Male Sterility System Research Articles

Identification of stable restorers and high-yielding hybrids using diverse sorghum male sterile cytoplasmic sources and established pollen parents under different water regimes

Sorghum hybrids demonstrated increased productivity and helped offset the decreasing cultivated areas, particularly in Asia. The diversity in cytoplasmic male sterility systems, stability of restorers and high yield of sorghum is an important factor for achieving food security and sustainability. In sorghum, hybrid production has been limited to A1 cytoplasmic source to date, primarily due to limited number of restorers on other cytoplasmic sources. This work aimed at filling this gap through diversifying and assessing the producibility and stability of cytoplasmic backgrounds across environments, evaluating the stability of restorers across cytoplasms and environments, and evaluating the performance of the hybrid F1 products under different water regimes across cropping seasons. The effects of genotypes and interactions between the genotypes and the tested environments were shown visually using GGE biplot, which also categorized the genotypes based on performance per se and stability. Analysis of variance revealed significant (P< 0.001) differences between genotypes, environments and their interaction components for all the plant characteristics studied. The various GGE biplot patterns revealed that the restorers G4 (IS 33844-5), G5 (M 35-1-19), G8 (ICSV 15014), and G10 (ICSR 13009) were stable across environments and cytoplasms. We observed the following order of superiority in cytoplasmic restoration and seed producibility, A2 >A1>A3 >A4. The A2 cytoplasm can therefore reliably offer seed producibility advantage to commercial seed producers. Furthermore, the which-won–where model for hybrid grain yield revealed specific adaptations of hybrid genotypes G143, G195 and G215 to first mega environment (E1 and E3), whereas G167, G110, and G112 were adapted to the second mega-environment (E2 and E4). With a GGE biplot goodness of fit of 70% the best possible yield- and stability-based ranking of hybrid genotypes was G143, G215, G189, G200, G69, G162, G119, G54, and G81. The newly uncovered hybrid products should therefore be considered for downstream testing stages and candidates for release and commercial cultivation. Clearly, this work resulted in novel findings particularly in terms of seed producibility, universal restorers across the 4 cytoplasms and environments, and superior and stable hybrid products, all of which are expected to add value to conventional and heterosis breeding in the process of sorghum cultivar development.

Insights into cellular crosstalk regulating cytoplasmic male sterility and fertility restoration.

Cytoplasmic male sterility has been a popular genetic tool in development of hybrids. The molecular mechanism behind maternal sterility varies from crop to crop. An understanding of underlying mechanism can help in development of new functional CMS gene in crops which lack effective and stable CMS systems. In crops where seed or fruit is the commercial product, fertility must be recovered in F1 hybrids so that higher yield gains can be realized. This necessitates the presence of fertility restorer gene (Rf) in nucleus of male parent to overcome the effect of sterile cytoplasm. Fertility restoring genes have been identified in crops like wheat, maize, sunflower, rice, pepper, sugar beet, pigeon pea etc. But in crops like eggplant, bell pepper, barley etc. unstable fertility restorers hamper the use of Cytoplasmic genic male sterility (CGMS) system. Stability of CGMS system is influenced by environment, genetic background or interaction of these factors. This review thus aims to understand the genetic mechanisms controlling mitochondrial-nuclear interactions required to design strong and stable restorers without any pleiotropic effects in F1 hybrids.

Marker Assisted Characterization of TGMS Gene in Rice Cultigen Ts 29 (Oryza Sativa L.) to Develop Two Line Hybrids

The application of the thermsensitive genic male sterility (TGMS) system has great potential for revolutionizing hybrid rice production through simple and effective seed production technology. For the successful utilization of this novel male sterility system, knowledge of the fertility behaviour and genetic control of a TGMS line is essential. In this study, an investigation was carried out to characterize the TGMS gene present in the mapping population of TS 29 x CO(R)49. Through Bulk Segregant Analysis RM 3476 alone produced a polymorphic relationship between the parents and corresponding bulks and was used for surveying the individual plants of F3/F4 population. The marker RM 3476 produced contrasting fragments between sterile and fertile plants. The result was associated with the phenotypic observations on pollen fertility under the field conditions, confirming co-segregation of the marker with the gene of interest. Hence, the tight linkage of marker with TGMS gene was identified by RM 3476 which was already identified as a marker located near tms 6 gene in chromosome 5. From this study four TGMS lines were also identified with desirable floral traits for high out crossing and medium slender grain type. Bangladesh J. Bot. 53(2): 345-351, 2024 (June)

Identification, Elucidation and Deployment of a Cytoplasmic Male Sterility System for Hybrid Potato.

