Sorghum is an important food and feed crop in the dry lowland areas of Ethiopia. Farmers grow both early-sown long-duration landraces and late-sown short-duration improved varieties. Because timing ...and intensity of drought stress can vary in space and time, an understanding of major traits (G), environments (E), management (M), and their interactions (G×E×M) is needed to optimize grain and forage yield given the limited available resources. Crop simulation modeling can provide insights into these complex G×E×M interactions and be used to identify possible avenues for adaptation to prevalent drought patterns in Ethiopia. In a previous study predictive phenology models were developed for a range of Ethiopian germplasm. In this study, the aims were to (1) further parameterize and validate the APSIM-sorghum model for crop growth and yield of Ethiopian germplasm, and (2) quantify by simulation the productivity-risk trade-offs associated with early vs late sowing strategies in the dry lowlands of Ethiopia. Field experiments involving Ethiopian germplasm with contrasting phenology and height were conducted under well-watered (Melkassa) and water-limited (Miesso) conditions and crop development, growth and yield measured. Soil characterization and weather records at the experimental sites, combined with model parameterization, enabled testing of the APSIM-sorghum model, which showed good correspondence between simulated and observed data. The simulated productivity for the Ethiopian dry lowlands environments showed trade-offs between biomass and grain yield for early and late sowing strategies. The late sowing strategy tended to produce less biomass except in poor seasons, whereas it tended to produce greater grain yield except in very good seasons. This study exemplified the systems approach to identifying traits and management options needed to quantify the production-risk trade-offs associated with crop adaptation in the Ethiopian dry lowlands and further exemplifies the general robustness of the sorghum model in APSIM for this task.
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. 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. 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.
Key message
GWAS analysis revealed variations at loci harboring seed storage, late embryogenesis abundant protein, and a tannin biosynthesis gene associated with sorghum grain mold resistance.
Grain ...mold is the most important disease of sorghum
Sorghum bicolor
(L.) Moench. It starts at the early stages of grain development due to concurrent infection by multiple fungal species. The genetic architecture of resistance to grain mold is poorly understood. Using a diverse set of 635 Ethiopian sorghum accessions, we conducted a multi-stage disease rating for resistance to grain mold under natural infestation in the field. Through genome-wide association analyses with 173,666 SNPs and multiple models, two novel loci were identified that were consistently associated with grain mold resistance across environments. Sequence variation at new loci containing sorghum
KAFIRIN
gene encoding a seed storage protein affecting seed texture and
LATE EMBRYOGENESIS ABUNDANT
3 (
LEA3
) gene encoding a protein that accumulates in seeds, previously implicated in stress tolerance, were significantly associated with grain mold resistance. The
KAFIRIN
and
LEA3
loci were also significant factors in grain mold resistance in accessions with non-pigmented grains. Moreover, we consistently detected the known SNP (S4_62316425) in
TAN1
gene, a regulator of tannin accumulation in sorghum grain to be significantly associated with grain mold resistance. Identification of loci associated with new mechanisms of resistance provides fresh insight into genetic control of the trait, while the highly resistant accessions can serve as sources of resistance genes for breeding. Overall, our association data suggest the critical role of loci harboring seed protein genes and implicate grain chemical and physical properties in sorghum grain mold resistance.
The study was carried out to assess the nature and magnitude of genetic variability for grain quality traits in lowland sorghum accessions. Understanding genetic diversity and trait association is ...crucial to designing an effective breeding plan to develop nutrient-rich varieties. Two hundred twenty-five accessions were evaluated using a simple lattice design with two replications at Weioto. Prepared samples per replication were scanned by mixing the grains and repacking the sample cup after each scan. Analysis of grain quality traits revealed significant (P ≥ 0.01) differences among the genotypes indicating a good chance for genetic improvement. Genotypic means of nutritional content showed that amylose (Am) content ranged from 19.11 to 20.80%, ash value ranged from 0.37 to 3.14%, starch content ranged from 42.29 to 72.77%, and protein (pr) in dry basis ranged from 2.62 to 10.45%. Similarly, iron (Fe) ranged from 1.38 to 73.21 ppm, zinc (Zn) ranged from 16.8 to 66.02 ppm, and tannin content ranged between -0.08 and 9105.21%. Broad-sense heritability (h2b) of all grain quality attributes such as amylose; ash; starch; moisture; iron; zinc; protein, and tannin was in the range of 13-92%. Principal component analysis showed the first three principal components with an eigenvalue equal to or greater than unity adequately explain the variation in the data. Significant positive genetic correlations (P < 0.001) with amylase, starch, iron, and zinc, while tannin had a weak association with grain yield. This result declares/signifies/a good prospect of southern Ethiopia lowland sorghum accessions for genetic improvement in grain yield and quality traits.
