Sugarcane Improvement Research Articles

Genomic Association and Prediction Study for Yield Traits in a Sugarcane (Saccharum spp. Hybrids) Mapping Population ‘LCP 85‐384’

ABSTRACTSugarcane (Saccharum spp. hybrids) are complex polyploid and aneuploid interspecific hybrids with 110–130 chromosomes. A traditional sugarcane breeding cycle takes 13–15 years and involves multiple years and locations testing of yield. To identify molecular markers associated with yield‐related traits, the LCP 85‐384 cultivar and its mapping population of 263 self‐progenies were planted in two randomly replicated field plots. The mapping population was genotyped with amplified fragment length polymorphism (AFLP), simple sequence repeats (SSR) and target region amplification polymorphism (TRAP) markers. Data on plant height, stalk number, stalk diameter and stalk weight were collected. A large variation was observed for each trait. A genome‐wide association study (GWAS) was conducted using mixed linear model (MLM), generalized linear model (GLM) and single marker regression (SMR) programmes of TASSEL 5 and FarmCPU of GAPIT 3. A total of 64 yield trait‐associated alleles were identified, including 11 for stalk number, 36 for stalk weight, 21 for stalk diameter and 5 for plant height. Of the 64 alleles, seven were linked to two traits and one to three traits. Genomic prediction (GP) was also performed by cross‐prediction with five models, namely, ridge regression best linear unbiased prediction (rrBLUP), Bayesian ridge regression (BRR), Bayesian A (BA), Bayesian B (BB), and Bayesian least absolute shrinkage and selection operator (BL). Prediction accuracy (r value) reached 0.40 for plant height, 0.36 for stalk number, 0.44 for stalk diameter and 0.54 for stalk weight with the standard errors from 0.009 to 0.012. Once verified, these markers will be a valuable tool to aid in the selection of yield‐related traits in sugarcane improvement programmes.

In Planta Androgenesis (Paternal Origin) in Saacharum X Erianthus Intergeneric Hybrid

The present investigation was carried in crosses made between Saccharum species hybrid clones i.e. Co 419, Co 7201 and Co 7224 (2n = 108-112) and Erianthus arundinaceus viz. IK 76-91 (2n = 60) and IK 76-99 (2n = 60) for introducing better ratoon ability, vigour, wide ecological adaptability, extensive root system, drought and water logging resistance, high biomass and disease resistance into modern sugarcane cultivars during 2020-23 at VSI-Sugarcane Breeding Centre, Amboli. Parental apomixis (paternal origin) has been recently noticed and it is unique in Saccharum X Erianthus intergeneric cross seedlings. A total of fifty-one seedlings were obtained from above three intergeneric crosses and out of these eighteen seedlings were reported as androgenetic seedlings as the female act as a surrogate mother. At the early stages, seed germination of seedlings was found two types i.e., one type resembling Saccharum and other resembling Erianthus with deep purple coloration. Morphologically androgenetic seedlings were similar to the male parents IK 76-91 and IK 76-99 with tall large tufted grass like clumps, vegetative stem with thick reproductive buds, root zone narrow and only one row of root eyes, the lamina gradually passes into leaf sheath with no auricle and dewlaps. Cytological studies were made in these seedlings and during metaphase the somatic chromosome number was observed to be 2n = 60 rather than expected 2n = 84-90. This paternal origin may be due to the ability of Erianthus male gametes to produce an embryo within the seed tissues of Saccharum species hybrids but without genetic contribution of the seed. Thus, in planta androgenesis is achieved through the combination of embryogenic behavior of male gametes which has entered in the ovule and the ability of ovules to act as a surrogate mother. They could derive either from the fusion of two male gametes or from the early natural diplodization of the haploid embryo. Such homozygous true breeding seedlings of Saccharum X Erianthus with hybrid vigour are extremely important in crop improvement. This system provides an unparalleled opportunity to shorten the breeding cycle and fix agronomic traits in the homozygous state. These androgenetic plants with Saccharum cytoplasm and Erianthus genome are male sterile making them highly useful for further hybridization and sugarcane improvement programme.

Pathogenesis-Related 1 (PR1) Protein Family Genes Involved in Sugarcane Responses to Ustilago scitaminea Stress.

