Sporisorium Scitamineum Research Articles

Sugarcane ScOPR1 gene enhances plant disease resistance through the modulation of hormonal signaling pathways.

Transgenic plants stably overexpressing ScOPR1 gene enhanced disease resistance by increasing the accumulation of JA, SA, and GST, as well as up-regulating the expression of genes related to signaling pathways. 12-Oxo-phytodienoate reductase (OPR) is an oxidoreductase that depends on flavin mononucleotide (FMN) and catalyzes the conversion of 12-oxophytodienoate (12-OPDA) into jasmonic acid (JA). It plays a key role in plant growth and development, and resistance to adverse stresses. In our previous study, we have obtained an OPR gene (ScOPR1, GenBank Accession Number: MG755745) from sugarcane. This gene showed positive responses to methyl jasmonate (MeJA), salicylic acid (SA), abscisic acid (ABA), and Sporisorium scitamineum, suggesting its potential for pathogen resistance. Here, in our study, we observed that Nicotiana benthamiana leaves transiently overexpressing ScOPR1 exhibited weaker disease symptoms, darker 3,3-diaminobenzidine (DAB) staining, higher accumulation of reactive oxygen species (ROS), and higher expression of hypersensitive response (HR) and SA pathway-related genes after inoculation with Ralstonia solanacearum and Fusarium solanacearum var. coeruleum. Furthermore, the transgenic N. benthamiana plants stably overexpressing the ScOPR1 gene showed enhanced resistance to pathogen infection by increasing the accumulation of JA, SA, and glutathione S-transferase (GST), as well as up-regulating genes related to HR, JA, SA, and ROS signaling pathways. Transcriptome analysis revealed that the specific differentially expressed genes (DEGs) in ScOPR1-OE were significantly enriched in hormone transduction signaling and plant-pathogen interaction pathways. Finally, a functional mechanism model of the ScOPR1 gene in response to pathogen infection was depicted. This study provides insights into the molecular mechanism of ScOPR1 and presents compelling evidence supporting its positive involvement in enhancing plant disease resistance.

Ceramides involve sugarcane defense response to Sporisorium scitamineum

AbstractSugarcane smut, a widespread and destructive disease induced by Sporisorium scitamineum, has a significant effect on sugarcane cultivation. Sphingolipids, crucial components of membranes, play a role in plant resistance regulation. However, the specific function of sphingolipids in sugarcane smut resistance has not been understood. This study revealed that following the S. scitamineum infection, ceramide (Cer) and hydroxyceramide (hCer) levels specifically increased in the sugarcane variety ROC22, along with significant alterations in plant hormone levels. Analysis of lipid composition in S. scitamineum‐sensitive and ‐resistant sugarcane varieties indicated that the resistant variety YT93‐159 had lower Cer and hCer levels compared to the sensitive variety ROC22. Additionally, YT93‐159 displayed an increased level of jasmonoyl‐isoleucine (JA‐Ile) and upregulated the expression of genes linked to the pathway of jasmonic acid (JA). Through experiments using the sugarcane protoplast system, it was observed that exogenous ceramide could influence the expression of genes associated with the salicylic acid and JA pathways. This research was the initial examination into the lipidomics‐based molecular mechanisms underlying sugarcane's resistance to S. scitamineum, offering a theoretical foundation for enhancing sugarcane resistance through genetic engineering.

Exploring Potential Surrogate Systems for Studying the Early Steps of the Sporisorium scitamineum Pathogenesis.

