Quick method for identification of inoculation nodules, efficiency of N2 fixation and cross inoculation of tropical legumes

Abstract

Experiments using leonard jars, soil pots, and field experiments were conducted to observe cross-inoculation in some tropical legumes, the possibility of using black nodule-producing strains for identification of Rhizobium nodules and also the efficiency of such strains in nitrogen fixation. The tropical legumes used were: glycine (Neotonia wightii), lablab (Lablab purpureus), centro (Centrosema pubescens), tropical kudzu (Pueraria phaseoloides) and calopo (Calopogonium mucunoides), inoculated with black nodule-producing strains and normal strains. In cross-inoculation behavior certain host specificity was observed in centro. Lablab and calopo formed black nodules with all black nodule-producing strains, centro with C-102 and CM-7, and glycine produced no black nodules. Strains showed differences in nitrogen fixation efficiency and, in a general way, black nodule-producing strains showed highest efficiency in nitrogen fixation. Results indicated that the black nodule-producing strains may be used in Rhizobium strain identification.