The eastern Africa region, Ethiopia and its surroundings, is considered as the center of origin and diversity for sorghum, and has contributed to global sorghum genetic improvement. The germplasm ...from this region harbors enormous genetic variation for various traits but little is known regarding the genetic architecture of most traits. Here, 1425 Ethiopian landrace accessions were phenotyped under field conditions for presence or absence of awns, panicle compactness and shape, panicle exsertion, pericarp color, glume cover, plant height and smut resistance under diverse environmental conditions in Ethiopia. In addition, F1 hybrids obtained from a subset of 1341 accessions crossed to an A1 cytoplasmic male sterile line, ATx623, were scored for fertility/sterility reactions. Subsequently, genotyping-by-sequencing generated a total of 879,407 SNPs from which 72,190 robust SNP markers were selected after stringent quality control (QC). Pairwise distance-based hierarchical clustering identified 11 distinct groups. Of the genotypes assigned to either one of the 11 sub-populations, 65% had high ancestry membership coefficient with the likelihood of more than 0.60 and the remaining 35% represented highly admixed accessions. A genome-wide association study (GWAS) identified loci and SNPs associated with aforementioned traits. GWAS based on compressed mixed linear model (CMLM) identified SNPs with significant association (FDR ≤ 0.05) to the different traits studied. The percentage of total phenotypic variation explained with significant SNPs across traits ranged from 2 to 43%. Candidate genes showing significant association with different traits were identified. The sorghum
transcription factor,
was identified as a strong candidate gene conditioning male fertility. Notably, sorghum CLAVATA1 receptor like kinase, known for regulation of plant growth, and the
gene RAP2-7, known to suppress transition to flowering, were significantly associated with plant height. In addition, the
like MYB transcription factor and
showed strong association with pericarp color validating previous observations. Overall, the genetic architecture of natural variation representing the complex Ethiopian sorghum germplasm was established. The study contributes to the characterization of genes and alleles controlling agronomic traits, and will serve as a source of markers for molecular breeding.
The identification of genomic regions underlying the root system architecture (RSA) is vital for improving crop abiotic stress tolerance. To improve sorghum (Sorghum bicolor L. Moench) for ...environmental stress tolerance, information on genetic variability and genomic regions linked to RSA traits is paramount. The aim of this study was, therefore, to investigate common quantitative trait nucleotides (QTNs) via multiple methodologies and identify genomic regions linked to RSA traits in a panel of 274 Ethiopian sorghum accessions. Multi‐locus genome‐wide association study was conducted using 265,944 high‐quality single nucleotide polymorphism markers. Considering the QTN detected by at least three different methods, a total of 17 reliable QTNs were found to be significantly associated with root angle, number, length, and dry weight. Four QTNs were detected on chromosome SBI‐05, followed by SBI‐01 and SBI‐02 with three QTNs each. Among the 17 QTNs, 11 are colocated with previously identified root traits quantitative trait loci and the remaining six are genome regions with novel genes. A total of 118 genes are colocated with these up‐ and down‐streams of the QTNs. Moreover, five QTNs were found intragenic. These QTNs are S5_8994835 (number of nodal roots), S10_55702393 (number of nodal roots), S1_56872999 (nodal root angle), S9_1212069 (nodal root angle), and S5_5667192 (root dry weight) intragenic regions of Sobic.005G073101, Sobic.010G198000, Sobic.001G273000, Sobic.009G013600, and Sobic.005G054700, respectively. Particularly, Sobic.005G073101, Sobic.010G198000, and Sobic.009G013600 were found responsible for the plant growth hormone‐induced RSA. These genes may regulate root development in the seedling stage. Further analysis on these genes might be important to explore the genetic structure of RSA of sorghum.
Core Ideas
The study used multi‐locus genome‐wide association to identify 17 quantitative trait nucleotides (QTNs) significantly associated with root traits.
Eleven QTNs colocated with previously identified root trait quantitative trait loci, while six were novel regions.
Several genes were found within the 17‐QTNs, located within up‐ and down‐streams of linkage‐disequilibrium decay regions.
Five QTNs were found in the intragenic region of the five genes.
This high‐resolution germplasm characterization provides a critical dataset for exploring sorghum root genetics.
