81 research outputs found
Stem Rust Resistance in 1BL.1RS and 2RL.2BS Double Wheat-Rye Translocation Lines
No full textThe wheat stem rust pathogen, Puccinia graminis f.sp. tritici, is a significant and devastating disease of wheat
crops worldwide. Wheat has many wild relatives in which to source new resistance genes, including the cereal
crop of rye in the tertiary genepool. The aim of this study was to assess the reaction of 1BL.1RS and 2RL.2BS
double wheat-rye translocation lines to virulent stem rust races from Africa and North America. BC1F3 and BC1F4
populations from a cross between the line KR99-139 (a double wheat-rye translocation line with 1BL.1RS and
2RL.2BS) and the bread wheat cultivar Topper were used in the study. Several of the populations homozygous for
1BL.1RS and heterozygous for 2RL.2BS showed resistance and low severity adult plant resistance (20RMR-50MSS)
to the African stem rust race TTKSK in the field. None of the tested populations with varying chromosome
combinations showed seedling resistance to any of the tested stem rust races. Thus, these resistant populations
likely carry gene/s effective at the adult plant stage since all stage resistance genes with major effect appear to
be absent based on the seedling assays. Resistant lines combined three chromosomes (1RS, 2RS and 2BS) which
make their direct use in breeding more complicated. Mapping studies followed by potential transfer of genes
between 2R and 2B will make the identified minor genes more useful in wheat breeding.Steffenson, Brian; Rahmatov, Mahbubjon; Garkava-Gustavsson, Larisa; Wanyera, Ruth; Rouse, Matthew; Johansson, Eva. (2015). Stem Rust Resistance in 1BL.1RS and 2RL.2BS Double Wheat-Rye Translocation Lines. Retrieved from the University Digital Conservancy, 10.17221/80/2015-CJGPB
Sources of resistance to yellow rust and stem rust in wheat-alien introgressions
No full textWheat is the staple food and the main source of caloric intake in most developing countries, and thereby an important source in order to maintain food security for the growing populations in those countries. Stem rust Puccinia graminis f. sp. tritici, and yellow rust P. striiformis f. sp. tritici of wheat continues to cause severe damage locally and globally, thereby contributing to food insecurity. In this paper biology and taxonomy of stem rust and yellow rust, breeding for resistance, utilization of resistance sources from different gene pools, molecular characterization and genetic dissection of resistance to rusts are discussed
Isolation and evaluation of different wheat-rye translocation lines obtained from a disease resistant double translocation line with 1BL/1RS and 2RL/2BS
No full textWheat-rye translocations involving 1RS and 2RL of rye are the most useful sources of genes for disease resistance in wheat breeding. Rye genes are known to control resistance to biotic and abiotic stresses. Wheat-rye translocations have been widely used by breeders all over the world because genes located on translocated chromosome arms or fragments from the rye genome can determine a number of useful traits in wheat, such as high yield, wide adaptation, diseases and pest resistance.
The wheat-rye translocation lines used in this study were derived from a cross between the Swedish bread wheat variety Topper and the line KR99-139 being homozygous for the two different wheat-rye translocations 1BL/1RS and 2RL/2BS. BC1F1 materials were obtained through one back-cross with either the line KR99-139 or the variety Topper. Thereafter, BC1F2 and BC1F3 were obtained by once and twice selfing. In the obtained material, it was thereafter possible to define four different possible homozygous translocation combinations. Thus, lines containing both 1RS and 2RL translocations, containing only 1RS or 2RL and without any translocation were identified.
For identification of the four possible homozygous wheat-rye translocation lines mentioned above, three different methods were used. First, lines of different types were characterized and isolated based on a phenotypical marker, i.e. if the plant showed red or green coleoptile colour. Plants with homozygous presence of 2RL were known to develop red coleoptile, as a gene for red coleoptile has been verified to be present at 2RL in these lines. The analyses of coleoptile colours were done in the BC1F2 (obtained from selfed BC1F1 lines determined by molecular markers at BAZ, Germany to be 1RS– –/2RL+–) and BC1F3 (obtained from the BC1F2 lines having a red coleoptile) wheat-rye translocation lines, where the variety Topper had been used for backcrossing. Moreover, the BC1F2 (obtained from selfed BC1F1 lines determined by molecular markers at BAZ, Germany to be 1RS++/2RL+–) wheat-rye translocation lines for which the KR99-139 line was used for backcrossing, was selfed, and analyses of coleoptile colours were done in the BC1F3 (on a representative sample of all combinations of presence and absence of 2RL). The results from the coleoptiles colour analyses generally showed that it was possible to distinguish lines having 2RL++ (red coleoptiles) and 2RL– – (green coleoptiles).
