Rhizobacteria-mediated Induced Resistance in Barley against Cochliobolus sativus under Field Conditions

The effect of four rhizobacterial strains on the severity of spot blotch disease caused by cochliobolus sativus was evaluated for two growing seasons under rainfed conditions. Three barley genotypes were used as host plant. All strains reduced C. sativus severity, with effect more pronounced when Pseudomonas putida BTP1 and Bacillus subtilis Bs2508 were used. The disease reduction was up to 56% in Arabi Abiad / P. putida BTP1. The grain yield was not obviously affected by the presence of the rhizobacteria, except some signifitive increase in season 2. Raising the resistance by soaking seed with rhizobacterial strains might be of ultimate value in agriculture

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

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

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

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

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

Translational considerations in injectable cell-based therapeutics for neurological applications: concepts, progress and challenges

Significant progress has been made during the past decade towards the clinical adoption of cell-based therapeutics. However, existing cell-delivery approaches have shown limited success, with numerous studies showing fewer than 5% of injected cells persisting at the site of injection within days of transplantation. Although consideration is being increasingly given to clinical trial design, little emphasis has been given to tools and protocols used to administer cells. The different behaviours of various cell types, dosing accuracy, precise delivery, and cell retention and viability post-injection are some of the obstacles facing clinical translation. For efficient injectable cell transplantation, accurate characterisation of cellular health post-injection and the development of standardised administration protocols are required. This review provides an overview of the challenges facing effective delivery of cell therapies, examines key studies that have been carried out to investigate injectable cell delivery, and outlines opportunities for translating these findings into more effective cell-therapy interventions

Expression of PAL and PR2 pathogenesis related genes in barley plants challenged with closely related Pyrenophora species

Net blotch and leaf stripe caused by Pyrenophora teres and Pyrenophora graminea, respectively, are economical diseases of barley worldwide. Relatively little is known about the defense responses of barley challenged with these two closely related species. In the current work, expression of two well known defense-related genes PAL and PR2 were monitored in resistant and susceptible barley cultivars at early points of infection using quantitative real-time PCR (qPCR). Data showed signifcant variance in the expression patterns of the both genes between barley P. teres or P. graminea interactions as compared to the non-inoculated controls. It is also noteworthy that PAL and PR2 genes have a higher constitutive expression and faster induction in the resistant cultivar as compared with the susceptible one after infection with each pathogen. However, PCR (qPCR) analysis revealed higher gene expression in resistant barley plants inoculated with P. graminea as compared with P. teres, with a maximum expression for PR2 (13.8 and 6.41-fold) and PAL (14.8 and 7.89-fold) respectively, at 6 days post inoculation. The obtained results suggest that PAL and PR2 genes, positively regulate P. teres and P. graminea—resistance in barley plants during disease progress, which can provide testable hypotheses that will need direct future tests to determine how these changes may be specifed in the genome of these closely related Pyrenophora species