Recent advances in diploid F1 hybrid potato breeding rely on the production of inbred lines using the S-locus inhibitor (Sli) gene. As a result of this method, female parent lines are self-fertile and require emasculation before hybrid seed production. The resulting F1 hybrids are self-fertile as well and produce many undesirable berries in the field. Utilization of cytoplasmic male sterility would eliminate the need for emasculation, resulting in more efficient hybrid seed production and male sterile F1 hybrids. We observed plants that completely lacked anthers in an F2 population derived from an interspecific cross between diploid S. tuberosum and S. microdontum. We studied the antherless trait to determine its suitability for use in hybrid potato breeding. We mapped the causal locus to the short arm of Chromosome 6, developed KASP markers for the antherless (al) locus and introduced it into lines with T and A cytoplasm. We found that antherless type male sterility is not expressed in T and A cytoplasm, proving that it is a form of CMS. We hybridized male sterile al/al plants with P cytoplasm with pollen from al/al plants with T and A cytoplasm and we show that the resulting hybrids set significantly fewer berries in the field. Here, we show that the antherless CMS system can be readily deployed in diploid F1 hybrid potato breeding to improve hybridization efficiency and reduce berry set in the field.

Usefulness of alien sterilizing cytoplasms for the hybrid breeding of triticale (xTriticosecale Wittmack): preliminary results.

To be useful for cereal breeding, cytoplasmic male sterility (CMS) should express the complete sterility of maternal lines and the full restoration of the male fertility of F1 hybrids. The most reliable source of sterilizing cytoplasm for triticale is Triticum timopheevi; however, due to the low frequency of efficient non-restorer genotypes for this cytoplasm, new sources of CMS are needed. In this study, aside from T. timopheevi (T) cytoplasm, three alternative CMS sources were tested: Pampa (P) from Secale cereale L., Aegilops sharonensis (A), and Ae. ventricosa (V). The suitability of these cytoplasms for breeding was assessed based on the male fertility/sterility of F1 hybrids obtained through the manual pollination of CMS maternal lines with 36 triticale cultivars and breeding strains. About half of the hybrids with each type of cytoplasm were fully fertile and produced more than 30 grains per bagged spike. The highest percentage was found in hybrids with P cytoplasm (58.33%) and the lowest in hybrids with A cytoplasm (44.44%). Male sterility was observed in hybrids with P cytoplasm (16.67%) and A cytoplasm (16.67%) but not in hybrids with T or V cytoplasm. In terms of practical aspects, male sterility systems with P or A cytoplasm exhibit similarity in their ability to restore male fertility that differ from the T and V cytoplasms. Although all studied cytoplasms exhibited some disadvantages for breeding purposes, none should be definitively classified as unacceptable for future breeding programs regarding the development of triticale hybrid cultivars.

Advances in Breeding for Oil Quality Enhancement in Indian Mustard (Brassica spp. L.): Achievements, Challenges, and Research Opportunities

Major objectives in oil crop improvement are enhancement of seed and oil yield, quality of oil according to its use, i.e. edible or industrial uses, breeding of varieties that fit in different cropping systems and breeding biotic and abiotic stress resistant/tolerant varieties. Despite traditional breeding approaches, including pure line breeding, yielding only modest gains in productivity, recent advancements in mustard breeding have led to significant breakthroughs in both productivity and oil quality. This review discusses the innovative breeding strategies that have contributed to these advancements, with a focus on hybrid development, oil quality enhancement, and biotechnological approaches. To enhance productivity, researchers at the University of Delhi have developed hybrid seed production techniques using transgenic Barnase-barstar systems and cytoplasmic male sterility (CMS) systems. These systems enable large-scale hybrid seed production, with field trials demonstrating significant yield heterosis ranging from 31% to 55% compared to national check varieties. In addition to productivity, improving oil and meal quality has been a key objective. By integrating genes from canola-quality mustard lines, breeders have achieved reductions in erucic acid and glucosinolates, enhancing the health profile and industrial applicability of mustard oil. A high-density linkage map developed using an F1 double haploid mapping population has facilitated the marker-assisted backcross breeding of desirable traits, enabling precise transfer of key quality traits. Transgenic approaches, such as antisense RNA technology, have led to the development of high-oleic, low-linoleic mustard lines with improved fatty acid profiles. These advancements reflect a strategic combination of conventional and biotechnological methods, demonstrating a clear pathway for boosting mustard yields while enhancing oil quality. Molecular markers reported for genetic diversity assessment, mapping and tagging genes/QTLs for different qualitative and quantitative traits and their use in marker-assisted selection have been presented. This progress not only addresses current challenges but also sets the stage for future research aimed at further optimizing productivity, oil quality, and resistance to pests and diseases in mustard cultivation.

