VIJAYA GOPAL, APRASANNA LAKSHMI, P2020-01-222020-01-222019http://krishikosh.egranth.ac.in/handle/1/5810141568D5774The present study ISOLATION AND MOLECULAR CHARACTERIZATION OF Paenibacillus spp. AND THEIR EFFECT ON GROWTH AND YIELD OF SORGHUM (Sorghum bicolor L.) was conducted at Agricultural Research Station, Amaravathi and Advanced Post Graduate Centre, Lam, ANGRAU, Guntur. The continuous use of higher levels of chemical fertilizers by the farmers has led to the problem of soil degradation, which is proving detrimental to crop production in our country. The best alternate strategy is to utilize microorganisms as biofertlizers. Therefore, biological nitrogen fixation can effectively contribute to the nitrogen content. Several Paenibacillus strains that were able to fix nitrogen from atmosphere were isolated from roots of different plants and shrubs. Species of the genus Paenibacillus, are promising candidates for crop inoculation which plays an important role by their nitrogen-fixing ability, capacity to solubilization of soil phosphorus, increase soil porosity, suppress plant pathogens and promote plant growth through the production of phytohormones (auxins and cytokinins) and antimicrobial substances. N2-fixing Paenibacillus species have increasingly been used in non legume crop species such as sugar beet, canola, wheat, and conifer species. Twenty eight Paenibacillus isolates were isolated from twenty seven rhizosphere soil samples of sorghum collected from different parts of Andhra Pradesh i.e., from Kurnool, Prakasam, Anantapur and Kadapa districts. All the 28 isolates were able to withstand heat treatment and grow on N- free media. All the isolates were characterized by their cultural, morphological and biochemical characteristics. Microscopy revealed that all the isolates were Gram positive, endospore forming rods. Further, all the Paenibacillus isolates were screened for plant growth promoting attributes. xix Results revealed that all the isolates showed negative result for HCN production, 26 isolates showed positive result for ammonia production, 15 isolates showed positive result for IAA production, 13 isolates showed to produce siderophores, 20 isolates showed phosphate solubilization and 20 isolates showed positive result for Acetylene Reduction Assay (ARA). The twenty Paenibacillus isolates that showed nitrogenase enzyme activity in ARA technique were further taken for molecular characterization of nifH genes (nitrogenase genes) for the detection nitrogen fixing ability. The nifH gene was observed in 4 isolates (PiPP-1, ARP-1, PNP-3 and PMP-1) at 360 bp similar to 2 reference strains. Among twenty isolates of Paenibacillus three efficient isolates were selected based on their PGPR characteristics i.e., isolates with nifH gene and high nitrogenase enzyme activity (PiPP-1, ARP-1 and PNP-3). Field experiment was conducted for evaluating the effect of Paenibacillus spp on growth and yield of sorghum. Results revealed that all microbial population (bacteria, fungi and actinobacteria) and Paenibacillus population were found highest in T8 (PB1 + PB2 + PB3 + 75 % RDN) at flowering stage of sorghum. pH was highest T13 (100 % RDF) and T1 (control) and gradually decreased in the Paenibacillus consortia inoculated treatments. EC was highest in T8 (PB1 + PB2 + PB3 + 75 % RDN) in the Paenibacillus consortia inoculated treatments and gradually decreased in inorganic fertilizer alone applied treatments and in control. Organic carbon, available nitrogen, phosphorus, potassium contents of the soil was highest in the treatment T8 (PB1 + PB2 + PB3 + 75 % RDN) 1.66 %, 265.45, 63.49 and 415.36 kg ha-1 of soil respectively at flowering stage of sorghum crop. Dehydrogenase, phosphatases both acidic and alkaline and urease enzyme activity were significantly higher at flowering stage in the treatment T8 (PB1 + PB2 + PB3 + 75 % RDN) 118.59 μg of TPF g-1 of soil d-1, 69.19, 97.73 μg pNP g-1 of soil h-1 and 147.17 μg NH4+ g-1 of soil h-1 respectively. The plant height, length, weight and the number of seeds per ear head, test weight, shoot and root biomass were significantly highest in the treatment T8 (PB1 + PB2 + PB3 + 75 % RDN) 183.93 cm, 32.73 cm, 67.72 g, 2236.00, 2.46 g, 73.62 g and 10.18 g respectively. N, P, K content of sorghum grain and stover were also found highest in the treatment T8 (PB1 + PB2 + PB3 + 75 % RDN) 1.20 %, 0.64 % and 0.47 % respectively in grain and 0.96 %, 0.43 % and 1.56 % respectively in stover. The grain and stover yield of sorghum crop was significantly highest in the treatment T8 (PB1 + PB2 + PB3 + 75 % RDN) 43.51 q ha-1 and 66.59 q ha-1 respectively which were 25.94 % and 12.79 % higher when compared to the application of inorganic fertilizers (100 % RDF) alone. The results of this study clearly showed that combined application of Paenibacillus consortia and inorganic fertilizers (PB1 + PB2 + PB3 + 75 % RDN) significantly improved the microbial population, available NPK in soil, soil enzyme activities and growth and yield of sorghum crop when compared to the application of inorganic fertilizers (100 % RDF) alone. Hence these isolates can be developed into effective biofertilizers either singly or in combination with other efficient biofertilizers as these are cost effective and eco-friendly in nature.en-USnullThesis