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Plants having 2RL+– were sometimes classified as having green and sometimes as having red coleoptiles. Therefore, if coleoptiles colour is going to be used for selection of lines with presence/absence of 2RL in homozygous form, at least two generations have to be analyzed and lines not segregating in either of the analyses can be judged as being homozygous as related to their coleoptiles colour. For identification of lines with presence of heterozygous 1RS+– and homozygous 2RL++ rye chromosome the Giemsa C-banding technique was used. The Giemsa C-banding techniques on the BC1F3 segregating population generally resulted in well-defined sharp, distinct bands in the wheat-rye translocation lines and both the rye chromosome arms, 1RS and 2RL were identified. Additionally, five microsatellite (SSR) markers SCM9, SCM39, SCM43, SCM69 and SCM75 were used for verification of the presence of 1RS and 2RL. Among the five SSR markers, SCM9 and SCM75 resulted in reliable amplification of expected products, 220 bp and 191 bp respectively. The line KR99-139 containing both 1RS and 2RL showed correct amplification products with both mentioned primers while the bread wheat variety Topper without any rye chromosome showed no amplification with both SSR primers pairs.
Resistance towards yellow rust and stem rust were evaluated through seedling resistance test in the greenhouse (Global Rust Reference Center, Denmark) to Puccinia striiformis, and adult plant resistance to Puccinia graminis, race Ug99 (TTKSK) in Njoro, Kenya. For the seedling resistance test, pathogenicity of 17 races/isolates of yellow rust was used. The BC1F3 which carries combination of 1RS++/2RL++, 1RS++/2RL+– and the KR99-139 were found to be highly resistant to some races/isolates whether the variety Topper was fully susceptible to all races/isolates. The results showed Yr9 to be one possible gene that could be responsible for the obtained yellow rust resistance. However, the results were not that clear so than not other possible genes could also be an alternative. For adult plant resistance towards Ug99, a total of 28 of the BC1F3 wheat-rye translocation lines and their parents were evaluated in the field of Njoro, Kenya. The results indicated that out of the 30 tested lines 20 were susceptible, 8 moderately susceptible to susceptible and in 2 lines the resistance to Ug99 was identified. The two BC1F3 wheat-rye translocation lines that were found to be resistant towards Ug99 were both being homozygous for 1RS++ and heterozygous for 2RL+–. Thus, these results indicated presence of several genes/QTLs controlling resistance indicating possible epistatic effects of the genes involved. The lines identified as resistant will be utilized in combination with Tajik germplasm
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to develop a mapping population for determining the underlying basis of resistance. To summarize results from the research outlined in this thesis indicate that wheat-rye translocation lines and used methods can be highly relevant for wheat breeding programs and further research
Genetic characterisation of novel resistance alleles to stem rust and stripe rust in wheat-alien introgression lines
No full textBread wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) is one of the most important food crops world-wide, but is attacked by many diseases and pests that cause significant yield losses. Globally, stem rust (Sr) (Puccinia graminis f. sp. tritici Erikss & E. Henning), stripe rust (Yr) (Puccinia striiformis Westend. f. sp. tritici Eriks) and leaf rust (Lr) (Puccinia triticina Eriks) are a great threat to wheat production. The majority of the Sr, Yr and Lr resistance genes are already defeated by numerous virulent races, so enhanced genetic resistance against these devastating diseases are essential. Wheat-alien introgressions from derivatives of Secale cereale L. (2n = 2x = 14, RR), Leymus mollis (2n = 4x = 28, NsNsXmXm), Leymus racemosus (2n = 4x = 28, NsXm) and Thinopyrum junceiforme (2n = 4x = 28; J1J1J2J2) are important genetic resources for new sources of resistance genes. To identify new sources of resistance, this thesis evaluated seedling and adult plant resistance to a wide array of stem rust and stripe rust races. Three wheat-rye disomic substitution lines 2R (2D) were found to carry new resistance gene/s to stem rust races and six multiple wheat-rye introgression lines with 5RS·5AL+4R+6R carried new resistance gene/s to stripe rust races. At adult plant stage, the wheat-rye translocation line with 1BL·1RS and 2RL·2BS exhibited low susceptibility to race TTKSK under field conditions.
The wheat-rye T2DS·2RL Robertsonian translocation line (TA5094) with a new stem rust resistance gene was developed through the breakage-fusion mechanism and verified using seedling resistance assays and molecular and cytogenetic analyses. Three kompetitive allele-specific PCR (KASP) markers located on rye chromosome 2RL were identified as being closely associated with the new stem rust resistance gene. Fluorescence in situ hybridisation (FISH) analysis confirmed the resistance gene in F3:4 homozygous lines. The stem rust resistance gene in TA5094 line on chromosome 2RL arm was designated Sr59.
