Authors: Endalkachew Woldemeskel Trygve Berg N Kent Peters Åsa Frostegård
Publish Date: 2004/04/09
Volume: 40, Issue: 1, Pages: 55-66
Abstract
The nodulation of provenances of Acacia seyal Acacia tortilis and Faidherbia albida and other indigenous multipurpose tree species were tested in 14 different soil samples collected from diverse agroecological zones in southern Ethiopia Associated rhizobia were isolated from these and from excavated nodules of field standing mature trees and phenotypically characterized Indigenous rhizobia capable of eliciting nodules on at least one or more of the woody legume species tested were present in most of the soils Tree species were markedly different in nodulation in the different site soils Sesbania sesban and Acacia abyssinica showed higher nodulation ability across the different sites indicating widespread occurrence of compatible rhizobia in the soils The nodulation patterns of the different provenances of Acacia spp suggested the existence of intraspecific provenance variations in rhizobial affinity which can be exploited to improve N fixation through tree selection Altogether 241 isolates were recovered from the root nodules of trap host species and from excavated nodules Isolates were differentiated by growth rate and colony morphology and there were very fast fast slow and very slowgrowing rhizobia The bulk of them 685 were fastgrowing acidproducing rhizobia while 253 were slowgrowing alkaliproducing types Fastgrowing alkaliproducing 29 and slowgrowing acidproducing strains 33 were isolated from trap host species and excavated nodules respectively All isolates fell into four colony types watery translucent white translucent dull glistering and milky curdled type The diversity of indigenous rhizobia in growth rate and colony morphology suggested that the collection probably includes several rhizobial generaThe authors gratefully acknowledge the financial support of the International Foundation for Science IFS for the seed collection and the Norwegian Universities Committee for Development Research and Education NUFU for the research the Lånekassen Norway for the stipend for the PhD study of E Woldemeskel at the Agricultural University of Norway and the Research and Extension Office and various departments at Awassa College of Agriculture Ethiopia for providing facilities for the research
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