SesamumGDB: a comprehensive platform for Sesamum genetics and genomics analysis.

Sesame (Sesamum indicum L., 2n = 26) is a crucial oilseed crop cultivated worldwide. The ancient evolutionary position of the Sesamum genus highlights its value for genomics and molecular genetics research among the angiosperms of other genera. However, Sesamum is considered a small orphan genus with only a few genomic databases for cultivated sesame to date. The urgent need to construct comprehensive, curated genome databases that include genus-specific gene resources for both cultivated and wild Sesamum species is being recognized. In response, we developed Sesamum Genomics Database (SesamumGDB), a user-friendly genomic database that integrates extensive genomic resources from two cultivated sesame varieties (S. indicum) and seven wild Sesamum species, covering all three chromosome groups (2n = 26, 32, and 64). This database showcases a total of 352 471 genes, including 6026 related to lipid metabolism and 17 625 transcription factors within Sesamum. Equipped with an array of bioinformatics tools such as BLAST (basic local alignment search tool) and JBrowse (the Javascript browser), SesamumGDB facilitates data downloading, screening, visualization, and analysis. As the first centralized Sesamum genome database, SesamumGDB offers extensive insights into the genomics and genetics of sesame, potentially enhancing the molecular breeding of sesame and other oilseed crops in the future. Database URL: http://www.sgbdb.com/sgdb/.

Overexpression of sesame O-acetylserine(thiol)lyase induces male sterility by delaying tapetum programmed cell death.

Male sterile lines are key resources for hybrid seed production and for ensuring high varietal purity. However, the genes and mechanisms underlying sesame male sterility remain largely unknown. Hence, this study identified an O-acetylserine(thiol)lyase gene SiOASTL1 and functionally characterized its roles in inducing defective anther development. Spatiotemporal expression analysis revealed that SiOASTL1 is significantly (2.7 fold) up-regulated in sterile sesame anthers at the microspore stage compared with fertile ones. Sequence and phylogenetic analyses showed that SiOASTL1 is homologous to Arabidopsis OAS-TL plastid isoforms. We thus overexpressed SiOASTL1 in Arabidopsis to unravel its regulatory roles. Cytological observation revealed that SiOASTL1 overexpression transformed transgenic plants into male sterile lines arising at the microspore development stage. SiOASTL1 overexpression decreased cysteine biosynthesis and down-regulated the expression of the sporopollenin synthesis-related genes, including AtTKPR1, AtTKPR2, AtPKSA, and AtPKSB in transgenic Arabidopsis. Consequently, the tapetum programmed cell death (PCD) was delayed, resulting in the formation of defective pollen grains with irregular walls and empty cytoplasm. Our findings prove that the induction of SiOASTL1 expression disrupts pollen development and contributes to sesame male sterility. Moreover, these results suggest that genetic manipulation of SiOASTL1 expression may facilitate the development of new hybrid varieties in sesame and other crops.

Refining flowering date enhances sesame yield independently of day-length.

BACKGROUND: The transition from vegetative to reproductive growth is a key factor in yield maximization. Sesame (Sesamum indicum), an indeterminate short-day oilseed crop, is rapidly being introduced into new cultivation areas. Thus, decoding its flowering mechanism is necessary to facilitate adaptation to environmental conditions. In the current study, we uncover the effect of day-length on flowering and yield components using F 2 populations segregating for previously identified quantitative trait loci (Si_DTF QTL) confirming these traits. RESULTS: Generally, day-length affected all phenotypic traits, with short-day preceding days to flowering and reducing yield components. Interestingly, the average days to flowering required for yield maximization was 50 to 55 days, regardless of day-length. In addition, we found that Si_DTF QTL is more associated with seed-yield and yield components than with days to flowering. A bulk-segregation analysis was applied to identify additional QTL differing in allele frequencies between early and late flowering under both day-length conditions. Candidate genes mining within the identified major QTL intervals revealed two flowering-related genes with different expression levels between the parental lines, indicating their contribution to sesame flowering regulation. CONCLUSIONS: Our findings demonstrate the essential role of flowering date on yield components and will serve as a basis for future sesame breeding.

Genome Size Variation in Sesamum indicum L. Germplasm from Niger.

