Artificial associative symbioses between tomato plants and fungistatic rhizobium

Biomethods in plant protection against pests and diseases considered the most prospective alternative to chemicals which pollute soil and water causing concern about public health. The possibility of creating an artificial association of nodule bacteria with plants to protect them from the adverse effects of pathogenic fungi can be realized using one of the specific mechanism of nodule bacteria attachment to the roots of leguminous plants by plant lectins, able to recognize and specifically bind with different carbohydrates, particularly polysaccharides of rhizobia cell wall. In our study we used the composite plants of tomato ( Lycopersicon esculentum ) Dubok variety and bacterial strains associated with the roots of wild legumes from the collection of Institute of Biochemistry and Genetics (IBG USC RAS). «Hairy rooted» tomato plants were obtained by treatment with Agrobacterium rhizogenes ATCC 15834, containing vehicle gene construction pCambia 1305.1 with inserted pea lectin gene psl under cauliflower mosaic virus 35S promoter. The antagonistic activity of bacteria towards pathogens was tested by dual culture study. The ability of microorganisms to produce siderophores and cyanide was analyzed. Few isolates were identified by sequencing of the 16S rRNA gene fragments. By screening of the collection of isolates from nodules of wild legume from tribe Viceae the candidate strains were detected, particularly Rhizobium leguminosarum, Pseudomonas sp. and Stenotrophomonas rhizophila, with fungistatic activity against Fusarium solani, F. oxysporum, Fusarium sp. and F. oxysporum f. sp. lycopersici. Prodiction of siderophores was detected in two members of Pseudomonas genus, S. rhizophila and R. leguminosarum. Two Pseudomonas strains, the 14M and 103, and S. rhizophila were shown to produce cyanide. It was also found that treatment of roots transgenic by psl gene with R. leguminosarum 116 strain reduced the amount of hyphae of the pathogen F. oxysporum f. sp. lycopersici in the rhizosphere of tomato plant that could potentially contribute to plant defense against pathogenic fungi. Thus, the use of lectins as transgenes in roots allows to obtain artificial association with rhizobia in non-symbiotic plants such as tomato, which in combination with the use of microorganisms possessing fungistatic activity can more effectively protect the plant root system o against pathogens.