Abstract

An experiment was conducted to test the growth efficiency of Rhizobium leguminosarum bv. phaseoli strain no. 46 on different nutrient media in laboratory and consecutively test the performance of the Phaseoli on nitrogen fixation and growth performance of the bean. Various treatment combinations were made for the Rhizobium growth study by replacing mannitol with sucrose, starch, and molasses as carbon (C) sources and yeast extract by baker’s yeast as nitrogen (N) source, respectively, in the standard yeast extract medium (YEM) medium; where mannitol as C and yeast extract as N sources, respectively, were used. The growth of the Rhizobium was highest (322.8 CFU/ml x 10²) in the medium where molasses was used as carbon and baker’s yeast was used as nitrogen sources, respectively, as compared to the standard YEM medium. When we compared the effect of the Rhizobium grown on different media on the growth performance and nitrogen fixation of the bean, highest nodule number (66 per plant) was obtained in bean plants inoculated with the Rhizobium grown on the medium where molasses as carbon and baker’s yeast as nitrogen sources, respectively, were used and higher shoot dry matter (2.85 g per plant) was obtained for the bean plants inoculated with the Rhizobium grown on the medium where molasses as carbon and yeast extract as nitrogen sources, respectively, were used. Highest N fixation (42.7%) was also observed in the bean plant tissues inoculated with the Rhizobium grown on medium where molasses as carbon and baker’s yeast as nitrogen sources were respectively used.

Key words: Baker’s yeast extract, Molasses, Nodulation, N2-fixation, Phaseolus vulgaris, Rhizobium leguminosarum bv. phaseoli, Rhizobium media, yeast extract.

Abbreviation

YEM, Yeast extract medium; EC, electrical conductivity; YEMM, yeast extract mannitol medium; YESM, yeast extract starch medium; BYEMM, Baker’s yeast extract mannitol medium; BYEMOM, Baker’s yeast extract molasses medium; YESUM,yeast extract sucrose medium; EMOM, yeast extract molasse medium; BYESUM,Baker’s yeast extract sucrose medium; BYESM, Baker’s yeast extract starch medium.