Leaf Rust Infection Research Articles

Temporal Transcriptional Changes in SAR and Sugar Transport-Related Genes During Wheat and Leaf Rust Pathogen Interactions

Leaf rust (Puccinia triticina Erikss.) is one of the most damaging pathogens of wheat (Triticum aestivum L.). With the rapid evolution of new races, worldwide distribution, and high genetic diversity, P. triticina has the ability to cause severe epidemics in wheat growing areas. In plants, salicylic acid (SA) and sugar-mediated defense pathways are expected to provide durable and broad-spectrum resistance. To understand the role of SA and sugar-mediated resistance mechanisms in wheat during early leaf rust infection, expression profiles of the key regulators of SA (TaEDS1, TaPAD4, TaNDR1, TaRAR1, TaSGT1, TaHSP90, TaEDS5, TaPAL, and TaNPR1) and sugar (TaHTP, TaSTP13A) pathways were analyzed in time-course experiments between two wheat near-isogenic lines (NILs) differing in the leaf rust resistance gene, Lr24. The quantification of candidate gene expression using reverse transcription quantitative real-time PCR at different time points post inoculation showed stage-specific transcriptional reprogramming between compatible and incompatible interactions. Interestingly, two distinct expression patterns were observed between two types of interactions. The genes acting upstream of SA in the SA pathway (TaEDS1, TaPAD4, TaNDR1, TaRAR1, TaSGT1, TaHSP90, TaEDS5) showed strong expressions at a later stage [48 h post inoculation (hpi)] of leaf rust infection in the compatible interaction compared to unchanged or slightly changed expressions in the incompatible interaction. Further, these genes showed similar expression patterns in either of the interactions, suggesting their cooperative or coordinated functions. On the other hand, the genes involved in SA biosynthesis (TaPAL), SA downstream signaling (TaNPR1), and sugar transportation (TaHTP, TaSTP13A) showed a strong expression at mid phase of infection between 6 and 24 hpi in the incompatible interaction compared to the compatible interaction. These expression patterns suggest that TaPAL and TaNPR1 play a positive regulatory role in the SA-mediated resistance pathway whereas TaHTP (Lr67) plays an important role in the sugar-mediated resistance pathway activated by the leaf rust resistance gene, Lr24.

Host-induced silencing of essential genes in Puccinia triticina through transgenic expression of RNAi sequences reduces severity of leaf rust infection in wheat.

SummaryLeaf rust, caused by the pathogenic fungus Puccinia triticina (Pt), is one of the most serious biotic threats to sustainable wheat production worldwide. This obligate biotrophic pathogen is prevalent worldwide and is known for rapid adaptive evolution to overcome resistant wheat varieties. Novel disease control approaches are therefore required to minimize the yield losses caused by Pt. Having shown previously the potential of host‐delivered RNA interference (HD‐RNAi) in functional screening of Pt genes involved in pathogenesis, we here evaluated the use of this technology in transgenic wheat plants as a method to achieve protection against wheat leaf rust (WLR) infection. Stable expression of hairpin RNAi constructs with sequence homology to Pt MAP‐kinase (PtMAPK1) or a cyclophilin (PtCYC1) encoding gene in susceptible wheat plants showed efficient silencing of the corresponding genes in the interacting fungus resulting in disease resistance throughout the T2 generation. Inhibition of Pt proliferation in transgenic lines by in planta‐induced RNAi was associated with significant reduction in target fungal transcript abundance and reduced fungal biomass accumulation in highly resistant plants. Disease protection was correlated with the presence of siRNA molecules specific to targeted fungal genes in the transgenic lines harbouring the complementary HD‐RNAi construct. This work demonstrates that generating transgenic wheat plants expressing RNAi‐inducing transgenes to silence essential genes in rust fungi can provide effective disease resistance, thus opening an alternative way for developing rust‐resistant crops.

