Stem Rust Disease Research Articles

Identification of some Monogenic Lines Resistant to Stem Rust Disease Using Molecular Markers

Identification of some Monogenic Lines Resistant to Stem Rust Disease Using Molecular Markers

Effectiveness of plant extracts for repressing stem rust disease severity of wheat caused by Puccinia graminis f.sp. tritici Pers under field conditions

BackgroundStem rust caused by Puccinia graminis f.sp. tritici Pers is one of the most devastating fungal foliar diseases, and causes substantial yield losses to wheat crops cultivated under field conditions. This study aimed to evaluate the efficacy of plant extract-based foliar sprays for wheat with carnation, ginger and cinnamon on the severity of stem rust infection of three wheat cultivars cultivated under field conditions for two consecutive winter seasons of (2020/21 and 2021/22).ResultsIn both seasons our data showed that all treatments were associated with some degree of disease suppression recorded as a range of 2.3–8.6% compared to 15.3–24.5% in untreated control treatment. The plant extract treatment was more effective than Amistar, a commercial fungicide. They recorded disease severity as: scores ranged between 2.3 and 3.2%; 3.0–4.5%, and 3.0–6% for wheat cvs. Giza 1, Misr 2, and Sids 14, in respective order. Meanwhile, scores of 4.1, 7.5, and 8.6% were recorded at fungicidal treatment. Spaying wheat plants with carnation extract showed the lowest disease prevalence followed by ginger and cinnamon extract, respectively. Increased in grain yield was associated with reduced disease severity.ConclusionsThe present investigation demonstrated the efficacy using plant extracts against foliar diseases caused by Puccinia and it was suggested that they may be an alternative to traditional chemical treatment.

Deciphering the Crosstalk Mechanisms of Wheat-Stem Rust Pathosystem: Genome-Scale Prediction Unravels Novel Host Targets.

Triticum aestivum (wheat), a major staple food grain, is affected by various biotic stresses. Among these, fungal diseases cause about 15–20% of yield loss, worldwide. In this study, we performed a comparative analysis of protein-protein interactions between two Puccinia graminis races (Pgt 21-0 and Pgt Ug99) that cause stem (black) rust in wheat. The available molecular techniques to study the host-pathogen interaction mechanisms are expensive and labor-intensive. We implemented two computational approaches (interolog and domain-based) for the prediction of PPIs and performed various functional analysis to determine the significant differences between the two pathogen races. The analysis revealed that T. aestivum-Pgt 21-0 and T. aestivum-Pgt Ug99 interactomes consisted of ∼90M and ∼56M putative PPIs, respectively. In the predicted PPIs, we identified 115 Pgt 21-0 and 34 Pgt Ug99 potential effectors that were highly involved in pathogen virulence and development. Functional enrichment analysis of the host proteins revealed significant GO terms and KEGG pathways such as O-methyltransferase activity (GO:0008171), regulation of signal transduction (GO:0009966), lignin metabolic process (GO:0009808), plastid envelope (GO:0009526), plant-pathogen interaction pathway (ko04626), and MAPK pathway (ko04016) that are actively involved in plant defense and immune signaling against the biotic stresses. Subcellular localization analysis anticipated the host plastid as a primary target for pathogen attack. The highly connected host hubs in the protein interaction network belonged to protein kinase domain including Ser/Thr protein kinase, MAPK, and cyclin-dependent kinase. We also identified 5,577 transcription factors in the interactions, associated with plant defense during biotic stress conditions. Additionally, novel host targets that are resistant to stem rust disease were also identified. The present study elucidates the functional differences between Pgt 21-0 and Pgt Ug99, thus providing the researchers with strain-specific information for further experimental validation of the interactions, and the development of durable, disease-resistant crop lines.

