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Introduction: Sorghum anthracnose, caused by Colletotrichum sublineola, is the most destructive disease of sorghum, which causes up to 80% grain yield loss in susceptible varieties. The use of resistance varieties is an effective, durable, and eco-friendly strategy for anthracnose control. Knowledge of the phenotypic and genetic variation in C. sublineola is vital for designing appropriate anthracnose management strategies. Methods: The present study examined the morphology and virulence of 25 C. sublineola isolates recovered from various sorghum-producing regions of Ethiopia against 18 known sorghum anthracnose differentials, 6 Ethiopian sorghum landraces, and a variety of Bonsa. Results: Analysis of variance (ANOVA) revealed significant differences among sorghum genotypes, C. sublineola isolates, and their interactions. There was a significant difference between the isolates in virulence, with each isolate exhibiting virulence in 8-72% of the sorghum genotypes tested. Among the 25 tested isolates, the top four most virulent isolates were from Pawe, suggesting that this area is suitable for pathogen diversity studies and host plant resistance screening. The sorghum genotypes IS_18760, Brandes, and Bonsa showed resistance to all tested isolates. Consequently, they may provide potential sources of resistance genes for sorghum breeding programs to develop cultivars resistant to different C. sublineola pathotypes. However, the resistant check SC748-5 was susceptible to isolates NK73_F37, while another resistant check SC112-14 was susceptible to isolates PW123_F47 and PW122_F47. Cluster analysis grouped 22 isolates into seven clusters based on their morphological characters, whereas 24 pathotypes were identified among 25 isolates that were tested on 25 sorghum genotypes. Discussion: Hence, this study revealed high variation in C. sublineola in Ethiopia suggesting the need for broad-spectrum resistance to control the disease. Sorghum genotypes resistant to various C. sublineola isolates were identified in this study, which can be used in sorghum breeding programs aiming to develop resistant cultivars to anthracnose. Highly virulent C. sublineola isolates were also identified which could be used in sorghum germplasm resistance screening. The report is the first to show the existence of C. sublineola pathotypes in Ethiopia. [ABSTRACT FROM AUTHOR]

Abstract Background Sorghum anthracnose is a major disease that hampers the productivity of the crop globally. The disease is caused by the hemibiotrophic fungal pathogen Colletotrichum sublineola. The identification of anthracnose-resistant sorghum genotypes, defining resistance loci and the underlying genes, and their introgression into adapted cultivars are crucial for enhancing productivity. In this study, we conducted field experiments on 358 diverse accessions of Ethiopian sorghum. Quantitative resistance to anthracnose was evaluated at locations characterized by a heavy natural infestation that is suitable for disease resistance screening. Results The field-based screening identified 53 accessions that were resistant across locations, while 213 accessions exhibited variable resistance against local pathotypes. Genome-wide association analysis (GWAS) was performed using disease response scores on 329 accessions and 83,861 single nucleotide polymorphisms (SNPs) generated through genotyping-by-sequencing (GBS). We identified 38 loci significantly associated with anthracnose resistance. Interestingly, a subset of these loci harbor genes encoding receptor-like kinases (RLK), nucleotide-binding leucine-rich repeats (NLRs), stress-induced antifungal tyrosine kinase that have been previously implicated in disease resistance. A SNP on chromosome 4 (S04_66140995) and two SNPs on chromosome 2 (S02_75784037, S02_2031925), localized with-in the coding region of genes that encode a putative stress-induced antifungal kinase, an F-Box protein, and Xa21-binding RLK that were strongly associated with anthracnose resistance. We also identified highly significant associations between anthracnose resistance and three SNPs linked to genes (Sobic.002G058400, Sobic.008G156600, Sobic.005G033400) encoding an orthologue of the widely known NLR protein (RPM1), Leucine Rich Repeat family protein, and Heavy Metal Associated domain-containing protein, respectively. Other SNPs linked to predicted immune response genes were also significantly associated with anthracnose resistance. Conclusions The sorghum germplasm collections used in the present study are genetically diverse. They harbor potentially useful, yet undiscovered, alleles for anthracnose resistance. This is supported by the identification of novel loci that are enriched for disease resistance regulators such as NLRs, LRKs, Xa21-binding LRK, and antifungal proteins. The genotypic data available for these accessions offer a valuable resource for sorghum breeders to effectively improve the crop. The genomic regions and candidate genes identified can be used to design markers for molecular breeding of sorghum diseases resistance.

