STUDIES ON MINERAL PHOSPHATE SOLUBIUZINC BACTERIA IN THE VERTISOLS OF NORTHERN KARNATAKA
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Date
2001
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, DHARWAD
Abstract
"Investigations were carried out on the mineral phosphate solubilizing
bacteria in the vertisols of Northern Kamataka and their relationship with soil
physical, chemical and microbiological properties was analysed. The correlation
coefficient worked for PSB population to that of soil properties indicated a strong
positive correlation between PSB population and that of total bacteria, soil organic
carbon and available N, whereas, other properties had no significant correlation
with PSB population. In a ftirther attempt to develop suitable strains of PSB for
vertisols, 55 PSB strains from rhizosphere of various crop plants grown on
vertisols were isolated, identified and screened for their efficacy to solubilize
different insoluble phosphates. Pseudomonas and Bacillus were the predominant
genera among the isolates. Thirty efficient PSB isolates were then analysed for
production of organic acids, lAA and GA. Most of the isolates produced 2 - 4
different organic acids, as well as lAA and GA. Based on the efficiency of
mineral phosphate solubilization, lAA and GA production, 16 strains were
selected for pot culture experiment with greengram and sorghum as test plants.
Most of the PSB strains significantly enhanced the nodulation, growth, drymatter
content and P uptake in greengram plants at 45 DAS over RP control. The growth,
drymatter content, P uptake and yield of sorghum plants were also enhanced
significantly over RP control by many strains. Based on the performance under
pot culture conditions, seven efficient strains were selected for field performance
with greengram crop. Six of them significantly increased the grain yield of
greengram over RP control. However, strain 98(2) showed significantly higher
grain yield over SSP control also. The transformation and expression ofpqq genes
in Azospirillum was done by mobilizing the construct pMCG898 into MPS""
Azospirillum by biparental mating and the transconjugants obtained were able to
solubilize dicalcium phosphate without alteration in their N2 fixing abilities"
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