Performance Evaluation of Ethiopian Bread Wheat (Triticum aestivum L.) Genotypes in Southern Ethiopia

Ethiopia is not self-sufficient to meet its increasing wheat demand from domestic production partly due to a lack of improved seeds. Efforts are undertaken to fill the gap through off-season production of wheat using supplemental irrigation and modern cultivars adapted to arid areas. This study was carried out to evaluate the genetic variability and adaptability of 15 Ethiopian bread wheat genotypes at different agroecologies in Wolaita and Dawuro zones, Ethiopia. The field experiment was conducted at three locations using a randomized complete block design with three replications during the 2019/2020 main cropping season. Analysis of variance based on 11 morphological agronomic traits and two major wheat diseases revealed that there were highly significant differences ( P < 0.01 ) among the genotypes for all the traits studied at each location and combined over locations. The top three cultivars viz. Alidoro, Galema, and Honqolo exhibited higher average grain yield (GY) of 4.54 t/ha, 4.36 t/ha, and 4.0 t/ha, respectively, combined over locations. Eight of the traits (72.73%) exhibited moderate (30–60%) to high broad-sense heritability ( h b 2 > 60%) values. High h b 2 associated with high genetic advance as percent of mean was observed for the severity of both stem and yellow rust diseases combined over locations. GY was significantly related to aboveground biomass at all locations. This study depicted that cultivar Alidoro had wider adaptability for grain yield and resistance to wheat rusts.

Evaluation of Advanced Kenyan Barley (Hordeum vulgare L.) Genotypes for Resistance to Stem Rust (Puccinia graminis Pers:.Pers. f.sp tritici Eriks. & E. Henn.) Race Ttksk and Its Variants

Stem rust caused by Puccinia graminis Pers:.Pers. f.sp tritici affects all the aerial parts of wheat and barley plants leading to yield losses. The objective of this study was to determine the level of resistance in advanced Kenyan barley lines to stem rust race TTKSK and its variants. The greenhouse and field experiments were laid in complete block design and randomized complete block design respectively with all experiments replicated three times. The experiments were conducted at Kenya Agricultural and Livestock Research Organization- Njoro. In the greenhouse experiment, forty genotypes were sown in perforated plastic pots and when the seedlings attained two-leaf stage, stem rust isolate collected from wheat variety, KS Mwamba was used to inoculate the genotypes. In the field, forty genotypes were sown in a one meter twin rows of each genotype were planted and all agronomic practices implement except management of stem rust disease. Infection types (IT) on the seedlings were observed and data collected following a scale described by Stakman et al. 1962. Disease severity data was collected according to modified Cobbs scale and then subjected to Area Under Disease Progress Curve (AUDPC). All genotypes showed immunity to moderate resistance at seedling level ranging from 0 to 2+. Adult plant reactions to race TTKSK and its variants ranged from an overlap of moderately resistant (MR) to susceptible (S). In all genotypes AUDPC ranged from 225.83 to 887.92 for under this study and the Coefficient of Infection ranged from 13 to 47. High levels of slow rusting were observed in only 12.5% of the genotypes tested while 10% of the genotypes had low levels. 77.5% of the genotypes had moderate levels of slow rusting. The genotypes with high levels of slow rusting can be advanced for release as varieties or be included in barley breeding.

Losses caused by stem rust (Puccinia graminis f.sp tritici) on durum wheat in Ethiopia

Stem rust caused by Puccinia graminis f.sp. tritici is one of the major biotic constraints of wheat production. The disease may cause substantial quantitative and qualitative yield losses but much of the work in Ethiopia on this pathosystem focuses on quantitative yield loss of durum wheat. This work was carried out at Debre Zeit Agriculture Research Centre during 2015/16 and 2016/17 main and off-seasons. Hence the current study was conducted with the objectives to quantify the amount of loss in grain yield due to stem rust and assess the relationship between disease parameters, grain yield, and physical quality parameters of improved durum wheat varieties grown in Ethiopia. Artificial inoculation was performed using a mixture of different dominant stem rust races. There were treated and untreated plots by fungicide that serves as protected and unprotected plots, respectively. Disease severity was recorded each 10 days interval and area under disease progress curve (AUDPC), terminal severity, and coefficient of infection were calculated. The tested cultivars exhibited different disease severity levels, having a mean value of 6.7-76%. High values of area under disease progress curve (AUDPC) were detected on Hitossa, Utuba (1225.7, 585.9). Whereas the lowest values of yield loss were recorded on CVS. Mangudo and Utuba have the mean value of yield loss of 40.2 and 44.8%, respectively. The highest yield loss was observed on susceptible variety Hitosa showing the mean value of 70%. Correlation coefficients were tested between yield losses and values of AUDPC, final stem rust severity, coefficient of infection, and rate of infection of the tested cultivars. There were strong correlation coefficients among disease parameters (r=0.72-0.99). There was also a moderately strong negative correlation coefficient among disease parameters and yield, hectoliter weight, and 1000-kernel weight of the test cultivars (r= -0.53 to -0.81). The current study indicated that the application of Rex Duo can be used in minimizing yield losses caused by the stem rust disease of durum wheat. Therefore, supporting the released durum wheat cultivars with fungicide application is the most pertinent issue in Ethiopia as most of the durum wheat cultivars in farmers' hands were moderately susceptible to susceptible cultivars Pgt races.

