The effect of native strains of nodule bacteria on the development of symbiotic apparatus and on the productivity of new soybean cultivars

Abstract

In 2018 and 2019, we studied new strains of nodule bacteria of soybean (Bradyrhizobium japonicum) in comparison with the standard (Noktin A) in field experiments on the experimental field of V.S. Pustovoit All-Russian Research Institute of Oil Crops (VNIIMK), Krasnodar on a leached extra heavy loam and weakly humus chernozem. The new strains were the strain 5/1, isolated from the meadow-chernozem soil of the Amur region and the strain 7p, isolated from the leached chernozem of the Krasnodar region. The aim of the research was to evaluate their effectiveness on promising soybean cultivars Slavia, Bars, Irbis and Opus by their influence on the development of symbiotic apparatus, development of root system and above-ground vegetative mass of plants in the phase of soybean vegetation, flowering and seed-filling, as well as on the seed yield and its quality.For 2 years, on average, all strains to varying degrees contributed to a more intensive development of a root system and an increase of above-ground mass of soybean plants at the beginning of the growth season. We observed the maximum increase in biomass by the seedfilling phase in the Bars cultivar with strains 5/1 and in the standard – by 45 and 48 %, respectively. However, the Slavia cultivar with bacterization variants in this phase had less dry above-ground plants mass than the control, by 30-51 %.Overall, the bacterization provided an increase in soybean productivity but to varying degrees by year and with different combinations of symbiotic partners (soybean cultivar – rhizobia strain). We observed the highest increase in seed productivity in Slavia and Opus cultivars: on average over 2 years - by 0.17-0.27 t/ha (8.7-13.0 %) and by 0.06-0.35 t/ha (2.6-15.1 %), respectively. The cultivars Bars and Irbis were less responsive to bacterization. We noted a certain cultivar-strain relation of preliminary complementary pairs: the Slavia cultivar – strains 5/1 and 7p; the Bars cultivar – strain 5/1; the Irbis cultivar – strains 5/1 and the standard; the Opus cultivar – strains 7p and the standard.