Background: Sorghum anthracnose is a major disease that hampers the productivity of the crop globally. The disease is caused by the hemibiotrophic fungal pathogen Colletotrichum sublineola. The identification of anthracnose-resistant sorghum genotypes, defining resistance loci and the underlying genes, and their introgression into adapted cultivars are crucial for enhancing productivity. In this study, we conducted field experiments on 358 diverse accessions of Ethiopian sorghum. Quantitative resistance to anthracnose was evaluated at locations characterized by a heavy natural infestation that is suitable for disease resistance screening. Results: The field-based screening identified 53 accessions that were resistant across locations, while 213 accessions exhibited variable resistance against local pathotypes. Genome-wide association analysis (GWAS) was performed using disease response scores on 329 accessions and 83,861 single nucleotide polymorphisms (SNPs) generated through genotyping-by-sequencing (GBS). We identified 38 loci significantly associated with anthracnose resistance. Interestingly, a subset of these loci harbor genes encoding receptor-like kinases (RLK), nucleotide-binding leucine-rich repeats (NLRs), stress-induced antifungal tyrosine kinase that have been previously implicated in disease resistance. A SNP on chromosome 4 (S04_66140995) and two SNPs on chromosome 2 (S02_75784037, S02_2031925), localized with-in the coding region of genes that encode a putative stress-induced antifungal kinase, an F-Box protein, and Xa21-binding RLK that were strongly associated with anthracnose resistance. We also identified highly significant associations between anthracnose resistance and three SNPs linked to genes (Sobic.002G058400, Sobic.008G156600, Sobic.005G033400) encoding an orthologue of the widely known NLR protein (RPM1), Leucine Rich Repeat family protein, and Heavy Metal Associated domain-containing protein, respectively. Other SNPs linked to predicted immune response genes were also significantly associated with anthracnose resistance. Conclusions: The sorghum germplasm collections used in the present study are genetically diverse. They harbor potentially useful, yet undiscovered, alleles for anthracnose resistance. This is supported by the identification of novel loci that are enriched for disease resistance regulators such as NLRs, LRKs, Xa21-binding LRK, and antifungal proteins. The genotypic data available for these accessions offer a valuable resource for sorghum breeders to effectively improve the crop. The genomic regions and candidate genes identified can be used to design markers for molecular breeding of sorghum diseases resistance. [ABSTRACT FROM AUTHOR]

IntroductionSorghum anthracnose, caused by Colletotrichum sublineola, is the most destructive disease of sorghum, which causes up to 80% grain yield loss in susceptible varieties. The use of resistance varieties is an effective, durable, and eco-friendly strategy for anthracnose control. Knowledge of the phenotypic and genetic variation in C. sublineola is vital for designing appropriate anthracnose management strategies.MethodsThe present study examined the morphology and virulence of 25 C. sublineola isolates recovered from various sorghum-producing regions of Ethiopia against 18 known sorghum anthracnose differentials, 6 Ethiopian sorghum landraces, and a variety of Bonsa.ResultsAnalysis of variance (ANOVA) revealed significant differences among sorghum genotypes, C. sublineola isolates, and their interactions. There was a significant difference between the isolates in virulence, with each isolate exhibiting virulence in 8–72% of the sorghum genotypes tested. Among the 25 tested isolates, the top four most virulent isolates were from Pawe, suggesting that this area is suitable for pathogen diversity studies and host plant resistance screening. The sorghum genotypes IS_18760, Brandes, and Bonsa showed resistance to all tested isolates. Consequently, they may provide potential sources of resistance genes for sorghum breeding programs to develop cultivars resistant to different C. sublineola pathotypes. However, the resistant check SC748-5 was susceptible to isolates NK73_F37, while another resistant check SC112-14 was susceptible to isolates PW123_F47 and PW122_F47. Cluster analysis grouped 22 isolates into seven clusters based on their morphological characters, whereas 24 pathotypes were identified among 25 isolates that were tested on 25 sorghum genotypes.DiscussionHence, this study revealed high variation in C. sublineola in Ethiopia suggesting the need for broad-spectrum resistance to control the disease. Sorghum genotypes resistant to various C. sublineola isolates were identified in this study, which can be used in sorghum breeding programs aiming to develop resistant cultivars to anthracnose. Highly virulent C. sublineola isolates were also identified which could be used in sorghum germplasm resistance screening. The report is the first to show the existence of C. sublineola pathotypes in Ethiopia.

