Complexity in evaluating resistance of barley (Hordeum vulgare L) to 2 pathotypes of BYDV-PAV: allelic variability at the Yd2 gene locus BA Chalhoub, A. Sarrafi and HD LapierreAgronomie, 15 7-8 (1995) 507DOI: https://doi.org/10.1051/agro:19950744