Stability and Performance Evaluation of Advanced Bread Wheat (Triticum aestivum L.) Genotypes in Optimum Areas of Ethiopia

Multi-environment trials were carried out at 11 locations in different wheat growing zones of Ethiopia during 2017–18 and 2018–19 to identify high yielding, stable, biotic and abiotic stresses resistant varieties with improved quality traits for commercial release. Twenty-eight advanced bread wheat genotypes have been evaluated against two released bread wheat varieties. The experiment was laid out using alpha lattice design with three replications. Nine stability models were employed in order to assess stability and performance of 28 advanced bread wheat genotypes across 18 diverse environments. Combined analysis of variance for grain yield has revealed that the environments, the genotypes and GEI effects were significantly different (p<0.001). Environments, GEI and Genotypic effects accounted for 71.99%, 22.97% and 5.03% of the total grain yield variation, respectively. Significant GEI showed variable performance of genotypes across environments. Eight advanced bread wheat genotypes namely ETBW8595, ETBW8668, ETBW8751, ETBW8991, ETBW8996, ETBW9547, ETBW9553 and ETBW9554 produced grain yield of more than 5.0 t ha-1, indicating their superior yielding potential. ETBW8595, ETBW8668, ETBW8751, ETBW8991 and ETBW9554 were found the most stable bread wheat genotypes as confirmed by five to eight stability models. ETBW8751, ETBW8991 and ETBW9554 were highest yielding, stable, adaptable, resistant and moderately resistant to prevailing stem and yellow rust diseases. Thus, these three genotypes were the most promising advanced bread wheat genotypes to be verified and released in Ethiopia. These promising bread wheat genotypes can be included in multipurpose bread wheat crossing blocks in order to correct shortcomings of commercial varieties.

Genetic diversity, antifungal evaluation and molecular docking studies of Cu-chitosan nanoparticles as prospective stem rust inhibitor candidates among some Egyptian wheat genotypes.

Wheat has a remarkable importance among cereals worldwide. Wheat stem and leaf rust constitute the main threats that destructively influence grain quality and yield production. Pursuing resistant cultivars and developing new genotypes including resistance genes is believed to be the most effective tool to overcome these challenges. This study is the first to use molecular markers to evaluate the genetic diversity of eighteen Egyptian wheat genotypes. Moreover, the molecular docking analysis was also used to assess the Cu-chitosan nanoparticle (CuChNp) treatment and its mode of action in disease control management. The tested genotypes were categorized into two main cluster groups depending on the similarity matrix, i.e the most resistant and susceptible genotypes to stem and leaf rust races. The results of SCoT primers revealed 140 polymorphic and 5 monomorphic bands with 97% polymorphism. While 121 polymorphic and 74 monomorphic bands were scored for SRAP primers (99% polymorphism). The genotypes Sakha 94, Sakha 95, Beni Sweif 4, Beni Sweif 7, Sohag 4 and Sohag 5 were resistant, while Giza 160 was highly susceptible to all stem rust races at the seedling stage. However, in the adult stage, the 18 genotypes were evaluated for stem and leaf rust-resistant in two different locations, i.e. Giza and Sids. In this investigation, for the first time, the activity of CuChNp was studied and shown to have the potential to inhibit stem and leaf rust in studied Egyptian wheat genotypes. The Spraying Cu-chitosan nanoparticles showed that the incubation and latent periods were increased in treated plants of the tested genotypes. Molecular modeling revealed their activity against the stem and leaf rust development. The SRAP and SCoT markers were highly useful tools for the classification of the tested wheat genotypes, although they displayed high similarities at the morphological stage. However, Cu-chitosan nanoparticles have a critical and effective role in stem and leaf rust disease control.

Distribution, dynamics, and physiological races of wheat stem rust (Puccinia graminis f.sp. tritici) on irrigated wheat in the Awash River Basin of Ethiopia.