Lipid and sugar metabolism play an essential role in pollen development and male sterility: a case analysis in Brassica napus.

The genic male sterility (GMS) system is an important strategy for generating heterosis in plants. To better understand the essential role of lipid and sugar metabolism and to identify additional candidates for pollen development and male sterility, transcriptome and metabolome analysis of a GMS line of 1205AB in B. napus was used as a case study. To characterize the GMS system, the transcriptome and metabolome profiles were generated for 24 samples and 48 samples of 1205AB in B. napus, respectively. Transcriptome analysis yielded a total of 156.52 Gb of clean data and revealed the expression levels of 109,541 genes and 8,501 novel genes. In addition, a total of 1,353 metabolites were detected in the metabolomic analysis, including 784 in positive ion mode and 569 in negative ion mode. A total of 15,635 differentially expressed genes (DEGs) and 83 differential metabolites (DMs) were identified from different comparison groups, most of which were involved in lipid and sugar metabolism. The combination of transcriptome and metabolome analysis revealed 49 orthologous GMS genes related to lipid metabolism and 46 orthologous GMS genes related to sugar metabolism, as well as 45 novel genes. The transcriptome and metabolome profiles and their analysis provide useful reference data for the future discovery of additional GMS genes and the development of more robust male sterility breeding systems for use in the production of plant hybrids.

Functional study of the soybean stamen-preferentially expressed gene GmFLA22a in regulating male fertility.

China has a high dependence on soybean imports, yield increase at a faster rate is an urgent problem that need to be solved at present. The application of heterosis is one of the effective ways to significantly increase crop yield. In recent years, the development of an intelligent male sterility system based on recessive nuclear sterile genes has provided a potential solution for rapidly harnessing the heterosis in soybean. However, research on male sterility genes in soybean has been lagged behind. Based on transcriptome data of soybean floral organs in our research group, a soybean stamen-preferentially expressed gene GmFLA22a was identified. It encodes a fasciclin-like arabinogalactan protein with the FAS1 domain, and subcellular localization studies revealed that it may play roles in the endoplasmic reticulum. Take advantage of the gene editing technology, the Gmfla22a mutant was generated in this study. However, there was a significant reduction in the seed-setting rate in the mutant plants at the reproductive growth stage. The pollen viability and germination rate of Gmfla22a mutant plants showed no apparent abnormalities. Histological staining demonstrated that the release of pollen grains in the mutant plants was delayed and incomplete, which may due to the locule wall thickening in the anther development. This could be the reason of the reduced seed-setting rate in Gmfla22a mutants. In summary, our study has preliminarily revealed that GmFLA22a may be involved in regulating soybean male fertility. It provides crucial genetic materials for further uncovering its molecular function and gene resources and theoretical basis for the utilization of heterosis in soybean.

Inheritance Pattern of A1 Cytoplasmic-nuclear Male Sterility System in Commercial Pearl Millet Hybrids [Pennisetum glaucum (L). R. Br.] in Summer and Post-rainy Seasons

Background: This study aimed to understand the genetic aspects and inheritance patterns that control the process of restoring fertility in the context of the A1 system of Cytoplasmic-Nuclear Male Sterility (CMS) in pearl millet. Methods: The experimentation was conducted in commercial pearl millet hybrids, utilizing three F2 populations and three BC1 populations. These populations underwent assessment during the rainy and post-rainy seasons at Rallis India Limited, Hyderabad During the Post-rainy (November-February) and summer (March-June) seasons of 2022-2023. Segregation data derived from observations on pollen shedding and seed set were gathered and subsequently, statistical analysis was performed. The Chi-square (χ2) test was employed to assess the conformity of the observed segregation data to the expected genetic ratios, thus evaluating the goodness of fit. Result: The hybrid combinations MP13P025A ×MP16P050R (MP7171) and MP18P069A × MP20P081R (MP7214) consistently displayed a 3:1 segregation ratio in the F2 generation and a 1:1 ratio in the BC1 generation, regardless of the rainy or post-rainy seasons. However, the cross between MP14030A and MP15P038R (MP7878) showed irregularities in both seasons due to modifiers and environmental factors. These irregularities stemmed from an excess of fertile plants (FF) in the post-rainy season or an excess of sterile plants (FS) in the summer season. These observations provide valuable insights into the genetic dynamics of the A1 Cytoplasmic-Nuclear Male Sterility (CMS) system within commercial pearl millet hybrids. The study indicates that fertility restoration in the A1-based CMS system is strongly influenced by a single Dominant gene control mechanism governing the interplay between male sterility and fertility restoration in these crosses.

