ROOT NODULE BACTERIA OF SOME TROPICAL LEGUMINOUS PLANTS

Abstract

The morphological and physiological characteristics of 54 strains of root nodule-forming bacteria isolated from 28 different leguminous plants growing in Hawaii were studied. Reactions of these strains were noted in litmus milk and on 5 plant extract media in combination with 15 carbohydrates. Cross-inoculation tests using these strains as sources of inocula for 20 plant members of the cowpea group have shown marked variations in the infectiveness and effectiveness of the rhizobia. Only about 1/4 of the strains produced nodules on all of the test plants. 89% of the strains were beneficial on more than 10 plant spp., 4 of the strains being beneficial on 19 spp. 10 of the test plants were nodulated by all sources of inocula. Vigna sinensis was the most susceptible, inasmuch as each strain of rhizobia not only produced nodules but enhanced the growth of the plant. The other extreme was represented by Phaseolus lunatus on which only 22 strains produced nodules, none of which were beneficial.