Characterization of the Barley Net Blotch Pathosystem at the Center of Origin of Host and Pathogen

Early Detection of Both Pyrenophora teres f. teres and f. maculata in Asymptomatic Barley Leaves Using Digital Droplet PCR (ddPCR)

Efficient early pathogen detection, before symptom apparition, is crucial for optimizing disease management. In barley, the fungal pathogen Pyrenophora teres is the causative agent of net blotch disease, which exists in two forms: P. teres f. sp. teres (Ptt), causing net-form of net blotch (NTNB), and P. teres f. sp. maculata (Ptm), responsible for spot-form of net blotch (STNB). In this study, we developed primers and a TaqMan probe to detect both Ptt and Ptm. A comprehensive k-mer based analysis was performed across a collection of P. teres genomes to identify the conserved regions that had potential as universal genetic markers. These regions were then analyzed for their prevalence and copy number across diverse Moroccan P. teres strains, using both a k-mer analysis for sequence identification and a phylogenetic assessment to establish genetic relatedness. The designed primer-probe set was successfully validated through qPCR, and early disease detection, prior to symptom development, was achieved using ddPCR. The k-mer analysis performed across the available P. teres genomes suggests the potential for these sequences to serve as universal markers for P. teres, transcending environmental variations.

Deep Learning-Based Barley Disease Quantification for Sustainable Crop Production

Net blotch disease caused by Drechslera teres is a major fungal disease that affects barley (Hordeum vulgare) plants and can result in significant crop losses. In this study, we developed a deep learning model to quantify net blotch disease symptoms on different days postinfection on seedling leaves using Cascade R-CNN (region-based convolutional neural network) and U-Net (a convolutional neural network) architectures. We used a dataset of barley leaf images with annotations of net blotch disease to train and evaluate the model. The model achieved an accuracy of 95% for Cascade R-CNN in net blotch disease detection and a Jaccard index score of 0.99, indicating high accuracy in disease quantification and location. The combination of Cascade R-CNN and U-Net architectures improved the detection of small and irregularly shaped lesions in the images at 4 days postinfection, leading to better disease quantification. To validate the model developed, we compared the results obtained by automated measurement with a classical method (necrosis diameter measurement) and a pathogen detection by real-time PCR. The proposed deep learning model could be used in automated systems for disease quantification and to screen the efficacy of potential biocontrol agents to protect against disease.

Pyrenophora teres: population structure, virulence and aggressiveness in Southern Russia

The barley net blotch agent Pyrenophora teres (Died) Drechs. is one of the dominant fungal pathogens in agricultural crops worldwide. Here we aim to study the aggressiveness and virulence of P. teres populations collected at different ontogenesis stages (BBCH 30 and BBCH 47) from winter barley cultivars of various resistance types: moderately resistant, moderately susceptible and highly susceptible. We observed a direct proportional relationship between cultivar resistance and the aggressiveness of P. teres populations collected in both growth phases of the host plant. The isolates collected at an early stage of host plant development have a large difference in aggressiveness criteria: colony growth rate, sporulation intensity, latency period, plant damage degree, and the number of identified races. At the BBCH 30 growth stage, the growth rate of fungus colonies selected from a resistant cultivar is 1.2 times higher than that of a susceptible cultivar. The growth rate of colonies selected from resistant and susceptible cultivars in the earlier BBCH 30 stage is 1.04 times higher than the growth rate of colonies selected from the later phase. The sporulation intensity of fungal populations selected from a resistant cultivar is higher than that of populations selected from a susceptible cultivar (for BBCH 30–5.4 times, for BBCH 47–4.0 times); and it is 1.3 times higher in an earlier phase of plant development. Correlation between colony growth rate and spore formation rate in the BBCH 30 is r = 0.4. A high correlation level (r = 0.9) and notable difference between the variants were revealed when studying the duration of the latent period. The average value of plant damage by the P. teres from resistant cultivar is 4 times higher than from the susceptible cultivar in the BBCH 30 stage; and 12 times – in the BBCH 47 stage. There is a moderate negative correlation between the plant damage degree and the number of races identified from the fungal population, r = −0.59 for the BBCH 30, r = −0.8 for the BBCH 47. The number of races identified from P. teres populations collected in the late phase of plant growth was one third less. Our study helped to acquire new knowledge about intrapopulation processes under the influence of various factors – plant growth stage and cultivar genotype. The results obtained are the basis for the development of adaptive-integrated techniques for managing populations of the hemibiotrophic pathogen, barley net blotch.

Plant Beneficial Bacteria as Bioprotectants against Wheat and Barley Diseases

Wheat and barley are the main cereal crops cultivated worldwide and serve as staple food for a third of the world's population. However, due to enormous biotic stresses, the annual production has significantly reduced by 30-70%. Recently, the accelerated use of beneficial bacteria in the control of wheat and barley pathogens has gained prominence. In this review, we synthesized information about beneficial bacteria with demonstrated protection capacity against major barley and wheat pathogens including Fusarium graminearum, Zymoseptoria tritici and Pyrenophora teres. By summarizing the general insights into molecular factors involved in plant-pathogen interactions, we show to an extent, the means by which beneficial bacteria are implicated in plant defense against wheat and barley diseases. On wheat, many Bacillus strains predominantly reduced the disease incidence of F. graminearum and Z. tritici. In contrast, on barley, the efficacy of a few Pseudomonas, Bacillus and Paraburkholderia spp. has been established against P. teres. Although several modes of action were described for these strains, we have highlighted the role of Bacillus and Pseudomonas secondary metabolites in mediating direct antagonism and induced resistance against these pathogens. Furthermore, we advance a need to ascertain the mode of action of beneficial bacteria/molecules to enhance a solution-based crop protection strategy. Moreover, an apparent disjoint exists between numerous experiments that have demonstrated disease-suppressive effects and the translation of these successes to commercial products and applications. Clearly, the field of cereal disease protection leaves a lot to be explored and uncovered.

Pyrenophora teres: Taxonomy, Morphology, Interaction With Barley, and Mode of Control

Net blotch, induced by the ascomycete Pyrenophora teres, has become among the most important disease of barley (Hordeum vulgare L.). Easily recognizable by brown reticulated stripes on the sensitive barley leaves, net blotch reduces the yield by up to 40% and decreases seed quality. The life cycle, the mode of dispersion and the development of the pathogen, allow a quick contamination of the host. Crop residues, seeds, and wild grass species are the inoculum sources to spread the disease. The interaction between the barley plant and the fungus is complex and involves physiological changes with the emergence of symptoms on barley and genetic changes including the modulation of different genes involved in the defense pathways. The genes of net blotch resistance have been identified and their localizations are distributed on seven barley chromosomes. Considering the importance of this disease, several management approaches have been performed to control net blotch. One of them is the use of beneficial bacteria colonizing the rhizosphere, collectively referred to as Plant Growth Promoting Rhizobacteria. Several studies have reported the protective role of these bacteria and their metabolites against potential pathogens. Based on the available data, we expose a comprehensive review of Pyrenophora teres including its morphology, interaction with the host plant and means of control.