Sesamum indicum L. (Pedaliaceae) is one of the most economically important oil crops in the world, thanks to the high oil content of its seeds and its nutritional value. It is cultivated all over the world, mainly in Asia and Africa. Well adapted to arid environments, sesame offers a good opportunity as an alternative subsistence crop for farmers in Africa, particularly Niger, to cope with climate change. For the first time, the variation in genome size among 75 accessions of the Nigerien germplasm was studied. The sample was collected throughout Niger, revealing various morphological, biochemical and phenological traits. For comparison, an additional accession from Thailand was evaluated as an available Asian representative. In the Niger sample, the 2C DNA value ranged from 0.77 to 1 pg (753 to 978 Mbp), with an average of 0.85 ± 0.037 pg (831 Mbp). Statistical analysis showed a significant difference in 2C DNA values among 58 pairs of Niger accessions (p-value < 0.05). This significant variation indicates the likely genetic diversity of sesame germplasm, offering valuable insights into its possible potential for climate-resilient agriculture. Our results therefore raise a fundamental question: is intraspecific variability in the genome size of Nigerien sesame correlated with specific morphological and physiological traits?

Transcriptome Analysis of Sesame (Sesamum indicum L.) Reveals the LncRNA and mRNA Regulatory Network Responding to Low Nitrogen Stress.

Nitrogen is one of the important factors restricting the development of sesame planting and industry in China. Cultivating sesame varieties tolerant to low nitrogen is an effective way to solve the problem of crop nitrogen deficiency. To date, the mechanism of low nitrogen tolerance in sesame has not been elucidated at the transcriptional level. In this study, two sesame varieties Zhengzhi HL05 (ZZ, nitrogen efficient) and Burmese prolific (MD, nitrogen inefficient) in low nitrogen were used for RNA-sequencing. A total of 3964 DEGs (differentially expressed genes) and 221 DELs (differentially expressed lncRNAs) were identified in two sesame varieties at 3d and 9d after low nitrogen stress. Among them, 1227 genes related to low nitrogen tolerance are mainly located in amino acid metabolism, starch and sucrose metabolism and secondary metabolism, and participate in the process of transporter activity and antioxidant activity. In addition, a total of 209 pairs of lncRNA-mRNA were detected, including 21 pairs of trans and 188 cis. WGCNA (weighted gene co-expression network analysis) analysis divided the obtained genes into 29 modules; phenotypic association analysis identified three low-nitrogen response modules; through lncRNA-mRNA co-expression network, a number of hub genes and cis/trans-regulatory factors were identified in response to low-nitrogen stress including GS1-2 (glutamine synthetase 1-2), PAL (phenylalanine ammonia-lyase), CHS (chalcone synthase, CHS), CAB21 (chlorophyll a-b binding protein 21) and transcription factors MYB54, MYB88 and NAC75 and so on. As a trans regulator, lncRNA MSTRG.13854.1 affects the expression of some genes related to low nitrogen response by regulating the expression of MYB54, thus responding to low nitrogen stress. Our research is the first to provide a more comprehensive understanding of DEGs involved in the low nitrogen stress of sesame at the transcriptome level. These results may reveal insights into the molecular mechanisms of low nitrogen tolerance in sesame and provide diverse genetic resources involved in low nitrogen tolerance research.

Double-digest restriction-associated DNA sequencing-based genotyping and its applications in sesame germplasm management.

Sesame (Sesamum indicum L.) is an ancient oilseed crop belonging to the family Pedaliaceae and a globally cultivated crop for its use as oil and food. In this study, 2496 sesame accessions, being conserved at the National Genebank of ICAR-National Bureau of Plant Genetic Resources (NBPGR), were genotyped using genomics-assisted double-digest restriction-associated DNA sequencing (ddRAD-seq) approach. A total of 64,910 filtered single-nucleotide polymorphisms (SNPs) were utilized to assess the genome-scale diversity. Applications of this genome-scale information (reduced representation using restriction enzymes) are demonstrated through the development of a molecular core collection (CC) representing maximal SNP diversity. This information is also applied in developing a mid-density panel (MDP) comprising 2515 hyper-variable SNPs, representing almost equally the genic and non-genic regions. The sesame CC comprising 384 accessions, a representative set of accessions with maximal diversity, was identified using multiple criteria such as k-mer (subsequence of length "k" in a sequence read) diversity, observed heterozygosity, CoreHunter3, GenoCore, and genetic differentiation. The coreset constituted around 15% of the total accessions studied, and this small subset had captured >60% SNP diversity of the entire population. In the coreset, the admixture analysis shows reduced genetic complexity, increased nucleotide diversity (π), and is geographically distributed without any repetitiveness in the CC germplasm. Within the CC, India-originated accessions exhibit higher diversity (as expected based on the center of diversity concept), than those accessions that were procured from various other countries. The identified CC set and the MDP will be a valuable resource for genomics-assisted accelerated sesame improvement program.