Despite its global importance as a primary source of table sugar and bioethanol, sugarcane faces a significant threat to its production due to diseases. One of these diseases, sugarcane smut, involves the emergence of a whip-like structure from the host apical shoot. The slow onset of this pathogenesis is the most substantial challenge for researchers to investigate the molecular events leading to resistance or susceptibility. In this study, we explored the early interaction between the smut fungus Sporisorium scitamineum and foliar tissues of the model plants Arabidopsis thaliana and Nicotiana benthamiana. Upon inoculation with the fungus, A. thaliana showed a compatible reaction, producing lesions during fungus colonization, whereas N. benthamiana showed signs of nonhost resistance. In addition, we propose a sugarcane detached leaf assay using plants cultivated in vitro to reveal sugarcane smut response outcomes. We used two sugarcane genotypes with known contrasting reactions to smut in the field. Although there is no evidence of sugarcane smut fungus infecting host leaves naturally, the sugarcane detached leaf assay enabled a rapid assessment of disease outcomes. Different symptoms in the detached leaves after inoculation distinguished smut-susceptible and smut-resistant sugarcane genotypes. Microscopic observations and gene expression analysis of S. scitamineum candidate effectors confirmed the fungal growth and its restriction on the compatible and incompatible interactions, respectively. These findings offer new prospects into the disease phenotyping of S. scitamineum, which could greatly expedite the comprehension of the initial stages of the pathogenesis and predict smut resistance in sugarcane genotypes.

Genomic prediction for sugarcane diseases including hybrid Bayesian-machine learning approaches.

Sugarcane smut and Pachymetra root rots are two serious diseases of sugarcane, with susceptible infected crops losing over 30% of yield. A heritable component to both diseases has been demonstrated, suggesting selection could improve disease resistance. Genomic selection could accelerate gains even further, enabling early selection of resistant seedlings for breeding and clonal propagation. In this study we evaluated four types of algorithms for genomic predictions of clonal performance for disease resistance. These algorithms were: Genomic best linear unbiased prediction (GBLUP), including extensions to model dominance and epistasis, Bayesian methods including BayesC and BayesR, Machine learning methods including random forest, multilayer perceptron (MLP), modified convolutional neural network (CNN) and attention networks designed to capture epistasis across the genome-wide markers. Simple hybrid methods, that first used BayesR/GWAS to identify a subset of 1000 markers with moderate to large marginal additive effects, then used attention networks to derive predictions from these effects and their interactions, were also developed and evaluated. The hypothesis for this approach was that using a subset of markers more likely to have an effect would enable better estimation of interaction effects than when there were an extremely large number of possible interactions, especially with our limited data set size. To evaluate the methods, we applied both random five-fold cross-validation and a structured PCA based cross-validation that separated 4702 sugarcane clones (that had disease phenotypes and genotyped for 26k genome wide SNP markers) by genomic relationship. The Bayesian methods (BayesR and BayesC) gave the highest accuracy of prediction, followed closely by hybrid methods with attention networks. The hybrid methods with attention networks gave the lowest variation in accuracy of prediction across validation folds (and lowest MSE), which may be a criteria worth considering in practical breeding programs. This suggests that hybrid methods incorporating the attention mechanism could be useful for genomic prediction of clonal performance, particularly where non-additive effects may be important.

Screening of Varieties Resistant to Sugarcane Smut Disease Caused by Sporosorium scitamineum under Sub- tropical India

Sugarcane (Saccharum spp.) is an important commercial crop, cultivated across the world in more than 90 countries including India. Diseases in sugarcane are mainly caused by fungi, bacteria, virus, and phytoplasma. Apart from the biotic factors nutritional imbalance is also responsible for various diseases. The major fungal diseases of sugarcane are red rot, smut, and wilt. The Smut of sugarcane is caused by the fungus Ustilago scitamineum. The first report of the disease incidence came from Natal, South Africa in 1877. Severe smut infection affects the sugar recovery as well as yield loss ranging from 10 to 70 per cent. The present study includes genotypes/varieties evaluation against smut disease (Sporisorium scitamineum) of sugarcane in sub-tropical region of India. The experiments were conducted in field condition during 2022-2023. Some total of 71 genotypes, maintained at ICAR-IISR, Lucknow. Three bud setts of each of the test genotypes were inoculated by dipping them in aqueous teliospores suspension (106/ml) for 30 minutes. Based on disease incidence of each genotype, these were categorized in five class intervals i.e., 0-1 (R), 1-10(MR), 10-20(MS), 20-30(S) & >30 % (HS) smut infection. Out of 71 genotypes tested, Forty five (45) genotype were rated as Resistant (R), Eight (8) genotypes were rated as Moderate Resistant (MR), Five (5) genotypes were rated as Moderate Susceptible (MS), and Ten (10) genotypes were rated as Susceptible (S) against smut disease of sugarcane. The genotypes rated resistant against smut of sugarcane can be exploited for development of smut resistant variety of sugarcane whereas rated susceptible genotypes can be exploited as susceptible check for screening against smut of sugarcane.