SUMMARY: Sorghum anthracnose caused by the fungus Colletotrichum sublineola (Cs) is a damaging disease of the crop. Here, we describe the identification of ANTHRACNOSE RESISTANCE GENES (ARG4 and ARG5) encoding canonical nucleotide‐binding leucine‐rich repeat (NLR) receptors. ARG4 and ARG5 are dominant resistance genes identified in the sorghum lines SAP135 and P9830, respectively, that show broad‐spectrum resistance to Cs. Independent genetic studies using populations generated by crossing SAP135 and P9830 with TAM428, fine mapping using molecular markers, comparative genomics and gene expression studies determined that ARG4 and ARG5 are resistance genes against Cs strains. Interestingly, ARG4 and ARG5 are both located within clusters of duplicate NLR genes at linked loci separated by ~1 Mb genomic region. SAP135 and P9830 each carry only one of the ARG genes while having the recessive allele at the second locus. Only two copies of the ARG5 candidate genes were present in the resistant P9830 line while five non‐functional copies were identified in the susceptible line. The resistant parents and their recombinant inbred lines carrying either ARG4 or ARG5 are resistant to strains Csgl1 and Csgrg suggesting that these genes have overlapping specificities. The role of ARG4 and ARG5 in resistance was validated through sorghum lines carrying independent recessive alleles that show increased susceptibility. ARG4 and ARG5 are located within complex loci displaying interesting haplotype structures and copy number variation that may have resulted from duplication. Overall, the identification of anthracnose resistance genes with unique haplotype stucture provides a foundation for genetic studies and resistance breeding. Significance Statement: We identified two tightly linked NLR genes conferring resistance to the sorghum anthracnose disease that is a major challenge to production of the crop globally. The two genes were identified among clusters of highly similar duplicate genes with resistant and susceptible lines having unique haplotypes, and amino acid substitutions in key positions, leading to changes in tertiary protein structure and disease resistance function. The results provide new opportunities for resistance breeding and genetic and molecular studies. [ABSTRACT FROM AUTHOR]

Anthracnose, incited by Colletotrichum sublineola, is the most destructive foliar disease of sorghum and, under severe conditions, yield losses can exceed 80% on susceptible cultivars. The hyper-variable nature of the pathogen makes its management challenging despite the occurrence of several resistant sources. In this study, the genetic variability and pathogenicity of 140 isolates of C. sublineola, which were sequenced using restriction site-associated sequencing (RAD-Seq), resulted in 1244 quality SNPs. The genetic relationship based on the SNP data showed low to high genetic diversity based on isolates' origin. Isolates from Georgia and North Carolina were grouped into multiple clusters with some level of genetic relationships to each other. Even though some isolates from Texas formed a cluster, others clustered with isolates from Puerto Rico. The isolates from Puerto Rico showed scattered distribution, indicating the diverse nature of these isolates. A population structure and cluster analysis revealed that the genetic variation was stratified into eight populations and one admixture group. The virulence pattern of 30 sequenced isolates on 18 sorghum differential lines revealed 27 new pathotypes. SC748-5, SC112-14, and Brandes were resistant to all the tested isolates, while BTx623 was susceptible to all. Line TAM428 was susceptible to all the pathotypes, except for pathotype 26. Future use of the 18 differentials employed in this study, which contains cultivars/lines which have been used in the Americas, Asia, and Africa, could allow for better characterization of C. sublineola pathotypes at a global level, thus accelerating the development of sorghum lines with stable resistance to the anthracnose pathogen. [ABSTRACT FROM AUTHOR]

Anthracnose, a disease primarily caused by the fungus Colletotrichum sublineola, affects sorghum production in China. However, the infection mechanisms and complex host interactions of C. sublineola remain to be elucidated. Thus, this study aimed to establish and optimize a protoplast transformation system of C. sublineola so as to lay a foundation for further research on the infection mechanisms and complex host interactions of C. sublineola. A genetic transformation system was established and optimized for C. sublineola strain HX‐5‐1 and used to introduce fluorescent reporter genes, namely, green fluorescent protein (GFP) and mCherry. Results showed that the growth of HX‐5‐1 was completely inhibited on a regenerating medium containing 300 μg mL−1 hygromycin B, indicating that hygromycin B acted as a transformant‐selective marker. HX‐5‐1 produced the highest yield of protoplasts when the mycelia were cultured for 60 h and dissolved in a 0.1% lysozyme solution (0.7 M NaCl) for 3 h. Subsequently, a 106 mL−1 protoplast solution transformed using 5 μg of plasmid DNA exhibited the highest transformation efficiency. Laser confocal microscopy showed that GFP and mCherry fluorescent signals were successfully expressed in the mycelia and spores of HX‐5‐1, indicating that they were stably inherited in the transformants and did not affect colony morphology, growth rate, or pathogenicity. In conclusion, we successfully established a genetic transformation system for C. sublineola and employed it to obtain stable fluorescent protein expression. This study may serve as a foundation for understanding the infection process of C. sublineola. [ABSTRACT FROM AUTHOR]