Novel treatment options for ectopic pregnancy: the effects of gonadotrophin releasing hormone receptor antagonists on trophoblast function

ROP is a subfamily of small GTP-binding proteins that uniquely exist in plants. It acts as versatile molecular switches that regulate various developmental processes. Some ROP proteins are also reported to affect defense responses, although their exact mechanism is not fully understood. Herein, ROP members in wheat were mined; the functions of three wheat ROP proteins were studied. RT-PCR results showed that the expression of TaRac1 was rapidly and strongly induced after leaf rust infection. TaRac1 interacted with TaCCR in yeast-hybridization assay. The overexpression of TaRac1 in tobacco promoted CCR and CAD gene expression, increased the total lignin content and sinapyl lignin proportion, and then enhanced resistance to tobacco black shank and bacterial wilt diseases. In contrast, TaRac3 and TaRac4 did not show to interact with TaCCR. Furthermore, the overexpression of TaRac3 and TaRac4 did not increase lignin gene expression and lignin accumulation either. Unlike TaRac1, the overexpression of TaRac3 increased susceptibility to both black shank and bacterial wilt pathogens, while overexpression of TaRac4 showed no effect on disease resistance but promoted the root growth in tobacco seedling. These data collectively suggest that TaRac1 in Group II is mainly involved in regulating lignin metabolism which, in turn, responsible for the observed roles in pathogen resistance. TaRac3 and TaRac4 have the minor roles in defense response but may act on regulation in plant developmental processes. These results shed light on the complexity and diverse function of ROP in plant defense pathway.

The expression of podoplanin in the placenta of HIV associated pre-eclampsia

ROP is a subfamily of small GTP-binding proteins that uniquely exist in plants. It acts as versatile molecular switches that regulate various developmental processes. Some ROP proteins are also reported to affect defense responses, although their exact mechanism is not fully understood. Herein, ROP members in wheat were mined; the functions of three wheat ROP proteins were studied. RT-PCR results showed that the expression of TaRac1 was rapidly and strongly induced after leaf rust infection. TaRac1 interacted with TaCCR in yeast-hybridization assay. The overexpression of TaRac1 in tobacco promoted CCR and CAD gene expression, increased the total lignin content and sinapyl lignin proportion, and then enhanced resistance to tobacco black shank and bacterial wilt diseases. In contrast, TaRac3 and TaRac4 did not show to interact with TaCCR. Furthermore, the overexpression of TaRac3 and TaRac4 did not increase lignin gene expression and lignin accumulation either. Unlike TaRac1, the overexpression of TaRac3 increased susceptibility to both black shank and bacterial wilt pathogens, while overexpression of TaRac4 showed no effect on disease resistance but promoted the root growth in tobacco seedling. These data collectively suggest that TaRac1 in Group II is mainly involved in regulating lignin metabolism which, in turn, responsible for the observed roles in pathogen resistance. TaRac3 and TaRac4 have the minor roles in defense response but may act on regulation in plant developmental processes. These results shed light on the complexity and diverse function of ROP in plant defense pathway.

Overexpression of AtGolS3 and CsRFS in poplar enhances ROS tolerance and represses defense response to leaf rust disease.

Plants respond to pathogens through an orchestration of signaling events that coordinate modifications to transcriptional profiles and physiological processes. Resistance to necrotrophic pathogens often requires jasmonic acid, which antagonizes the salicylic acid dependent biotrophic defense response. Recently, myo-inositol has been shown to negatively impact salicylic acid (SA) levels and signaling, while galactinol enhances jasmonic acid (JA)-dependent induced systemic resistance to necrotrophic pathogens. To investigate the function of these compounds in biotrophic pathogen defense, we characterized the defense response of Populus alba × grandidentata overexpressing Arabidopsis GALACTINOL SYNTHASE3 (AtGolS) and Cucumber sativus RAFFINOSE SYNTHASE (CsRFS) challenged with Melampsora aecidiodes, a causative agent of poplar leaf rust disease. Relative to wild-type leaves, the overexpression of AtGolS3 and CsRFS increased accumulation of galactinol and raffinose and led to increased leaf rust infection. During the resistance response, inoculated wild-type leaves displayed reduced levels of galactinol and repressed transcript abundance of two endogenous GolS genes compared to un-inoculated wild-type leaves prior to the up-regulation of NON-EXPRESSOR OF PR1 and PATHOGENESIS-RELATED1. Transcriptome analysis and qRT-PCR validation also revealed the repression of genes participating in calcium influx, phosphatidic acid biosynthesis and signaling, and salicylic acid signaling in the transgenic lines. In contrast, enhanced tolerance to H2O2 and up-regulation of antioxidant biosynthesis genes were exhibited in the overexpression lines. Thus, we conclude that overexpression of AtGolS and CsRFS antagonizes the defense response to poplar leaf rust disease through repressing reactive oxygen species and attenuating calcium and phosphatidic acid signaling events that lead to SA defense.

