In the present study, 24 Azotobacter strains were isolated from soils of different areas of southern Rajasthan and characterized at biochemical, functional, and molecular levels. The isolated Azotobacter strains were gram negative and cyst forming when viewed under the microscope. These strains were also screened for their plant growth promoting activities and the ability of these isolates to survive under abiotic stress conditions viz. salt, pH, temperature, and drought stress. All the isolates showed IAA, siderophore, HCN, and ammonia production, whereas seven Azotobacter strains showed phosphate solubilization. Amplified Ribosomal DNA Restriction Analysis (ARDRA) revealed significant diversity among Azotobacter strains and the dendrogram obtained differentiated twenty-four of the strains into two major clusters at a similarity coefficient of 0.64. Qualitative and quantitative N2 fixation abilities of these strains were also detrained, and the amounts of acetylene reduced by Azotobacter strains were in the range of 1.31 to 846.56 nmol C2H4 mg protein−1 h−1. The strains showing high nitrogen fixation ability with multiple PGP activities were selected for further pot studies, and these Azotobacter strains significantly increased the various plant growth parameters of maize plantlets. Furthermore, the best Azotobacter isolates were subjected to 16S rRNA sequencing and confirmed their identities as Azotobacter sp. The indigenous Azotobacter strains with multiple PGP activities could be further used for commercial production.

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Amongst the various DNA fingerprinting methodologies, randomly amplified polymorphic DNA (RAPD) was used to estimate genetic diversity and relationship amongst 22 black gram genotypes. A total of 25 randomly selected decamers were screened, out of which only 16 got amplified. A total of 133 amplified bands were obtained, out of which 120 were polymorphic. The average percentage of polymorphism was 90.23. The total number of amplified bands varied between 3 (primer OPK-03) and 15 (primer OPC-08) with an average of 9 bands per primer. The overall size of PCR amplified products ranged between 200 bp to 2600 bp. The average PIC was 0.30 ranging from 0.17 to 0.43. Five unique bands (ranging from 200-1200 bp) were detected in four genotypes using 5 RAPD primers. Jaccard's similarity coefficient values for RAPD primers ranged from 0.58-0.85 with an average of 0.71. Based on dendrogram generated through UPGMA method and PCA, most of the genotypes got divided into three main clusters. Genotypes U-17 and STY-2289 were lying close and thus showed minimum genetic distance while genotypes UH-177 and IPU99-233 had minimum similarity value of 0.42, thus showing maximum divergence. Thus, these results could be used to assess other black gram accessions in the Vigna germplasm pool that can provide useful information towards molecular classification and the genetic marker assisted breeding for crop improvement.

A total twenty three genotypes of green gram (Vigna radiata) were subjected to Randomly amplified polymorphic DNA (RAPD) analysis for molecular characterization. A total of 25 randomly selected decamers were screened, out of which only 15 generated 126 amplification products from which 117 bands were found polymorphic, the average polymorphism being 93.48%. The total number of amplified bands varied between 2 (primer OPP-09) to 17 (primer OPA-1) with an average of 9.5 bands per primer. The overall size of PCR amplified products ranged between 200 bp to 2900 bp. The average Polymorphism Information Content(PIC) was 0.32 ranging from 0.17 to 0.46. Primer OPA-01 and OPP-06 detected two unique bands ranged between 250 bp to 2500 bp in two genotypes (PUSA-672 and HUM-12). Jaccard's similarity coefficient values ranged from 0.28-0.90 with an average of 0.59. Based on dendrogram generated through UPGMA method and PCA, most of the genotypes got divided into four main clusters. Genotype EC-398885 lay far apart and thus showed maximum genetic distance. The assessment of genetic diversity is a prerequisite and important step for the improvement of any legume crop. Thus, present results of the present study could be further extrapolated to other green gram accessions in Vigna germplasm.