Puccinia Triticina Research Articles

Assessment of Wheat Foliar Rust Infestations in the Upper, Middle, and Lower Pothwar Regions of Punjab, Pakistan

In the present study, the incidence and severity of yellow rust and brown rust in different regions of Pothwar have been studied. The lower Pothwar region (Jhelum) had the highest incidence of brown rust with a prevalence of 54.3%, while Rawalpindi had the highest incidence of yellow rust in the upper region with a prevalence of 26.8%. In the middle region (Attock), brown rust incidence was the lowest with a prevalence of 4.6%. The severity of both rusts varied among locations, with some locations experiencing severe outbreaks while others had little or no incidence. The highest incidence of both rusts was observed in Harrial for yellow rust (90%) and Balla for brown rust (100%). The severity of rusts ranged from Resistant to Moderately Susceptible. The study examined the yield attributes of wheat crops in the Upper, Middle, and Lower Pothwar regions of Pakistan. The results showed that Rawalpindi district had the highest crop yield, while Jhelum had the lowest. The study also found a correlation between disease incidence and various environmental factors such as temperature, humidity, precipitation, tillers per meter length, tillers per meter square, number of grains per spike, and grain weight. Yellow rust had a strong correlation with humidity, tillers per meter square, and grain weight, while brown rust showed a strong correlation with temperature, precipitation, and humidity. The study highlights the importance of understanding the relationship between environmental factors and crop yield to ensure food security.

Genetic mapping of the wheat leaf rust resistance gene Lr19 and development of translocation lines to break its linkage with yellow pigment.

The leaf rust resistance gene Lr19, which is present on the long arm of chromosome 7E1 in Thinopyrum ponticum, was mapped within a 0.3-cM genetic interval, and translocation lines were developed to break its linkage with yellow pigmentation The leaf rust resistance locus Lr19, which was transferred to wheat (Triticum aestivum) from its relative Thinopyrum ponticum in 1966, still confers broad resistance to most known races of the leaf rust pathogen Puccinia triticina (Pt) worldwide. However, this gene has not previously been fine-mapped, and its tight linkage with a gene causing yellow pigmentation has limited its application in bread wheat breeding. In this study, we genetically mapped Lr19 using a bi-parental population from a cross of two wheat-Th. ponticum substitution lines, the Lr19-carrying line 7E1(7D) and the leaf rust-susceptible line 7E2(7D). Genetic analysis of the F2 population and the F2:3 families showed that Lr19 was a single dominant gene. Genetic markers allowed the gene to be mapped within a 0.3-cM interval on the long arm of Th. ponticum chromosome 7E1, flanked by markers XsdauK3734 and XsdauK2839. To reduce the size of the Th. ponticum chromosome segment carrying Lr19, the Chinese Spring Ph1b mutant was employed to promote recombination between the homoeologous chromosomes of the wheat chromosome 7D and the Th. ponticum chromosome 7E1. Two translocation lines with short Th. ponticum chromosome fragments carrying Lr19 were identified using the genetic markers closely linked to Lr19. Both translocation lines were resistant to 16 Pt races collected throughout China. Importantly, the linkage between Lr19 and yellow pigment content was broken in one of the lines. Thus, the Lr19 linked markers and translocation lines developed in this study are valuable resources in marker-assisted selection as part of common wheat breeding programs.

Genetic mapping of the wheat leaf rust resistance gene Lr2a and its importance in Canadian wheat cultivars.

