Diversity and specificity of Rhizobium leguminosarum biovar viciae on wild and cultivated legumes

TY - JOUR

T1 - Diversity and specificity of Rhizobium leguminosarum biovar viciae on wild and cultivated legumes

AU - Mutch, L A

AU - Young, J P W

N1 - © 2004 Blackwell Science Ltd. This is an electronic version of an article published in Molecular Ecology: complete citation information for the final version of the paper, as published in the print edition of Molecular Ecology, is available on the Blackwell Synergy online delivery service, accessible via the journal's website at http://www.blackwellpublishing.com/journal.asp?ref=0962-1083 or www.blackwell-synergy.com

PY - 2004/8

Y1 - 2004/8

N2 - The symbiotic partnerships between legumes and their root-nodule bacteria (rhizobia) vary widely in their degree of specificity, but the underlying reasons are not understood. To assess the potential for host-range evolution, we have investigated microheterogeneity among the shared symbionts of a group of related legume species. Host specificity and genetic diversity were characterized for a soil population of Rhizobium leguminosarum biovar viciae (Rlv) sampled using six wild Vicia and Lathyrus species and the crop plants pea (Pisum sativum) and broad bean (Vicia faba). Genetic variation among 625 isolates was assessed by restriction fragment length polymorphism (RFLP) of loci on the chromosome (ribosomal gene spacer) and symbiosis plasmid (nodD region). Broad bean strongly favoured a particular symbiotic genotype that formed a distinct phylogenetic subgroup of Rlv nodulation genotypes but was associated with a range of chromosomal backgrounds. Host range tests of 80 isolates demonstrated that only 34% of isolates were able to nodulate V. faba. By contrast, 89% were able to nodulate all the local wild hosts tested, so high genetic diversity of the rhizobial population cannot be ascribed directly to the diversity of host species at the site. Overall the picture is of a population of symbionts that is diversified by plasmid transfer and shared fairly indiscriminately by local wild legume hosts. The crop species are less promiscuous in their interaction with symbionts than the wild legumes.

AB - The symbiotic partnerships between legumes and their root-nodule bacteria (rhizobia) vary widely in their degree of specificity, but the underlying reasons are not understood. To assess the potential for host-range evolution, we have investigated microheterogeneity among the shared symbionts of a group of related legume species. Host specificity and genetic diversity were characterized for a soil population of Rhizobium leguminosarum biovar viciae (Rlv) sampled using six wild Vicia and Lathyrus species and the crop plants pea (Pisum sativum) and broad bean (Vicia faba). Genetic variation among 625 isolates was assessed by restriction fragment length polymorphism (RFLP) of loci on the chromosome (ribosomal gene spacer) and symbiosis plasmid (nodD region). Broad bean strongly favoured a particular symbiotic genotype that formed a distinct phylogenetic subgroup of Rlv nodulation genotypes but was associated with a range of chromosomal backgrounds. Host range tests of 80 isolates demonstrated that only 34% of isolates were able to nodulate V. faba. By contrast, 89% were able to nodulate all the local wild hosts tested, so high genetic diversity of the rhizobial population cannot be ascribed directly to the diversity of host species at the site. Overall the picture is of a population of symbionts that is diversified by plasmid transfer and shared fairly indiscriminately by local wild legume hosts. The crop species are less promiscuous in their interaction with symbionts than the wild legumes.

KW - domestication

KW - host range

KW - legumes

KW - nodD

KW - Rhizobium leguminosarum bv. viciae

KW - symbiosis

KW - FRAGMENT-LENGTH-POLYMORPHISM

KW - PISUM-SATIVUM-L

KW - BV-VICIAE

KW - POPULATION-GENETICS

KW - ENZYME POLYMORPHISM

KW - SYMBIOTIC RHIZOBIUM

KW - STRAIN SPECIFICITY

KW - FIELD POPULATIONS

KW - NODULATION FACTOR

KW - AFGHANISTAN PEAS

U2 - 10.1111/j.1365-294X.2004.02259.x

DO - 10.1111/j.1365-294X.2004.02259.x

M3 - Article

SN - 0962-1083

VL - 13

SP - 2435

EP - 2444

JO - Molecular Ecology

JF - Molecular Ecology

IS - 8

ER -