Transcriptional Regulation of SugarCane Response to Sporisorium scitamineum: Insights from Time-Course Gene Coexpression and Ca2+ Signaling.

Sugarcane response to Sporisorium scitamineum is determined by multiple major genes and numerous microeffector genes. Here, time-ordered gene coexpression networks were applied to explore the interaction between sugarcane and S. scitamineum. Totally, 2459 differentially expressed genes were identified and divided into 10 levels, and several stress-related subnetworks were established. Interestingly, the Ca2+ signaling pathway was activated to establish the response to sugarcane smut disease. Accordingly, two CAX genes (ScCAX2 and ScCAX3) were cloned and characterized from sugarcane. They were significantly upregulated under ABA stress but inhibited by MeJA treatment. Furthermore, overexpression of ScCAX2 and ScCAX3 enhanced the susceptibility of transgenic plants to the pathogen infection, suggesting its negative role in disease resistance. A regulatory model for ScCAX genes in disease response was thus depicted. This work helps to clarify the transcriptional regulation of sugarcane response to S. scitamineum stress and the function of the CAX gene in disease response.

An efficient inoculation method to evaluate virulence differentiation of field strains of sugarcane smut fungus.

Sugarcane smut, caused by the fungal pathogen Sporisorium scitamineum, is a prominent threat to the sugarcane industry. The development of smut resistant varieties is the ultimate solution for controlling this disease, due to the lack of other efficient control methods. Artificial inoculation method is used to evaluate the virulence differentiation of pathogens. The mostly used artificial inoculation methods are soaking of the seed canes in the teliospore solution and injection of teliospores or haploid sporidia into the sugarcane sprouts. However, due to the infection nature of the pathogen that invades the sugarcane plant through meristem tissue of the sprout or shoot, the rate of successful infection is often low and fluctuated, resulting in low confidence of the assays. We recently reported a rapid and high-throughput inoculation method called plantlet soaking by using tissue culture-derived sugarcane plantlets as the test plants. Here, we compare different inoculation methods and report the characterization of parameters that may affect the sensitivity and efficiency of the plantlet soaking technique. The results showed that sugarcane plantlets were highly vulnerable to infection, even with the inoculum density at 6.0 × 105 basidial spores/ml, and this method could be applied to all varieties tested. Notably, varieties showing high smut resistance in the field exhibited high susceptibility when inoculated with the plantlet soaking method, suggesting that the plantlet soaking method is a good complement to the traditional methods for screening germplasms with internal resistance. In addition, this method could also be used to monitor the variation of cellular virulence of the smut pathogen strains in the field.