Plant resistance against biotic stressors is significantly influenced by pathogenesis-related 1 (PR1) proteins. This study examines the systematic identification and characterization of PR1 family genes in sugarcane (Saccharum spontaneum Np-X) and the transcript expression of selected genes in two sugarcane cultivars (ROC22 and Zhongtang3) in response to Ustilago scitaminea pathogen infection. A total of 18 SsnpPR1 genes were identified at the whole-genome level and further categorized into four groups. Notably, tandem and segmental duplication occurrences were detected in one and five SsnpPR1 gene pairs, respectively. The SsnpPR1 genes exhibited diverse physio-chemical attributes and variations in introns/exons and conserved motifs. Notably, four SsnpPR1 (SsnpPR1.02/05/09/19) proteins displayed a strong protein-protein interaction network. The transcript expression of three SsnpPR1 (SsnpPR1.04/06/09) genes was upregulated by 1.2-2.6 folds in the resistant cultivar (Zhongtang3) but downregulated in the susceptible cultivar (ROC22) across different time points as compared to the control in response to pathogen infection. Additionally, SsnpPR1.11 was specifically upregulated by 1.2-3.5 folds at 24-72 h post inoculation (hpi) in ROC22, suggesting that this gene may play an important negative regulatory role in defense responses to pathogen infection. The genetic improvement of sugarcane can be facilitated by our results, which also establish the basis for additional functional characterization of SsnpPR1 genes in response to pathogenic stress.

Whole-genome sequencing of a worldwide collection of sugarcane cultivars (Saccharum spp.) reveals the genetic basis of cultivar improvement.

Sugarcane is the main source of sugar worldwide, and 80% of the sucrose production comes from sugarcane. However, the genetic differentiation and basis of agronomic traits remain obscure. Here, we sequenced the whole-genome of 219 elite worldwide sugarcane cultivar accessions. A total of approximately 6 million high-quality genome-wide single nucleotide polymorphisms (SNPs) were detected. A genome-wide association study identified a total of 2198 SNPs that were significantly associated with sucrose content, stalk number, plant height, stalk diameter, cane yield, and sugar yield. We observed homozygous tendency of favor alleles of these loci, and over 80% of cultivar accessions carried the favor alleles of the SNPs or haplotypes associated with sucrose content. Gene introgression analysis showed that the number of chromosome segments from Saccharum spontaneum decreased with the breeding time of cultivars, while those from S. officinarum increased in recent cultivars. A series of selection signatures were identified in sugarcane improvement procession, of which 104 were simultaneously associated with agronomic traits and 45 of them were mainly associated with sucrose content. We further proposed that as per sugarcane transgenic experiments, ShN/AINV3.1 plays a positive role in increasing stalk number, plant height, and stalk diameter. These findings provide comprehensive resources for understanding the genetic basis of agronomic traits and will be beneficial to germplasm innovation, screening molecular markers, and future sugarcane cultivar improvement.

CRISPR/Cas-Mediated Genome Editing for Sugarcane Improvement

CRISPR/Cas-Mediated Genome Editing for Sugarcane Improvement

A Large-Scale Candidate-Gene Association Mapping for Drought Tolerance and Agronomic Traits in Sugarcane.

Dissection of the genetic loci controlling drought tolerance traits with a complex genetic inheritance is important for drought-tolerant sugarcane improvement. In this study, we conducted a large-scale candidate gene association study of 649 candidate genes in a sugarcane diversity panel to identify genetic variants underlying agronomic traits and drought tolerance indices evaluated in plant cane and ratoon cane under water-stressed (WS) and non-stressed (NS) environments. We identified 197 significant marker-trait associations (MTAs) in 141 candidate genes associated with 18 evaluated traits with the Bonferroni correction threshold (α = 0.05). Out of the total, 95 MTAs in 78 candidate genes and 62 MTAs in 58 candidate genes were detected under NS and WS conditions, respectively. Most MTAs were found only in specific water regimes and crop seasons. These MTAs explained 7.93-30.52% of phenotypic variation. Association mapping results revealed that 34, 59, and 104 MTAs involved physiological and molecular adaptation, phytohormone metabolism, and drought-inducible genes. They identified 19 pleiotropic genes associated with more than one trait and many genes related to drought tolerance indices. The genetic and genomic resources identified in this study will enable the combining of yield-related traits and sugar-related traits with agronomic value to optimize the yield of sugarcane cultivars grown under drought-stressed and non-stressed environments.

Evaluation of sugarcane promising clones based on the morphophysiological traits developed from fuzz.