Effect of Insect Feeding, Pathogen Infection, and Heat Stress on Antioxidant Properties of Wheat Bran

The potential of hard winter wheat (Triticum aestivum L) to produce antioxidant‐rich crops has been considered as a value addition strategy to increase farm profitability, but the inherent variability in phenolics concentrations in wheat crops is a barrier. This problem also makes marketing the health‐promoting benefits of whole wheat products difficult. Although some variability is explained by genetic diversity, a significant portion is owing to stress factors such as elevated temperatures, fungal attack, and insect damage. Limited information is available on formal trials designed to investigate these relationships. In this study, wheat (Triticum aestivum L) cultivar Karl 92 was stressed by bird‐cherry oat aphid (Rhopalosiphum padi) feeding, leaf rust (Puccinia triticina) infection, and postanthesis high‐temperature stress. Total phenolic content (TPC) and 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity (%DPPH) of the resulting wheat bran and those of nonstressed plants were measured. Plant fitness parameters such as the number of spikes and grain yield were also evaluated. Heat‐stressed plants had the lowest number of spikes (P < 0.0151), shriveled kernels, and lowest TPC and %DPPH in wheat bran‐free (P < 0.0633, P < 0.0048) and bound (P < 0.0003, P < 0.0009) phenolic extracts. Aphid feeding explained some of the variation in TPC (P < 0.0719) and %DPPH (P < 0.0038) of free phenolic extracts, so this stress factor has potential to produce antioxidant‐rich wheat bran. Rust infection did not change the antioxidant concentration on the bran, but it showed potential to produce wheat crops with high phenolics per acreage due to high grain yield (P ≤ 0.0821).

EFFECT OF LEAF RUST DISEASE ON VARIOUS MORPHO-PHYSIOLOGICAL AND YIELD ATTRIBUTES IN BREAD WHEAT

Leaf rust of wheat caused by Puccinia triticina is one of the most important diseases in the Pakistan and cause both yield and quality reduction. To investigate the effect of leaf rust of wheat on morph-physiological processes and grain yield, a field experiment was conducted using different wheat lines and varieties. The morpho-physiological attributes of the infected plant leaves were badly affected by the infection of leaf rust of wheat. The experiment comprised two treatments, one was inoculated with leaf rust spores manually and Morocco as a spreader while other keeping as a control. The results showed that there was -42.92, -23.72, -23.01, and -11.42, % decrease in chlorophyll content, flag leaf area, specific flag leaf area and relative water content in leaf rust (diseased) plot respectively while 21.24, 160.16% increase in relative dry weight and relative membrane permeability in the leaf rust plot. The results also revealed that leaf rust of wheat also reduces the yield components like number of grains per spike, spike length and 1000 grain weight (-52.38, -43.37 and -45.50 respectively). Thus, it could be concluded that leaf rust of wheat affect the morph-physiological process of wheat plants and badly reduce the yield as well.

Wheat ROP proteins modulate defense response through lignin metabolism

ROP is a subfamily of small GTP-binding proteins that uniquely exist in plants. It acts as versatile molecular switches that regulate various developmental processes. Some ROP proteins are also reported to affect defense responses, although their exact mechanism is not fully understood. Herein, ROP members in wheat were mined; the functions of three wheat ROP proteins were studied. RT-PCR results showed that the expression of TaRac1 was rapidly and strongly induced after leaf rust infection. TaRac1 interacted with TaCCR in yeast-hybridization assay. The overexpression of TaRac1 in tobacco promoted CCR and CAD gene expression, increased the total lignin content and sinapyl lignin proportion, and then enhanced resistance to tobacco black shank and bacterial wilt diseases. In contrast, TaRac3 and TaRac4 did not show to interact with TaCCR. Furthermore, the overexpression of TaRac3 and TaRac4 did not increase lignin gene expression and lignin accumulation either. Unlike TaRac1, the overexpression of TaRac3 increased susceptibility to both black shank and bacterial wilt pathogens, while overexpression of TaRac4 showed no effect on disease resistance but promoted the root growth in tobacco seedling. These data collectively suggest that TaRac1 in Group II is mainly involved in regulating lignin metabolism which, in turn, responsible for the observed roles in pathogen resistance. TaRac3 and TaRac4 have the minor roles in defense response but may act on regulation in plant developmental processes. These results shed light on the complexity and diverse function of ROP in plant defense pathway.

