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Appl. Environ. Microbiol., 03 1996, 979-985, Vol 62, No. 3
C Rouvier, Y Prin, P Reddell, P Normand and P Simonet
DNA extracted directly from nodules was used to assess the genetic
diversity of Frankia strains symbiotically associated with two species of
the genus Casuarina and two of the genus Allocasuarina naturally occurring
in northeastern Australia. DNA from field-collected nodules or extracted
from reference cultures of Casuarina-infective Frankia strains was used as
the template in PCRs with primers targeting two DNA regions, one in the
ribosomal operon and the other in the nif operon. PCR products were then
analyzed by using a set of restriction endonucleases. Five distinct genetic
groups were recognized on the basis of these restriction patterns. These
groups were consistently associated with the host species from which the
nodules originated. All isolated reference strains had similar patterns and
were assigned to group 1 along with six of the eight unisolated Frankia
strains from Casuarina equisetifolia in Australia. Group 2 consisted of two
unisolated Frankia strains from C. equisetifolia, whereas groups 3 to 5
comprised all unisolated strains from Casuarina cunninghamiana,
Allocasuarina torulosa, and Allocasuarina littoralis, respectively. These
results demonstrate that, contrary to the results of previous molecular
studies of isolated strains, there is genetic diversity among Frankia
strains that infect members of the family Casuarinacaeae. The apparent high
homogeneity of Frankia strains in these previous studies probably relates
to the single host species from which the strains were obtained and the
origin of these strains from areas outside the natural geographic range of
members of the family Casuarinaceae, where genetic diversity could be lower
than in Australia.
Copyright © 1996, American Society for Microbiology
Genetic diversity among Frankia strains nodulating members of the family Casuarinaceae in Australia revealed by PCR and restriction fragment length polymorphism analysis with crushed root nodules
Laboratoire d'Ecologie Microbienne du Sol, Villeurbanne, France.
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