Sugarcane is one of the critical commercial crops and principal sources of ethanol and sugar worldwide. Unfavorable conditions and poor seed setting rates hinder variety development in sugarcane. Countries like Pakistan directly import fuzz (true seed) and other propagation material from the USA, China, Brazil, etc. In this study, we imported fuzz from China, developed 29 genotypes germinating in the glasshouse, and evaluated at field conditions along with two local checks (CPF-251 and HSF-240). Morphophysiological data were recorded, including plant height (PH), cane length (CL), internodal length (IL), tiller number (TN), brix percentage (B), cane diameter (CD), chlorophyll a (Chl. a), chlorophyll b (Chl. b), and total chlorophyll (T. Chl). Results showed highly significant (p < 0.001) differences among the sugarcane accessions for all the studied traits. High broad-sense heritability (81.89% to 99.91%) was recorded for all the studied parameters. Genetic Advance (GA) ranges from 4.6% to 65.32%. The highest GA was observed for PH (65.32%), followed by CL (63.28%). Chlorophyll leaching assay was also performed at different time points (0, 50, 100, 150, and 200 min). All the genotypes showed the same leaching trend at all times, and better performing genotypes showed less leaching compared to poor performing, indicating the high amount of cutin and wax on the leaf surface. Correlation analysis showed that PH, CL, IL, and TN had significant associations. Principal components analysis (PCA) further confirms these results. Based on PCA and correlation results, PH, CL, IL, and TN can be utilized as a selection criterion for sugarcane improvement. Genotypes such as NS-4a, NS-5, NS-6, NS-8, NS-9, and NS-15 are recommended for future breeding programs related to sugarcane variety development.

Drought-triggered leaf transcriptional responses disclose key molecular pathways underlying leaf water use efficiency in sugarcane (Saccharum spp.).

Drought is a major constraint to sugarcane (Saccharum spp.) production and improving the water use efficiency (WUE) is a critical trait for the sustainability of this bioenergy crop. The molecular mechanism underlying WUE remains underexplored in sugarcane. Here, we investigated the drought-triggered physiological and transcriptional responses of two sugarcane cultivars contrasting for drought tolerance, 'IACSP97-7065' (sensitive) and 'IACSP94-2094' (tolerant). After 21 days without irrigation (DWI), only 'IACSP94-2094' exhibited superior WUE and instantaneous carboxylation efficiency, with the net CO2 assimilation being less impacted when compared with 'IACSP97-7065'. RNA-seq of sugarcane leaves at 21 DWI revealed a total of 1,585 differentially expressed genes (DEGs) for both genotypes, among which 'IACSP94-2094' showed 617 (38.9%) exclusive transcripts (212 up- and 405 down-regulated). Functional enrichment analyses of these unique DEGs revealed several relevant biological processes, such as photosynthesis, transcription factors, signal transduction, solute transport, and redox homeostasis. The better drought-responsiveness of 'IACSP94-2094' suggested signaling cascades that foster transcriptional regulation of genes implicated in the Calvin cycle and transport of water and carbon dioxide, which are expected to support the high WUE and carboxylation efficiency observed for this genotype under water deficit. Moreover, the robust antioxidant system of the drought-tolerant genotype might serve as a molecular shield against the drought-associated overproduction of reactive oxygen species. This study provides relevant data that may be used to develop novel strategies for sugarcane breeding programs and to understand the genetic basis of drought tolerance and WUE improvement of sugarcane.

Genome-Wide Identification, Evolution, and Expression Analyses of AP2/ERF Family Transcription Factors in Erianthus fulvus.

The AP2/ERF transcription factor family is one of the most important gene families in plants and plays a vital role in plant abiotic stress responses. Although Erianthus fulvus is very important in the genetic improvement of sugarcane, there are few studies concerning AP2/ERF genes in E. fulvus. Here, we identified 145 AP2/ERF genes in the E. fulvus genome. Phylogenetic analysis classified them into five subfamilies. Evolutionary analysis showed that tandem and segmental duplication contributed to the expansion of the EfAP2/ERF family. Protein interaction analysis showed that twenty-eight EfAP2/ERF proteins and five other proteins had potential interaction relationships. Multiple cis-acting elements present in the EfAP2/ERF promoter were related to abiotic stress response, suggesting that EfAP2/ERF may contribute to adaptation to environmental changes. Transcriptomic and RT-qPCR analyses revealed that EfDREB10, EfDREB11, EfDREB39, EfDREB42, EfDREB44, EfERF43, and EfAP2-13 responded to cold stress, EfDREB5 and EfDREB42 responded to drought stress, and EfDREB5, EfDREB11, EfDREB39, EfERF43, and EfAP2-13 responded to ABA treatment. These results will be helpful for better understanding the molecular features and biological role of the E. fulvus AP2/ERF genes and lay a foundation for further research on the function of EfAP2/ERF genes and the regulatory mechanism of the abiotic stress response.