Leaf rust infection reduces herbivore-induced volatile emission in black poplar and attracts a generalist herbivore.

Plants release complex volatile blends after separate attack by herbivores and pathogens, which play many roles in interactions with other organisms. Large perennials are often attacked by multiple enemies, but the effect of combined attacks on volatile emission is rarely studied, particularly in trees. We infested Populus nigra trees with a pathogen, the rust fungus Melampsora larici-populina, and Lymantria dispar caterpillars alone and in combination. We investigated poplar volatile emission and its regulation, as well as the behavior of the caterpillars towards volatiles from rust-infected and uninfected trees. Both the rust fungus and the caterpillars alone induced volatile emission from poplar trees. However, the herbivore-induced volatile emission was significantly reduced when trees were under combined attack by the herbivore and the fungus. Herbivory induced terpene synthase transcripts as well as jasmonate concentrations, but these increases were suppressed when the tree was additionally infected with rust. Caterpillars preferred volatiles from rust-infected over uninfected trees. Our results suggest a defense hormone crosstalk upon combined herbivore-pathogen attack in poplar trees which results in lowered emission of herbivore-induced volatiles. This influences the preference of herbivores, and might have other far-reaching consequences for the insect and pathogen communities in natural poplar forests.

Genome-wide identification and characterization of NB-ARC resistant genes in wheat (Triticum aestivum L.) and their expression during leaf rust infection

NB-ARC domain-containing resistance genes from the wheat genome were identified, characterized and localized on chromosome arms that displayed differential yet positive response during incompatible and compatible leaf rust interactions. Wheat (Triticum aestivum L.) is an important cereal crop; however, its production is affected severely by numerous diseases including rusts. An efficient, cost-effective and ecologically viable approach to control pathogens is through host resistance. In wheat, high numbers of resistance loci are present but only few have been identified and cloned. A comprehensive analysis of the NB-ARC-containing genes in complete wheat genome was accomplished in this study. Complete NB-ARC encoding genes were mined from the Ensembl Plants database to predict 604 NB-ARC containing sequences using the HMM approach. Genome-wide analysis of orthologous clusters in the NB-ARC-containing sequences of wheat and other members of the Poaceae family revealed maximum homology with Oryza sativa indica and Brachypodium distachyon. The identification of overlap between orthologous clusters enabled the elucidation of the function and evolution of resistance proteins. The distributions of the NB-ARC domain-containing sequences were found to be balanced among the three wheat sub-genomes. Wheat chromosome arms 4AL and 7BL had the most NB-ARC domain-containing contigs. The spatio-temporal expression profiling studies exemplified the positive role of these genes in resistant and susceptible wheat plants during incompatible and compatible interaction in response to the leaf rust pathogen Puccinia triticina. Two NB-ARC domain-containing sequences were modelled in silico, cloned and sequenced to analyze their fine structures. The data obtained in this study will augment isolation, characterization and application NB-ARC resistance genes in marker-assisted selection based breeding programs for improving rust resistance in wheat.

REDUCTION IN GRAIN YIELD CAUSED BY LEAF RUST INFECTION IN SEVEN EGYPTIAN WHEAT CULTIVARS

Leaf rust caused by Puccinia triticina, is the most a widespread foliar disease of wheat in Egypt and worldwide. Yield losses of seven wheat cultivars as affected by leaf rust infection were estimated under field conditions at El-Nubariya Agricultural Research Station, during 2013/14 and 2014/15 growing seasons. Disease severity (%) was recorded (seven days intervals),and each of final rust severity(%) area under disease progress curve (AUDPC) was calculated for the tested cultivars. Final rust severity (%) ranged from 10 % to 90 % in 2013/14 growing season, while it was ranged from in 20 % to 80 %.2014/15. Also, area under disease progress curve (AUDPC) ranged from 101.50 to 1330.0 in 2013/14 growing season, but it was ranged from 185.50 to 1225 during 2014/15 season. The losses grain yield per plot ranged from 3.89% to 32.9 during 2013/14 growing season 5 % on the check variety Giza 139.Likewise, loss in 1000 kerne weigh ranged from 3.54% to 31.24% in 2013/14 from 4.65% to 28.49% in 2014/15, relevant to the two cvs.,sids-12 and Giza139 (check variety) ,respectively. Moreover, yield losses of the other tested cultivars were in between depends on the percentages of rust severity and AUDPC values for each. While, during 2014/15 yield losses per plot ranged from 4.81 % in the wheat cultivar Sids 12 to 28.21 % in the check variety Giza 139. The amount of losses in 1000 kernel weight and plot weight were positively correlated with area under disease progress curve, which means that high levels of has-genetic resistance are needed to reduce or avoid a significant yield loss.