Sorghum is the fifth most important crop globally. Researching interactions between sorghum and fungal pathogens is essential to further elucidate plant defense mechanisms to biotic stress, which allows breeders to employ genetic resistance to disease. A variety of creative and useful inoculation and screening methods have been developed by sorghum pathologists to study major fungal diseases. As inoculation and screening methods can be keys for successfully conducting experiments, it is necessary to summarize the techniques developed by this research community. Among many fungal pathogens of sorghum, here we summarize inoculation and screening methods for five important fungal pathogens of sorghum: Claviceps africana, Colletotrichum sublineola, Sporisorium reilianum, Peronosclerospora sorghi and Macrophomina phaseolina. The methods described within will be useful for researchers who are interested in exploring sorghum-fungal pathogen interactions. Finally, we discuss the latest biotechnologies and methods for studying plant-fungal pathogen interactions and their applicability to sorghum pathology. [ABSTRACT FROM AUTHOR]

Anthracnose, incited by Colletotrichum sublineola, is the most destructive foliar disease of sorghum and, under severe conditions, yield losses can exceed 80% on susceptible cultivars. The hyper-variable nature of the pathogen makes its management challenging despite the occurrence of several resistant sources. In this study, the genetic variability and pathogenicity of 140 isolates of C. sublineola, which were sequenced using restriction site-associated sequencing (RAD-Seq), resulted in 1244 quality SNPs. The genetic relationship based on the SNP data showed low to high genetic diversity based on isolates’ origin. Isolates from Georgia and North Carolina were grouped into multiple clusters with some level of genetic relationships to each other. Even though some isolates from Texas formed a cluster, others clustered with isolates from Puerto Rico. The isolates from Puerto Rico showed scattered distribution, indicating the diverse nature of these isolates. A population structure and cluster analysis revealed that the genetic variation was stratified into eight populations and one admixture group. The virulence pattern of 30 sequenced isolates on 18 sorghum differential lines revealed 27 new pathotypes. SC748-5, SC112-14, and Brandes were resistant to all the tested isolates, while BTx623 was susceptible to all. Line TAM428 was susceptible to all the pathotypes, except for pathotype 26. Future use of the 18 differentials employed in this study, which contains cultivars/lines which have been used in the Americas, Asia, and Africa, could allow for better characterization of C. sublineola pathotypes at a global level, thus accelerating the development of sorghum lines with stable resistance to the anthracnose pathogen.

SUMMARY: Sorghum is an important food and feed crop globally; its production is hampered by anthracnose disease caused by the fungal pathogen Colletotrichum sublineola (Cs). Here, we report identification and characterization of ANTHRACNOSE RESISTANCE GENE 2 (ARG2) encoding a nucleotide‐binding leucine‐rich repeat (NLR) protein that confers race‐specific resistance to Cs strains. ARG2 is one of a cluster of several NLR genes initially identified in the sorghum differential line SC328C that is resistant to some Cs strains. This cluster shows structural and copy number variations in different sorghum genotypes. Different sorghum lines carrying independent ARG2 alleles provided the genetic validation for the identity of the ARG2 gene. ARG2 expression is induced by Cs, and chitin induces ARG2 expression in resistant but not in susceptible lines. ARG2‐mediated resistance is accompanied by higher expression of defense and secondary metabolite genes at early stages of infection, and anthocyanin and zeatin metabolisms are upregulated in resistant plants. Interestingly, ARG2 localizes to the plasma membrane when transiently expressed in Nicotiana benthamiana. Importantly, ARG2 plants produced higher shoot dry matter than near‐isogenic lines carrying the susceptible allele suggesting an absence of an ARG2 associated growth trade‐off. Furthermore, ARG2‐mediated resistance is stable at a wide range of temperatures. Our observations open avenues for resistance breeding and for dissecting mechanisms of resistance. Significance Statement: Sorghum is a crop of global importance that is used for food, feed and biofuel. The crop feeds millions of people, especially small holder framers around the world. The productivity of sorghum is constrained by anthracnose diseases caused by the fungus Colletotrichum sublineola. Genetic resistance provides the most sustainable disease control method. We identified and characterized a sorghum anthracnose resistance gene encoding a nucleotide‐binding leucine‐rich repeat protein by exploring natural variation in the crop. Our findings will have significant implications for improvement of disease resistance in sorghum, as well as for future studies in the molecular genetics of pathogen resistance. [ABSTRACT FROM AUTHOR]

