Kulkarni, J HRanjitha, K2019-10-172019-10-172000No. of Reference 207http://krishikosh.egranth.ac.in/handle/1/5810131898Investigations were carried out on the native population o f beneficial microrganisms in the rhizosphere o f black pepper and inoculation effect of selected isolates on the rooting and growth of the plant in nursery. The rhizosphere samples were collected from Sirsi and Coorg regions in Kamataka and Kasargod district in Kerala. The study revealed a higher population of free living nitrogen fixers in rhizosphere soil, Azospirillum in endorhizosphere and percent root colonization (PRC) of vesicular arbuscular mycorrhiza (VAM) in samples collected from Coorg and Sirsi regions. But, the average number of phosphate solubilizers maintained the same level in all the major locations. Correlation studies revealed a significant association of soil organic carbon with population of Azospirillum in the endorhizosphere, PRC of VAM and the free living nitrogen fixers in soil. The available nitrogen positively correlated with PRC ofVAM. The significant correlation oiAzospirillum with phosphate solubilizers confirmed the synergism among these microorganisms. Thirty eight isolates of Azospirillum and 31 isolates o f phosphate solubilizers were obtained in this study. The nitrogen fixation efficiency of Azospirillum isolates ranged from 9.4 to 23.7 mg N2/ g malate used and the _ phosphate solubilizing efficiency o f the phosphate solubilizers varied from a Pi release of 8.1 to 19.1 mg/ 100ml Pikovskaya's broth.In vitro screening of the isolates for phytohormone synthesis indicated the varying efficiency among the isolates and a Azospirillum isolates as superior ones. Inoculation of pepper cuttings with Azospirillum cultures prior to planting resulted in an improved rooting percentage and better root growth compared to control. Single and dual inoculation of Azospirillum and phosphate solubilizing bacteria improved the vigour and nutrient status of the black pepper plants. The Azospirillum stiains AZBR 9 and the phosphate solubilizer BRPS 16 was found to be superior in vivo.ennullThesis