A chromosome-level genome assembly for Erianthus fulvus provides insights into its biofuel potential and facilitates breeding for improvement of sugarcane

Erianthus produces substantial biomass, exhibits a good Brix value, and shows wide environmental adaptability, making it a potential biofuel plant. In contrast to closely related sorghum and sugarcane, Erianthus can grow in degraded soils, thus releasing pressure on agricultural lands used for biofuel production. However, the lack of genomic resources for Erianthus hinders its genetic improvement, thus limiting its potential for biofuel production. In the present study, we generated a chromosome-scale reference genome for Erianthus fulvus Nees. The genome size estimated by flow cytometry was 937 Mb, and the assembled genome size was 902 Mb, covering 96.26% of the estimated genome size. A total of 35 065 protein-coding genes were predicted, and 67.89% of the genome was found to be repetitive. A recent whole-genome duplication occurred approximately 74.10 million years ago in the E. fulvus genome. Phylogenetic analysis showed that E. fulvus is evolutionarily closer to S. spontaneum and diverged after S. bicolor. Three of the 10 chromosomes of E. fulvus formed through rearrangements of ancestral chromosomes. Phylogenetic reconstruction of the Saccharum complex revealed a polyphyletic origin of the complex and a sister relationship of E. fulvus with Saccharum sp., excluding S. arundinaceum. On the basis of the four amino acid residues that provide substrate specificity, the E. fulvus SWEET proteins were classified as mono- and disaccharide sugar transporters. Ortho-QTL genes identified for 10 biofuel-related traits may aid in the rapid screening of E. fulvus populations to enhance breeding programs for improved biofuel production. The results of this study provide valuable insights for breeding programs aimed at improving biofuel production in E. fulvus and enhancing sugarcane introgression programs.

Global Responses of Autopolyploid Sugarcane Badila (Saccharum officinarum L.) to Drought Stress Based on Comparative Transcriptome and Metabolome Profiling.

Sugarcane (Saccharum spp. hybrid) is frequently affected by seasonal drought, which causes substantial declines in quality and yield. To understand the drought resistance mechanisms of S. officinarum, the main species of modern sugarcane, at a molecular level, we carried out a comparative analysis of transcriptome and metabolome profiling of the sugarcane variety Badila under drought stress (DS). Compared with control group (CG) plants, plants exposed to DS had 13,744 (6663 up-regulated and 7081 down-regulated) differentially expressed genes (DEGs). GO and KEGG analysis showed that the DEGs were enriched in photosynthesis-related pathways and most DEGs had down-regulated expression. Moreover, the chlorophyll content, photosynthesis (Photo), stomatal conductance (Cond), intercellular carbon dioxide concentration (Ci) and transpiration rate (Trmmol) were sharply decreased under DS. These results indicate that DS has a significant negative influence on photosynthesis in sugarcane. Metabolome analysis identified 166 (37 down-regulated and 129 up-regulated) significantly regulated metabolites (SRMs). Over 50% of SRMs were alkaloids, amino acids and their derivatives, and lipids. The five most significantly enriched KEGG pathways among SRMs were Aminoacyl-tRNA biosynthesis, 2-Oxocarboxylic acid metabolism, Biosynthesis of amino acids, Phenylalanine metabolism, and Arginine and proline metabolism (p < 0.05). Comparing CG with DS for transcriptome and metabolome profiling (T_CG/DS and M_CG/DS, respectively), we found three of the same KEGG-enriched pathways, namely Biosynthesis of amino acids, Phenylalanine metabolism and Arginine and proline metabolism. The potential importance of Phenylalanine metabolism and Arginine and proline metabolism was further analyzed for response to DS in sugarcane. Seven SRMs (five up-regulated and two down-regulated) and 60 DEGs (17 up-regulated and 43 down-regulated) were enriched in Phenylalanine metabolism under DS, of which novel.31261, Sspon.04G0008060-1A, Sspon.04G0008060-2B and Sspon.04G0008060-3C were significantly correlated with 7 SRMs. In Arginine and proline metabolism, eight SRMs (seven up-regulated and one down-regulated) and 63 DEGs (32 up-regulated and 31 down-regulated) were enriched, of which Sspon.01G0026110-1A (OAT) and Sspon.03G0002750-3D (P5CS) were strongly associated with proline (r > 0.99). These findings present the dynamic changes and possible molecular mechanisms of Phenylalanine metabolism as well as Arginine and proline metabolism under DS and provide a foundation for future research and sugarcane improvement.