Leaf rust resistance gene Lr2a was located to chromosome arm 2DS in three mapping populations, which will facilitate map-based cloning and marker-assisted selection of Lr2a in wheat breeding programs. Incorporating effective leaf rust resistance (Lr) genes into high-yielding wheat cultivars has been an efficient method of disease control. One of the most widely used genes in Canada is the multi-allelic resistance gene Lr2, with alleles Lr2a, Lr2b, Lr2c, and Lr2d. The Lr2a allele confers complete resistance to a large portion of the Puccinia triticina (Pt) population in Canada. In this study, Lr2a was genetically mapped in two doubled haploid populations developed from the crosses Superb/BW278 and Superb/86ISMN 2137, and an F2 population developed from the cross Chinese Spring/RL6016. Seedlings were tested with the Lr2a avirulent Pt races 74-2 MGBJ (Superb/BW278) and 12-3 MBDS (Superb/86ISMN 2137 and Chinese Spring/RL6016) in greenhouse assays and were genotyped with 90K wheat Infinium SNP and kompetitive allele-specific PCR (KASP) markers. Lr2a was mapped to a collinear position on chromosome arm 2DS in all three populations, within a 1.00cM genetic interval between KASP markers kwm1620 and kwm1623. This corresponded to a 305kb genomic region of chromosome 2D in Chinese Spring RefSeq v2.1. The KASP marker kwh740 was predictive of Lr2a in all mapping populations. A panel of 260 wheats were tested with three Pt isolates, which revealed that Lr2a is common in Canadian wheats. The KASP markers kwh740 and kwm1584 were highly associated with resistance at the Lr2 locus, while kwm1622 was slightly less correlated. Genetic mapping of the leaf rust resistance gene Lr2a and DNA markers developed here will facilitate its use in wheat breeding programs.

Puccinia Spore Concentrations in Relation to Weather Factors and Phenological Development of a Wheat Crop in Northwestern Spain

Rust is one of the main diseases affecting wheat crops in Spain, causing significant yield and quality losses. Research on its identification and quantification in the air is a worldwide priority due to the importance of this crop as a source of food and feed. The objective of this study is to determine the temporal variation of airborne spores of Puccinia and their relationship with meteorological variables and the phenological development of a wheat crop in Northwestern Spain during two growing seasons. The study was conducted in A Limia, Ourense, located in Northwestern Spain, during the wheat growing seasons of 2021 and 2022. The Lanzoni VPPS 2010 spore trap was used to collect airborne spores, which were identified using optical microscopy. The wheat growing season was less than 95 days during both years, and wheat rust spores were detected during all phenological stages of the crop. Concentrations were higher than 100 spores/m3 from the booting stage to senescence, mainly in 2021. Statistical analyses showed that temperature was the meteorological variable that most influenced Puccinia concentrations in the air in both years. The modification of a prediction model proposed by other authors for wheat rust, which takes into account mean temperature (10–25 °C), dew point temperature (<5 °C), and nighttime temperature (10–20 °C), allowed us to tentatively predict the increase in Puccinia concentrations in the year 2022 when these conditions occurred for four or five consecutive days. This research is the first in Spain to report the presence of rust-causing Puccinia spores in the air during all phenological stages of the wheat crop and provides useful information for designing management strategies, considering temperature values.

Integrated digital image processing techniques and deep learning approaches for wheat stripe rust disease detection and grading

This study proposes integrated image processing and deep learning approaches for wheat rust disease detection and grading. Wheat stripe rust is one of the diseases affecting the crop in nearly all wheat-growing countries, where humidity and high temperatures characterize the growing season. The early and prompt detection of this disease is essential for establishing timely remedial measures to contain its spread. We present several image-processing and deep-learning approaches for detecting wheat stripe rust. The image processing techniques used in this research include single-band and dual-band processing, computing the Visual Atmospheric Resistance Index (VARI), image segmentation, and image cropping. These techniques are evaluated with different deep learning approaches like transfer learning and other Convolutional Neural Networks (CNNs) architectures. The results obtained on the dataset show that processing the images to eliminate the background as much as possible before training a suitable deep learning model with a low number of epochs optimally classifies the wheat stripe rust into the target classes (i.e., healthy, resistant, and susceptible) with an overall accuracy of 84.1% on the holdout test set. Besides the comparative analysis of various image processing approaches with different deep learning models, this study suggests multiple future research directions.

Modeling the effectiveness of bacillus subtilis strains depending on natural and climatic factors in the soft wheat cultivation