Anthracnose caused by Colletotrichum species is one of the most destructive fungal diseases of sorghum with annual yield losses of up to 100%. Although the resistance to anthracnose has been identified elsewhere, the usefulness of the resistance loci differs depending on the pathogen species and pathotypes. Accurate species identification of the disease-causing fungal pathogens is essential for developing and implementing suitable management strategies. The use of host resistance is the most effective strategy of anthracnose management and therefore identification of sources for resistance against unique pathogen pathotypes is fundamental. The aims of this study were to identify and characterize Colletotrichum species associated with sorghum anthracnose and screen sorghum germplasm for resistance to anthracnose. Symptomatic sorghum leaf samples were collected from smallholder farmers in lower eastern Kenya and used for the isolation, identification and characterization of Colletotrichum species using morpho-cultural and phylogenetic analyses with the sequences of the rDNA internal transcribed spacer (ITS) region. Pathogenicity tests of the seven fungal isolates showed that there were no significant differences in the pathogenicity on host plants. The fungal isolates were variable in cultural and morphological characters such as colony type and color, colony diameter, mycelia growth and hyaline. The phenotypic characters observed were useful in the identification of the genus Colletotrichum and not the species. Based on the sequence and phylogenetic analysis of ITS, Colletotrichum sublineola was revealed to be associated with anthracnose on sorghum. Germplasm screening for resistance to anthracnose showed differential reactions of sorghum genotypes to anthracnose under greenhouse and field conditions. The results revealed four resistant genotypes and ten susceptible genotypes against Colletotrichum sublineola. Significant (p ≤ 0.05) differences were observed in grain weight, grain yield, weight of 100 seeds and harvest index among the tested sorghum genotypes. The present study indicated that the Kenyan accessions could be an important source of resistance to anthracnose. The findings from this study provide a platform towards devising efficient disease control strategies and resistance breeding. [ABSTRACT FROM AUTHOR]

Background: Colletotrichum sublineola is the pathogenic fungus that causes sorghum anthracnose, which seriously threatens sorghum yield. Benzovindiflupyr is a succinate dehydrogenase inhibitor with good control effects on various crop diseases. However, the control of sorghum anthracnose by benzovindiflupyr and the risk of resistance to benzovindiflupyr in this pathogen are not well studied. Therefore, this study aimed to evaluate the benzovindiflupyr resistance and underlying mechanisms in C. sublineola., Results: Analysis of the sensitivity of 126 C. sublineola strains to benzovindiflupyr revealed that the average EC 50 of the fungicide was 0.0503 ± 0.0189 μg mL -1 , with a unimodal normal distribution curve. The survival fitness of 10 benzovindiflupyr-resistant strains decreased to varying degrees compared with that of the wild-type parental strains. Additionally, a significant positive cross-resistance was observed between benzovindiflupyr and carboxin. Sequencing analyses identified two mutation sites, CsSdhB H249Y and CsSdhC G81V , in the resistant strains. Further molecular docking and site-directed mutagenesis experiments confirmed that the CsSdhB H249Y and CsSdhC G81V substitutions conferred resistance to benzovindiflupyr in C. sublineola., Conclusion: Colletotrichum sublineola is sensitive to benzovindiflupyr and shows a moderate resistance risk to benzovindiflupyr. Two specific point substitutions, CsSdhB H249Y and CsSdhC G81V , are responsible for the resistance of C. sublineola to benzovindiflupyr. These findings offer a theoretical foundation for strategic application of the fungicide in controlling sorghum anthracnose, and for potentially delaying the emergence and progression of resistance. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Anthracnose caused by Colletotrichum species is one of the most destructive fungal diseases of sorghum with annual yield losses of up to 100%. Although the resistance to anthracnose has been identified elsewhere, the usefulness of the resistance loci differs depending on the pathogen species and pathotypes. Accurate species identification of the disease-causing fungal pathogens is essential for developing and implementing suitable management strategies. The use of host resistance is the most effective strategy of anthracnose management and therefore identification of sources for resistance against unique pathogen pathotypes is fundamental. The aims of this study were to identify and characterize Colletotrichum species associated with sorghum anthracnose and screen sorghum germplasm for resistance to anthracnose. Symptomatic sorghum leaf samples were collected from smallholder farmers in lower eastern Kenya and used for the isolation, identification and characterization of Colletotrichum species using morpho-cultural and phylogenetic analyses with the sequences of the rDNA internal transcribed spacer (ITS) region. Pathogenicity tests of the seven fungal isolates showed that there were no significant differences in the pathogenicity on host plants. The fungal isolates were variable in cultural and morphological characters such as colony type and color, colony diameter, mycelia growth and hyaline. The phenotypic characters observed were useful in the identification of the genus Colletotrichum and not the species. Based on the sequence and phylogenetic analysis of ITS, Colletotrichum sublineola was revealed to be associated with anthracnose on sorghum. Germplasm screening for resistance to anthracnose showed differential reactions of sorghum genotypes to anthracnose under greenhouse and field conditions. The results revealed four resistant genotypes and ten susceptible genotypes against Colletotrichum sublineola. Significant (p ≤ 0.05) differences were observed in grain weight, grain yield, weight of 100 seeds and harvest index among the tested sorghum genotypes. The present study indicated that the Kenyan accessions could be an important source of resistance to anthracnose. The findings from this study provide a platform towards devising efficient disease control strategies and resistance breeding.

