Pollution Research Paper

ISOLATION AND BIOCHEMICAL CHARACTERIZATION OF RHIZOBIUM FOR PLANT GROWTH PROMOTION AND ANTAGONISTIC ACTIVITIES AND COMPATIBILITY WITH COMMONLY USED PESTICIDES

J. SAI PRASAD, R. SUBHASH REDDY, B.H. SARVANI, R. NAVEEN KUMAR AND P. NARAYAN REDDY

Abstract

Twenty three (23) isolates of Plant Growth Promoting Rhizobacteria (PGPR) from rhizospheric soils of Rajendranagar and Amaravathi were isolated and identified based on their morphological, physiological and biochemical characteristics using standard methods. These test isolates were screened in vitro for PGPR properties like phosphate solubilization, siderophore, IAA, HCN productions, Antagonistic activity against Rhizoctonia solani, Sclerotium rolfsii and compatibility with commonly used pesticide molecules. The results revealed that all the Rhizobium isolates showed nodulation on ground nut, black gram and soybean crops, 82.60% of isolates showed phosphate solubilization, 91.3% for ammonia, 47.82% for IAA, 70.83% for siderophores and 52.17% for HCN productions. Out of 23 Rhizobium isolates 4 isolates ABuR2, ABpR2, ARpR1 and AmaR showed inhibition potential against both Rhizoctonia solani and Sclerotium rolfsii. The maximum per cent inhibition against Rhizoctonia solani was showed by AmaR (40.66%). The maximum per cent inhibition against Sclerotium rolfsii was showed by SBpR (37.50%). The isolate that showed maximum inhibition potential against Rhizoctonia solani was also inhibitory to Sclerotium rolfsii to a lesser extent based on per cent inhibition and vice versa. Hence it can be inferred that the Rhizobium isolates CRuR1, CRuR2, SBpR, SRuR2 and SRpR could be considered for their bio control activity. Among the pesticides tested Tebuconazole (fungicide), Thiacloprid (insecticide) and Pretilachlor (herbicide) were found to inhibit Rhizobium at recommended / half recommended dosage. However other fungicides, insecticides and herbicides were compatible with all the isolates tested. Out of the 23 isolates tested for their compatibility with the four each of the fungicides, insecticides, herbicides and based on their PGPR attributes and antagonistic activity, the isolate of Rhizobium isolate ARpR1 showed potential as PGPR.