B.F. MULLEN¹, V.E. FRANK¹ and R.A. DATE²

¹Department of Agriculture, The University of Queensland, Brisbane, Queensland, Australia
²CSIRO Tropical Agriculture, St Lucia, Queensland, Australia

Abstract

Twenty-seven accessions of Leucaena, representing 19 species, were assessed for effective N-fixing symbioses in association with 13 strains of Rhizobium (derived primarily from Leucaena spp. hosts) in N-free conditions in a glasshouse experiment. Two major leucaena accession groups were identified using pattern analysis. Fifteen of the 27 accessions of Leucaena associated with a wide range of rhizobial strains and only 4 accessions appeared to have specific rhizobial strain requirements for effective nitrogen fixation.
Nine of the 13 strains of Rhizobium formed highly effective associations with most accessions of Leucaena and only 1 strain (CB3299) was ineffective for N₂ fixation with all accessions. Rhizobial strains CB3126, NGR8 and CB3060 were the most broadly effective, associating highly effectively with 22, 17 and 21 accessions of Leucaena, respectively.
Accessions of Leucaena were grouped according to rhizobial strain effectiveness, but biological characters such as native range, ploidy level and chromosome number correlated poorly with accession groups.