Phenotypic diversity, heritability, and association of characters in sugarcane genotypes at Metehara Sugar Estate, Ethiopia

ABSTRACT Genetic improvement of sugarcane (Saccharum spp. hybrids) yield is crucial in the improvement of crop productivity. This study was conducted with the objectives to estimate the degree of phenotypic diversity, heritability, and association of various traits and recommend sugarcane genotypes for commercial production and small-scale farmers. Fifteen sugarcane genotypes and one standard check variety were evaluated in plant, first and second ratoon crops for 14 quantitative traits including stalk and juice quality. Highly significant (p ≤ 0.01) differences among the genotypes for all the traits were observed. Phenotypic diversity of genotypes by principal component analysis (PCA) and cluster analysis indicated genetically diverse genotypes from divergent cluster groups, which can be exploited as desirable parents to use in hybridization programs. All traits had low to high correlations (r = 0.132 to 0.719) with cane yield. High broad-sense heritability (h2) was detected for single cane weight (82.55), number of millable canes (76.85), plant height (76.79), stalk diameter (73.22), and internode length (73.69) indicating that these traits could be selected for easily. Highest expected genetic gains were recorded in single cane weight (30.12) and number of millable canes (28.6). Path coefficient analysis of cane yield revealed that single cane weight and number of millable canes were the major contributors to cane yield. Results showed that millable cane number and single cane weight can be used as reliable selection criteria to improve sugarcane yield. Genotypes FG03104, FG05414, and FG05300 can be considered for commercial production at Metehara Sugar Estate and similar agroecologies.

Bioinformatics Analysis of WRKY Family Genes in Erianthus fulvus Ness.

One of the most prominent transcription factors in higher plants, the WRKY gene family, is crucial for secondary metabolism, phytohormone signaling, plant defense responses, and plant responses to abiotic stresses. It can control the expression of a wide range of target genes by coordinating with other DNA-binding or non-DNA-binding interacting proteins. In this study, we performed a genome-wide analysis of the EfWRKY genes and initially identified 89 members of the EfWRKY transcription factor family. Using some members of the OsWRKY transcription factor family, an evolutionary tree was built using the neighbor-joining (NJ) method to classify the 89 members of the EfWRKY transcription factor family into three major taxa and one unclassified group. Molecular weights ranged from 22,614.82 to 303,622.06 Da; hydrophilicity ranged from (-0.983)-(0.159); instability coefficients ranged from 40.97-81.30; lipid coefficients ranged from 38.54-91.89; amino acid numbers ranged from 213-2738 bp; isoelectric points ranged from 4.85-10.06. A signal peptide was present in EfWRKY41 but not in the other proteins, and EfWRK85 was subcellularly localized to the cell membrane. Chromosome localization revealed that the WRKY gene was present on each chromosome, proving that the conserved pattern WRKYGQK is the family's central conserved motif. Conserved motif analysis showed that practically all members have this motif. Analysis of the cis-acting elements indicated that, in addition to the fundamental TATA-box, CAAT-box, and light-responsive features (GT1-box), there are response elements implicated in numerous hormones, growth regulation, secondary metabolism, and abiotic stressors. These results inform further studies on the function of EfWRKY genes and will lead to the improvement of sugarcane.

Genetic Improvement of Sugarcane (Saccharum spp.) Contributed to High Sucrose Content in China Based on an Analysis of Newly Developed Varieties

