STUDIES ON THE INHERITANCE OF RESISTANCE TO SIX STEM RUST CULTURES USING CHROMOSOME SUBSTITUTION LINES OF A MARQUIS WHEAT SELECTION

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Abstract
Three of the 21 chromosome substitution lines derived from a Marquis selection were found to differ from the susceptible recurrent parent Chinese in reaction to one or more of 6 narrowly virulent stem rust genotypes used. Resistance to cultures of races 111 and 121 is conferred by 2 independently inherited dominant loci on chromosome 2A. A dominant gene (Srl2) on chromosome 3B confers a high resistance to the culture of race 111 only. This locus appears linked with a second locus at which a recessive allele conditioned mesothetic reactions to the cultures of NR2 and races 11, 186 and 198. A test for allelism indicates presence of same loci on the chromosome 3B substitution line of Thatcher. A dominant allele on the 6D substitution line conditions immune reactions to the cultures of races 121 and 198, but no resistance to the other rust genotypes. When two loci conditioning resistance were combined it was found that the resulting reaction to a given rust genotype was typically that associated with the locus conferring the higher level of resistance, i.e., no evidence of non-allelic interaction was observed.