Nodulation pattern in different legumes by Rhizobia isolated from rajma

Abstract

Rhizobium is an important symbiotic nitrogen fixing bacteria. The bacteria colonize leguminous plant cells within root nodules, where they convert atmospheric nitrogen into ammonia using the enzyme nitrogenase and then provide organic nitrogenous compounds such as glutamine or ureides to the plant. The plant, in turn, provides the bacteria with organic compounds made by photosynthesis. In this study, rhizosphere soil samples and nodules were collected from rajma plants of hilly Paderu region of Andhra Pradesh. Rhizobia were isolated from these samples using Yeast Extract Manitol Agar (YEMA) medium. There were 5 Rhizobium isolates obtained from the rhizosphere soil and nodules of rajma. These isolates were purified and inoculated to different legumes viz, black gram, green gram, red gram, Bengal gram and groundnut through seed treatment, planted in glass jars and maintained in green house. Nodulation pattern was studied 45 days after sowing. Rhizobium isolates 1 and 5 produced nodules in black gram and green gram, and Rhizobium isolate 2 produced nodules in black gram and red gram. Rhizobium isolate 3 produced nodules in black gram, green gram and red gram, and Rhizobium isolate 4 produced nodules in blackgram, greengram and groundnut. This study clearly showed that there is a possibility for Rhizobium isolate obtained from one legume to form nodules in other legumes but with variation in nodulation pattern.