In China, sugarcane (Saccharum spp.) hybrid cross-breeding began in 1953; approximately 70 years since then, &gt;100 commercial sugarcane varieties have been created. In this study, 88 commercial varieties bred in China between 1953 and 2010 and 12 original foundational varieties were planted to investigate the effect of improving sugarcane varieties in China. Considering 20 years as a time node, the commercial varieties were classified into four improved generations. Retrospective analysis showed significant improvements in sucrose and other technological characteristics of commercial sugarcane varieties. The adoption of improved varieties over generations has continuously increased sugarcane’s sucrose, juice sugar, and gravity purity, and the difference was significant between Gen1 and Gen3, and between Gen2 and Gen4. Gen4 showed 2.06%, 2.35%, and 3.69% higher sugarcane sucrose (p &lt; 0.01), juice sugar (p &lt; 0.01), and purity (p &lt; 0.05), respectively, and 1.13% lower sugarcane fiber (p &lt; 0.01) than Gen1, the original foundational hybrid varieties. The development of new varieties has improved the technological characteristics of Chinese sugarcane. Sugarcane sucrose, juice sugar, and purity showed an increasing trend. Sugarcane fiber content did not significantly change with the development of new varieties but declined in comparison with the original foundational hybrid varieties.

Efficient Anchoring of Erianthus arundinaceus Chromatin Introgressed into Sugarcane by Specific Molecular Markers

Erianthus arundinaceus is a valuable gene reservoir for sugarcane improvement. However, insufficient molecular markers for high-accuracy identification and tracking of the introgression status of E. arundinaceus chromatin impede sugarcane breeding. Fortunately, suppression subtractive hybridization (SSH) technology provides an excellent opportunity for the development of high-throughput E. arundinaceus-specific molecular markers at a reasonable cost. In this study, we constructed a SSH library of E. arundinaceus. In total, 288 clones of E. arundinaceus-specific repetitive sequences were screened out and their distribution patterns on chromosomes were characterized by fluorescence in situ hybridization (FISH). A subtelomeric repetitive sequence Ea086 and a diffusive repetitive sequence Ea009, plus 45S rDNA-bearing E. arundinaceus chromosome repetitive sequence EaITS were developed as E. arundinaceus-specific molecular markers, namely, Ea086-128, Ea009-257, and EaITS-278, covering all the E. arundinaceus chromosomes for high-accuracy identification of putative progeny. Both Ea086-128 and Ea009-257 were successfully applied to identify the authenticity of F1, BC1, BC2, BC3, and BC4 progeny between sugarcane and E. arundinaceus. In addition, EaITS-278 was a 45S rDNA-bearing E. arundinaceus chromosome-specific molecular marker for rapid tracking of the inherited status of this chromosome in a sugarcane background. Three BC3 progeny had apparently lost the 45S rDNA-bearing E. arundinaceus chromosome. We reported herein a highly effective and reliable SSH-based technology for discovery of high-throughput E. arundinaceus-specific sequences bearing high potential as molecular markers. Given its reliability and savings in time and efforts, the method is also suitable for development of species-specific molecular markers for other important wild relatives to accelerate introgression of wild relatives into sugarcane.

Integrated Approach in Genomic Selection to Accelerate Genetic Gain in Sugarcane.

Marker-assisted selection (MAS) has been widely used in the last few decades in plant breeding programs for the mapping and introgression of genes for economically important traits, which has enabled the development of a number of superior cultivars in different crops. In sugarcane, which is the most important source for sugar and bioethanol, marker development work was initiated long ago; however, marker-assisted breeding in sugarcane has been lagging, mainly due to its large complex genome, high levels of polyploidy and heterozygosity, varied number of chromosomes, and use of low/medium-density markers. Genomic selection (GS) is a proven technology in animal breeding and has recently been incorporated in plant breeding programs. GS is a potential tool for the rapid selection of superior genotypes and accelerating breeding cycle. However, its full potential could be realized by an integrated approach combining high-throughput phenotyping, genotyping, machine learning, and speed breeding with genomic selection. For better understanding of GS integration, we comprehensively discuss the concept of genetic gain through the breeder’s equation, GS methodology, prediction models, current status of GS in sugarcane, challenges of prediction accuracy, challenges of GS in sugarcane, integrated GS, high-throughput phenotyping (HTP), high-throughput genotyping (HTG), machine learning, and speed breeding followed by its prospective applications in sugarcane improvement.

