The nodD1 Gene from Rhizobium Strain NGR234 Is a Key Determinant in the Extension of Host Range to the Nonlegume Parasponia. Gregory L. Bender. Plant Molecular Biology, Research School of Biological Sciences, Australian National University, Box 475 P.O., Canberra City, A.C.T. 2601. Murali Nayudu, Kathryn K. Le Strange, and Barry G. Rolfe. Plant Molecular Biology, Research School of Biological Sciences, Australian National University, Box 475 P.O., Canberra City, A.C.T. 2601.. MPMI 1:259-266. Accepted 15 September 1988. Copyright 1988 The American Phytopathological Society.

The narrow host range of Rhizobium leguminosarum biovar trifolii strain ANU843 can be extended from clovers to the nonlegume Parasponia by the addition of the nodD1 gene from Rhizobium strain NGR234. The presence of the nodD1 gene from NGR234 enabled induction of a nodA::MudII1734 fusion in strain ANU843 by seedling extracts from Parasponia and other nonlegumes, including Trema (a tree genus closely related to Parasponia), Casuarina (a genus that forms symbiotic relationships with the actinomycete Frankia) and the cereals wheat, rice, and maize. There was also an increase in the range of flavonoids causing induction, suggesting that the nodD1 gene from the broad host range strain NGR234 is nonspecific in action rather than host specific, as found for the nodD genes from narrow host range species. Although the presence of the nodD1 gene from NGR234 enabled the induction of nod genes by a range of nonlegume extracts, no nodules were elicited on any nonlegumes other than Parasponia.