E. Geniaux et al., COMPARISON OF GEOGRAPHICALLY DISTANT POPULATIONS OF RHIZOBIUM ISOLATED FROM ROOT-NODULES OF PHASEOLUS-VULGARIS, Molecular ecology, 2(5), 1993, pp. 295-302
Seventy-two rhizobial strains were isolated from the root nodules of f
rench beans (Phaseolus vulgaris). They were sampled from two geographi
cally distant field populations and 18 additional different sites in F
rance. They were characterized by a) plasmid profiles (b) RFLP analysi
s of total cellular DNA using various chromosomal and symbiotic gene p
robes (including nifH from Rhizobium etli bv. phaseoli) and c) their a
bility to nodulate a potential alternative host, L. leucocephala. Over
half of the isolates were ascribed to Rhizobium leguminosarum bv. pha
seoli on the basis of the hybridization analysis, the possession of mu
ltiple copies of nifH and their inability to nodulate L. leucocephala.
The remaining isolates belonged to 2 groups which were shown to be ge
nomically distinct from R. leguminosarum bv. phaseoli, R. etli bv. pha
seoli and R. tropici. Most members of these two groups shared with R.
tropici the ability to nodulate L. leucocephala and, for isolates of o
nly one of these groups, the presence of one copy of nifH. Members of
each of the 3 taxa were widely distributed in France and circumstantia
l evidence of pSym transfer between them was shown. R. leguminosarum b
v. phaseoli and one of the two novel groups co-occurred within the two
geographically distant populations. Individual genotypes were conserv
ed between them. The finding of a third taxon at various other locatio
ns indicated additional diversity among rhizobia nodulating beans.