Induced mutation in the SiALS gene offers new weed management opportunities for sesame crop.

Weeds are the primary biotic constraint affecting sesame growth and production. Here, we applied EMS mutagenesis to an elite sesame cultivar and discovered a novel point mutation in the sesame SiALS gene conferring resistance to imidazolinone, a group of acetolactate-synthase (ALS)-inhibitors. The mutant line exhibited high resistance to imazamox, an ALS-inhibitor, with hybrid plants displaying an intermediate response. Field-based validation confirmed the mutant line's substantial resistance, leading to a significantly higher yield under imazamox treatment. Under pre-emergence application of imazapic, the mutant plants sustained growth, whereas wild-type and weed were effectively controlled. Field trials using s-metolachlor and imazapic combined resulted in weed-free plots compared to untreated controls. Consequently, this treatment showed a significantly greater yield (2280 vs. 880 Kg ha-1) than the commercial practice (s-metolachlor). Overall, our study unveils the potential of utilizing this point mutation in sesame breeding programs, offering new opportunities for integrated weed management strategies for sesame cultivation. Developing herbicide-resistant crop plants holds promise for supporting sustainable production and addressing the challenges of weed infestations in sesame farming.

Potassium attenuates drought damage by regulating sucrose metabolism and gene expression in sesame leaf.

Drought has been considered the most restrictive environmental constraint on agricultural production worldwide. Photosynthetic carbohydrate metabolism is a critical biochemical process connected with crop production and quality traits. A pot experiment was carried out under four potassium (K) rates (0, 0.75, 1.5 and 2.25 g pot-1 of K, respectively) and two water regimes to investigate the role of K in activating defense mechanisms on sucrose metabolism against drought damage in sesame. The soil moisture contents are 75 ± 5% (well-watered, WW) and 45 ± 5% (drought stress, DS) of field capacity respectively. The results showed that DS plants without K application have lower activities of ribulose-1,5-bisphosphate carboxylase (Rubisco), sucrose phosphate synthase (SPS), soluble acid invertase (SAI), and chlorophyll content and higher activity of sucrose synthase (SuSy), which resulted in declined synthesis and distribution of photosynthetic products to reproductive organs. Under drought, there was a significant positive correlation between leaf sucrose metabolizing enzymes and sucrose content. Plants subjected to drought stress increased the concentrations of soluble sugar and sucrose to produce osmo-protectants and energy sources for plants acclimating to stress but decreased starch content. Conversely, K application enhanced the carbohydrate metabolism, biomass accumulation and partitioning, thereby contributing to higher seed oil and protein yield (28.8%-43.4% and 27.5%-40.7%) as compared to K-deficiency plants. The positive impacts of K application enhanced as increasing K rates, and it was more pronounced in drought conditions. Furthermore, K application upregulated the gene expression of SiMYB57, SiMYB155, SiMYB176 and SiMYB192 while downregulated SiMYB108 and SiMYB171 in drought conditions, which may help to alleviate drought susceptibility. Conclusively, our study illustrated that the enhanced photo-assimilation and translocation process caused by the changes in sucrose metabolism activities under K application as well as regulation of MYB gene expression contributes towards drought resistance of sesame.

The expression of genes encoding novel Sesame oleosin variants facilitates enhanced triacylglycerol accumulation in Arabidopsis leaves and seeds.