Assessment of Wheat Diseases in South Omo Zone of Ethiopia

Wheat is one of the most important cereal cultivated in Ethiopia. It ranks fourth after Teff (Eragrostis tef), Maize (Zea mays) and Sorghum (Sorghum bicolor) in area coverage and third in total production. But, its production and productivity is prone to divers biotic and abiotic factors. Among biotic factor diseases are the one. But, the relative importance of each disease across locations has not been known and well profiled to develop sound management strategy in the studied areas. So, the assessment was done to watch and monitor the status of wheat diseases and observe wheat varieties response to wheat diseases and to determine the prevalence of new virulence races and monitor new stem rust race (ug99) spread in the region. The assessment was carried out in two kebeles of South Ari districts of South Omo zone i.e. Senegal and Senmamer kebeles of South Ari woreda in 2014 Meher cropping season. Results indicated that the highest mean infection of leaf rust (70%) was recorded on local variety at Senmamer kebele followed by Digalo variety in Senegal kebele which is 65% and fusarium head blight (47%) on Huluka variety followed by ETBW5890 variety which is 40% were recorded at Senegal kebele. Whereas at Senegal kebele 30% fusarium head blight was recorded as the highest mean infection. Whereas the mean infection of powdery mildew is 20% at Senmamer kebele which is less as compared to mean infection of leaf rust and fusarium head blight. Different studies reported that wheat is affected by different diseases. The current assessment indicated that complex diseases exists in different wheat varieties and their occurrence across kebeles was highly variable. In addition to introduction and promotion of different management practices, holistic and cumulative integrated approach is required to manage the complex wheat diseases in the studied areas.

Вплив щавлевої кислоти та нітропрусиду натрію на продуктивність і стійкість озимої пшениці до збудників септоріозу та бурої іржі

Вплив щавлевої кислоти та нітропрусиду натрію на продуктивність і стійкість озимої пшениці до збудників септоріозу та бурої іржі

Separability of coffee leaf rust infection levels with machine learning methods at Sentinel-2 MSI spectral resolutions

Coffee leaf rust (CLR) caused by the fungus Hemileia vastarix is a devastating disease in almost all coffee producing countries and remote sensing approaches have the potential to monitor the disease. This study evaluated the potential of Sentinel-2 band settings for discriminating CLR infection levels at leaf levels. Field spectra were resampled to the band settings of the Sentinel-2, and evaluated using the random forest (RF) and partial least squares discriminant analysis (PLS-DA) algorithms with and without variable optimization. Using all variables, Sentinel-2 Multispectral Imager (MSI)-derived vegetation indices achieved higher overall accuracy of 76.2% when compared to 69.8% obtained using raw spectral bands. Using the RF out-of-bag (OOB) scores, 4 spectral bands and 7 vegetation indices were identified as important variables in CLR discrimination. Using the PLS-DA Variable Importance in Projection (VIP) score, 3 Sentinel-2 spectral bands (B4, B6 and B5) and 5 vegetation indices were found to be important variables. Use of the identified variables improved the CLR discrimination accuracies to 79.4 and 82.5% for spectral bands and indices respectively when discriminated with the RF. Discrimination accuracy slightly increased through variable optimization for PLS-DA using spectral bands (63.5%) and vegetation indices (71.4%). Overall, this study showed the potential of the Sentinel 2 MSI band settings for CLR discrimination as part of crop condition assessment. Nevertheless further studies are required under field conditions.

