Root Colonization and Symbiotic Effectiveness of Acid Tolerant and Acid Sensitive Strains of Bradyrhizobia in Acid Soils

Abstract

Acid soil is characterized by numerous growth limIting factors. Low pH may reduce the availability of element such as Ca, Mg, P and Mo, and increase the availability of Al and Mn, limiting plant growth and survival and effectiveness of bradyrhtzobia. The formation of symbiosis between legumes and bradyrhizobia is affected by acid soil stresses factors. A pot ezperiment was conducted to study the usefulness of screening of Bradyrhizobiunt japonicum in acidic agar media In predicting their performance in acid soils. Four strains of B. Japonkum that were similar In their effectiveness at neutral pH sand culture bnt different in their tolerance of acid soil stress factors in agar media were used for testing their ability to colonize Al tolerant soybean P1 416937 rhizosphere and their effectiveness in three acid soils differing in their chemical characteristics. The treatments were arranged in a completely randomized block design with 4 replicates. The results showed that soybean Inoculated with the acid tolerant strains had significantly greater nodulatlon and symbiotic effectiveness than plants Inoculated with the acid sensitive strain. This result confirmed that the performance of B. japonicum in acid soils can be predicted from their perfonnance in acidic agar media.