Registration of ‘CP 10‐1620’ sugarcane

Abstract‘CP 10‐1620’ (Reg. no. CV‐216, PI 693837) sugarcane (a complex hybrid of Saccharum spp.) was developed through cooperative research conducted by the USDA–ARS, the University of Florida, and the Florida Sugar Cane League, Inc. At the June 7, 2018, Florida Sugarcane Variety Committee Meeting, CP 10‐1620 was released to growers for mineral (sand) soils in Florida, and seed was available in September 2018. CP 10‐1620 was selected from a polycross of ‘CP 00‐1100’ × ‘CP 05‐1740’ (Cross no. X07‐1225) made at Canal Point, FL, in December 2007. Neither the female parent, CP 00‐1100, nor the male parent, CP 05‐1740, is a commercial cultivar. Cane yield of CP 10‐1620 on sand soils, averaged across 12 harvests through three crop cycles (plant cane, first ratoon, and second ratoon), was 11.0% higher (P < 0.05) than the combined mean of three checks, ‘CL 88‐4730’, ‘CP 96‐1252’, and ‘CPCL 97‐2730’, which are commercial checks for sand soils. The commercial recoverable sucrose for CP 10‐1620 was not significantly lower than the combined mean of the checks but the higher cane yield resulted in 8.4% higher (P < 0.05) sucrose yield than the combined mean of the checks. CP 10‐1620 was released because of its high cane yields on sand soils, and its acceptable levels of resistance to brown rust (caused by Puccinia melanocephala H. & P. Sydow), leaf scald (caused by Xanthomonas albilineans Ashby, Dowson), Sugarcane mosaic virus strain E (mosaic), smut (caused by Sporisorium scitamineum), Sugarcane yellow leaf virus, and ratoon stunt [caused by Leifsonia xyli subsp. xyli (Davis et al.) Evtushenko]. CP 10‐1620 was moderately susceptible to orange rust (caused by Puccinia kuehnii E. J. Butler), and it has high freeze tolerance. CP 10‐1620 tested positive for the Bru1 locus, which is an indicator of brown rust resistance.

Four sugarcane ScDIR genes contribute to lignin biosynthesis and disease resistance to Sporisorium scitamineum

Sugarcane (Saccharum spp.) is a major sucrose and bioenergy crop in the world. The fungal pathogen Sporisorium scitamineum causes sugarcane smut, a devastating disease that destroys stalks and reduces sugar content in sugarcane. This disease can be controlled most effectively by applying smut-resistant sugarcane varieties. Previous studies have shown that Dirigent (DIR) genes are involved in the synthesis of the lignin precursor pinoresinol, which plays a crucial role in plant resistance to biotic stresses. However, the immune response of the DIR homologs in sugarcane (ScDIR) has not been reported yet. In this study, we found that the lignin content of smut-resistant sugarcane varieties (ZZ1, ZZ6, and ZZ9) was significantly higher than that of smut-susceptible varieties (GT42, ROC22, and FN41), and the lignin content of sugarcane increased after smut infection. The smut-resistant and smut-susceptible clones derived from the same genetic population (ROC25 × YZ89-7) showed similar patterns. Quantitative real-time PCR assays revealed that among the 64 DIR genes in sugarcane, ScDIR5, ScDIR7, ScDIR11, and ScDIR40 showed elevated expression after S. scitamineum infection. In vitro coupling reactions showed that the four corresponding ScDIR proteins could mediate the coupling of coniferyl alcohol and its conversion into the lignin precursor pinoresinol. Overexpression of the four ScDIR genes in Nicotiana benthamiana enhanced disease resistance to the fungal pathogens Sclerotium rolfsii, Rhizoctonia solani, and Botrytis cinerea. Moreover, transgenic sugarcane overexpressing these ScDIR genes showed enhanced resistance to smut disease. Taken together, our findings provide evidence that sugarcane ScDIR genes can improve the resistance of plants to fungal pathogens and highlight their potentials in sugarcane breeding for disease resistance.

Factors affecting the germination of teliospores of Sporisorium scitamineum and the development of sugarcane smut in the field

