The thesis paper presents the results of researching the aspects of formation and functioning of symbiotic system “Mesorhizobium ciceri – Cicer arietinum” when using highly effective, virulent and competitive strain of M. ciceri ND-64 for inoculation of seeds which is capable to form effective symbiosis with chickpea plants of Ukrainian selection in the agrocenoses of Polissia and Steppe of Ukraine. It was shown for the first time that the populations of chickpea nodule bacteria in the soils of Ukraine are heterogeneous: they are represented by rhizobia, which differ in growth rate and other cultural and morphological, physiological and biochemical properties.
A new strain of M. ciceri ND-64 was selected, which is able to form an effective symbiosis with such chickpea varieties as Skarb, Admiral, Odysei, Budzhak, Triumf and Pami'at'. It was shown that the use of inoculation of seeds of these varieties using bacterial suspension of M. ciceri ND-64 contributed to an increase in the number (by 5–89 %), weight of nodules (by 10–190 %) and their nitrogenase activity (by 26–290 %) compared with positive control, as well as structural parameters of chickpea yield: number of beans (by 5–34 %), seeds from the plant (by 7–27 %), weight of seeds from the plant (by 8–26 %) and yield (by 4–19 %) compared to the positive control (without inoculation) in the zones of the Steppe and Polissia of Ukraine. The presented results indicate a high complementarity of M. ciceri ND-64 to all studied varieties. The dynamics of the formation of symbiosis between nodule bacteria and chickpea plants in Polissia was studied for the first time and it was shown that nodules on chickpea roots begin to form already in the branching phase (10 to 14 days after germination). Under the conditions of the field experiment, the variant with inoculation of seeds with bacterial suspension of M. ciceri ND-64 shown the highest parameters of symbiotic activity during the whole vegetation period of plants, which have achieved the maximum values at the beginning of the bean formation phase (number of nodules – 43 units/plant, weight of nodules – 1.06 g/plant, nitrogenase activity – 3,597 nmol of ethylene/plant•h).
It was found that M. ciceri ND-64 with high nitrogen-fixing activity is characterized by the ability to synthesize substances of phytohormonal nature: auxins, cytokinins and gibberellins. For example, when treating wheat coleoptiles with a suspension of M. ciceri ND-64, the highest increase in their length was registered at a dilution of 1:1000 (20 %), the highest increase in cucumber cotyledons weight at the same dilution – by 50 %, and gain in the length of corn mesocotyles was 23 % at a concentration of 1:500. High-performance liquid chromatography in the culture fluid of M. ciceri ND-64 revealed a high content of auxin substance with a total concentration of 29.6 μg/g absolutely dry biomass. The serological affinity of chickpea nodule bacteria and their competitiveness during cultivation in the Polissia zone, where the formation of the local rhizobia population is just beginning, was studied for the first time. Studies have shown that M. ciceri H-101 and Mesorhizobium sp. ND-601 isolated from chickpea nodules of Skarb and Pami'at' varieties reacted positively with antiserum to M. ciceri ND-64. Agglutination method allowed to find that in the field experiment in the variant with inoculation by M. ciceri ND-64 100 % of nodules were formed by representatives of this serogroup.
It was shown that M. ciceri ND-64, which provided the highest increments in nodule nitrogenase activity, also increased the intensity of photosynthesis of chickpea plants, as evidenced by the increase in chlorophyll a and b in the leaves of inoculated plants relative to control by 42 % end also provided an increase in nitrogen content in the seeds by 0.2–0.4 %, weight content of protein by 1.6–2.8 % relative to positive and absolute control in terms of dry matter. Inoculation of chickpea seeds with a bacterial suspension of a highly effective strain of M. ciceri ND-64 contributed to a significant increase in the yield of this crop in the Polissia zone of Ukraine by 27 % (Pami'at' variety) and 37 % (Skarb variety) and in the Steppe zone of Ukraine by 17 % (Pami'at' variety) and 33 % (Skarb variety) relative to absolute control. It is shown that the use of M. ciceri ND-64 for inoculation of seeds allows to reduce production costs and earn a profit in the amount of UAH 10 795, and a payback of each hryvnia of additional costs associated with the use of M. ciceri ND-64 as additional income is UAH 30,88.
Production tests conducted in the Forest-Steppe zone (Region of Kirovohrad) at the Private Enterprise “Daprynda” on an area of 8 hectares, indicate a high efficiency of inoculation. Gain in the yield reached 26 % when chickpea seeds of Pami'at' variety were bacterized with a suspension of M. ciceri ND-64.
