BENEFICIAL RHIZOSPHERE MICROFLORA OF BLACK PEPPER (Piper nigrum L.) AND THEIR ROLE IN GROWTH OF THE PLANT
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Date
2001-08-08
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
Abstract
Investigations 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.
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