Triacylglycerols (TAG), accumulate within lipid droplets (LD), predominantly surrounded by OLEOSINs (OLE), that protect TAG from hydrolysis. We tested the hypothesis that identifying and removing degradation signals from OLE would promote its abundance, preventing TAG degradation and enhancing TAG accumulation. We tested whether mutating potential ubiquitin-conjugation sites in a previously reported improved Sesamum indicum OLE (SiO) variant, o3-3 Cys-OLE (SiCO herein), would stabilize it and increase its lipogenic potential. SiCOv1 was created by replacing all five lysines in SiCO with arginines. Separately, six cysteine residues within SiCO were deleted to create SiCOv2. SiCOv1 and SiCOv2 mutations were combined to create SiCOv3. Transient expression of SiCOv3 in Nicotiana benthamiana increased TAG by two-fold relative to SiCO. Constitutive expression of SiCOv3 or SiCOv5, containing the five predominant TAG-increasing mutations from SiCOv3, in Arabidopsis along with mouse DGAT2 (mD) increased TAG accumulation by 54% in leaves and 13% in seeds compared with control lines coexpressing SiCO and mD. Lipid synthesis rates increased, consistent with an increase in lipid sink strength that sequesters newly synthesized TAG, thereby relieving the constitutive BADC-dependent inhibition of ACCase reported for WT Arabidopsis. These OLE variants represent novel factors for potentially increasing TAG accumulation in a variety of oil crops.

First nanoplate digital PCR method to trace allergenic foods: Improved sensitivity for the detection of sesame.

Sesame (Sesamum indicum L.) is an important allergenic food whose presence can be the cause of severe allergic reactions in sensitised individuals. In this work, nanoplate digital PCR (ndPCR) was used to develop two methods to detect trace amounts of sesame in processed foods and compared with previously proposed real-time PCR assays. Two independent ndPCR approaches were successfully advanced, achieving sensitivities of 5 and 0.1 mg/kg of sesame in dough/biscuits, targeting the CO6b-1 and ITS regions, respectively. The sensitivity using both targets was improved by one order of magnitude comparing with real-time PCR and was not affected by food processing. CO6b-1 system was not influenced by food matrix, exhibiting similar performance regardless the use of complex matrix extracts or serial diluted DNA. Herein, ndPCR was proposed for the first time for the detection of allergenic foods with the advantage of providing better performance than real-time PCR regarding sensitivity and robustness.

Analysis of genes specific to the early maturation stage of Sesamum indicum seeds by subtraction method*,*.

The mechanisms regulating the content ratio of unsaturated fatty acid in sesame oil need to be clarified in order to breed novel varieties with high contents of unsaturated fatty acids. Full-length cDNA libraries prepared from sesame seeds 1 to 3 weeks after flowering were subtracted with cDNAs from plantlets of 4 weeks after germination. A total of 1545 cDNA clones was sequenced. The functions of novel genes expressed specifically during the early maturation of sesame seeds were investigated by the transformation of Arabidopsis thaliana. Thirteen genes for a transcription factor were identified, four of which were involved in ethylene signaling. Fifty-nine genes, including those for the aquaporin-like protein and ethylene response factor, were analyzed by overexpression in A. thaliana. The overexpression of novel genes and the aquaporin-like protein gene in A. thaliana increased the content of unsaturated fatty acids. The localization of these products was investigated by the induction of the expression vectors for the GFP fusion protein into onion epidermal cells and sesame root cells with a particle gun. As a result, two cDNA clones were identified as good candidate genes to clarify the regulation in the yield and the ratio of unsaturated fatty acids in sesame seeds. Sein60414 (Accession No. LC603128), an intrinsic membrane protein, may be involved in the increase of unsaturated fatty acids, and Sein61074 (Accession No. LC709278) MAP3K δ-1 protein kinase in the regulation of the total ratio of unsaturated fatty acids in sesame seeds.

Genomic evolution and insights into agronomic trait innovations of Sesamum species.

