| Some 176 events involving genetic reassortment within the Rp1 complex were screened for novel resistance specificities with a set of 11 different rust biotypes. Most (150/176) of the events were susceptible to all the tested rust biotypes. Eleven events selected as double-resistant recombinants showed a combined resistance of the two parental types. Nine events selected as having partial resistance or complete susceptibility to a single biotype possessed resistance to a subset of the biotypes that the parents were resistant to. Four events gave rise to novel specificities being resistant to at least one rust biotype to which both parents were susceptible.; Crosses were made to estimate the stability of three unlinked rp loci, rp3, rp4, rp7. Susceptible progeny were identified in several of the rp3 test crosses, most of which were associated with flanking marker exchange. No susceptible progeny were identified in the Rp3-B family, suggesting that this allele would be suitable for transposon tagging. No susceptible derivatives were identified in the crosses with rp4. One susceptible was identified at rp7.; Two clones were identified using a degenerate primers approach to identify potential receptor-like kinases (RLKs). One clone, rlk1, detected two loci in the maize genome. One locus mapped to chromosome 2, while the other locus mapped to chromosome 7. The chromosome 2 copy mapped close to the disease resistance locus, Ht1 (northern corn leaf blight resistance). The chromosome 7 copy mapped near two QTLs for northern corn leaf blight resistance. The chromosome 2 RLK failed to co-segregate with Ht1. |
