Effect of Rhizobium UVmutants on Blackgram

Abstract

The isolated Rhizobium strains were allowed for UV irradiation for different time intervals to cause mutation and observed for their consequent action on the growth of blackgram.   The maximum growth with healthy appearance was resulted in the samples, treated with UV irradiation for 30 min. Among them, five mutants (MB1, MG1, MS1, MC1 and MGn1) were selected and subjected to temperature (35 to 50°C) and pH (5.5 and 6.0) stress. Isolates obtained from these studies were tested for their symbiotic efficiency on the specific hosts such as blackgram, greengram, groundnut, cowpea and soybean. Temperature as well as acid tolerant (T2) rhizobial isolates of black gram, cowpea, groundnut and soybean (Bcp 1, Ccp1, Gncp 1 and Scp 1) recorded maximum nodule (5) number. Antibiotic resistant mutants of black gram showed maximum nodule (6.0) number followed by groundnut, soybean, and cowpea isolates were performed well in inducing nodulation, leghaemoglobin content and nitrogen fixation activity (48.5 µ moles C2H4 plant h-1).