Premium
Relative genetic structure of a population of Rhizobium meliloti isolated directly from soil and from nodules of alfalfa ( Medicago sativa ) and sweet clover ( Melilotus alba )
Author(s) -
BROMFIELD E. S. P.,
BARRAN L. R.,
WHEATCROFT R.
Publication year - 1995
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/j.1365-294x.1995.tb00207.x
Subject(s) - biology , medicago sativa , rhizobium , population , melilotus , legume , agronomy , medicago , rhizobium leguminosarum , root nodule , botany , microbial inoculant , inoculation , nitrogen fixation , symbiosis , horticulture , rhizobiaceae , bacteria , gene , biochemistry , genetics , demography , sociology
Insertion sequence (IS) hybridization was used to define the structure of a population of Rhizobium meliloti isolated directly from soil and from nodules of Medicago sativa (alfalfa) and Melilotus alba (sweet clover) grown under controlled conditions and inoculated with a suspension of the same soil. The detection of R. meliloti isolated from soil on agar plates was facilitated by use of a highly species specific DNA probe derived from ISR m 5. All R. meliloti obtained directly from soil proved to be symbiotic (i.e. nodulated and fixed nitrogen with alfalfa). Analysis of 293 R. meliloti isolates revealed a total of 17 distinct IS genotypes of which 9, 9 and 15 were from soil, M. alba and M. sativa , respectively; 8 genotypes were common to soil and both plant species. The frequency of R. meliloti genotypes from soil differed markedly from that sampled from nodules of both legume species: 5 genotypes represented about 90% of the isolates from soil whereas a single genotype predominated among isolates from nodules accounting for more than 55% of the total. The distribution of genotypes differed between M. sativa and M. alba indicating species variation in nodulation preferences for indigenous R. meliloti . The data are discussed in the context of competition for nodulation of the host plant and the selection of Rhizobium strains for use in legume inoculants. This study has ecological implications and suggests that the composition of R. meliloti populations sampled by the traditionally used host legume may not be representative of that actually present in soil.