Wheat cultivars, advanced lines and landraces from Tajikistan were assessed at seedling and adult plant stages against Sr, Yr and Lr races. Based on multipathotype assessment and molecular markers, the presence of Sr6, Sr31/Yr9/Lr26, Sr38/Yr17/Lr37, Yr2 and Yr27 and pleiotropic resistance genes Sr57/Lr34/Yr18/ and Sr2/Yr30/Lr27 was postulated.
Overall, this thesis identified novel genetic resistance resources against stem rust, stripe rust and leaf rust in Tajik wheat and in wheat-alien introgressions. This resistance gene/s will be useful in diversifying the current set of resistance genes deployed to control these devastating diseases
Characterization of stem, stripe and leaf rust resistance in Tajik bread wheat accessions
No full textStem rust [causal organism: Puccinia graminis f. sp. tritici (Pgt)], stripe rust [Puccinia striiformis f. sp. tritici (Pst)], and leaf rust [Puccinia triticina (Pt)] are important fungal diseases of wheat in Central Asia and worldwide. Therefore, identification of seedling and adult plant resistance (APR) genes is of major importance for the national wheat breeding program in many countries. The objectives of this study were to identify genes that confer seedling and APR resistances in widely grown wheat cultivars, landraces and advanced lines from Tajikistan. A total of 41 wheat accessions were inoculated with eleven races of Pgt, twelve races of Pst and nine races of Pt for postulation of Sr (stem rust), Yr (yellow or stripe rust), and Lr Lr (leaf rust) resistance genes at the seedling stage. In addition, all of the accessions were tested in field trials for the response to stem rust and stripe rust. Genes for seedling stem rust resistance (i.e. Sr5, Sr6, Sr11, Sr31, and Sr38), stripe rust resistance (Yr9, Yr17, and Y27), and leaf rust resistance (Lr16 and Lr26) were postulated in the Tajik wheat. The presence of the pleiotropic APR genes Sr2/Yr30/Lr27 (associated with pseudo-black chaff phenotype) and Lr34/Yr18/Sr57 (associated with leaf tip necrosis phenotype), and also Lr37 were assessed in the field and confirmed with linked molecular markers. In most of the wheat accessions, resistance genes could not be postulated because their infection types did not match the avirulence or virulence profile of the Pgt, Pst and Pt races tested. Six, seven, and nine accessions were identified that likely possess new genes for resistance to stem rust, stripe rust, and leaf rust, respectively, which have not been described previously. The research demonstrates the presence of effective seedling resistance and APR genes in widely grown wheat accessions that could facilitate further rust resistance breeding in the national wheat breeding program in Tajikistan
Cytogenetic and molecular identification of novel wheat-Elymus sibiricus addition lines with resistance to leaf rust and the presence of leaf pubescence trait
No full textIntroduction Emerging new races of leaf rust (Puccinia triticina Eriks) are threatening global wheat (Triticum aestivum L.) production. Identifying additional resistance genes from all available gene pools is crucial to expanding wheat resistance to these virulent leaf rust races. Siberian wild rye (Elymus sibiricus L.) possesses numerous beneficial traits that can be valuable in wheat improvement. Three new wheat-E. sibiricus addition lines, O27-2 (BC8), O27-3 (BC12) and O193-3 (BC12), were developed through a backcrossing scheme in this study, using leaf rust field evaluations, molecular marker assays and cytogenetic analysis.Methods These three lines were derived from progeny of the bread wheat cultivar 'Obriy' (2n = 6x = 42, AABBDD) and partial octoploid amphiploid wheat-E. sibiricus (2n = 8x = 56, AABBDDStSt).Results and discussion The lines (O27-2, O27-3 and O193-3) demonstrated strong specific leaf pubescence (hairiness) and resistance at the adult stage to a local population of leaf rust races. The response to leaf rust in these three lines significantly differed from that of the Lr24 gene, providing evidence for a distinct resistance mechanism associated with the 3St chromosome. This study is the first to report the transfer of an E. sibiricus chromosome into wheat that confers leaf rust resistance. Molecular marker analysis and genomic in situ hybridization confirmed that lines O27-2, O27-3 and O193-3 each possess one pair of E. sibiricus 3St chromosomes. The resistance gene was determined to be on the additional alien chromosome in these lines. Molecular markers (Xwmc221, Lr29F18, Sr24/Lr24) confirmed that the lines O27-2, O27-3, and O193-3 each contain a pair of E. sibiricus 3St chromosomes carrying leaf rust resistance genes. These findings demonstrate that the E. sibiricus 3St chromosome carries the leaf rust resistance gene and that the O27-2, O27-3, and O193-3 lines can serve as novel germplasm sources for introducing this resistance into wheat breeding programs. This study contributes to broadening the genetic diversity of resistance genes available for combating leaf rust in wheat
