Host Specific Nodulation of Plants of the Pea Cross-inoculation Group is Influenced by Genes in Fast Growing Rhizobium downstream nodC

Tn5 induced mutants in nodI and nodJ of the Rhizobium leguminosarum biovar viceae Sym plasmid pRL1JI nodulated Vicia sativa and Vicia hirsuta plants slightly delayed. Complementation experiments showed that nodI,J were part of the nodA,B,C transcriptional unit. A Rhizobium strain in which two Sym plasmids were present, almost completely lost the ability to nodulate V sativa plants when nodI,J on both Sym plasmids were inactivated. Several other plants of the pea cross-inoculation group showed a likewise difference in their nodulation response. In addition we investigated the nodulation of Afghanistan peas. R. leguminosarum biovar viceae strains do not nodulate Afghanistan peas. When a Sym plasmid from such a strain was transferred to wild type R. leguminosarum biovar trifolii strains, the resulting strains nodulated Afghanistan peas. We provide evidence for the existence of a new gene, necessary for the nodulation of Afghanistan peas, which is located in the nodA,B,C,I,J operon of R. leguminosarum biovar trifolii strain ANU843.