Sesame is an ancient oilseed crop with high oil content and quality. However, the evolutionary history and genetic mechanisms of its valuable agronomic traits remain unclear. Here, we report chromosome-scale genomes of cultivated sesame (Sesamum indicum L.) and six wild Sesamum species, representing all three karyotypes within this genus. Karyotyping and genome-based phylogenic analysis revealed the evolutionary route of Sesamum species from n = 13 to n = 16 and revealed that allotetraploidization occurred in the wild species Sesamum radiatum. Early divergence of the Sesamum genus (48.5-19.7 million years ago) during the Tertiary period and its ancient phylogenic position within eudicots were observed. Pan-genome analysis revealed 9164 core gene families in the 7 Sesamum species. These families are significantly enriched in various metabolic pathways, including fatty acid (FA) metabolism and FA biosynthesis. Structural variations in SiPT1 and SiDT1 within the phosphatidyl ethanolamine-binding protein gene family lead to the genomic evolution of plant-architecture and inflorescence-development phenotypes in Sesamum. A genome-wide association study (GWAS) of an interspecific population and genome comparisons revealed a long terminal repeat insertion and a sequence deletion in DIR genes of wild Sesamum angustifolium and cultivated sesame, respectively; both variations independently cause high susceptibility to Fusarium wilt disease. A GWAS of 560 sesame accessions combined with an overexpression study confirmed that the NAC1 and PPO genes play an important role in upregulating oil content of sesame. Our study provides high-quality genomic resources for cultivated and wild Sesamum species and insights that can improve molecular breeding strategies for sesame and other oilseed crops.

Integrated physiological, biochemical, and transcriptomics analyses reveal the underlying mechanisms of high nitrogen use efficiency of black sesame.

Cultivating high nitrogen use efficient varieties is a sustainable solution to mitigating adverse effects on the environment caused by excessive nitrogen fertilizer application. However, in sesame, although immoderate nitrogen fertilizers are used to promote yield, the molecular basis of high nitrogen use efficiency (NUE) is largely unknown. Hence, this study aimed to identify high NUE black sesame variety and dissect the underlying physiological and molecular mechanisms. To achieve this, seventeen seedling traits of 30 black sesame varieties were evaluated under low nitrogen (LN) and high nitrogen (HN) conditions. Dry matter accumulation, root parameters, shoot nitrogen accumulation, and chlorophyll content are important factors for evaluating the NUE of sesame genotypes. The variety 17-156 was identified as the most efficient for N utilization. Comparative physiological and transcriptomics analyses revealed that 17-156 possesses a sophisticated nitrogen metabolizing machinery to uptake and assimilate higher quantities of inorganic nitrogen into amino acids and proteins, and simultaneously improving carbon metabolism and growth. Specifically, the total nitrogen and soluble protein contents significantly increased with the increase in nitrogen concentrations. Many important genes, including nitrate transporters (NPFs), amino acid metabolism-related (GS, GOGAT, GDH, etc.), phytohormone-related, and transcription factors, were significantly up-regulated in 17-156 under HN condition. In addition, 38 potential candidate genes were identified for future studies toward improving sesame's NUE. These findings offer valuable resources for deciphering the regulatory network of nitrogen metabolism and developing sesame cultivars with improved NUE.

Genome-wide characterization of the wall-associated kinase-like (WAKL) family in sesame (Sesamum indicum) identifies a SiWAKL6 gene involved in resistance to Macrophomina Phaseolina.

BACKGROUND: Sesame charcoal rot caused by Macrophomina phaseolina is one of the most serious fungal diseases in sesame production, and threatens the yield and quality of sesame. WAKL genes are important in the plant response to biotic stresses by sensing and transmitting external signals to the intracellular receptor. However, there is still a lack about the WAKL gene family and its function in sesame resistance to M. phaseolina. The aim of this study was to interpret the roles of WAKL genes in sesame resistance to M. phaseolina. RESULTS: In this study, a comprehensive study of the WAKL gene family was conducted and 31 WAKL genes were identified in the sesame genome. Tandem duplication events were the main factor in expansion of the SiWAKL gene family. Phylogenetic analysis showed that the sesame SiWAKL gene family was divided into 4 groups. SiWAKL genes exhibited different expression patterns in diverse tissues. Under M. phaseolina stress, most SiWAKL genes were significantly induced. Notably, SiWAKL6 was strongly induced in the resistant variety "Zhengzhi 13". Functional analysis showed that SiWAKL6 was induced by salicylic acid but not methyl jasmonate in sesame. Overexpression of SiWAKL6 in transgenic Arabidopsis thaliana plants enhanced their resistance to M. phaseolina by inducing the expression of genes involved in the salicylic acid signaling pathway and reconstructing reactive oxygen species homeostasis. CONCLUSIONS: Taken together, the results provide a better understanding of functions about SiWAKL gene family and suggest that manipulation of these SiWAKL genes can improve plant resistance to M. phaseolina. The findings contributed to further understanding of functions of SiWAKL genes in plant immunity.