Wheat is one of the high-value major crops in the world. However, wheat stem rust is considered one of the determinant threats to wheat production in Ethiopia and the world. So this study was conducted to assess the disease intensity, seasonal distribution dynamics pattern, the genetic variability of Puccinia graminis f. sp. tritici, and to determine the virulence spectrum in the irrigated ecology of the Awash River Basin. Totally 137 wheat farms were evaluated, from 2014/15-2019/20 in six districts representing the Upper, Middle, and Lower Awash River Basin. Farm plots were assessed, in every 5-10 km intervals, with 'X' fashion, and data on disease incidence, severity, healthy plants were counted and recorded. Diseased samples were collected from the diseased wheat stem by Puccinia graminis physiological and genetic race analysis. The seasonal trend of stem rust disease progress showed its importance to infer the future progresses of the disease for the country's potential production plan of irrigated wheat. The result revealed that the disease prevalence, disease incidence, and severity were significantly varied; among the different districts and seasons in the two regions. The survey results also indicated that about 71.7% of the wheat fields were affected by stem rust during the 2018/19 growing period. The disease's overall incidence and mean severity during the same season were 49.02% and 29.27%, respectively. In 2019/20, about 63.7% of the wheat fields were affected by stem rust, disease incidence 30.97%, and severity 17.22% were lower than the previous season. In 2019/20, even though seasonal disease distribution decreased, the spatial distribution was expanding in Afambo and Dubti districts. Four, stem rust dominant races were identified (TTTTF, TKTTF TKKTF, and TTKTF) by physiological and genetic race analysis during 2018/19 and one additional race (TKPTF) in 2019/20, production year. The result indicated that the races are highly virulent and affect most Sr genes except Sr31 and Sr24. From the race analysis result, TTTTF, and TKKTF have the broadest virulence spectrum race, which affects 90% of the Sr genes. Generally, we can conclude that the spatial and seasonal distribution of the disease is expanding. Most of the races in the irrigated areas in the Basin were similar to that of rain-fed wheat production belts in Ethiopia, so care must be given, to effective management of the diseases, in both production ecologies towards controlling the spore pressure than race variability. Therefore, these findings provide inputs for wheat producers to reduce the spread and disease' damage in the irrigated ecologies of Ethiopia. Also, it gives an insight for breeders to think about the breeding program in their crossing lines.

Potentiality of some essential oils and algae extract spray treatments on suppressing wheat stem rust severity under field conditions

Evaluation of some essential oils as well as algal extracts on stem rust severity of three wheat cultivars were conducted for two successive growing seasons under field conditions. Suppressing disease severity in response to the applied treatments was observed at the two growing seasons. Spraying wheat plants with tested essential oils had superior effect against disease severity followed by algal extracts, the fungicide (Topsin M70) and untreated control, respectively. Garlic oil revealed the highest suppression of disease severity followed by cinnamon, thyme, onion and clove oils, respectively. Meanwhile, the algal extract of S. platensis showed the highest reduction in disease severity followed by A. coffeaeformis and N. oculata, in respective order. The increase in produced yield showed in reverse relation with disease severity. The applied treatments showed their effectivity to suppress stem rust disease severity as a safe alternative method to chemical fungicides under field conditions.

The stem rust fungus Puccinia graminis f. sp. tritici induces centromeric small RNAs during late infection that are associated with genome-wide DNA methylation

BackgroundSilencing of transposable elements (TEs) is essential for maintaining genome stability. Plants use small RNAs (sRNAs) to direct DNA methylation to TEs (RNA-directed DNA methylation; RdDM). Similar mechanisms of epigenetic silencing in the fungal kingdom have remained elusive.ResultsWe use sRNA sequencing and methylation data to gain insight into epigenetics in the dikaryotic fungus Puccinia graminis f. sp. tritici (Pgt), which causes the devastating stem rust disease on wheat. We use Hi-C data to define the Pgt centromeres and show that they are repeat-rich regions (~250 kb) that are highly diverse in sequence between haplotypes and, like in plants, are enriched for young TEs. DNA cytosine methylation is particularly active at centromeres but also associated with genome-wide control of young TE insertions. Strikingly, over 90% of Pgt sRNAs and several RNAi genes are differentially expressed during infection. Pgt induces waves of functionally diversified sRNAs during infection. The early wave sRNAs are predominantly 21 nts with a 5′ uracil derived from genes. In contrast, the late wave sRNAs are mainly 22-nt sRNAs with a 5′ adenine and are strongly induced from centromeric regions. TEs that overlap with late wave sRNAs are more likely to be methylated, both inside and outside the centromeres, and methylated TEs exhibit a silencing effect on nearby genes.ConclusionsWe conclude that rust fungi use an epigenetic silencing pathway that might have similarity with RdDM in plants. The Pgt RNAi machinery and sRNAs are under tight temporal control throughout infection and might ensure genome stability during sporulation.