Improving sorghum resistance is a sustainable method to reduce yield losses due to anthracnose, a devastating disease caused by Colletotrichum sublineola. Elucidating the molecular mechanisms of sorghum– C. sublineola interactions would help identify biomarkers for rapid and efficient identification of novel sources for host-plant resistance improvement, understanding the pathogen virulence, and facilitating resistance breeding. Despite concerted efforts to identify resistance sources, the knowledge about sorghum–anthracnose interactions remains scanty. Hence, in this review, we presented an overview of the current knowledge on the mechanisms of sorghum- C. sublineola molecular interactions, sources of resistance for sorghum breeding, quantitative trait loci (QTL), and major (R -) resistance gene sequences as well as defense-related genes associated with anthracnose resistance. We summarized current knowledge about C. sublineola populations and its virulence. Illustration of the sorghum- C. sublineola interaction model based on the current understanding is also provided. We highlighted the importance of genomic resources of both organisms for integrated omics research to unravel the key molecular components underpinning compatible and incompatible sorghum–anthracnose interactions. Furthermore, sorghum-breeding strategy employing rapid sorghum germplasm screening, systems biology, and molecular tools is presented. [ABSTRACT FROM AUTHOR]

Sorghum (Sorghum bicolor) is the fifth most cultivated cereal crop in the world, traditionally providing food, feed, and fodder, but more recently also fermentable sugars for the production of renewable fuels and chemicals. The hemibiotrophic fungal pathogen Colletotrichum sublineola, the causal agent of anthracnose disease in sorghum, is prevalent in the warm and humid climates where much of the sorghum is cultivated and poses a serious threat to sorghum production. The use of anthracnose-resistant sorghum germplasm is the most environmentally and economically sustainable way to protect sorghum against this pathogen. Even though multiple anthracnose resistance loci have been mapped in diverse sorghum germplasm in recent years, the diversity in C. sublineola pathotypes at the local and regional levels means that these resistance genes are not equally effective in different areas of cultivation. This review summarizes the genetic and cytological data underlying sorghum's defense response and describes recent developments that will enable a better understanding of the interactions between sorghum and C. sublineola at the molecular level. This includes releases of the sorghum genome and the draft genome of C. sublineola, the use of next-generation sequencing technologies to identify gene expression networks activated in response to infection, and improvements in methodologies to validate resistance genes, notably virus-induced and transgenic gene silencing approaches. [ABSTRACT FROM AUTHOR]

Anthracnose, incited by Colletotrichum sublineola, is the most destructive foliar disease of sorghum and, under severe conditions, yield losses can exceed 80% on susceptible cultivars. The hyper-variable nature of the pathogen makes its management challenging despite the occurrence of several resistant sources. In this study, the genetic variability and pathogenicity of 140 isolates of C. sublineola, which were sequenced using restriction site-associated sequencing (RAD-Seq), resulted in 1244 quality SNPs. The genetic relationship based on the SNP data showed low to high genetic diversity based on isolates' origin. Isolates from Georgia and North Carolina were grouped into multiple clusters with some level of genetic relationships to each other. Even though some isolates from Texas formed a cluster, others clustered with isolates from Puerto Rico. The isolates from Puerto Rico showed scattered distribution, indicating the diverse nature of these isolates. A population structure and cluster analysis revealed that the genetic variation was stratified into eight populations and one admixture group. The virulence pattern of 30 sequenced isolates on 18 sorghum differential lines revealed 27 new pathotypes. SC748-5, SC112-14, and Brandes were resistant to all the tested isolates, while BTx623 was susceptible to all. Line TAM428 was susceptible to all the pathotypes, except for pathotype 26. Future use of the 18 differentials employed in this study, which contains cultivars/lines which have been used in the Americas, Asia, and Africa, could allow for better characterization of C. sublineola pathotypes at a global level, thus accelerating the development of sorghum lines with stable resistance to the anthracnose pathogen.

