Use of Antisera to identify Nodule produced by the Inoculation of Legumes in the Field

Abstract

IN field trials with leguminous crops ‘inoculated’ with nodule bacteria (Rhizobium), it is sometimes important to know what percentage of the nodules that may develop are, in fact, produced by the culture used for inoculation. This problem arose in some work the object of which was to replace ineffective strains of Rhizobium trifolii, which are abundant in some British soils, with a more effective strain used for inoculating clover. It was first important to discover whether the inoculant strain could be established in the nodules of the crop under field conditions in which it would have to compete with the native population of Rhizobium trifolii already present in the soil. In inoculation trials on such soils, a proportion of the nodules formed in the inoculated plots will be produced by native Rhizobium of which a considerable variety of strains may be present. Isolations can readily be made from nodules taken at random from the crop roots; but the identity of these isolates with the strain used for inoculation is difficult or even impossible to determine by cultural methods, because of the similarity between strains of Rhizobium in their appearance and behaviour on laboratory media.