CMS1 (IR69625A) than the local checks (AgraRice and Jasmine 85) and could be used as a restorer to develop a locally adapted, high-yielding hybrid. Conversion of WAS 127 -12-1-6-3-1 into a local CMS line was stopped because of sterility instability in the BC1F1 generation. Continued testcrosses to the set of identified potential maintainers could help identify a stable one that can successfully be converted into a locally adapted CMS line.

Significant association of the novel Rf4-targeted SNP marker with the restorer for WA-CMS in different rice backgrounds and its utilization in molecular screening

AbstractIn the rice cytoplasmic-genetic male sterility (CMS) system, the combination of a CMS line, maintainer line and restorer line carrying the restorer gene to restore fertility, is indispensable for the development of hybrids. However, the process of screening for the trait of fertility restoration is laborious and time-consuming. In the present study, we analyzed the nucleotide sequence of the Rf4 gene, which is the major locus controlling fertility restoration, to identify allele-specific variation. A single nucleotide polymorphism (SNP) A/C at +474 in the coding sequence (CDS) was found to be capable of strictly distinguishing groups of alleles Rf4 (A) and rf4 (C). Using KASP genotyping, this valuable SNP was converted to an allele-specific PCR marker. We evaluated and validated the marker among three-line parents with different backgrounds, and the results revealed a complete correlation between SNP alleles and the fertility restoration phenotype. Molecular screening was subsequently carried out for the presence of alleles of Rf4 and Rf3 among 328 diverse rice cultivars with worldwide distribution. The results demonstrate that this SNP marker could be the optimal choice for the molecular identification of potential restorers.

Genetic Analysis of Some Quantitative Traits in Hybrid Rice with Utilizing Cytoplasmic Genetic Male Sterility System

Genetic Analysis of Some Quantitative Traits in Hybrid Rice with Utilizing Cytoplasmic Genetic Male Sterility System

Gene action studies over different environments in sorghum [Sorghum bicolor (L.) Moench

ABSTRACT : An experiment was conducted to estimate the combining ability using three females [Cytoplasmic-Genetic Male Sterile (CGMS) Lines], 18 males (testers) and their 54hybrids developed through line x tester mating design in three diverse seasons (environments). Result of analysis of variance for means revealed significant differences for all the twelve characters. Combining ability analysis over environments revealed importance of both additive and nonadditive components. Close agreement between GCA and per se performance of parents was observed for most of the characters studied. Combination having high per se performance also had high SCA effects and involved at least one good general combining parent. The female parents 28A and 86A and among male parents, KR 125, KR 191, KR 196, PMSC-43, GJ 38, GSF 5 and CSV 21F were good general combiners for grain yield and its component traits. While considering the SCA effects and per se value, 10 hybrids were best for grain yield and component characters. All these hybrids were combination of parents having either good x good or good x poor GCA for grain yield.

Assessment of per se performance, combining ability, hybrid vigour and reaction to major diseases in pigeonpea [Cajanus cajan (L.) Millsp.

An experiment was carried out using seven cytoplasmic-genetic male sterile (CGMS) lines as females and seven diversified testers as males in a line × tester design. The analysis of variance for parents, females x males, hybrids and parents vs hybrids showed significant differences for almost all characters studied indicating the presence of sufficient variability among parents. Analysis of variance for combining ability revealed that mean squares due to females and line x tester interaction were significant for most of the characters. Thereby it is suggested that the variation in hybrids in respect of seed yield may be strongly influenced by the female lines. Analysis of variance revealed that the ratio of variance due to GCA to SCA was less than unity for all the characters indicating that these traits may be under the influence of non additive gene action and these characters are more likely to be improved through heterosis breeding. The gca effects of parents revealed that ICPA-2043, ICPA-2047, ICPA-2078, AKT-9913, BDN-2 and GRG-811 were good general combiners for seed yield and it’s direct compo-nents. The top three crosses exhibiting high specific combing ability effects along with their Per se performance, standard heterosis and gca status of the parents indicated that the cross combinations ICPA-2092 x GRG-811, ICPA-2043 x ICP-7035 and ICPA-2047 x RVKP-261 were good specific combiners for seed yield. These parental combinations are being used for exploitation of hybrid vigour. The good general combiners (ICPA-2043, ICPA-2047, ICPA-2078, AKT-9913, BDN-2 and GRG-811) and promising crosses viz. ICPA-2047 x GRG-811 and ICPA-2047 x BDN-2 were resistant for SMD and Fusarium wilt diseases, having high mean performance, positive sca effects for seed yield were identified from the present investigation and these may be useful in future breeding program.

Evaluation of pigeonpea [Cajanus cajan (L.) Millsp.] hybrids for heterosis, combining ability, wilt and sterility mosaic diseases

An experiment was carried out using three cytoplasmic-genetic male sterile (CGMS) lines as females and four diversified testers as males in a line × tester design. The analysis of variance for combining ability showed that the mean squares due to general and specific combining ability effects indicated involvement of both additive and non additive gene action. The mean sum of squares due to lines × testers and their interactions were highly significant for seed yield and it’s component characters further indicated the importance of sca variance, and consequently the non-additive genetic variation in the inheritance of these characters are more likely to be improved through heterosis breeding. The gca effects of parents revealed that female lineTS-3RA was good general combiners with JKM-197 and ASHA for seed yield and it’s direct components. Crosses exhibiting high specific combing ability effects along with their per se performance, standard heterosis and gca status of the parents indicated that the cross combinations MARUTI-A x ASHA, WRP-1A x GC-11-39 and TS-3RA x JKM-197 were good specific combiners for seed yield. These parental combinations are being used for exploitation of hybrid vigour.Two hybrids TS-3RA x GRG-2009 and WRP-1A x GRG-2009 were moderately resistant for both the diseases with per cent disease incidence value of 3.57 and 25.00 for Fusarium wilt and 16.00 and 15.79 for sterility mosaic disease (SMD) respectively.