Safflower heterosis for yield and its contributed characters

Safflower (Carthamus tinctorius L.) is one of the major edible oilseed crops grown in winter season in India. The first safflower hybrid released in India for commercial cultivation in all safflower growing regions was based on genetic male sterility system. Twenty two hybrids were tested using line x tester design involving two cytoplasmic male sterile lines during rabi 2018, using Randomized block design with three replications. Twenty two along with three checks 'A-1, PBNS-12, PKV Pink' were evaluated at the field of Oilseeds Research Unit, Dr. PDKV, Akola during rabi 2019-2020 to estimate extent of heterosis in safflower genotypes. Among all the crosses, AKS CMS 2A x GMU 1183 (46.15 % and 44.30%) exhibited highly significant and positive average heterosis for number of seeds per plant over mid and better parent. crosses, AKS CMS 2A x GMU 184 (49.26% and 34.44%) exhibited highly significant and positive average heterosis for 100 seed weight, whereas, cross AKS CMS 2A x GMU 5149 (15.28% and 9.32%) exhibited highly significant and positive average heterosis for volume weight. The highest heterosis and heterobeltiosis in desirable direction were recorded for seed yield per plant in AKS CMS 2A x GMU 1654 (246.96. %) and the cross AKS CMS 3A x GMU 1183 (206.75%) showed highest and significantly positive standard heterosis over the checks i.e. PKV PINK, AKS 207 and PBNS-12.Biotechnological tools, such as genetic engineering need to be perfected for incorporation of mitochondrial male sterility causing factor of sunflower into safflower to develop safflower hybrids which can be more easily produced.

A P-type pentatricopeptide repeat protein ZmRF5 promotes 5' region partial cleavages of atp6c transcripts to restore the fertility of CMS-C maize by recruiting a splicing factor.

A fast evolution within mitochondria genome(s) often generates discords between nuclear and mitochondria, which is manifested as cytoplasmic male sterility (CMS) and fertility restoration (Rf) system. The maize CMS-C trait is regulated by the chimeric mitochondrial gene, atp6c, and can be recovered by the restorer gene ZmRf5. Through positional cloning in this study, we identified the nuclear restorer gene, ZmRf5, which encodes a P-type pentatricopeptide repeat (PPR) family protein. The over-expression of ZmRf5 brought back the fertility to CMS-C plants, whereas its genomic editing by CRISPR/Cas9 induced abortive pollens in the restorer line. ZmRF5 is sorted to mitochondria, and recruited RS31A, a splicing factor, through MORF8 to form a cleaving/restoring complex, which promoted the cleaving of the CMS-associated transcripts atp6c by shifting the major cleavage site from 480th nt to 344 th nt for fast degradation, and preserved just right amount of atp6c RNA for protein translation, providing adequate ATP6C to assembly complex V, thus restoring male fertility. Interestingly, ATP6C in the sterile line CMo17A, with similar cytology and physiology changes to YU87-1A, was accumulated much less than it in NMo17B, exhibiting a contrary trend in the YU87-1 nuclear genome previously reported, and was restored to normal level in the presence of ZmRF5. Collectively these findings unveil a new molecular mechanism underlying fertility restoration by which ZmRF5 cooperates with MORF8 and RS31A to restore CMS-C fertility in maize, complemented and perfected the sterility mechanism, and enrich the perspectives on communications between nucleus and mitochondria.

