Isolates of Drechslera teres that cause net or spot-type symptoms on barley {Hordeum vulgare) were collected in 1986 and 1987 from fields in different regions of France. Variations in pathogenicity were to all isolates except R5 and S5. The Ethiopian cultivar Cl 5791, previously reported to be resistant, was susceptible to the R5 and S5 biotypes. There was a high correlation coefficient between the classification of cultivars for resistance to D. teres f. sp. teres and D. teres f. sp. maeulata. A method for conserving the virulence of the isolates on straw is evaluated. The virulence level of the isolates was the same after 4 years of storage using this method.

Reciprocal crosses were made between 9 different barley genotypes with high genetic variability for net blotch resistance. Parents and 72 F| plants were used to determine the inheritance of partial resistance to net blotch. Four experiments, one in a growth chamber on seedlings and 3 others m the field on adult plants, were undertaken using a randomised complete block design. An isolate of net blotch from local cultivars was used for inoculation. Non-inoculated plants of one of the field experiments were used for the detached leaf test in petri dishes.Results show that the cultivars 'Banteng', and 'Arrivate', the Ethiopian line CI 5791, and the Syrian line 79 SIO-10, had a high partial resistance in all experiments. Diallel analysis showed high significant general and specific combining ability when maternal and reciprocal effects were not significant. As the resistance genotypes have a high additive genetic effect, they could be successfully used for breeding purposes.

Seven barley genotypes with high genetic vari,ibility for resistanee to bacterial leal streak {Xantbomonas eampestris pv, hordei) were crossed in diallel fashion to determine the inheritance of resistance to this disease. Two experiments were undertaken in a controlled growth chamber using a complete-bloek design with four replieates. Each replicate consisted of a row of 20 seedlings per parent or F, hybrid. An Iranian strain of baeterial leaf streak was used for inoculation ot 12-day-old seedlings. Results showed that the cultivars T^xpress' and 'Morex' and the Iranian pure line lran-3a h,id a high partial resistance in both experiments. Diallel analysis showed highly significant general and speeific combining abilities. 'Morcx' and Iran-3a were the best combiners for partial resistance to bacterial leaf streak in barley ancl eciuld be successfully used for breeding purposes.

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