Genetic variation in agronomic traits of Erianthus germplasm under multiple‐ratoon crops in Thailand

AbstractErianthus species have potential as breeding materials for sugarcane and as a biomass crop for fiber production. However, limited information about their genetic variation in agronomic traits hinders their practical utilization. Thus, in this study, we evaluated genetic variation and genetic correlations among 11 agronomic traits in plants grown as multiple‐ratoon crops (plant crop to the third ratoon crop) for 98 clones of E. arundinaceus and 32 clones of E. procerus collected across Thailand. Among the clones tested, large genetic variation was observed in the 4‐yr average, range, and genetic coefficient of variation of dry matter yield for both E. arundinaceus (12.1, 2.2 to 30.6 kg stool−1, and 41.7%, respectively) and E. procerus (8.0, 2.7 to 16.3 kg stool−1, and 25.5%, respectively). Many clones provided better dry matter yield and lower yield reductions in ratoon crops than a sugarcane cultivar (Saccharum spp. hybrid, 5.2 kg stool−1) and Napier grass (Pennisetum purpureum, 6.6 kg stool−1). Genetic variation was observed for stalk number, stalk length, stalk diameter, single stalk weight, Brix, dry matter content, and proportions of both pith and stem parts in stalks, which are important traits in sugarcane breeding. The dry matter yield showed the highest genetic correlation with stalk number (.958 in E. arundinaceus and .700 in E. procerus). Based on the results, clones with various combinations of advantageous traits were identified as promising genetic resources. These results provide important agronomic information that can be used to exploit this Erianthus germplasm for sugarcane improvement and fiber production in Thailand.

Identification and Expression Profiling of WRKY Family Genes in Sugarcane in Response to Bacterial Pathogen Infection and Nitrogen Implantation Dosage.

WRKY transcription factors (TFs) are essential players in different signaling cascades and regulatory networks involved in defense responses to various stressors. This study systematically analyzed and characterized WRKY family genes in the Saccharum spp. hybrid R570 and their expression in two sugarcane cultivars LCP85-384 (resistant to leaf scald) and ROC20 (susceptible to leaf scald) in response to bacterial pathogen infection and nitrogen implantation dosage. A total of 53 ShWRKY genes with 66 alleles were systematically identified in R570 based on the query sequence SsWRKY in S. spontaneum AP85-441. All ShRWKY alleles were further classified into four groups with 11 (16.7%) genes in group I, 36 (54.5%) genes in group II, 18 (27.3%) genes in group III, and 1 (1.5%) gene in group IV. Among them, 4 and 11 ShWRKY gene pairs displayed tandem and segmental duplication events, respectively. The ShWRKY genes exhibited conserved DNA-binding domains, which were accompanied by variations in introns, exons, and motifs. RT-qPCR analysis of two sugarcane cultivars triggered by Xanthomonas albilineans (Xa) revealed that four genes, ShWRKY13-2/39-1/49-3/125-3, exhibited significant upregulation in leaf scald-resistant LCP85-384. These WRKY genes were downregulated or unchanged in ROC20 at 24–72 h post-inoculation, suggesting that they play an important role in defense responses to Xa infection. Most of the 12 tested ShWRKYs, ShWRKY22-1/49-3/52-1 in particular, functioned as negative regulators in the two cultivars in response to a range of nitrogen (N) implantation doses. A total of 11 ShWRKY proteins were predicted to interact with each other. ShWRKY43 and ShWRKY49-3 are predicted to play core roles in the interaction network, as indicated by their interaction with six other ShWRKY proteins. Our results provide important candidate gene resources for the genetic improvement of sugarcane and lay the foundation for further functional characterization of ShWRKY genes in response to coupling effects of Xa infection and different N levels.

Biotechnological Intervention for Sugarcane Improvement Under Salinity

Biotechnological Intervention for Sugarcane Improvement Under Salinity

Genomic insights into the recent chromosome reduction of autopolyploid sugarcane Saccharum spontaneum.

Saccharum spontaneum is a founding Saccharum species and exhibits wide variation in ploidy levels. We have assembled a high-quality autopolyploid genome of S. spontaneum Np-X (2n = 4x = 40) into 40 pseudochromosomes across 10 homologous groups, that better elucidates recent chromosome reduction and polyploidization that occurred circa 1.5 million years ago (Mya). One paleo-duplicated chromosomal pair in Saccharum, NpChr5 and NpChr8, underwent fission followed by fusion accompanied by centromeric split around 0.80 Mya. We inferred that Np-X, with x = 10, most likely represents the ancestral karyotype, from which x = 9 and x = 8 evolved. Resequencing of 102 S. spontaneum accessions revealed that S. spontaneum originated in northern India from an x = 10 ancestor, which then radiated into four major groups across the Indian subcontinent, China, and Southeast Asia. Our study suggests new directions for accelerating sugarcane improvement and expands our knowledge of the evolution of autopolyploids.