Receptivity of barley to puccinia graminis f. Sp. tritici

The receptivity of barley genotypes (Hordeum vulgare) was studied in seedlings and adult plants in the greenhouse and in adult plants in the field to races I13-RTQ and 151-QSH of Puccinia graminis f. sp. tritici. In the greenhouse, significant differences in number of u redia/cm 2 of leaf were detected due to the effects of races, host genotypes, and their interaction. The cultivar Hiproly was most receptive (had the most uredia) and 80-TT-29 was least receptive (had the fewest uredia) to both races at both growth stages. With race 151-QSH, genotypes with the T-gene, 80-TT-29 and Manker had low weighted infection types (seedling stage), moderately resistant host responses (adult stage), and lower receptivity (both growth stages) than cultivars lacking this gene. With race 113-RTQ, the T-gene was associated with low receptivity only in 80-TT-29. The da ta suggest th at gene(s) other than the T-gene may confer receptivity to P. graminis f. sp. tritici. The ranking of genotypes and the relative differences in receptivity were similar in seedling and adult plants. In the field, genotypes with the T-gene had mostly moderately resistant reactions and fewer uredia than those without the gene. The significant race x host genotype interaction in this study suggests that receptivity in barley varies due to the specific host-parasite combination. Additional key words: Disease resistance, wheat stem rust, infection frequency, Hordeum vulgare.