Genome-wide identification, cloning and characterization of SNARE genes in bread wheat (Triticum aestivum L.) and their response to leaf rust

SNAREs (soluble N-ethylmaleimide sensitive factor adaptor protein receptors) are small polypeptides characterized by a particular domain called the SNARE motif. Compared with the genome of other eukaryotes, monocotyledonous and dicotyledonous plants have more SNAREs indicating their important roles in higher plant species. Higher plants have the capability to form SNARE complexes that are important in determining the precise process of vesicle fusion for intracellular trafficking pathways. SNAREs have been reported to be engaged in the delivery of cell wall precursors to the newly formed cell plate during cytokinesis. The role of SNARE genes in response to plant-pathogen interaction is still not well understood. We found 35 SNARE genes in the wheat genome using a Hidden Markov Model. In this study with combined usage of in silico and molecular cloning technologies, we identified and characterized three SNARE genes (SNARE3, SNARE5 and SNARE6). The deduced amino acid sequences of these SNARE genes contained two characteristic conserved domains – a SNARE motif and a transmembrane domain, and they showed a high degree of homology with other eukaryotic SNARE genes. Phylogenetic analysis and three dimensional structures built with the help of Modeller software confirmed the presence of SNARE motifs in the proteins. The spatio-temporal expression profiling studies exemplify the positive role of SNARE transcripts have in resistant and susceptible wheat plants during incompatible and compatible interaction respectively, in response to Puccinia triticina induced leaf-rust infection. Taken together, our study suggests a role for SNARE genes in vesicle mediated resistance to leaf rust in wheat.

Efficacy of plant extracts in controlling wheat leaf rust disease caused by Puccinia triticina

The efficacy of eight plant extracts (garlic, clove, garden quinine, Brazilian pepper, anthi mandhaari, black cumin, white cedar and neem) in controlling leaf rust disease of wheat was investigated in vitro and in vivo. In vitro, all treatments inhibited spore germination by more than 93%. Neem extract recorded 98.99% inhibition of spore germination with no significant difference from the fungicide Sumi-8 (100%). Under greenhouse conditions, seed soaking application in neem extract (at concentration of 2ml/L) resulted in 36.82% reduction in the number of pustules/leaf compared with the untreated control. Foliar spraying of plant extracts on wheat seedlings decreased the number of pustules/leaf. Foliar spraying of plant extracts four days after inoculation led to the highest resistance response of wheat plants against leaf rust pathogen. Spray application of wheat seedlings with neem, clove and garden quinine extracts, four days after inoculation with leaf rust pathogen completely prevented rust development (100% disease control) and was comparable with the fungicide Sumi-8. Foliar spray application of wheat plants at mature stage with all plant extracts has significantly reduced the leaf rust infection (average coefficient of infection, ACI) compared with the untreated control and neem was the most effective treatment. This was reflected on grain yield components, whereas the 1000-kernel weight and the test weight were improved whether under one- or two-spray applications, with two-spray application being more effective in this regard. Thus, it could be concluded that plant extracts may be useful to control leaf rust disease in Egypt as a safe alternative option to chemical fungicides.

Autophagy is induced in haustorial mother cells of Puccinia triticina and is necessary for plant infection

Autophagy is a highly conserved pathway that mediates bulk degradation of cellular components in lysosomes/vacuoles and plays an important role in filamentous fungi by impacting growth, morphology and development. However, in leaf rust, the role of autophagy is poorly understood. In this study, we identified the structure of autophagy in leaf rust infection structures by using transmission electron microscopy (TEM). The results suggest that autophagy can be strongly induced in the haustorium mother cell (HMC) but did not occur in other special infection structures, such as the appressorium, substomatal vesicle and haustorial. Applying the autophagy inhibitor 3-mehyladenine (3-MA) to leaf rust resulted in significant arrest of mycelial growth and delays in leaf rust infection. These results suggest that autophagy can be induced in HMC and is important for fungal infection of wheat. This research will help us to expand our understanding of the physiological functions of autophagy in filamentous fungi.

Оценка экологической пластичности и устойчивости к бурой ржавчине интрогрессивных линий мягкой пшеницы с генами <i>Agropyron elongatum</i>

Сборы зерна пшеницы могут быть повышены за счет использования в производстве устойчивых к болезням и экологически пластичных сортов. Перспективным источником генов устойчивости к абиотическим и биотическим стрессовым факторам является пырей удлиненный Agropyron elongatum (Host.) Beauv. В статье представлены результаты испытания 11 интрогрессивных линий с генами Ag. elongatum и сортов яровой мягкой пшеницы на устойчивость к бурой ржавчине и экологическую пластичность. Эксперименты проводили в лесостепной зоне юга Западной Сибири (Омск) на ежегодном естественном фоне бурой ржавчины. В 2013 и 2014 гг. в регионе отмечена жесткая засуха с большими перепадами температур, а в 2015 г. условия были благоприятны для роста и развития растений. В период наблюдений устойчивость к бурой ржавчине двух интрогрессивных линий с генами Ag. elongatum была преодолена, но шесть линий проявили иммунитет или высокую устойчивость к болезни, резистентность остальных была нестабильна. Контрастные условия среды позволили оценить экологическую пластичность материала. Три устойчивые к бурой ржавчине линии проявили экологическую пластичность в сочетании со стабильной продуктивностью в условиях засухи и при сильных колебаниях температуры, их показатели находились на уровне адаптированных к зоне сортов местной селекции. Эти линии показали продуктивность выше стандартов, а по длине вегетационного периода относились к среднепоздней или позднеспелой группам. Данные линии представляют ценный материал для селекции пшеницы на устойчивость к бурой ржавчине и экологическую пластичность.

