108 research outputs found
Mycorrhizal Application as a Biocontrol Agent against Common Root Rot of Barley
This study was conducted to assess the biocontrol efficacy of vesicular arbuscular mycorrhizae (VAM) against barley common root rot caused by Cochliobolus sativus. Mycorrhization of barley was achieved by growing the plants in expanded clay mixed with 10% (v/v) VAM fungus inoculum in pots experiments. Large differences in disease reactions were observed among genotypes and among treatments. VAM treatments significantly reduced the percentage of disease severity in infected barley plants and increased significantly root biomass, which could be attributed to enhanced nutrients uptake, via an increase in the absorbing surface area. It can be concluded that the application of VAM as a biocontrol agent played an important role in plant resistance and exhibit greater potential to protect barley plants against C. sativus
Viability and pathogenicity of Rhynchosporium secalis after long-term storage
Long-term storage of Rhynchosporium secalis cultures is a challenge for any lab managing a working collection of isolates. In this work, the viability and pathogenicity of R. secalis stock cultures were tested after four years of storage at −20 °C in different concentrations of glycerol. Germinability were measured after each storage by collecting spores by coverslips and placing them on water agar in closed Petri dishes at 20–22 °C in the dark and allowed to germinate for 24 h. Additionally, at the end of each storage treatment, conidia were collected by coverslips from sporulated leaf lesions of symptomatic barley leaves and placed under similar conditions as non-stored controls.
Cultures of all stored isolates were viable with a spore germination rate of 72.28% (Rs22) after four years of storage at −20 °C in 60% glycerol. Low viability and contamination were observed when spores were stored in sterile distilled water and in Lima bean agar. All isolates continued to infect barley leaves after 4 years of storage. However, the pathogenicity was significantly (P <0.05) reduced in isolates stored in glycerol as compared with controls.
This work helps to preserve R. secalis for a long term period at −20 °C without any contamination; therefore, due to the low costs our results could be applicable for laboratories that have limited resources
Changes in PR2 and PAL Patterns in Barley Challenged with Leaf Stripe (Pyrenophora graminea) and Powdery Mildew (Blumeria graminis) Diseases
The seed-borne (Pyrenophora graminea; Pg) and foliar
(Blumeria graminis; Bg) are two economically important
fungal pathogens of barley worldwide. Barley plant resistance genes, as the
pathogenesis related proteins play an important role in defense mechanisms. This
study aimed to monitor the expression of PR2 and
PAL pathogenesis related genes during
compatible/incompatible barley interaction with Pg and
Bg at different time points of disease development using
the Quantitative Real-time PCR technique (qRT-PCR).
Comparison of data showed that PR2 and PAL were
significantly over expressed in infected resistant and susceptible plants as
against their lower expression in controls,. Upregulation of these
defense-related genes during Pg and Bg
infections was companied with a slow development of disease symptoms at the time
course in the resistant genotype. qRT-PCR analysis revealed higher gene
expression in resistant barley plants inoculated with Pg as
compared with Bg, with a maximum expression for
PR2 (13.8 and 5.06-fold) and PAL (14.8 and
4.51-fold) respectively, at the latest stage of each disease development. It was
also noteworthy that PR2 and PAL genes, had
higher constitutive expression and faster induction for the both pathogens in
the resistant genotype as compared with the susceptible one.
Obtained results suggest that both genes, PR2 and
PAL, positively regulate Pg- and
Bg-resistance in barley plants during disease progress.
These expression patterns can provide useful insights to better understanding of
the barley–fungus interactions with different fungal lifestyles
Identification of Barley Lines with Resistance to Powdery Mildew Based on Seedling and Adult Plant Responses
Screening of barley breeding lines for resistance to common root rot disease through incidence and severity parameters
Cochliobolus sativus, the causal agent of common root rot (CRR), is a devastating fungal pathogen of barley that can cause significant yield losses worldwide. The development of resistant cultivars has proven difficult, therefore, in this work, CRR-resistant barley germplasm was developed by crossing three resistant-by-susceptible cultivars currently used in Europe and West Asia. Following greenhouse evaluations of 150 doubled haploid lines derived from these crosses, 40 lines were evaluated under artificial infection conditions using incidence and severity parameters during two consecutive seasons. Data showed significant differences among barley lines with a continuum of resistance levels ranging from highly susceptible to resistant which were consistent in both seasons. However, five promising lines had slightly lower CRR disease than the others. Additionally, significant differences (P <0.05) in mean incidence and severity values were found among lines, with values being consistently higher in the susceptible ones. However, CRR severity increased linearly as incidence increased in both seasons. All together, the present study suggests that, the newly identified resistance lines can serve as potential donors for ongoing CRR resistance breeding program to generate high-yielding commercial barley cultivars, and that the positive correlation between CRR parameters I and S may be beneficial for many types of studies on this disease
Characterization of barley germplasm for leaf stripe (Pyrenophora graminea) resistance based on incidence and severity parameters
Barley leaf stripe (BLS) caused by Pyrenophora graminea is an important seed-borne disease of barley causing significant yield and quality losses worldwide. The development of resistant cultivars has proven difficult, therefore, in this work, BLSresistant barley germplasm was developed by crossing six barley cultivars currently used in Europe and West Asia. Out of 270 doubled haploid lines derived from these crosses, 40 lines were evaluated under field artificial infection conditions using incidence (I; proportion of diseased plants) and severity (S; proportion of infected leaf area per plant). Disease resistance parameters showed a broad range of variation in mean I and S values with a continuum of resistance levels ranging from highly susceptible to highly resistant with values being consistently higher in the susceptible ones. However, eight promising resistant lines with high yield per plant were identified. Moreover, BLS severity increased linearly as incidence increased (r = 0.76, P < 0.001). This work suggests that BLS resistance sources identified in this study can be used for further genetic analysis and introgression for varietal improvement, and that the positive correlation between I and S parameters may be beneficial for many types of studies on this disease
