Study of the viability of bacteria of the genus Bradyrhizobium on the surface of inoculated seeds during storage

Abstract

Inoculants based on bacteria of the genus Bradyrhizobium have long been used in soybean cultivation to provide plants with nitrogen and improve crop productivity. At the same time, inoculants are an economically and environ mentally sound alternative to nitrogen mineral fertilizers. In contrast, the use of inoculants allows reducing economic costs of production and environmental risks. However, in agricultural practice, there are several factors that reduce the efficiency of seed inoculation, which disrupts the formation of legume-rhizobium symbiosis. One of these factors is a decrease in the number of nodule bacteria on the surface of inoculated seeds by the sowing time. In this regard, the purpose of the current work was to study the viability of bacteria of the genus Bradyrhizobium, which are the active substance of liquid inoculants used in the Russian Federation, during long-term storage of inoculated seeds. The study has shown that after inoculation, the number of Bradyrhizobium bacteria was 3.2–8.0×10⁶ CFU/seed depending on the applied product. After 14 days of seed storage at 24–28 °C, the number of viable cells was 4.0×10⁴– 1.4×10⁶ CFU/seed, after which there was a significant viability decrease. Storage of inoculated seeds for three months resulted in a complete or almost complete reduction in the number of rhizobia and did not exceed 82 CFU/seed. The studied inoculants had a high titer of 1.0–4.6×10¹⁰ CFU/ml, which exceeded the indicator declared by the manufacturer.