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  • Author or Editor: H. Alek x
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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.

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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.

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