Colletotrichum sublineola is an aggressive fungal pathogen that causes anthracnose in sorghum [Sorghum bicolor (L.) Moench]. The obvious symptoms of anthracnose are leaf blight and stem rot. Sorghum, the fifth most widely grown cereal crop in the world, can be highly susceptible to the disease, most notably in hot and humid environments. In the southeastern United States the acreage of sorghum has been increasing steadily in recent years, spurred by growing interest in producing biofuels, bio-based products, and animal feed. Resistance to anthracnose is, therefore, of paramount importance for successful sorghum production in this region. To identify anthracnose resistance loci present in the highly resistant cultivar ‘Bk7’, a biparental mapping population of F3:4 and F4:5 sorghum lines was generated by crossing ‘Bk7’ with the susceptible inbred ‘Early Hegari-Sart’. Lines were phenotyped in three environments and in two different years following natural infection. The population was genotyped by sequencing. Following a stringent custom filtering protocol, totals of 5186 and 2759 informative SNP markers were identified in the two populations. Segregation data and association analysis identified resistance loci on chromosomes 7 and 9, with the resistance alleles derived from ‘Bk7’. Both loci contain multiple classes of defense-related genes based on sequence similarity and gene ontologies. Genetic analysis following an independent selection experiment of lines derived from a cross between ‘Bk7’ and sweet sorghum ‘Mer81-4’ narrowed the resistance locus on chromosome 9 substantially, validating this QTL. As observed in other species, sorghum appears to have regions of clustered resistance genes. Further characterization of these regions will facilitate the development of novel germplasm with resistance to anthracnose and other diseases.

Sorghum anthracnose, caused by Colletotrichum sublineola (Ces.) Wilson is widely distributed in most sorghum-producing areas of China, especially in Sichuan, Yunnan, Guizhou, Gansu and Liaoning provinces. The use of genetic resistance is the most appropriate and advantageous strategy for anthracnose control. However, the effectiveness and durability of this practice depends on knowledge concerning the genetic variability of C. sublineola. In this study, the pathogenicity of 61 sorghum isolates of C. sublineola collected from infected leaves of sorghum plants cultivated in 19 cities of China was tested on 10 sorghum genotypes. Base on reaction class and disease severity, six pathotypes of C. sublineola were identified and designated as GT1 to GT6. Pathotype GT6 was predominant pathotype in China. This is the first study showing the occurrence of C. sublineola pathotypes in China. • The results supported at least six different pathotypes of C. sublineola associated with sorghum anthracnose in China. • Pathotype GT6 was the most dominant pathotype in the sorghum growing regions, especially in the northern China. • The results explained the reasons why sorghum anthracnose outbreak occurred in recent years in China. [ABSTRACT FROM AUTHOR]

Colletotrichum sublineola is an aggressive fungal pathogen that causes anthracnose in sorghum [Sorghum bicolor (L.) Moench]. The obvious symptoms of anthracnose are leaf blight and stem rot. Sorghum, the fifth most widely grown cereal crop in the world, can be highly susceptible to the disease, most notably in hot and humid environments. In the southeastern United States the acreage of sorghum has been increasing steadily in recent years, spurred by growing interest in producing biofuels, bio-based products, and animal feed. Resistance to anthracnose is, therefore, of paramount importance for successful sorghum production in this region. To identify anthracnose resistance loci present in the highly resistant cultivar 'Bk7', a biparental mapping population of F3:4 and F4:5 sorghum lines was generated by crossing 'Bk7' with the susceptible inbred 'Early Hegari-Sart'. Lines were phenotyped in three environments and in two different years following natural infection. The population was genotyped by sequencing. Following a stringent custom filtering protocol, totals of 5186 and 2759 informative SNP markers were identified in the two populations. Segregation data and association analysis identified resistance loci on chromosomes 7 and 9, with the resistance alleles derived from 'Bk7'. Both loci contain multiple classes of defense-related genes based on sequence similarity and gene ontologies. Genetic analysis following an independent selection experiment of lines derived from a cross between 'Bk7' and sweet sorghum 'Mer81-4' narrowed the resistance locus on chromosome 9 substantially, validating this QTL. As observed in other species, sorghum appears to have regions of clustered resistance genes. Further characterization of these regions will facilitate the development of novel germplasm with resistance to anthracnose and other diseases. [ABSTRACT FROM AUTHOR]

Four isolates of Colletotrichum sublineola were inoculated on excised leaf blades and rhizomes of nine Johnsongrass accessions and leaf blades of two sorghum accessions, BTx623 (+) and SC748-5 (−). Successful acervuli formations were observed in seven Johnsongrass accession- C. sublineola isolate combinations. Although infection leading to pathogen reproduction was rarely observed, this is the first study that confirmed Johnsongrass rhizomes can be colonized by C. sublineola. • Johnsongrass rhizome tissue could be infected by Colletotrichum sublineola. • Acervulus formation was rare, even in positive cultivar by isolate inoculations. • Johnsongrass cultivar SH1247 was infected by all 4 isolates tested. • Three Johnsongrass cultivars were positive only with one isolate. [ABSTRACT FROM AUTHOR]