AbstractTemperature and water potential are critical factors influencing the germination of Sporisorium scitamineum teliospores and subsequent crop infection. This paper reports on the effect of temperature, water potential and incubation time on S. scitamineum teliospore germination. A field trial was conducted to determine the influence of temperature and length of exposure to teliospores on smut incidence. A 200 μL aliquot of teliospore (1.5 × 106 teliospores/mL) was cultured on water agar (WA) amended by potassium chloride (KCl) or sucrose. The plates were incubated across a range of temperatures and incubation times. For the field trial, sugarcane setts were inoculated and incubated at different temperatures and for varying incubation periods. The results demonstrated that germination decreased with declining water potential with either KCl or sucrose. The greatest germination (95.8%) occurred on unamended WA incubated at 30°C for 6 h. Even at the lowest water potential of −45 bars and 30°C, 50% teliospores were still able to germinate. These results indicate that 30°C is the optimum temperature for teliospore germination and that S. scitamineum may still germinate in fairly dry conditions. However, high temperatures (40°C), greatly reduce S. scitamineum germination. These results are consistent with field trial outcomes, which showed that the highest disease incidence (40.4%) occurred when temperature of inoculation was maintained at 30°C. On the other hand, the incidence was significantly reduced to 5.7% at 35°C. The results suggested consistent conditions for teliospore germination and sugarcane bud infection, with a temperature of 30°C being optimal for both.

A Comprehensive Analysis of Transcriptomics and Metabolomics Revealed Key Pathways Involved in Saccharum spontaneum Defense against Sporisorium scitamineum.

Sugarcane smut, caused by Sporisorium scitamineum, poses a severe threat to sugarcane production. The genetic basis of sugarcane resistance to S. scitamineum remains elusive. A comparative transcriptomic and metabolomic study was conducted on two wild Saccharum species of S. spontaneum with contrast smut resistance. Following infection, the resistant line exhibited greater down-regulation of genes and metabolites compared to the susceptible line, indicating distinct biological processes. Lignan and lignin biosynthesis and SA signal transduction were activated in the resistant line, while flavonoid biosynthesis and auxin signal transduction were enhanced in the susceptible line. TGA2.2 and ARF14 were identified as playing positive and negative roles, respectively, in plant defense. Exogenous auxin application significantly increased the susceptibility of S. spontaneum to S. scitaminum. This study established the significant switching of defense signaling pathways in contrast-resistant S. spontaneum following S. scitamineum infection, offering a hypothetical model and candidate genes for further research into sugarcane smut disease.

Discovery of N-Benzyl-4-(1-bromonaphthalen-2-yl)oxybutan-1-amine as a Potential Antifungal Agent against Sporidia Growth and Teliospore Germination of Sporisorium scitamineum.

The cultivation of sugar cane using perennial roots is the primary planting method, which is one of the reasons for the serious occurrence of sugar cane smut disease caused by the basidiomycetous fungus Sporisorium scitamineum in the sugar cane perennial root planting area. Consequently, it is crucial to eliminate pathogens from perennial sugar cane buds. In this study, we found that MAP kinase Hog1 is necessary for heat stress resistance. Subsequent investigations revealed a significant reduction in the expression of the heat shock protein 104-encoding gene, SsHSP104, in the ss1hog1Δ mutant. Additionally, the overexpression of SsHSP104 partially restored colony growth in the ss1hog1Δ strain following heat stress treatment, demonstrating the crucial role of SsHsp104 in SsHog1-mediated heat stress tolerance. Hence, we constructed the ss1hsp104:eGFP fusion strain in the wild type of S. scitamineum to identify small-molecule compounds that could inhibit the heat stress response, leading to the discovery of N-benzyl-4-(1-bromonaphthalen-2-yl)oxybutan-1-amine as a potential compound that targets the SsHog1 mediation SsHsp104 pathway during heat treatment. Furthermore, the combination of N-benzyl-4-(1-bromonaphthalen-2-yl)oxybutan-1-amine and warm water treatment (45 °C for 15 min) inhibits the growth of S. scitamineum and teliospore germination, thereby reducing the occurrence of sugar cane smut diseases and indicating its potential for eliminating pathogens from perennial sugar cane buds. In conclusion, these findings suggest that N-benzyl-4-(1-bromonaphthalen-2-yl)oxybutan-1-amine is promising as a targeted compound for the SsHog1-mediated SsHsp104 pathway and may enable the reduction of hot water treatment duration and/or temperature, thereby limiting the occurrence of sugar cane smut diseases caused by S. scitamineum.

