Association of dominant loci for resistance to Pseudomonas syringae pv. pisi with linkage groups II, VI and VII of Pisum sativum

Morphological characters, isoenzymes and recombinant inbred lines were empl oyed to assign four loci for resistance to Pseudomonas syringae pv pisi to genetic linkage groups in Pisum sativum. A total of five morphological mark ers and I I isoenzyme loci were screened in two independent F-2 P. sativum populations: Vinco x Hurst's Greenshaft (VxHGS) and Partridge x Early Onwar d (PxEO). Mapping was also carried out in two recombinant inbred population s, unrelated to the F-2 populations. Previously reported linkage between re sistance genes Ppi3 and Ppi4 was confirmed. Linkage was also detected betwe en resistance gene Ppi2 and the isoenzyme locus Aldo (linkage group VII). T he linked loci Ppi3 and Ppi4 were associated with a (linkage group II). A f urther resistance gene Ppi1 was associated with linkage group VI close to t he hilum colour gene Pl. RAPD markers tested in the cross PxEO were not wel l targeted. however, one marker, OPA-20(0.71), showed linkage to Ppi3.