The anthracnose pathogen Colletotrichum sublineola and its sorghum host provide an excellent system to examine concepts associated with gene-for-gene resistance. In this study, an excised-leaf spot inoculation assay method was used to evaluate host-pathogen interactions across several sorghum cultivars that serve as host differentials for defining races of the pathogen. Host cultivars tested included sorghum cultivars BTx398, RTx2536, Theis and johnsongrass cultivar SH1152. The cultivars were inoculated at varying conidia concentrations both singly and in pairs with conidia from strains of C. sublineola that differ in ability to incite the disease anthracnose. The hypothesis tested was that host defense triggered by effectors produced by an avirulent strain will limit infection when simultaneously inoculated with a strain that otherwise would lead to disease. Observations revealed significant changes in disease ratings based on conidial concentrations of the C. sublineola isolates used. However, disease rating scores for combined inocula in the excised-leaf spot inoculation assays led to scores either between the scores generated by single isolates or near the score of the more virulent isolate. • Sorghum plants were co-inoculated with strains of C. sublineola expected to cause different disease responses. • It was hypothesized that an avirulent strain will trigger host defense to limit disease by the virulent strain. • Although variations were observed, the excised-leaf spot inoculation assays did not support that hypothesis. • Significant changes in disease ratings were observed based on conidial concentrations of the C. sublineola isolates used. [ABSTRACT FROM AUTHOR]

Two fungicides, pyraclostrobin and pyraclostrobin + fluxapyroxad, were evaluated on five grain sorghum hybrids to manage foliar diseases in a three-year field study. Anthracnose (leaf phase) caused by Colletotrichum sublineola Henn. ex Sacc. and Trotter was observed each year in Arkansas, while target leaf spot caused by Bipolaris sorgicola (Lefebvre and Sherwin) Alcorn was observed in 2016. Overall disease severity at growth stage 8 (hard-dough) was severe in 2016 and 2017, but low in 2018. The fungicides were similar in efficacy to control anthracnose and target leaf spot. Grain sorghum hybrids varied in susceptibility to anthracnose with Pioneer 83P99 and Pioneer 84P80 being susceptible compared to Dyna-Gro M73GR55, Sorghum Partners 7715, and Terral REV 9782. Pioneer 84P80 and Terral REV 9782 were susceptible to target leaf spot. A greater grain yield was observed on the anthracnose-resistant hybrids when foliar disease was severe (>20%) compared to susceptible hybrids. When anthracnose was severe (>20%), yield protection by a fungicide averaged 70% on the susceptible and 7% on anthracnose-resistant hybrids. Fungicides were more frequently profitable on susceptible hybrids when anthracnose severity was >20% than on the anthracnose-resistant hybrids. At best, fungicide profitability was inconsistent on susceptible hybrids where disease pressure was low (<1%). These data provide some guidelines for fungicide use on grain sorghum that vary in susceptibility to anthracnose and target leaf spot in Arkansas and the Mid-southern United States. • Anthracnose is an important foliar disease of grain sorghum. • Fungicides applied at half-bloom effectively managed anthracnose. • Fungicides were more consistently profitable on susceptible hybrids. • However, grain yield was greater on anthracnose-resistant hybrids. • An integrated approach to manage anthracnose was effective and profitable. [ABSTRACT FROM AUTHOR]

Colletotrichum sublineola is an aggressive fungal pathogen that causes anthracnose in sorghum [Sorghum bicolor (L.) Moench]. The obvious symptoms of anthracnose are leaf blight and stem rot. Sorghum, the fifth most widely grown cereal crop in the world, can be highly susceptible to the disease, most notably in hot and humid environments. In the southeastern United States the acreage of sorghum has been increasing steadily in recent years, spurred by growing interest in producing biofuels, bio-based products, and animal feed. Resistance to anthracnose is, therefore, of paramount importance for successful sorghum production in this region. To identify anthracnose resistance loci present in the highly resistant cultivar 'Bk7', a biparental mapping population of F3:4 and F4:5 sorghum lines was generated by crossing 'Bk7' with the susceptible inbred 'Early Hegari-Sart'. Lines were phenotyped in three environments and in two different years following natural infection. The population was genotyped by sequencing. Following a stringent custom filtering protocol, totals of 5186 and 2759 informative SNP markers were identified in the two populations. Segregation data and association analysis identified resistance loci on chromosomes 7 and 9, with the resistance alleles derived from 'Bk7'. Both loci contain multiple classes of defense-related genes based on sequence similarity and gene ontologies. Genetic analysis following an independent selection experiment of lines derived from a cross between 'Bk7' and sweet sorghum 'Mer81-4' narrowed the resistance locus on chromosome 9 substantially, validating this QTL. As observed in other species, sorghum appears to have regions of clustered resistance genes. Further characterization of these regions will facilitate the development of novel germplasm with resistance to anthracnose and other diseases., (Copyright © 2016 Felderhoff et al.)