The studies were carried out in 2017-2022 in order to identify natural and climatic factors that can influence the effectiveness of B. subtilis strains in relation to morphometric indicators and soft wheat productivity, the diseases development. The responsiveness of Leningradka 6, k-64900 spring wheat to the microbiological preparation Vitaplan, SP (titer of viable cells ×1011 CFU/g) and cultural liquid (CL) of the B. subtilis VKM B-2604D and B. subtilis VKM B-2605D (at a ratio of 1:1 with the titer of viable cells ×1010 CFU/ml). In the field conditions of the North- West of the Russian Federation, wheat seeds were treated before sowing and plants were sprayed three times during the growing season. The effectiveness of bacterial strains in relation to productivity and especially dangerous wheat diseases depended more on the indicators of moisture availability of the growing season. This was confirmed by the results of multidimensional scaling, correlation, factor analysis of indicators. In the variant «Vitaplan, SP» in F1, high positive factor loads were revealed for the precipitation amount in June, July, August, HTC in July, relative humidity in June (0.73…0.93), plant phase, plant height, area of ag and pre-flag leaves, vegetative part weight (0.71…0.80), and when using CL «B. subtilis VKM V-2604D + B. subtilis VKM B-2605D» - for the precipitation amount in June, August, HTC in July and August (0.71…0.88), productive bushiness, root weight, spike length, spikelets number per spike, grains number, spike grain weight, biological, potential yield (0.71…0.85). The B. subtilis strains application allowed to increase biological and potential yields by 32.5± 7.2 % and 24.3±7.0 %, and to reduce the intensity of diseases development (root rot - by 11.7 ± 1.6 %; powdery mildew, brown and yellow rust - by 7.6 ± 0.7 %), however, the effectiveness of bacterial strains significantly depended on the climatic factors of wheat growing season.

Genetic diversity and population structure of Saccharum hybrids.

Sugarcane breeding programs incorporate foreign material to broaden the genetic base, expanding the gene pool. In South America, the Inter-university Network for the Development of the Sugarcane Industry (RIDESA) and Estación Experimental Agroindustrial Obispo Colombres (EEAOC) sugarcane breeding programs from Brazil and Argentina, respectively, have never exchanged materials. In that sense, the knowledge of the genetic diversity and population structure among sugarcane genotypes of both germplasm banks, determined in a reliable way through their molecular profiles, will provide valuable information to select the best parental accessions for crossing aimed at the efficient introgression of desirable alleles. For that, the aim was to determine the genetic diversity and population structure of 96 Saccharum commercial hybrids from RIDESA and EEAOC sugarcane breeding programs by using TRAP, SSR and markers related to disease resistance (e.g. Bru1 and G1). Genetic structure was determined through genetic similarity analysis, analysis of molecular variance (AMOVA), Multidimensional scaling (MDS), and a Bayesian method. Average PIC values were 0.25 and 0.26, Ho values were 0.24 and 0.28, and He values were 0.25 and 0.28, for TRAP and SSR primers, respectively. Genetic similarity, MDS, and analysis of structure revealed that Brazilian and Argentinean genotypes clustered in two groups clearly differentiated, whereas AMOVA suggested that there is more variability within programs than between them. Regarding Bru1 markers, Brazilian genotypes showed high frequency of haplotype 1 (71.4%) whereas Argentinean genotypes showed high frequency of haplotype 4 (80.8%); haplotypes 1 and 4 are indicated for the presence and absence of the brown rust resistance gene (Bru1), respectively. Respecting the G1 marker, most of the evaluated genotypes (60.4%) showed the presence of the fragment, in a similar proportion for genotypes of both programs. In conclusion, the exchange of materials, at least the most diverse genotypes, between RIDESA and EEAOC breeding programs will allow extending the genetic base of their germplasm banks, and the knowledge of genetic diversity will help breeders to better manage crosses, increasing the probability of obtaining more productive varieties.

The Expression of Triticum aestivum Cysteine-Rich Receptor-like Protein Kinase Genes during Leaf Rust Fungal Infection.

Understanding the role of cysteine-rich receptor-like kinases (CRKs) in plant defense mechanisms is crucial for enhancing wheat resistance to leaf rust fungus infection. Here, we identified and verified 164 members of the CRK gene family using the Triticum aestivum reference version 2 collected from the international wheat genome sequencing consortium (IWGSC). The proteins exhibited characteristic features of CRKs, including the presence of signal peptides, cysteine-rich/stress antifungal/DUF26 domains, transmembrane domains, and Pkinase domains. Phylogenetic analysis revealed extensive diversification within the wheat CRK gene family, indicating the development of distinct specific functional roles to wheat plants. When studying the expression of the CRK gene family in near-isogenic lines (NILs) carrying Lr57- and Lr14a-resistant genes, Puccinia triticina, the causal agent of leaf rust fungus, triggered temporal gene expression dynamics. The upregulation of specific CRK genes in the resistant interaction indicated their potential role in enhancing wheat resistance to leaf rust, while contrasting gene expression patterns in the susceptible interaction highlighted potential susceptibility associated CRK genes. The study uncovered certain CRK genes that exhibited expression upregulation upon leaf rust infection and the Lr14a-resistant gene. The findings suggest that targeting CRKs may present a promising strategy for improving wheat resistance to rust diseases.

