**5. Conclusions**

Intimate associations of beneficial soil microbes with the host plants described above in detail are applicable in sustainable crop production if taken either separately or in combination. Many authors are now recognizing the need for using the multi-microbial plant inoculants and the advantages of using the indigenous plants (or varieties of local breeding) and microbes.

The authors' team proposes its own concept which offers fundamentally new approaches to plant production. Firstly, it is necessary to consider plant genetic systems controlling interac‐ tions with different beneficial soil microbes in unison. Secondly, plants used as a component of this complex plant-microbe system controlling its effectiveness should be bred to improve the effectiveness of interactions with all types of beneficial soil microbes. Increases of plant biomass production due to plant-microbe symbiosis should be used as the main parameter for an evaluation of plant effectiveness in interactions with beneficial soil microbes. The plant production should be done with inoculation composed of multi-component microbial inocula consisting of AM fungi, rhizobia, PGPR and/or beneficial endophytic bacteria. Finally, taking into consideration the importance of legumes for global agriculture, greater emphasis should be placed on plant-microbial systems in the development of low-input agro-biotechnologies enabling wider cultivation of leguminous crops.

Molecular markers are considered to be a convenient tool to facilitate breeding via MAS (marker-assisted selection) approach. But, search for suitable markers that are associated with symbiotic effectiveness trait is rather complicated problem. To our knowledge, there was no direct link between sequences of symbiotic genes and symbiotic effectiveness, and there are only a few examples of successful use of QTL analysis in legumes to trace loci associated with some symbiotic traits in pea [238] and *Lotus* [239]. So there's a gap between molecular genetic bases of symbioses development, from one side, and effective functioning the symbiotic systems in field conditions, from the other side. In our opinion, substantial improvement of methods of molecular genetics and bioinformatics, such as next-generation sequencing and proteome analysis, could help to build a bridge between fundamental and applied science in this area, and to improve the sustainability of the legume crop production.