Evaluation of Xylanase Production from Filamentous Fungi with Different Lifestyles
Xylanase plays an important role in the food, feed, and pulp/paper industry. Filamentous fungi have been considered as useful producers of this enzyme from an industrial point of view, due to the fact that they excrete xylanases into the medium. In this study, four fungal species belonging to different genera, i.e. Aspergillus, Cochliobolus, Pyrenophora, and Penicillium were isolated from different sources and compared for their ability to produce xylanase in submerged culture. The fungal species showed enzyme activity as determined by dinitrosalicylic acid (DNS) method. It was found that the two saprophytic Aspergillus strains, i.e A. terreus (Fss 129) and A. niger (SS7) had the highest xylanase activity of 474 and 294 U ml–1 at pH 7 and 8, respectively, in the presence of corn cob hulls after 120 h of incubation. The production of xylanase seemed to be strongly influenced by the interactive effect of initial pH on the fungi. Interestingly, xylanase was better produced by the saprophytic fungi of Aspergillus and Penicillium than by the plant pathogenic ones of Cochliobolus and Pyrenophora. This work provides additional information to support future research on fungi with different lifestyles for food industrial production of xylanase
Genetic diversity within local and introduced cultivars of wheat (Triticum aestivum L.) grown under Mediterranean environment as revealed by AFLP markers
Information on genetic diversity among cultivars is critical in wheat improvement. In this work, heterogeneity within local and introduced cultivars of bread wheat grown in Syria was investigated using amplified fragment length polymorphism (AFLP) markers. The eight primer pairs were used to detect 177 polymorphic bands among the 21 cultivars resulting in an average of 22.13 (57.3%) polymorphic loci per primer pair. Major allelic frequency ranged from 0.50 to 0.75 with a mean 0.64, and estimated gene diversity was 0.45. Values of average polymorphic information content (PIC) for these markers were estimated to be 0.34. This low value might be attributed to the rigorous selection pressure aimed at cultivar purity and associated breeding practices. Dissimilarity values ranged from 0.32 to 0.66 with an average of 0.54, indicating that such techniques sample distinct genome regions. Three major subgroups of wheat cultivars were identified using the unweighted pair-group method with arithmetic means analysis (UPGMA), with all local cultivars falling into one cluster, which was confirmed by a principal component analysis (PCA). The narrow genetic diversity observed among Syrian wheat cultivars suggests the need of broadening the genetic base of wheat breeding materials, including local landraces
Cooperative functioning of salicylic acid and phenylalanine ammonia lyase in barley plant challenged with spot blotch and powdery mildew diseases
Salicylic acid (SA) and phenylalanine ammonia-lyase (PAL) have been suggested as important signals during plant resistance towards several fungal pathogens. In this work, to better understand the defense responses initiated by resistant and susceptible barley genotypes challenged with a necrotrophic (Cochliobolus sativus; Cs) and a biotrophic (Blumeria graminis; Bg) pathogens, the relative contributions of SA and PAL were investigated at early time points of infection. SA signaling was activated in both genotypes 24 hours post infection (hpi) as compared with the non-inoculated plants. However, with or without pathogen pretreatment, SA significantly increased (P = 0.001) in the resistant genotype that contained three-folds of total SA in comparison with the susceptible one for Bg. Reverse transcription-polymerase chain reaction (RTPCR) analysis revealed that PAL expression increases in the resistant and susceptible genotypes over the inoculation time points, with the maximum expression observed 48 hpi. PAL expression was paralleled by an increase in SA content in leaves as shown by the test coincidence (F3, 32 = 1.09, P = 0.49 for Cs and F3, 32 = 1.03, P = 0.48 for Bg). Results showed that the cooperatively function of SA and PAL in barley responses to both Cs and Bg appeared to be dependent on the plant genotype, and that SA signaling and PAL play a role in barley interactions with these both pathogens. This study might increase our understanding for a deeper molecular research on barley defense responses against pathogens with different lifestyles
Proposed Diagnostic Criteria and Classification of Canine Mast Cell Neoplasms: A Consensus Proposal
Mast cell neoplasms are one of the most frequently diagnosed malignancies in dogs. The clinical picture, course, and prognosis vary substantially among patients, depending on the anatomic site, grade and stage of the disease. The most frequently involved organ is the skin, followed by hematopoietic organs (lymph nodes, spleen, liver, and bone marrow) and mucosal sites of the oral cavity and the gastrointestinal tract. In cutaneous mast cell tumors, several grading and staging systems have been introduced. However, no comprehensive classification and no widely accepted diagnostic criteria have been proposed to date. To address these open issues and points we organized a Working Conference on canine mast cell neoplasms in Vienna in 2019. The outcomes of this meeting are summarized in this article. The proposed classification includes cutaneous mast cell tumors and their sub-variants defined by grading- and staging results, mucosal mast cell tumors, extracutaneous/extramucosal mast cell tumors without skin involvement, and mast cell leukemia (MCL). For each of these entities, diagnostic criteria are proposed. Moreover, we have refined grading and staging criteria for mast cell neoplasms in dogs based on consensus discussion. The criteria and classification proposed in this article should greatly facilitate diagnostic evaluation and prognostication in dogs with mast cell neoplasms and should thereby support management of these patients in daily practice and the conduct of clinical trials
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