Sugarcane transcription factor ScWRKY4 negatively regulates resistance to pathogen infection through the JA signaling pathway

WRKY transcription factors, transcriptional regulators unique to plants, play an important role in defense response to pathogen infection. However, the resistance mechanisms of WRKY genes in sugarcane remain unclear. In the present study, gene ontology (GO) enrichment analysis revealed that WRKY gene family in sugarcane was extensively involved in the response to biotic stress and in defense response. We identified gene ScWRKY4, a class IIc member of the WRKY gene family, in sugarcane cultivar ROC22. This gene was induced by salicylic acid (SA) and methyl jasmonate (MeJA) stress. Interestingly, expression of ScWRKY4 was down-regulated in smut-resistant sugarcane cultivars but up-regulated in smut-susceptible sugarcane cultivars infected with Sporisorium scitamineum. Moreover, stable overexpression of the ScWRKY4 gene in Nicotiana benthamiana enhanced susceptibility to Fusarium solani var. coeruleum and caused down-regulated expression of immune marker-related genes. Transcriptome analysis indicated suppressed expression of most JAZ genes in the signal transduction pathway. ScWRKY4 interacted with ScJAZ13 to repress its expression. We thus hypothesized that the ScWRKY4 gene was involved in the regulatory network of plant disease resistance, most likely through the JA signaling pathway. The present study depicting the molecular involvement of ScWRKY4 in sugarcane disease resistance lays a foundation for future investigation.

Registration of ‘Ho 13‐739’ sugarcane

Abstract‘Ho 13‐739’ (Reg. no. CV‐214, PI 703499) sugarcane (a Saccharum spp. complex polyploid) was selected and evaluated by scientists at the USDA‐ARS in Houma, LA, in cooperation with the Louisiana State University Agricultural Center and the American Sugar Cane League, Inc. It was released to growers in Louisiana in 2020. Results from evaluations in plant‐cane and first‐ and second‐ratoon crops at 13 field locations revealed that sucrose content and stalk weight of Ho 13‐739 were significantly greater than ‘L 01‐299’ in every crop and across the crop cycle. Sucrose yield was not significantly different than L 01‐299 for all crops evaluated and across the crop cycle. Ho 13‐739 is an early‐maturing cultivar with poor mature‐stalk cold tolerance. The cultivar is resistant to smut (Sporisorium scitamineum) and Sorghum mosaic virus and moderately suspectable to brown rust (caused by Puccinia melanocephala) and leaf scald (caused by Xanthomonas albilineans). It was also moderately susceptible to the sugarcane borer (Diatraea saccharalis F). Ho 13‐739 has important traits for producers such as high sucrose content, early maturity, and adequate disease resistance.

FIELD ASSESSMENT OF PROMISING SUGARCANE GERMPLASM AGAINST WHIP SMUT DISEASE UNDER ARTIFICIAL INOCULATED CONDITION

Twenty four promising sugarcane germplasm of different maturity groups along with checks were screened against whip smut disease under artificial condition during season 2020-21 to identify sources of disease resistance at Central Sugarcane Research Station, Padegaon Maharashtra. Fourteen germplasm designated viz., Co PDN 19004, Co PDN 19007, Co PDN 19011, Co PDN 19016, Co PDN 19017, Co PDN 19025, Co PDN 19028, Co PDN 19041, Co PDN 19042, PDN 15012, CoM 11082, MS 10001, Co 86032 and CoM 0265 showed resistant reaction to smut disease while 10 genotypes exhibited moderately resistant reaction to smut disease under artificially inoculated conditions in the field. Susceptible checks Co 740 had susceptible reaction indicated much disease pressure with susceptible reaction. This resistant germplasm may be further utilized as donor for further breeding programs to evolve new resistant variety against whip smut of sugarcane.

Assessment of IDM modules with some fungicides for whip smut of sugarcane in Chhattisgarh

Assessment of IDM modules with some fungicides for whip smut of sugarcane in Chhattisgarh

Comparative mitogenomic analysis of Sporisorium reilianum f. sp. zeae suggests recombination events during its evolutionary history.