Wheat stem rust leaf disease detection using image processing

New method for Detection wheat stem rust disease using Image processing methods, Converting RGB image To Hue Saturation Value then setting HSV parameters for background deleting. Texture analyses used for feature extractions. Feature selections where used to accelerate accuracy of detection. Backpropagation neural network used for classifications.

Marker assisted pyramiding of stem rust, leaf rust and powdery mildew resistance genes for durable resistance in wheat (Triticum aestivum L.)

Wheat production is essential for food security. Stem and leaf rust diseases continually pose threat to wheat production. In recent years, climate change and intensive crop cultivation practices are making powdery mildew as a potential threat to wheat production. Deploying resistant cultivars are the most economic, reliable and sustainable way to manage the stem rust, leaf rust and powdery mildew of wheat. Using conventional selection system, it is difficult to select two or more genes in a single genotype. In such a situation, phenotype neutral selection based on marker-trait association along with seedling and adult plant reaction become inevitable. Stem rust, leaf rust and powdery mildew resistance genes, Sr24/Lr24 , Sr26 and Sr36/Pm6 were pyramided in the background of nine Indian wheat cultivars through marker assisted backcross approach. The presence of the rust and powdery mildew resistance genes were confirmed using microsatellite markers such as Sr24#12 ( Sr24/Lr24 ), Sr26#43 ( Sr26 ) and stm773 ( Sr36/Pm6 ) in the pyramided lines. Stable lines were selected at BC 3 F 4 generation. Seedling and adult plant reaction of pyramided lines showed resistance to most of the stem and leaf rust pathotypes prevailing in India. Using gene pyramids ( Sr24/Lr24 , Sr26 and Sr36/Pm6 ) that confer resistance to the predominant pathotypes of stem rust, leaf rust and powdery mildew could impart durability to the cultivars than single gene deployment.

Early growth evaluation and estimation of heritability in a sengon (Falcataria moluccana) progeny testing at Kediri, East Java, Indonesia

Abstract. Nugroho A, Matra DD, Siregar IZ, Haneda NF, Istikorini Y, Rahmawati R, Amin Y, Siregar UJ. 2021. Early growth evaluation and estimation of heritability in a sengon (Falcataria moluccana) progeny testing at Kediri, East Java, Indonesia. Biodiversitas 22: 2728-2736. Sengon (Falcataria moluccana) is widely cultivated as a monoculture plantation in community forests that still poses a high risk of pest and disease attacks. Although plants naturally show signs of resistance, there is still however a lack of understanding on the influence of relative plant resistance on growth due to environmental and genetic factors. This study was aimed to evaluate the early growth of a sengon progeny testing in Kediri, East Java and to estimate the genetic parameters with respect to its resistance and susceptibility to stem borer and rust disease. Progeny test was designed using randomized complete block design (RCBD) with four blocks as replications. Each block consists of 100 families which was grouped into two categories, 50 families for resistant group and 50 families for susceptible group. Observations were made at the age of 0 and 9 months after planting on 9 individuals per plot in each family. Growth characteristics were measured as germination (%), height (m), and diameter (cm). Results indicated that the sengon growth rate from resistant and susceptible plant groups showed a significant difference. Heritability values are classified as moderate, ranging between 0.107 to 0.133 and 0.102 to 0.150 for height and diameter variables, respectively. These information may be used for gradual selection by considering the appropriate intensity.

Identification of Candidate Susceptibility Genes to Puccinia graminis f. sp. tritici in Wheat.