The NWRD Dataset: An Open-Source Annotated Segmentation Dataset of Diseased Wheat Crop.

Wheat stripe rust disease (WRD) is extremely detrimental to wheat crop health, and it severely affects the crop yield, increasing the risk of food insecurity. Manual inspection by trained personnel is carried out to inspect the disease spread and extent of damage to wheat fields. However, this is quite inefficient, time-consuming, and laborious, owing to the large area of wheat plantations. Artificial intelligence (AI) and deep learning (DL) offer efficient and accurate solutions to such real-world problems. By analyzing large amounts of data, AI algorithms can identify patterns that are difficult for humans to detect, enabling early disease detection and prevention. However, deep learning models are data-driven, and scarcity of data related to specific crop diseases is one major hindrance in developing models. To overcome this limitation, in this work, we introduce an annotated real-world semantic segmentation dataset named the NUST Wheat Rust Disease (NWRD) dataset. Multileaf images from wheat fields under various illumination conditions with complex backgrounds were collected, preprocessed, and manually annotated to construct a segmentation dataset specific to wheat stripe rust disease. Classification of WRD into different types and categories is a task that has been solved in the literature; however, semantic segmentation of wheat crops to identify the specific areas of plants and leaves affected by the disease remains a challenge. For this reason, in this work, we target semantic segmentation of WRD to estimate the extent of disease spread in wheat fields. Sections of fields where the disease is prevalent need to be segmented to ensure that the sick plants are quarantined and remedial actions are taken. This will consequently limit the use of harmful fungicides only on the targeted disease area instead of the majority of wheat fields, promoting environmentally friendly and sustainable farming solutions. Owing to the complexity of the proposed NWRD segmentation dataset, in our experiments, promising results were obtained using the UNet semantic segmentation model and the proposed adaptive patching with feedback (APF) technique, which produced a precision of 0.506, recall of 0.624, and F1 score of 0.557 for the rust class.

Effectiveness of known wheat resistance genes Triticum aestivum L. to Puccinia triticina Eriks. leaf rust of wheat in 2019–2020

The wheat leaf rust is widespread throughout Ukraine, which makes it necessary to monitor the effectiveness of host plant resistance genes. In 2019–2020, under the conditions of the subpopulation of the pathogen, typical for the Right Bank Forest-Steppe zone of Ukraine, the effectiveness of known resistance genes was determined. Evaluation was conducted after the 2018 epiphytotypic series on a series of nearly isogenic Thatcher wheat lines and cultivars that expand the core gene set. According to the research results, they are distributed into several groups according to the level of expression: 1) genes capable of determining a very high level of resistance to all local races of the pathogen (score 9 – no signs of the disease; score 8 – single necrotic spots) Lr9, Lr18, Lr19, Lr21, Lr25, Lr27+31, Lr28, Lr35, Lr41, Lr43+24, Lr50, LrTm; 2) genes determining resistance – plants are slightly affected by the pathogen (score 8 – single necrotic spots and urediniopustules with an intensity of up to 5 %; score 7 – urediniopustules with an intensity of up to 10 %; score 6 – small and medium urediniopustules with an intensity of up to 15 %) – Lr22a, Lr32, Lr34, Lr42, Lr43, Lr46; 3) resistance genes whose expression level is defined as labile (heterogeneous) – Lr2a, Lr2b, Lr12, Lr14a, Lr14b, Lr20, Lr23, Lr24, Lr39, Lr40. The last group is characterized by variability and depends on the level of infectious load and virulence of the pathogen population as a whole. We recommend using the listed resistance genes in the selection process, taking into account the characteristics of the last group. The genes Lr1, Lr2c, Lr3, Lr3ka, Lr3bg, Lr10, Lr11, Lr13, Lr15, Lr16, Lr17, Lr26, Lr29, Lr30, Lr33, Lr37, LrB are ineffective against all races of the leaf rust pathogen population in the Right Bank Forest Steppe zone of Ukraine. If they are associated with useful traits, their use in selection should be carried out at the expense of pyramiding with other more effective resistance genes.

