Symbiotic efficiency of Bradyrhizobium japonicum for development of a commercial soybean inoculant for western Canada

Abstract

Soybean production has increased substantially in western Canada in recent years. Current soybean inoculants ( Bradyrhizobium japonicum ) have not performed the same in western Canada as they have in other regions. B. japonicum exhibit genetic change in soil over time and may result in novel rhizobial lines capable of performing better than the original introduced strain. Greenhouse experiments performed on 60 isolates of B. japonicum from previously inoculated fields assessed symbiotic efficiency - ability to induce nodulation and fix nitrogen - compared to commercial inoculants 532C and USDA110. A pre-screening stage using one cultivar selected 10 isolates for second stage screening. In second screening using three cultivars, inoculated treatments had higher biomass and tissue nitrogen contents than nitrogen-fertilized and untreated controls confirming the need for inoculation in virgin soils. Five isolates (2-37, 2-38, 3-49, 3-50 & 3-57) resulted in high plant tissue nitrogen contents and biomass and should be tested in a crop setting.