Wheat stem rust disease caused by Puccinia graminis f. sp. tritici (Pgt) is a global threat to wheat production. Fast evolving populations of Pgt limit the efficacy of plant genetic resistance and constrain disease management strategies. Understanding molecular mechanisms that lead to rust infection and disease susceptibility could deliver novel strategies to deploy crop resistance through genetic loss of disease susceptibility. We used comparative transcriptome-based and orthology-guided approaches to characterize gene expression changes associated with Pgt infection in susceptible and resistant Triticum aestivum genotypes as well as the non-host Brachypodium distachyon. We targeted our analysis to genes with differential expression in T. aestivum and genes suppressed or not affected in B. distachyon and report several processes potentially linked to susceptibility to Pgt, such as cell death suppression and impairment of photosynthesis. We complemented our approach with a gene co-expression network analysis to identify wheat targets to deliver resistance to Pgt through removal or modification of putative susceptibility genes.

A semi-dominant NLR allele causes whole-seedling necrosis in wheat.

Programmed cell death (PCD) and apoptosis have key functions in development and disease resistance in diverse organisms; however, the induction of necrosis remains poorly understood. Here, we identified a semi-dominant mutant allele that causes the necrotic death of the entire seedling (DES) of wheat (Triticum aestivum L.) in the absence of any pathogen or external stimulus. Positional cloning of the lethal allele mDES1 revealed that this premature death via necrosis was caused by a point mutation from Asp to Asn at amino acid 441 in a nucleotide-binding leucine-rich repeat protein containing nucleotide-binding domain and leucine-rich repeats. The overexpression of mDES1 triggered necrosis and PCD in transgenic plants. However, transgenic wheat harboring truncated wild-type DES1 proteins produced through gene editing that exhibited no significant developmental defects. The point mutation in mDES1 did not cause changes in this protein in the oligomeric state, but mDES1 failed to interact with replication protein A leading to abnormal mitotic cell division. DES1 is an ortholog of Sr35, which recognizes a Puccinia graminis f. sp. tritici stem rust disease effector in wheat, but mDES1 gained function as a direct inducer of plant death. These findings shed light on the intersection of necrosis, apoptosis, and autoimmunity in plants.

Genome-wide association analysis of Mexican bread wheat landraces for resistance to yellow and stem rust.

Deploying under-utilized landraces in wheat breeding has been advocated to accelerate genetic gains in current era of genomics assisted breeding. Mexican bread wheat landraces (Creole wheats) represent an important resource for the discovery of novel alleles including disease resistance. A core set of 1,098 Mexican landraces was subjected to multi-location testing for rust diseases in India, Mexico and Kenya. The landrace core set showed a continuous variation for yellow (YR) and stem rust (SR) disease severity. Principal component analysis differentiated Mexican landraces into three groups based on their respective collection sites. Linkage disequilibrium (LD) decay varied from 10 to 32 Mb across chromosomes with an averge of 23Mb across whole genome. Genome-wide association analysis revealed marker-trait associations for YR resistance in India and Mexico as well as for SR resistance in Kenya. In addition, significant additive-additive interaction effects were observed for both YR and SR resistance including genomic regions on chromosomes 1BL and 3BS, which co-locate with pleiotropic genes Yr29/Lr46/Sr58/Pm39/Ltn2 and Sr2/Yr30/Lr27, respectively. Study reports novel genomic associations for YR (chromosomes 1AL, 2BS, and 3BL) and SR (chromosomes 2AL, 4DS, and 5DS). The novel findings in Creole wheat landraces can be efficiently utilized for the wheat genetic improvement.

Survey of Major Wheat Diseases in South Eastern Ethiopia

Wheat foliar mainly rusts, and root and foot diseases are important biological constraints to wheat production in Ethiopia especially in Arsi and West Arsi - main wheat belt areas of Ethiopia. Both fungal diseases incurred huge economic losses annually. In 2020 main growing season, assessment was carried out with the stress to ascertain the state of major foliar, root and foot diseases of wheat in Arsi and West Arsi zones of Ethiopia. The assessment result showed yellow rust, septoria leaf blotch and stem rust diseases among foliar; fusarium head blight from spike diseases; eyespot and take all from foot and root were found prevalent. The incidence of foliar diseases viz septoria leaf blotch, yellow and stem rust was 100%, 92.7% and 11.8% respectively. While take all and eyespot were observed 52.4% and 48.5% in the same order. Unlike its incidence, maximum disease severity was caused by yellow rust with higher epidemics on Kubsa and Ogolcho varieties that occupied largest volume in assessed farms. Take- all and eyespots were observed on fields where continuous monocropping is practiced with severity ranges of 0-5 and 0-3 respectively. Thus, it is advisable that much works are needed to train producers to use up-to-date released wheat varieties in order to reduce rust diseases and conduct crop rotation and residue management for the control of foot and root diseases thereby decline associated yield losses.