Screening of Various Wheat Lines Against Puccinia Triticina and its Management through Synthetic Fungicides

Wheat is an important grain crop in the world and in Pakistan. Leaf rust is one of the detrimental disease and widespread in the world due to its distribution and higher adaptive capabilities. For screening of wheat germplasm against leaf and stripe rust, 150 varieties/lines were evaluated each entry was planted as single row and Morocco (susceptible) was included to every 10 entry in the nursery Moreover the use of fungicide on wheat crop is prohibited in Pakistan as it is being consumed as staple food, because of the widespread losses being caused by the leaf rust fungicides are being used to minimized the losses being caused by the disease so the potential of different chemicals for controlling leaf rust caused by Puccinia triticina was evaluated under this study. Therefore, three foliar different fungicides/chemicals were selected for evaluation named as Mycoguard (Azoxysterobin), Score (Diaphenaconazole) and Tilt (Propioconazol), with doses of 125ml/10L, 125ml/10L and 200ml/10L respectively were tested under field conditions and T4 was kept as control these chemicals, when applied at booting and leaf emergence stages. Screening result showed, out of 150 varieties/advanced lines screened against leaf rust of wheat. 26 were moderately resistant, 28 lines showed moderately susceptible response, 51 were resistant and remaining lines were susceptible. Among above captioned fungicides Mycoguard significantly reduced the disease upto 56%. The second best treatment was score which induced reduction upto 50%. All the data was statistically analyzed. Therefore, it is suggested that Mycoguard can be effectively employed to control leaf rust disease in wheat crop.

Phytopathological situation in crops of spring wheat varieties in Belarus

Monitoring of phytopathological situation in crops is the basis for biological justification of the need for protective measures, allowing to obtain a yield close to the potentially possible. The results of phytopathological situation monitoring in crops of spring wheat varieties are presented in the paper. Studies were carried out in 2019–2021 in the laboratory of phytopathology and in the experimental field of the Institute of Plant Protection. Standard methods in phytopathology were used during the work. The main criteria for assessing the degree of plant infestation were disease development (%) and area under disease process curve (AUDPC, in conditional units). Analysis of phytopathological state of spring wheat crops showed that during the growing season the crop varieties were affected by diseases of vegetative and generative organs: root and byroot rots, powdery mildew, leaf and ear septoriosis, pyrenophorosis, brown rust, and fusariosis of ear. Root rot, leaf spot disease, septoriosis, and spikelet fusariosis are among the dominant diseases annually present in spring wheat crops. Variety differences in disease incidence are a factor influencing the emerging phytopathological situation in the crop. Cultivation of resistant varieties reduces the risk of epiphytotics. According to the sum of infectious loads experienced by the plants during the whole period of vegetation, the evaluated varieties of spring wheat were ranked in ascending order: Lyubava (60,5 %), Slavyanka (61,9 %), Sudarynya (66,9 %), Laska (71,3 %), and Darya (83,9 %). The results of the studies allow to give preference to the most interesting varieties, based on the available opportunities to ensure the proper level of protection against diseases.

Slow stripe rusting in Chinese wheat Jimai 44 conferred by Yr29 in combination with a major QTL on chromosome arm 6AL.

YrJ44, a more effective slow rusting gene than Yr29, was localized to a 3.5-cM interval between AQP markers AX-109373479 and AX-109563479 on chromosome 6AL. "Slow rusting" (SR) is a type of adult plant resistance (APR) that can provide non-specific durable resistance to stripe rust in wheat. Chinese elite wheat cultivar Jimai 44 (JM44) has maintained SR to stripe rust in China since its release despite exposure to a changing and variable pathogen population. An F2:6 population comprising 295 recombinant inbred lines (RILs) derived from a cross between JM44 and susceptible cultivar Jimai 229 (JM229) was used in genetic analysis of the SR. The RILs and parental lines were evaluated for stripe rust response in five field environments and genotyped using the Affymetrix Wheat55K SNP array and 13 allele-specific quantitative PCR-based (AQP) markers. Two stable QTL on chromosome arms 1BL and 6AL were identified by inclusive composite interval mapping. The 1BL QTL was probably the pleiotropic gene Lr46/Yr29/Sr58. QYr.nwafu-6AL (hereafter named YrJ44), mapped in a 3.5-cM interval between AQP markers AX-109373479 and AX-109563479, was more effective than Yr29 in reducing disease severity and relative area under the disease progress curve (rAUDPC). RILs harboring both YrJ44 and Yr29 displayed levels of SR equal to the resistant parent JM44. The AQP markers linked with YrJ44 were polymorphic and significantly correlated with stripe rust resistance in a panel of 1,019 wheat cultivars and breeding lines. These results suggested that adequate SR resistance can be obtained by combining YrJ44 and Yr29 and the AQP markers can be used in breeding for durable stripe rust resistance.

