No abstract

Objective. Conduct screening of a wide variety of transgenic mutagenesis strains of Bradyrhizobium japonicum nodule bacteria by the sensitivity to Fever, Standak Top, Akanto Plus, Maxym XL, and Benorad fungicides, and obtain Tn5 mutants resistant to different normal rates of the above pesticides. Methods. Microbiological, statistical. Results. Under the conditions of laboratory experiments, Tn5 mutants of B. japonicum, resistant to the production and dual production normal rate of Fever, Standak Top, Akanto Plus, Maxym XL, and Benorad, were selected. It was shown that the active substances of the products with fungicidal activity Fever, Standak Top, Akanto Plus, Maxym XL do not have bactericidal effect on cell viability of the majority of Tn5 mutants obtained as a result of intergeneric conjugation between Escherichia coli S17-1 with different plasmid vectors and strains of B. japonicum 646 and 634b, and only in some cases reduce the intensity of their reproduction. It was established that Tn5 mutants of B. japonicum under study have different sensitivity to the influence of the normal rates of benomil-based Benorad recommended by the manufacturer and twice-increased. Nine Tn5 mutants were evaluated as low-sensitive to the production normal rate of Benorad, 11 were characterized by a higher sensitivity to fungicide, as evidenced by the zones of delayed growth of bacterial lawn around wells with the product over 15 mm. The influence of the double Benorad normal rate on transposon mutants was significantly stronger compared with other fungicides. Three Tn5 mutants, low-sensitive to the influence of the double rate of this product were selected, and delay of the reproduction of cells in these variants of the experiment was 14-15 mm around the wells. Conclusion. The use of bacterial fertilizers for soybeans based on Tn5 mutants of B. japonicum resistant to modern fungicides will help to reduce the consequences of chemical stress on the formation and functioning of symbiotic systems.

На основі аналізу відомих методів добору активних штамів ризобій представлено стратегію первинного скринінгу за симбіотичними властивостями бульбочкових бактерій сої Bradyrhizobium japonicum в умовах модельних вегетаційних дослідів за природних освітлення і температури. Сою сорту Лісабон інокулювали мутантами В. japonicum, отриманими методом транспозонового мутагенезу за використання плазмідного вектора pSUP5011::Tn5. Наведено результати селекції ризобій за господарсько-корисними властивостями (вірулентність, нодуляція, азотфіксувальна активність, стимуляція росту надземної маси рослин сої). Виявлено відмінності між транспозоновими мутантами В. japonicum за здатністю викликати утворення бульбочок на коренях рослини-хазяїна, динамікою та інтенсивністю асиміляції атмосферного азоту симбіотичними системами соя-ризобії. Зазначено доцільність проведення селекції мікросимбіонтів не лише у ранній період формування симбіотичних систем сої, а й у найактивнішу фазу їх функціонування. Це забезпечує можливість добору штамів із різними типами динаміки азотфіксувальної активності, найагресивніших та високовірулентних штамів у період становлення симбіозу. Відібрано Tn5-мутанти з поліпшеним симбіотичним фенотипом порівняно зі штамом-контролем Bradyrhizobium japonicum 634б.

The physiological reaction of legume plants to inoculation with algal-rhizobial associations was studied, based on the nodule bacteria, their Tn5 mutants and the cyanobacterium Nostoc punctiforme . It was shown that binary inoculation with rhizobia and cyanobacteria may have a positive effect if the inoculation agents and their ratio are correctly chosen. The data obtained on the effect of complex bacterization on the development and productivity of plants under legume-rhizobial symbiotic conditions indicate the prospects of bacterial preparations based on cyanobacteria and rhizobia, including their genetically modified strains.

Objective. Evaluate the efficiency of soybean inoculation with pesticide-resistant nodule bacteria Bradyrhizobium japonicum under the influence of pre-sowing seed dressing with Maxym XL,Standak Top and Fever and preventive spraying of plants with the fungicide Akanto Plus. Methods. Physiological, microbiological, gas chromatographic, vegetation experiment, statistical.Results. The number and weight of nodules formed on soybean roots during the growing seasonunder the action of the prothioconazole-based fungicide Fever were reported to be lower comparedwith the control and other variants of experiment. Pesticides Maxym XL and Standak Top had a lesspronounced toxic effect on the formation of legume-rhizobial symbiosis with the participation offungicide-resistant B. japonicum B78 Tn5 mutant compared to Fever. A decrease in the level of N2assimilation by 10.9–41.1 % in the three-leaf phase was found with the combined use of seed pesticides and nodule bacteria included in the study, relative to the variant with inoculation only. However, during the growing season, the negative effect of fungicidal preparations on the functioning oflegume-rhizobial symbiosis decreased. Conclusion. Under the conditions of the model vegetationexperiment with the concomitant use of Standak Top and Fever and bacterization, a decrease in individual plant productivity by 7.0 and 14.1 %, respectively, has been reported. The complex actionof the pesticide Maxym XL and inoculation with pesticide-resistant B. japonicum B78 transposonmutant, contributed to the maximum increase in yield by 27.2 %. The obtained data confirm the expediency of selection of fungicides and nitrogen-fixing microorganisms for concomitant use to ensure high economic and protective effects.