Modern understanding of the concept of genetic diversity must include the study of both nuclear and organellar DNA, which differ greatly in terms of their structure, organization, gene content and distribution. This study comprises an analysis of the genetic diversity of the smut fungus Sporisorium reilianum f. sp. zeae from a mitochondrial perspective. Whole-genome sequencing data was generated from biological samples of S. reilianum collected from different geographical regions. Multiple sequence alignment and gene synteny analysis were performed to further characterize genetic diversity in the context of mitogenomic polymorphisms. Mitochondria of strains collected in China contained unique sequences. The largest unique sequence stretch encompassed a portion of cox1, a mitochondrial gene encoding one of the subunits that make up complex IV of the mitochondrial electron transport chain. This unique sequence had high percent identity to the mitogenome of the related species Sporisorium scitamineum and Ustilago bromivora. The results of this study hint at potential horizontal gene transfer or mitochondrial genome recombination events during the evolutionary history of basidiomycetes. Additionally, the distinct polymorphic region detected in the Chinese mitogenome provides the ideal foundation to develop a diagnostic method to discern between mitotypes and enhance knowledge on the genetic diversity of this organism.

Sugarcane Smut Pathogenic Races in Tanzania: Current Knowledge of Resistance, Characterization, Detection, and Management Strategies

Sugarcane Smut Pathogenic Races in Tanzania: Current Knowledge of Resistance, Characterization, Detection, and Management Strategies

Triagem de genótipos brasileiros de cana-de-açúcar à reação ao carvão

ABSTRACT: The main method of sugarcane smut (Sporisoriumscitamineum)control is the genetic resistance. This study assessed the reaction of Brazilian sugarcane genotypes to the smut. The design used was randomized blocks, with 41 genotypes and four replications. The experimental unit consisted of five seedlings per genotype. The genotypes were inoculated by immersing the buds in a smut spores’ suspension. For each genotype, it was obtained the disease incidence in percentage of stalk with whip and with the disease incidence data over time the area under the disease progress curve (AUDPC) were calculated for each genotype. Based in the AUDPC, three genotypes were classified as highly resistant (7.3%), eighteen as resistant (43.9%), twelve as moderately resistant (29.3%), three as moderately susceptible (7.3%) and five as susceptible (12.2%). Genotypes with higher levels of resistance to smut sugarcane can be used for integrated disease management and can be used as parents in new crosses in order to obtain progenies with higher proportion of genotypes resistant to smut.

Genetic mapping of quantitative trait loci controlling smut resistance in Louisiana sugarcane using a bi-parental mapping population

Sugarcane smut, caused by Sporisorium scitamineum, is a major disease worldwide. Breeding resistant cultivars is the main management strategy. However, occasional failure to detect susceptible clones due to unfavorable environmental conditions, inconsistency in disease ratings between experiments, and continued clone losses due to pathogen adaptability are some of the challenges for this strategy. The development and use of molecular markers associated with smut resistance may overcome these limitations allowing more accurate identification of resistant parents and progeny. A genetic analysis was conducted using an inoculated population of 162 F1 progeny from a biparental cross between susceptible/female and resistant/male parents to identify quantitative trait loci (QTLs) associated with resistance. A total of 1574 single dose (SD) single-nucleotide polymorphisms (SNP) markers used to construct a genetic map resulted in 253 linkage groups (LGs) of which 150 LGs were assigned to the female parent and 204 LG to the male parent with a genome coverage of 24,580 cM. (Composite) interval mapping with selective sub-populations identified six consistent QTLs that cumulatively explained 25.74% of the phenotypic variance with LOD scores ranging from 3.17 to 23.7. Four out of 12 SNP markers closest to the QTL peaks had effect >10 for resistance in the heterozygous condition. Genes known to be involved in disease resistance, such as cellulose synthase, expansin, protein degradation, and receptor-kinase were linked to the genomic regions associated with smut resistance. The markers upon validation in different populations can be utilized for marker-assisted selection.