Phenotyping and Identification of Molecular Markers Associated with Leaf Rust Resistance in the Wheat Germplasm from Kazakhstan, CIMMYT and ICARDA.

Leaf rust (LR) is the most widespread disease of common wheat worldwide. In order to evaluate leaf rust resistance, 70 uncharacterized wheat cultivars and promising lines with unknown leaf rust resistance genes (Lr genes) were exposed to Kazakhstani Puccinia triticina (Pt) races at the seedling stage. Field tests were performed to characterize leaf rust responses at the adult plant growth stage in the 2020-2021 and 2021-2022 cropping seasons. The wheat collection showed phenotypic diversity when tested with two virulent races of Pt. Thirteen wheat genotypes (18.6%) showed high resistance at both seedling and adult plant stages. In most cases, breeding material originating from international nurseries showed higher resistance to LR. Nine Lr genes, viz. Lr9, Lr10, Lr19, Lr26, Lr28, Lr34, Lr37, Lr46, and Lr68, either singly or in combination, were identified in 47 genotypes. Known Lr genes were not detected in the remaining 23 genotypes. The most commonly identified resistance genes were Lr37 (17 cultivars), Lr34 (16 cultivars), and Lr46 (10 cultivars), while Lr19, Lr68, Lr26, and Lr28 were the least frequent. Four Lr genes were identified in Keremet and Hisorok, followed by three Lr genes in Aliya, Rasad, Reke, Mataj, Egana and Almaly/Obri. The molecular screening revealed twenty-nine carriers of a single Lr gene, ten carriers of two genes, six carriers of three genes, and two carriers of four genes. Most of these accessions showed a high and moderate level of APR (Adult plant resistance) and may be utilized for the incorporation of Lr genes in well-adapted wheat cultivars. The most effective combination was Lr37, Lr34, and Lr68, the carriers of which were characterized by a low disease susceptibility index. The obtained results will facilitate breeding programs for wheat resistance in Kazakhstan.

Effective leaf rust resistance genes of wheat in Novosibirsk Province in connection with the variability of the <i>Puccinia triticina</i> population

Background. Information on the races of Puccinia triticina Erikss. in Novosibirsk Province is needed to identify sources of effective genes for leaf rust resistance. The goal hereof was monitoring genetic variability of the P. triticina population in the Ob riverside forest-steppe, Novosibirsk Province, and detecting effective resistance genes to develop wheat cultivars resistant to the disease. Materials and methods. In 2015–2019, affliction of Thatcher lines (Tc) and cultivars under the disease pressure was assessed, and P. triticina structure in the Ob forest-steppe of Novosibirsk Province was monitored. P. triticina genotypes were identified using the Long–Kolmer system. Additionally, a set of cultivars with the Lr19, Lr20, Lr28, Lr39; 6 – Lr6Agi2, Lr6Agi1, LrKu, andLrSp2 genes was employed. Results. A high frequency of virulence was detected for cultivars with the Lr3ka, Lr10, Lr1, Lr2a, Lr2c, Lr3a, Lr11, Lr18, Lr20, Lr30, Lr16, Lr17, and LrB genes (66.7–100 %). The P. triticina structure consisted of 27 races, including 12 common ones: TGTT GB, TGTR GB, TQTT GB, TQTR GB, TGPT GB, THFR GB, KHTT GB, PHKT GB, PQTT GB, THTP BB, PGFR GB, and SGPR GB. Genotypes with the Lr6Agi2, Lr6Agi1, LrKu, Lr39, Lr42, Lr12, Lr19, Lr24, Lr25, Lr28, Lr35, Lr45, Lr47, Lr50, Lr52, LrSp2, Lr6Agi1+Lr19, Lr6Agi2+Lr10+Lr34, Lr11+Lr13+Lr22a, Lr13+LrTb, Lr24+Lr26, Lr37+Lr13, Lr37+Lr1, Lr34+Lr13, Lr43+Lr24, and Lr49+Lr34 genes were resistant to P. triticina under the infection pressure. Some wheat genotypes varied in leaf rust resistance across the years (0–5 % for TcLr29 and TcLr21, 0–10 % for CSP 44 and TcLr44, 0–20 % for TcLr13, 1–30 % for TcLr37, and 15–80 % for Pavon F 76). Conclusion. The local leaf rust population has changed slightly over the years of study (the Lr18 and Lr38 genes have lost resistance), and was very different from the population before 2010.