APETALOID AND PETALOID FEMALE PERFORMANCE ON HORTICULTURAL CHARACTERISTICS OF F1 AMERICAN MARIGOLD (TAGETES ERECTA L.) HYBRIDS

This research’s objectives focused on using two male-sterile systems, apetaloid and petaloid types, as female parents for the F1 marigold cut flower hybrid development. These female lines’ creation came from the same original line, the gynomonoecious line, with five backcrosses to obtain two female lines, FY1502 and FY1502AP. Their crossing with 10 male lines progressed during the summer from April to August 2016. Then, growing the progenies of 20 crosses and four commercial varieties as checks for characterization and evaluation continued in a lattice design with two replications. Planting them in six blocks contained 10 plants per treatment. The data recorded on eight horticultural characteristics include flower diameter, number of petals per flower, calyx length, peduncle length, flower weight, the number of days from sowing to first flowering, plant height, and plant bush diameter, as well as, the morphology of flowers. The results showed that progenies from two female apetaloid and petaloid with the same male line gave similar outcomes; all progenies produced male sterile double-flowers with golden-yellow flowers, except progenies of MY1501 and MY1502, which created yellow flowers. FY1502 gave the same superior F1 progenies as FY1502AP in the diameter of the flower. Based on the results, both females could give good characteristics on flower diameter, calyx length, plant height and bush diameter, and early flowering. However, the heterobeltiosis of the F1 progenies of a few vegetative and reproductive characteristics differed. The FY1502AP gave better progenies in peduncle length heterobeltiosis than those of FY1502 and slightly better for plant bush diameter, whereas FY1502 gave slightly better in flower weight heterobeltiosis than those of FY1502AP. The findings of this study indicate that this apetaloid type could benefit Thailand’s marigold seed production program.

Targeted knockout of a conserved plant mitochondrial gene by genome editing

Fusion proteins derived from transcription activator-like effectors (TALEs) have emerged as genome editing tools for mitochondria. TALE nucleases (TALENs) have been applied to delete chimaeric reading frames and duplicated (redundant) genes but produced complex genomic rearrangements due to the absence of non-homologous end-joining. Here we report the targeted deletion of a conserved mitochondrial gene, nad9, encoding a subunit of respiratory complex I. By generating a large number of TALEN-mediated mitochondrial deletion lines, we isolated, in addition to mutants with rearranged genomes, homochondriomic mutants harbouring clean nad9 deletions. Characterization of the knockout plants revealed impaired complex I biogenesis, male sterility and defects in leaf and flower development. We show that these defects can be restored by expressing a functional Nad9 protein from the nuclear genome, thus creating a synthetic cytoplasmic male sterility system. Our data (1) demonstrate the feasibility of using genome editing to study mitochondrial gene functions by reverse genetics, (2) highlight the role of complex I in plant development and (3) provide proof-of-concept for the construction of synthetic cytoplasmic male sterility systems for hybrid breeding by genome editing.

Genetics of sterility behaviour in Thermo Sensitive Genic Male Sterility system in rice (Oryza sativa L. )

Genetics of sterility behaviour in Thermo Sensitive Genic Male Sterility system in rice (Oryza sativa L. )

Manipulation of tapetal degradation provides a dominant male-sterility system for pyramiding breeding in rice.

Overexpression of a transcription factor in rice induces premature tapetal degradation and offers an efficient dominant male-sterility system for modern breeding.

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.

Rapid generation of a tomato male sterility system and its feasible application in hybrid seed production.

A practical approach for the rapid generation and feasible application of green hypocotyl male-sterile (GHMS) tm6 dfr lines in tomato hybrid breeding was established. Male sterility enables reduced cost and high seed purity during hybrid seed production. However, progress toward its commercial application has been slow in tomato due to the disadvantages of most natural male-sterile mutants. Here, we developed a practical method for efficient tomato hybrid seed production using a male-sterile system with visible marker, which was rapidly generated by CRISPR/Cas9-mediated gene editing. Two closely linked genes, TM6 and DFR, which were reported to be candidates of ms15 (male sterile-15) and aw (anthocyanin without) locus, respectively, were knocked out simultaneously in two elite tomato inbred lines. Mutagenesis of both genes generated green hypocotyl male-sterile (GHMS) lines. The GHMS lines exhibited male sterility across different genetic backgrounds and environmental conditions. They also showed green hypocotyl due to defective anthocyanin accumulation, which serves as a reliable visible marker for selecting male-sterile plants at the seedling stage. We further proposed a strategy for multiplying the GHMS system and verified its high efficiency in stable male sterility propagation. Moreover, elite hybrid seeds were produced using GHMS system for potential side effects evaluation, and no adverse influences were found on seed yield, seed quality as well as important agronomic traits. This study provides a practical approach for the rapid generation and feasible application of male sterility in tomato hybrid breeding.

