Genetic resources of nodule bacteria |
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Authors: | M L Roumiantseva |
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Institution: | 1.All-Russia Research Institute of Agricultural Microbiology,Russian Agricultural Academy,St. Petersburg, Pushkin,Russia |
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Abstract: | Nodule bacteria (rhizobia) form highly specific symbiosis with leguminous plants. The efficiency of accumulation of biological
nitrogen depends on molecular-genetic interaction between the host plant and rhizobia. Genetic characteristics of microsymbiotic
strains are crucial in developing highly productive and stress-resistant symbiotic pairs: rhizobium strain-host plant cultivar
(species). The present review considers the issue of studying genetic resources of nodule bacteria to identify genes and their
blocks, responsible for the ability of rhizobia to form highly effective symbiosis in various agroecological conditions. The
main approaches to investigate of intraspecific and interspecific genetic and genomic diversity of nodule bacteria are considered,
from MLEE analysis to the recent methods of genomic DNA analysis using biochips. The data are presented showing that gene
centers of host plants are centers of genetic diversification of nodule bacteria, because the intraspecific polymorphism of
genetic markers of the core and the accessory rhizobial genomes is extremely high in them. Genotypic features of trapped and
nodule subpopulations of alfalfa nodule bacteria are discussed. A survey of literature showed that the genomes of natural
strains in alfalfa gene centers exhibit significant differences in genes involved in control of metabolism, replication, recombination,
and the formation of defense response (hsd genes). Natural populations of rhizobia are regarded as a huge gene pool serving as a source of evolutionary innovations. |
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