QTL analysis of traits related to seed size and shape in sesame (Sesamum indicum L.).

Seed size and shape are important traits that determine seed yield in sesame. Understanding the genetic basis of seed size and shape is essential for improving the yield of sesame. In this study, F2 and BC1 populations were developed by crossing the Yuzhi 4 and Bengal small-seed (BS) lines for detecting the quantitative trait loci (QTLs) of traits related to seed size and shape. A total of 52 QTLs, including 13 in F2 and 39 in BC1 populations, for seed length (SL), seed width (SW), and length to width ratio (L/W) were identified, explaining phenotypic variations from 3.68 to 21.64%. Of these QTLs, nine stable major QTLs were identified in the two populations. Notably, three major QTLs qSL-LG3-2, qSW-LG3-2, and qSW-LG3-F2 that accounted for 4.94-16.34% of the phenotypic variations were co-localized in a 2.08 Mb interval on chromosome 1 (chr1) with 279 candidate genes. Three stable major QTLs qSL-LG6-2, qLW-LG6, and qLW-LG6-F2 that explained 8.14-33.74% of the phenotypic variations were co-localized in a 3.27 Mb region on chr9 with 398 candidate genes. In addition, the stable major QTL qSL-LG5 was co-localized with minor QTLs qLW-LG5-3 and qSW-LG5 to a 1.82 Mb region on chr3 with 195 candidate genes. Gene annotation, orthologous gene analysis, and sequence analysis indicated that three genes are likely involved in sesame seed development. These results obtained herein provide valuable in-formation for functional gene cloning and improving the seed yield of sesame.

A 4.43-Kb deletion of chromosomal segment containing an ovate family protein confers long capsule in sesame (Sesamum indicum L.).

KEY MESSAGE: A 4.43-Kb structural variation in the sesame genome results in the deletion of the Siofp1 gene and induces the long capsule length trait. Capsule length (CL) has a positive effect on seed weight and yield in various agronomically important species; however, the molecular mechanism underlying long capsule trait regulation in sesame remains unknown. The inheritance analysis showed that long capsule traits (CL > 4.0 cm) were dominant over normal length (average CL = 3.0 cm) and were controlled by a single gene pair. Association mapping with a RIL population and 259 natural sesame germplasm accessions indicated that the target interval was 52,830-730,961 bp of SiChr.10 in sesame. Meanwhile, the structural variation (SV) of the association mapping revealed that only SV_414325 on chromosome 10 was significantly associated with the CL trait, with a P value of 1.1135E-19. SV_414325 represents a 4430-bp deletion from 414,325 to 418,756 bp on SiChr.10, covering Sindi_2155000 (named SiOFP1). In the normal length type, Siofp1 encodes 411 amino acids of the ovate family proteins and is highly expressed in the leaf, stem, bud, and capsule tissues of sesame. In accordance with the transcriptional repressor character, Siofp1 overexpression in transgenic Arabidopsis (T0 and T1 generations) induced a 25-39% greater shortening of silique length than the wild type (P < 0.05), as well as round cauline leaves and short carpels. These results confirm that SiOFP1 plays a key role in regulating CL trait in sesame and other flowering plants. These findings provide a theoretical and material basis for sesame capsule development and high-yield breeding research.

Improving desirable agronomic traits of M2 lines on fourteen Ethiopian Sesame (Sesamum indicum L.) genotypes using Ethyl Methane Sulphonate (EMS).