Cytogenetic and molecular identification of novel wheat-Elymus sibiricus addition lines with resistance to leaf rust and the presence of leaf pubescence trait [Elektronisk resurs]
No full textIntroduction Emerging new races of leaf rust (Puccinia triticina Eriks) are threatening global wheat (Triticum aestivum L.) production. Identifying additional resistance genes from all available gene pools is crucial to expanding wheat resistance to these virulent leaf rust races. Siberian wild rye (Elymus sibiricus L.) possesses numerous beneficial traits that can be valuable in wheat improvement. Three new wheat-E. sibiricus addition lines, O27-2 (BC8), O27-3 (BC12) and O193-3 (BC12), were developed through a backcrossing scheme in this study, using leaf rust field evaluations, molecular marker assays and cytogenetic analysis.Methods These three lines were derived from progeny of the bread wheat cultivar 'Obriy' (2n = 6x = 42, AABBDD) and partial octoploid amphiploid wheat-E. sibiricus (2n = 8x = 56, AABBDDStSt).Results and discussion The lines (O27-2, O27-3 and O193-3) demonstrated strong specific leaf pubescence (hairiness) and resistance at the adult stage to a local population of leaf rust races. The response to leaf rust in these three lines significantly differed from that of the Lr24 gene, providing evidence for a distinct resistance mechanism associated with the 3St chromosome. This study is the first to report the transfer of an E. sibiricus chromosome into wheat that confers leaf rust resistance. Molecular marker analysis and genomic in situ hybridization confirmed that lines O27-2, O27-3 and O193-3 each possess one pair of E. sibiricus 3St chromosomes. The resistance gene was determined to be on the additional alien chromosome in these lines. Molecular markers (Xwmc221, Lr29F18, Sr24/Lr24) confirmed that the lines O27-2, O27-3, and O193-3 each contain a pair of E. sibiricus 3St chromosomes carrying leaf rust resistance genes. These findings demonstrate that the E. sibiricus 3St chromosome carries the leaf rust resistance gene and that the O27-2, O27-3, and O193-3 lines can serve as novel germplasm sources for introducing this resistance into wheat breeding programs. This study contributes to broadening the genetic diversity of resistance genes available for combating leaf rust in wheat
Unveiling the influences of P fertilization on bioactive compounds and antioxidant activity in grains of four sorghum cultivars
No full textBackgrounds Phosphorus is a critical nutrient in agriculture, influencing plant growth and nutritional quality. Objectives This study, uniquely designed to investigate the effects of phosphorus (P) fertilization levels, sorghum cultivars, and growing locations on phytochemical content and antioxidant activity in sorghum grains, employed four sorghum cultivars (Hakeka, P954063, Tabat, and Tetron) grown under three P levels (0P, 1P, 2P) in two locations (Gezira and White Nile) in Sudan. Methods In this study, four sorghum cultivars were grown in two distinct locations in Sudan, employing a split-plot design with three (P) fertilization levels. P was applied as triple super phosphate directly with the seeds, and additional fertilization included urea applied in two split doses. At physiological maturity, representative sorghum panicles were harvested, processed, and analyzed for bioactive compounds and antioxidant activities using standard extraction and quantification techniques such as Folin-Ciocalteu for phenolics and colorimetric flavonoid assays. Antioxidant activities were assessed through various assays, including DPPH and FRAP. Statistical analyses were performed using a three-way ANOVA to examine the effects of cultivar, P level, and location on the measured parameters, supplemented by multivariate analysis to further elucidate the interactions between these factors. Results Significant interactions (p<0.001) were observed among cultivars, P levels, and locations for total phenolic content (TPC), total flavonoid content (TFC), carotenoids, tannins, and various antioxidant activity measures (DPPH, FRAP, ABTS, TRP, H2O2). P fertilization significantly increased all measured phytochemicals and antioxidant activities compared to non-treated cultivars, except for H2O2, which decreased with P application. Among cultivars, Hakeka consistently exhibited the highest TFC, carotenoid content, and antioxidant activities (DPPH, FRAP, TRP, ABTS), particularly at the 2P level. P954063 showed the highest TPC and tannin concentrations. Tetron generally had the lowest phytochemical and antioxidant levels. White Nile showed higher TPC, carotenoids, DPPH, FRAP, TRP, and ABTS levels, while Gezira had higher TFC, tannins, and H2O2 concentrations. The impact of phosphorus fertilization often varies between locations. Strong positive correlations were found between TPC and all antioxidant assays (r = 0.68-0.90) and total carotenoids and antioxidant activities (r = 0.73-0.93). Conclusions This study recommended cultivating the Tabat variety with 2P doses in Gezira. In addition, the Hakeka cultivar showed the highest increases in total flavonoid content, carotenoids, and antioxidant activities, particularly under the highest P level (2P). The findings highlight that P plays a critical role in enhancing sorghum's nutritional and health-promoting qualities, which are essential for leveraging this staple crop for food and nutrition security strategies in semi-arid regions
