Kulkarni, Dr. J. H.RANJITHA, K.2019-09-182019-09-182001-08-08Th-6045http://krishikosh.egranth.ac.in/handle/1/5810128576Investigations were carried out on the native population of beneficial microrganisms in the rhizosphere of black pepper and inoculation effect of selected isolates on the rooting and growth of the plant in nursery. The riiizosphere samples were collected from Sirsi and Coorg regions in Karnataka 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 ai buscular 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 orgamc carbon with population oi Azospirillum in the endorhizosphere, PRC of VAM and the free living nitrogen fixers in soil. The available nitrogen positively correlated with PRC of VAM. The significant correlation of Azospirillum with phosphate solubilizers confirmed the synergism among these microorganisms. Thirty eight isolates of Azospirillum and 31 isolates of phosphate solubilizers were obtained in this study. The nitrogen fixation efficiency of Azospirillum isolates ranged from 9.4 to 23.7 mg N^/ g malate used and the ^ phosphate solubilizing efficiency of the phosphate solubilizers varied from a Pi release of 8.1 to 19.1 mg /100ml Pikovskaya's broth.//iv/zro screening of the isolates for phytohormone synthesis indicated the varying e fficiency among the isolates and a few 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 strains AZBR 9 and the phosphate solubilizer BRPS 16 was found to be superior in vivo.ennullThesis