Sesame is an important oilseed crop cultivated in Ethiopia as a cash crop for small holder farmers. However, low yield is one of the main constraints of its cultivation. Boosting and sustaining production of sesame is thus timely to achieve the global oil demand. This study was, therefore, aimed at identifying mutant genotypes targeted to produce better agronomic traits of M2 lines on fourteen Ethiopian sesame genotypes through seed treatment with chemical mutagens. EMS was used as a chemical mutagen to treat the fourteen sesame genotypes. Quantitative and qualitative data were recorded and analyzed using analysis of variance with GenStat 16 software. Post-ANOVA mean comparisons were made using Duncan's Multiple Range Test (p≤ 0.01). Statistically significant phenotypic changes were observed in both quantitative and qualitative agronomic traits of the M2 lines. All mutant genotypes generated by EMS treatment showed a highly significant variation for the measured quantitative traits, except for the traits LBL and LTL. On the other hand, EMS-treated genotypes showed a significant change for the qualitative traits, except for PGT, BP, SSCS, LC, LH and LA traits. Mutated Baha Necho, Setit 3, and Zeri Tesfay showed the most promising changes in desirable agronomic traits. To the best of our knowledge, this study represents the first report on the treatment of sesame seeds with EMS to generate desirable agronomic traits in Ethiopian sesame genotypes. These findings would deliver an insight into the genetic characteristics and variability of important sesame agronomic traits. Besides, the findings set up a foundation for future genomic studies in sesame agronomic traits, which would serve as genetic resources for sesame improvement.

Genome-wide identification and expression analysis of the trihelix transcription factor family in sesame (Sesamum indicum L.) under abiotic stress.

BACKGROUND: The plant trihelix gene family is among the earliest discovered transcription factor families, and it is vital in modulating light, plant growth, and stress responses. METHODS: The identification and characterization of trihelix family members in the sesame genome were analyzed by bioinformatics methods, and the expression patterns of sesame trihelix genes were assessed by quantitative real-time PCR. RESULTS: There were 34 trihelix genes discovered in the genome of sesame, which were irregularly distributed among 10 linkage groups. Also, the genome contained 5 duplicate gene pairs. The 34 trihelix genes were divided into six sub-families through a phylogenetic study. A tissue-specific expression revealed that SiTH genes exhibited spatial expression patterns distinct from other trihelix genes in the same subfamily. The cis-element showed that the SiTHs gene promoter contained various elements associated with responses to hormones and multiple abiotic stresses. Additionally, the expression patterns of 8 SiTH genes in leaves under abiotic stresses demonstrated that all selected genes were significantly upregulated or downregulated at least once in the stress period. Furthermore, the SiTH4 gene was significantly induced in response to drought and salt stress, showing that SiTH genes may be engaged in the stress response mechanisms of sesame. CONCLUSION: These findings establish a foundation for further investigation of the trihelix gene-mediated response to abiotic stress in sesame.

Effectiveness of repeated mutagenesis of sesame crosses for enhancing polygenic variability in F2M2 generation.

The value of combining hybridization and mutagenesis in sesame was examined to determine if treating hybrid sesame plant material with mutagens generated greater genetic variability in four key productivity traits than either the separate hybridization or mutation of plant material. In a randomized block design with three replications, six F2M2 varieties, three F2varieties, and three parental varieties were assessed at Odisha University of Agriculture and Technology, Bhubaneswar, Odisha, India. The plant characteristics height, number of seed capsules per plant, and seed yield per plant had greater variability in the F2M2 generation than their respective controls (F2), however, the number of primary branches per plant varied less than in the control population. The chances for trait selection to be operative were high for all the characteristics examined except the number of primary branches per plant, as indicated by heritability estimates. Increases in the mean and variability of the characteristics examined indicted a greater incidence of beneficial mutations and the breakdown of undesirable linkages with increased recombination. At both phenotypic and genotypic levels strong positive correlations between both primary branch number and capsule number with seed yield suggest that these traits are important for indirect improvement in sesame seed yield. As a result of the association analysis, sesame seed yield and its component traits improved significantly, which may be attributed to the independent polygenic mutations and enlarged recombination of the polygenes controlling the examined characteristics. Compared to the corresponding control treatment or to one cycle of mutagenic treatment, two cycles of mutagenic treatment resulted in increased variability, higher transgressive segregates, PTS mean and average transgression for sesame seed yield. These findings highlight the value of implementing two EMS treatment cycles to generate improved sesame lines. Furthermore, the extra variability created through hybridization may have potential in subsequent breeding research and improved seed yield segregants may be further advanced to develop ever-superior sesame varieties.