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Recombination Events Generating a Novel Rp1 Race Specificity

Genes at the maize Rpl rust resistance complex often mispair in meiosis, which allows genes to recombine unequally, creating recombinant haplotypes. Four recombinant haplotypes were identified from progeny of an Rpl-D/Rpl-I heterozygote that conferred a nonparental resistance specificity designated Rpl-I*. Sequence comparisons of paralogs in the recombinant and parental haplotypes demonstrated that all four recombinants were derived from intergenic (between gene) recombination events. The sequence of paralogs in the HRpl-I parental haplotype indicated this haplotype includes 41 or more rpl genes, at least 31 of which are transcribed. The results indicate that most of the novel resistance specificities that have arisen spontaneously at Rp1 are the result of reassortment of existing Rpl genes.