ANEUPLOID ANALYSIS OF RESISTANCE IN A KENYA WHEAT TO ISOLATES OF STEM RUST RACE 15B

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Abstract
Study of F2 progenies from monosomic F1 hybrids between monosomics of highly susceptible Chinese Spring and a resistant selection of Kenya 338 indicates that no single chromosome of the resistant parent confers a high level of resistance to either of 2 rust cultures used. The mean reactions of chromosomes 2A, 4A, 4B, 5B, and 5D suggests the presence of genes conditioning some resistance to the pathogen cultures. Further study of the reactions to 5 rust cultures of the Kenya 338 chromosomes substituted individually into Chinese Spring revealed that 2 of the chromosomes confer some resistance by themselves. Chromosome 4B gave a moderately susceptible reaction to 4 of the cultures and a somewhat more resistant reaction to the 5th culture. Chromosome 2A conferred moderately resistant reactions to 2 of the cultures, and a reaction not sensibly different from that of the susceptible parent to 2 of the cultures. A 5th culture, to which chromosome 2A by itself conditioned a typical moderately resistant reaction, was used in both the monosomic F2 and chromosome substitution line studies. Inconsistent reactions of the 2 types of materials to this culture suggest the presence on chromosomes 3B and 7D of genes that function to inhibit the resistance reactions conditioned by other loci.