Selection of effective strains of Bradyrhizobium for Caatinga stylo (Stylosanthes seabrana)

Abstract

Caatinga stylo (Stylosanthes seabrana) is recommended as a forage legume for permanent and long-term ley pastures on clay soils of southern (cv. Primar CPI92838B) and central (cv. Unica CPI110361) Queensland. The release of the 2 cultivars was contingent on the availability of an effective and persistent strain of Bradyrhizobium, because suitable effective nitrogen-fixing strains do not occur naturally in the soils of the target regions. Effective strains of Bradyrhizobium (strains CB3480 and CB3481), suitable as inocula for Caatinga stylo, were selected from nodule material collected in Bahia, Brazil. This paper documents soil-pot and field experiments that led to the selection of these persistent and effective strains of Bradyrhizobium and the eventual release of CPI92838B and CPI110361, respectively, as cvv. Primar and Unica.