Introduction of barnase/barstar in soybean produces a rescuable male sterility system for hybrid breeding.

Hybrid breeding for increased vigour has been used for over a century to boost agricultural outputs without requiring higher inputs. While this approach has led to some of the most substantial gains in crop productivity, breeding barriers have fundamentally limited soybean (Glycine max) from reaping the benefits of hybrid vigour. Soybean flowers self-pollinate prior to opening and thus are not readily amenable to outcrossing. In this study, we demonstrate that the barnase/barstar male sterility/rescue system can be used in soybean to produce hybrid seeds. By expressing the cytotoxic ribonuclease, barnase, under a tapetum-specific promoter in soybean anthers, we are able to completely block pollen maturation, creating male sterile plants. We show that fertility can be rescued in the F1 generation of these barnase-expressing lines when they are crossed with pollen from plants that express the barnase inhibitor, barstar. Importantly, we found that the successful rescue of male fertility is dependent on the relative dosage of barnase and barstar. When barnase and barstar were expressed under the same tapetum-specific promoter, the F1 offspring remained male sterile. When we expressed barstar under a relatively stronger promoter than barnase, we were able to achieve a successful rescue of male fertility in the F1 generation. This work demonstrates the successful implementation of a biotechnology approach to produce fertile hybrid offspring in soybean.

Identification of Good Restorer Lines through Molecular Confirmation of Rf3 and Rf4 Genes in Rice Hybrids

Pollen fertility can be restored by nuclear-encoded genes known as fertility restorer (Rf) genes. The initial stage in creating high-yielding heterotic hybrids involves the identification of restorers capable of effectively restoring the fertility of CMS lines. Hybrid rice breeding programs have proven effective in achieving these goals by utilizing cytoplasmic male sterility (CMS) systems in combination with restorer genes. Among these, Rf3 and Rf4 genes play critical roles in restoring male fertility and are essential components of successful hybrid rice breeding. In this study, we aimed to investigate the molecular conformation of Rf3 and Rf4 genes in a set of restorer lines and hybrids in rice. DNA was isolated from 10 restorer lines and 30 rice hybrids, two checks and KMR3R were used for comparison for positive alleles. Two functional markers, RM SF21-5 for Rf3 and RMS-PRR-9-1 for Rf4, were employed to identify the allelic status of the fertility restorer genes. Results revealed that among the 42 rice entries screened, five rice hybrids lacked both Rf3 and Rf4 genes and Four rice restorer lines and four hybrids were found to possess both Rf3 and Rf4 genes, making them valuable for hybrid breeding programs. Conversely, five hybrids lacked restorer genes and were unsuitable for such breeding programs. These findings establish Rf3and Rf4 as major fertility restoring genes in rice, consistently contributing to complete fertility restoration. The genotyping results provide valuable insights for selecting appropriate parental lines and restorers in hybrid rice breeding programs. The presence or absence of these fertility-restoring genes plays a crucial role in developing high-yielding and productive rice varieties through effective breeding strategies.

Development of alloplasmic male sterile lines and their assessment for heterotic potential in eggplant (Solanum melongena L.)

ABSTRACT The use of Solanum aethiopicum as the female parent with S. melongena led to the development of a cytoplasmic-genic male sterility system (CGMS) in eggplant. The male sterility was complete and expressed as rudimentary anthers with no pollen grains. Ten backcross progenies of male sterile lines in diverse genetic backgrounds of S. melongena were characterised after BC7 generation for 14 horticultural traits. It was observed that male sterile lines and their respective maintainer parents were isogenic for all the traits, except stamen size and days to 50% flowering. The fertility of male sterile lines was restored after hybridising with plants derived from an S. melongena × S. aethiopicum cross. The fertility restoration was governed by a single dominant gene. The maternal cytoplasm of S. aethiopicum in male sterile lines and of S. melongena in maintainers and restorers was confirmed with mitochondria and chloroplast DNA-specific molecular markers. Further, to assess the heterotic potential, 10 cytoplasmic male sterility lines were crossed with three restorers to develop 30 F1 hybrids, out of which D−67A × R−6 and D−104A × R−6 were found consistently better than the standard check for yield plant−1 over two years. In this manuscript a comprehensive study on development and utilisation of an alloplasmic CGMS system in eggplant has been discussed.