Resistance that stacks up: engineering rust and mildew disease control in the cereal crops wheat and barley.

Staying ahead of the arms race against rust and mildew diseases in cereal crops is essential to maintain and preserve food security. The methodological challenges associated with conventional resistance breeding are major bottlenecks for deploying resistance (R) genes in high-yielding crop varieties. Advancements in our knowledge of plant genomes, structural mechanisms, innovations in bioinformatics, and improved plant transformation techniques have alleviated this bottleneck by permitting rapid gene isolation, functional studies, directed engineering of synthetic resistance and precise genome manipulation in elite crop cultivars. Most cloned cereal R genes encode canonical immune receptors which, on their own, are prone to being overcome through selection for resistance-evading pathogenic strains. However, the increasingly large repertoire of cloned R genes permits multi-gene stacking that, in principle, should provide longer-lasting resistance. This review discusses how these genomics-enabled developments are leading to new breeding and biotechnological opportunities to achieve durable rust and powdery mildew control in cereals.

Virulence and genetic analysis of Puccinia graminis tritici in the Indian sub-continent from 2016 to 2022 and evaluation of wheat varieties for stem rust resistance.

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), has re-emerged as one of the major concerns for global wheat production since the evolution of Ug99 and other virulent pathotypes of Pgt from East Africa, Europe, Central Asia, and other regions. Host resistance is the most effective, economic, and eco-friendly approach for managing stem rust. Understanding the virulence nature, genetic diversity, origin, distribution, and evolutionary pattern of Pgt pathotypes over time and space is a prerequisite for effectively managing newly emerging Pgt isolates through host resistance. In the present study, we monitored the occurrence of stem rust of wheat in India and neighboring countries from 2016 to 2022, collected 620 single-pustule isolates of Pgt from six states of India and Nepal, analyzed them on Indian stem rust differentials, and determined their virulence phenotypes and molecular genotypes. The Ug99 type of pathotypes did not occur in India. Pathotypes 11 and 40A were most predominant during these years. Virulence phenotyping of these isolates identified 14 Pgt pathotypes, which were genotyped using 37 Puccinia spp.-specific polymorphic microsatellites, followed by additional phylogenetic analyses using DARwin. These analyses identified three major molecular groups, demonstrating fewer lineages, clonality, and long-distance migration of Pgt isolates in India. Fourteen of the 40 recently released Indian wheat varieties exhibited complete resistance to all 23 Pgt pathotypes at the seedling stage. Twelve Sr genes were postulated in 39 varieties based on their seedling response to Pgt pathotypes. The values of slow rusting parameters i.e. coefficient of infection, area under disease progress curve, and infection rates, assessed at adult plant stage at five geographically different locations during two crop seasons, indicated the slow rusting behavior of several varieties. Six Sr genes (Sr2, Sr57, Sr58, Sr24, Sr31, and Sr38) were identified in 24 wheat varieties using molecular markers closely linked to these genes. These findings will guide future breeding programs toward more effective management of wheat stem rust.

