Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Genetics

Wild barley (Hordeum spontaneum) is the progenitor of the cultivated barley (Hordeum vulgare L.). In an attempt to evaluate the potential use of the Egyptian wild barley as a source of salt tolerance related genes, its response to salt stress was assessed at the physiological and molecular levels. The physiological evaluation was conducted at 10 levels of salinity along with the control by measuring some photosynthesis parameters (OJIP, Fv/Fm and PI). Photosynthesis efficiency began to be affected by salt stress at 125 mM and continued at 150, 175, 200, 225 and 250 mM NaCl. The DDRT- PCR of wild barley from plants treated with 0, 125 and 200 mM NaCl using 14 arbitrary primers revealed the overexpression of seven genes (thi4, B2, vps29, lhc3, oee1, shmt and sbt). Validation of the identified up-regulated genes was performed using the Real-time PCR analysis. Out of the seven genes, B2 revealed the highest up-regulated expression followed by shmt. This study was extended to evaluate the response of ten Egyptian barley cultivars (Giza 129, 132, 123, 127, 2000, 130, 126, 135, 128 and 133) to salinity stress. The ten cultivars were assessed under open field conditions by measuring the OJIP, Fv/Fm and PI. In addition, the growth parameters (No. of leaves, plant height and total leaves area) and other photosynthesis parameters (RC/CS, TFm, RC/ABS and ABS/RC) at 0,100 and 200 mM NaCl were assessed. Giza 129 was identified as the most salt tolerant and Giza 123 as the most salt sensitive. Both cultivars along with Giza 132 (moderately salt tolerant) were used to evaluate the relative expression of the B2 and shmt genes at 0,100 and 200 mM NaCl. The expression of both genes increased in the tested cultivars upon salinity treatment, while at 200 mM NaCl the fold increase in gene expression in Giza 129 was significantly higher followed by Giza 132 and 123. Repeating the same experiment for Giza 129, 132 and 123 along with wild barley under growth chamber revealed that the effect of salinity was more vigorous at the physiological and morphological levels. In addition, the gene expression was in general higher than that of the open field conditions although exhibiting similar trend of expression pattern

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