Distinct morphological differences were demonstrated within single-spores of five Drechslera teres isolates, obtained from Siwa, Maryout and Ras Sudr Agricultural Experimental Stations of Desert Research Centre (DRC). The morphological parameters data classified D. teres isolates to different five isolates which showed great differences among them. Where, D. teres isolates spore length ranged from 6.41 µ and 9.49 µ for the isolate No. 3 and No. 2, respectively. In addition, similarity in the number of septa was found, where the spore septa length ranged from 0.79 µ to 5.9 µ for isolates No. 3 and No. 4, respectively. Moreover, there was a slight difference in the length of the germ tube. Under greenhouse conditions, the five D. teres isolates showed different levels of virulence, where isolates No. 3 and No. 4 were the most virulent, while isolate No. 2 was the least virulent. On the other hand, barley genotypes varied in their reaction to D. teres isolates, where, genotypes L26, Gl26, and G13l were classified as moderately resistant while genotypes L3, H6, H7 and H10 were classified as resistant. The PCR product using degenerate primer of MLO1 indicated the appearance of one fragment sizes about 500 bp. This was detected in four resistant barley genotypes (L3, H6, H7 and H10), but was absent in the moderately resistant genotypes (L26, GJ 26 and G 131). Therefore, this study may add a molecular based value to the application of MLO1 in plant diseases molecular diagnostics for detection of net blotch resistance in different barley genotypes. This may indicate that such barley genotypes could be cultivated in different geographic locations according to their response to biotic stress by different D. teres isolates.