Using Ground and UAV Vegetation Indexes for the Selection of Fungal-Resistant Bread Wheat Varieties

The productivity of wheat in the Mediterranean region is under threat due to climate-change-related environmental factors, including fungal diseases that can negatively impact wheat yield and quality. Wheat phenotyping tools utilizing affordable, high-throughput plant phenotyping (HTPP) techniques, such as aerial and ground RGB images and quick canopy and leaf sensors, can aid in assessing crop status and selecting tolerant wheat varieties. This study focused on the impact of fungal diseases on wheat productivity in the Mediterranean region, considering the need for a precise selection of tolerant wheat varieties. This research examined the use of affordable HTPP methods, including imaging and active multispectral sensors, to aid in crop management for improved wheat health and to support commercial field phenotyping programs. This study evaluated 40 advanced lines of bread wheat (Triticum aestivum L.) at five locations across northern Spain, comparing fungicide-treated and untreated blocks under fungal disease pressure (Septoria, brown rust, and stripe rust observed). Measurements of leaf-level pigments and canopy vegetation indexes were taken using portable sensors, field cameras, and imaging sensors mounted on unmanned aerial vehicles (UAVs). Significant differences were observed in Dualex flavonoids and the nitrogen balance index (NBI) between treatments in some locations (p < 0.001 between Elorz and Ejea). Measurements of canopy vigor and color at the plot level showed significant differences between treatments at all sites, highlighting indexes such as the green area (GA), crop senescence index (CSI), and triangular greenness index (TGI) in assessing the effects of fungicide treatments on different wheat cultivars. RGB vegetation indexes from the ground and UAV were highly correlated (r = 0.817 and r = 0.810 for TGI and NGRDI). However, the Greenseeker NDVI sensor was found to be more effective in estimating grain yield and protein content (R2 = 0.61–0.7 and R2 = 0.45–0.55, respectively) compared to the aerial AgroCam GEO NDVI (R2 = 0.25–0.35 and R2 = 0.12–0.21, respectively). We suggest as a practical consideration the use of the GreenSeeker NDVI as more user-friendly and less affected by external environmental factors. This study emphasized the throughput benefits of RGB UAV HTPPs with the high similarity between ground and aerial results and highlighted the potential for HTPPs in supporting the selection of fungal-disease-resistant bread wheat varieties.

Biocontrol potential of the endophytic Epicoccum nigrum HE20 against stripe rust of wheat

Biological control using endophytic microorganisms represents an eco-friendly and effective alternative to the health-hazardous chemical fungicides used to control devastating plant diseases such as stripe rust in wheat. In this study, the inhibitory potential of the endophytic Epicoccum nigrum HE20, isolated from a healthy wheat plant, was screened against uredospores germination in vitro. A high suppression (96%) in the germination of the uredospores was recorded. GC‐MS analysis of the culture filtrate of E. nigrum HE20 showed a production of various secondary metabolites with an antifungal background such as butyric acid, α-linolenic acid, hexanoic acid, lactic acid, 10,12-Tricosadiynoic acid, and pentadecanoic acid. Results from the greenhouse experiment revealed that the application of E. nigrum HE20 suspension led to a reduction in the disease severity by 87.5%, compared with the untreated-infected plants. Real-time PCR results exhibited an overexpression in three defensive genes (JERF3, GLU, and PR1) in the infected wheat plants, in response to the application of E. nigrum HE20, recorded 8-, 15.8-, and 3.5-fold, respectively. In addition, an increment in the phenolic content, activity of POD, PPO, and CAT, and a reduction in the lipid peroxidation were recorded due to the endophyte application. Transmission electron microscopic observations indicated mitigation of the pathogen in wheat cells after the treatment with E. nigrum HE20 metabolite. Furthermore, a growth-promoting effect was also observed due to E. nigrum HE20 application, as well as an increment in the total photosynthetic pigments in wheat leaves. Based on these results, it can be concluded that E. nigrum HE20 is a probable efficient bioagent against stripe rust in wheat. However, its field evaluation is highly necessary in the future studies.

Stem rust severity and AUDPC values of different wheat varieties in response to Puccinia graminis f. sp tritici

Wheat is the important cereal and is highest produced grain in the world after corn and rice. It is the second most important crop in India next to rice. Like several crops, wheat is also prone to diseases. Among various diseases, wheat stem rust is the main biotic constraint to wheat production and it is important to understand and analyze the disease in terms of pathological responses. Out of six cultivars tested, three wheat varieties showed a resistance response, while the other three varieties showed a susceptible response against stem rust of wheat. Disease severity and area under disease progressive curve (AUDPC) data of three susceptible varieties revealed that the highest AUDPC value (1785.93) was recorded in A-9-30-1 which showed the most susceptible response followed by Agra Local (1762.93) and Kharachia (1645.90). There was no development of stem rust symptoms on three varieties viz., GDW 1255, GW 496 and GW 451.