Losses Caused by Stem Rust (<i>Puccinia graminis</i> f.sp. <i>tritici</i>) on Durum Wheat in Ethiopia

Stem rust caused by <i>Puccinia graminis</i> f.sp. <i>tritici</i> is one of the major biotic constraints of wheat production. The disease may cause substantial quantitative and qualitative yield losses but much of the work in Ethiopia on this pathosystem focuses on quantitative yield loss of durum wheat. This work was carried out at Debre Zeit Agriculture Research Centre during 2015/16 and 2016/17 main and off seasons. Hence the current study was conducted with the objectives to quantify the amount of loss in grain yield due to stem rust and assess the relationship between disease parameters, grain yield and physical quality parameters of improved durum wheat varieties grown in Ethiopia. Artificial inoculation was performed using a mixture of different dominant stem rust races. There were treated and untreated plots by fungicide that serves as protected and unprotected plots, respectively. Disease severity was recorded each 10 days interval and area under disease progress curve (AUDPC), terminal severity and coefficient of infection were calculated. The tested cultivars exhibited different disease severity level, having the mean value of 6.7-76%. High values of area under disease progress curve (AUDPC) were detected on Hitossa, Utuba (1225.7, 585.9). Whereas the lowest values of yield loss were recorded on cvs. Mangudo and Utuba having the mean value of yield loss 40.2 and 44.8%, respectively. The highest yield loss was observed on susceptible variety Hitosa showing the mean value of 70%. Correlation coefficients were tested between yield losses and values of AUDPC, final stem rust severity, coefficient of infection and rate of infection of the tested cultivars. There was strong correlation coefficients among disease parameters (r=0.72-0.99). There was also moderate strong negative correlation coefficient among disease parameters and yield, hectoliter weight and 1000-kernel weight of the test cultivars (r=-0.53 to -0.81). The current study indicated that application of Rex Duo can be used in minimizing yield losses caused by stem rust disease of durum wheat. Therefore, supporting the released durum wheat cultivars with fungicide application is the most pertinent issue in Ethiopia as most of the durum wheat cultivars in farmers hand were moderately susceptible to susceptible cultivars Pgt races.

Evaluation of Bread Wheat Genotypes for Adult Plant Resistance to Stem Rust

Wheat stem rust ( Puccinia graminis f. sp tritici ) also known as 'polio of agriculture' is a ravaging disease of wheat ( Triticum aestivum L.) making it a foremost confront to wheat production in Ethiopia and other wheat producing countries of the world due to the frequently evolving of virulent pathogen races. Because of this, searching novel genes in wheat genotypes is a critical issue. Twenty eight advanced bread wheat genotypes were evaluated for their response against stem rust caused by Puccinia graminise under field conditions at Kulumsa and Asassa during 2018 main growing season. Evaluation was carried out through disease assessment including terminal stem rust severity (TRS) and coefficient of infection (ACI) under natural infection. Twenty two wheat genotypes viz; ETBW-8858, ETBW-8870, ETBW-8583, ETBW-8684, ETBW-9548, ETBW-9549, ETBW-9554, ETBW-9558, ETBW-9559, ETBW-9560, ETBW-8751, ETBW-8862, ETBW-8804, ETBW-8896, ETBW-8991, ETBW-9560, ETBW-9556, ETBW-9486, ETBW-9561, ETBW-9550, ETBW-9553 and ETBW-9555 out of twenty-eight evaluated genotypes were discovered to be adult plant resistant (TRS &lt; 30 and ACI &lt; 20 ) to stem rust disease at both screening sites. Therefore, these genotypes with high stem rust resistance could be backcrossed to widely acclimatized and high yielding but susceptible Ethiopian wheat varieties to prevent further wheat yield declines. However, may need to evaluate for seedling response to confirm whether the genotypes are true adult plant resistant. Keywords: Adult plant, Puccinia graminis, Stem rust, TRS, Wheat genotypes. DOI: 10.7176/JBAH/10-23-05 Publication date: December 31 st 2020