EFFECT OF LEAF RUST INFECTION ON YIELD AND TECHNICAL PROPERTIES IN GRAINS OF SOME EGYPTIAN WHEAT CULTIVARS

Wheat leaf rust disease, caused by Puccinia triticina f. sp. tritici, is one of the most important wheat diseases in Egypt and worldwide. In the present study, Four epidemiological parameters; final rust severity (%), area under disease progress curve (AUDPC), relative area under disease progress curve (rAUDPC) and rate of disease increase (r-value) and technical properties were estimated for seven Egyptian bread wheat cultivars. The highest percentages of final rust severity (FRS), the highest values of area under disease progress curve (AUDPC), the highest values of relative area under disease progress curve (rAUDPC) and the highest rates of disease increase (r-value) were recorded with the cvs.; Gemmeiza-7, Gemmeiza-11 and Sids-1 during 2014/15 and 2015/16 growing seasons. Accordingly, they recorded high loss (%) in 1000 kernel weight, yield/feddan and Egyptian pound (LE). There were a positive relations between the four parameters under study and loss (%) of yield/feddan, where the relation between FRS (%) and loss (%) of yield/feddan was the strongest (R2 = 0.994). Therefore, the loss (%) of yield/feddan could be predicted from FRS (%). Whereas, there were negative relations between FRS (%) and each of 1000 kernel weight and yield/feddan of the infected wheat cultivars during the two successive seasons. As for, the physical properties, the protected plots of wheat cultivars under study recorded the highest values in the hectoliter and flour extraction comparing to the infected plots of the same cultivars. On the other hand, protein and ash contents increased in the flour of infected wheat cultivars compared with the flour of the same protected ones. Also, farinograph parameters of dough improved slightly for infected cultivars, where values of water absorption and stability time showed little increase, compared with the same protected wheat cultivars. Accordingly, baking quality and sensory of balady bread made from the flour of protected and infected wheat cultivars were slightly increased in layers separation, crumb texture and odor bread. Thus, it could be concluded that the leaf rust infection, negatively affected both grain quality and quantity of wheat cultivars under study.

Effect of Lr34/Yr18 on agronomic and quality traits in a spring wheat mapping population and implications for breeding

The locus Lr34/Yr18 plays an important role in conferring resistance to a number of fungal diseases and is thus an important component of global wheat breeding efforts. We investigated the differences in disease response and agronomic traits of the ‘CDC Teal’ × ‘CDC Go’ spring wheat population of 187 recombinant inbred lines (RILs) in relation to the presence/absence of the rust resistance gene Lr34/Yr18. Lines carrying the resistant allele of Lr34/Yr18 were taller, matured earlier, and yielded less grain with lower test weights than lines without Lr34/Yr18. Lines with or without the resistant allele of Lr34/Yr18 did not differ for grain protein content, SDS sedimentation volume, and for resistance to leaf spotting and common bunt. Lines with Lr34/Yr18 exhibited lower leaf and stripe rust infection than lines without it. We selected superior lines from the population based on high yield, protein content, SDS sedimentation, and the presence of the resistant allele of Lr34/Yr18 and grew them with continued selection in replicated yield trials over nine site-years. We attempted to combine Lr34/Yr18 with high yield, protein content, and SDS sedimentation suitable for the Canadian western red spring wheat class. Our results suggested that the population size we used was not large enough to obtain recombinants with high yield potential, high grain protein, and acceptable quality attributes. Moreover, selection for Lr34/Yr18 resulted in the elimination of lines with high yield potential. We therefore suggest using a population size of at least 310 to increase the potential of pooling Lr34/Yr18 with high grain yield and desirable agronomic and end-use quality attributes.