Plain Language Summary
Sorghum is an important crop for many people, but it can be affected by drought and other environmental factors. Root system architecture has been identified as a critical factor for drought adaptation in the crop. This study looked at the genetic makeup of sorghum plants to find specific parts of their DNA that are linked to traits related to the roots. The researchers found 17 regions of the DNA that are associated with traits like the angle, number, length, and weight of the roots. Some of these regions contain genes that we already knew were important for root traits, while others are new discoveries. Five of these regions are within genes that control plant growth hormones and may affect how the roots develop. Understanding these genes could help us improve the ability of sorghum plants to tolerate environmental stress. Further study of these genes could help us better understand and improve the root system of sorghum plants.
An experiment was carried out to evaluate the response of sorghum stay-green quantitative trait locus (QTL) introgression lines under induced post-flowering drought stress. The QTL introgression was ...done in 2006 to 2008 from known stay-green lines to the locally adapted varieties through marker assisted backcrossing. The field experiment was carried out in 2009/2010 and involved two irrigation levels and 14 genotypes organized in a split plot design with three replications. Analysis of variance showed significant difference among the genotypes for all the measured nine morpho-physiological quantitative characters. Significant differences were also observed in leaf area, head exsertion, grain yield and hundred seed weight for irrigation indicating that the two irrigation levels were able to differentiate the genotypes for these characters. Genotype-by-irrigation interaction was significant only for head weight and 100 seed weight. In general, a yield reduction of up to 49% was observed in an induced post-flowering moisture deficit. Grain yield had strong positive correlation with head weight (r=0.66) and hundred seed weight (r=0.52) under conditions of moisture deficit. Most of the stay-green introgression lines included in this experiment maintained at least 25% of their green leaf area until maturity though some showed early leaf senescence, but there was no associated increase in grain yield. Possible reasons are discussed.
Understanding population genetic structure and diversity of a crop is essential in designing selection strategies in plant breeding. About 2010 Ethiopian sorghum accessions were phenotyped for ...different traits at multiple locations. A subset of the collection, 1628 accessions, predominantly landraces, some improved varieties, and inbred lines were genotyped by sequencing. Phenotypic data revealed association of important traits with different sorghum growing agro‐climatic regions, high genetic diversity and the presence of rare natural variation in the Ethiopian sorghum germplasm. Subsequent genotypic analysis determined optimum number of sub‐populations, distinct cluster groups and ancestries of each sorghum accessions. To improve utilization of germplasm, a core subset of 387 lines were selected following posteriori grouping of genotypes based on cluster groups obtained through GBS analysis followed by stratified random sampling using quantitative traits. In order to evaluate how well this new sorghum and millet innovation lab (SMIL) collection from Ethiopia is represented within the largest world sorghum collection at United States Department of Agriculture ‐ National Plant Germplasm System (USDA‐NPGS) and the sorghum association panel (SAP), comparisons were conducted based on SNP data. The SMIL collection displayed high genetic diversity with some redundancy with the USDA‐NPGS germplasm but SAP showed clear distinction. Furthermore, genome‐environment association analysis identified candidate genes associated with adaptation to abiotic factors, that will be important for exploitation of adaptive potential to different environments. In summary, our results described the diversity and relationship of sorghum collections, representativeness of developed core and provide novel insights into candidate genes associated to abiotic stress tolerance.
Abstract
Background and Aims
Main shoot total leaf number (TLN) is a key determinant of plant leaf area and crop adaptation. Environmental factors other than photoperiod can affect TLN in sorghum, ...implying that leaf appearance rate (LAR) and development rate can differ in response to temperature. The objectives of this study were to determine (1) if temperature effects on TLN can be explained as a consequence of differences in temperature responses across phenological processes and (2) if genotypic differences in these responses can be linked to agroecological adaptation.
Methods
Nineteen sorghum genotypes were sown on 12 dates at two locations in Ethiopia with contrasting altitude, creating temperature differences independent of photoperiod. TLN and temperature were recorded in all experiments and LAR for six sowing dates.
Key Results
Eleven of the genotypes showed a temperature effect on TLN, which was associated with a significantly higher base temperature (Tbase) for LAR than for pre-anthesis development rate (DR). In contrast, genotypes with no effect of temperature on TLN had similar Tbase for LAR and DR. Across genotypes, Tbase for LAR and DR were highly correlated, but genotypes with low Tbase had the greatest difference in Tbase between the two processes. Genotypic differences were associated with racial grouping.
Conclusions
Genotypic and racial differences in responses of phenological processes to temperature, in particular in Tbase, can affect specific adaptation to agroecological zones, as these differences can affect TLN in response to temperature and hence canopy size and the duration of the pre-anthesis period. These can both affect the amount of water used and radiation intercepted pre-anthesis. A multi-disciplinary approach is required to identify genotype × environment × management combinations that can best capture the ensuing specific adaptation.
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