Identification and characterization of Sr59-mediated stem rust resistance in a novel wheat-rye translocation T2BL 2BS-2RL
No full textEmerging new races of wheat stem rust (Puccinia graminis f. sp. tritici) are threatening global wheat (Triticum aestivum L.) production. Host resistance is the most effective and environmentally friendly method of controlling stem rust. The stem rust resistance gene Sr59 was previously identified within a T2DS 2RL wheat-rye whole arm translocation, providing broad-spectrum resistance to various stem rust races. Seedling evaluation, molecular marker analysis, and cytogenetic studies identified wheat-rye introgression line #284 containing a new translocation chromosome T2BL 2BS-2RL. This line has demonstrated broad-spectrum resistance to stem rust at the seedling stage. Seedling evaluation and cytogenetic analysis of three backcross populations between the line #284 and the adapted cultivars SLU-Elite, Navruz, and Linkert confirmed that Sr59 is located within the short distal 2RL translocation. This study aimed physical mapping of Sr59 in the 2RL introgression segment and develop a robust molecular marker for marker-assisted selection. Using genotyping-by-sequencing (GBS), GBS-derived SNPs were aligned with full-length annotated rye nucleotide-binding leucine-rich repeat (NLR) genes in the parental lines CS ph1b, SLU238, SLU-Elite, Navruz, and Linkert, as well as in 33 BC4F5 progeny. Four NLR genes were identified on the 2R chromosome, with Chr2R_NLR_60 being tightly linked to the Sr59 resistance gene. In-silico functional enrichment analysis of the translocated 2RL region (25,681,915 bp) identified 223 genes, with seven candidate genes associated with plant disease resistance and three linked to agronomic performance, contributing to oxidative stress response, protein kinase activity, and cellular homeostasis. These findings facilitate a better understanding of the genetic basis of stem rust resistance provided by Sr59. (c) 2025 Crop Science Society of China and Institute of Crop Science, CAAS. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Harnessing genetic diversity in Sudanese sorghum wild relatives for stay-green drought tolerance via microsatellite (SSR) marker assessment
No full textSudan is the birthplace of sorghum, and vast genetic diversity exists among its wild relatives. To assess the genetic potential of Sudan wild sorghum accessions, we used 41 stay-green-specific microsatellite (SSR) markers to analyze the genetic variability and population structure of 256 accessions. Overall, 17 SSR markers were polymorphic, with 55 alleles on average 3.3 per locus. The polymorphic information content (PIC) ranged from 0.49 to 0.57, with an overall mean of 0.53, indicating the potential of these markers for capturing the genetic construction of wild sorghum. Linkage disequilibrium analysis identified the two most informative markers, Xcup05 and Xtxp212. Accordingly, the Nei gene diversity of the populations varied from 0.032 to 0.127, with an overall mean of 0.083. Molecular variance analysis (AMOVA) demonstrated that 99% and 1% of the genetic variations were within and among populations (Fst = 0.066; P 0.001), respectively. However, gene flow (Nm) values varied from 0.058 in populations 1 and 2 to 1.018 in populations 2 and 3. Neighbor-joining trees identified from 21 Sudanese wild sorghum accessions clustered closely to the universally drought-tolerant landrace B35. Structural analysis generated the highest Delta K value (58.2) at K = 2, revealing two distinct subpopulations. While this work provides valuable information about the potential of sorghum wild relatives from Sudan as sources for stay-green drought tolerance, further research should be directed toward identifying the exact mechanisms and genes underlying this stay-green trait using advanced molecular omics techniques. In conclusion, this study highlights the potential role of Sudanese sorghum accessions as reservoirs of ready-to-use stay-green genes for the design of climate-resilient sorghum cultivars in drought-prone areas of Sudan and beyond. However, these wild relatives would require extensive pre-breeding and validation efforts before their genes can be effectively incorporated into elite cultivars
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