Assessment of functional diversity of culturable phosphate solubilizing fluorescent pseudomonads

The experiment was conducted during 2006-08 in SKUAST-K, Shalimar, Srinagar Rhizosphere soil samples were collected from different strawberry fields in Srinagar and Baramulla districts. Among phosphate solubilizing bacteria that colonize aggressively the plant roots fluorescent pseudomonads have been considered as an important group due to their biofertilizing and biocontrol properties. Fluorescent pseudomonad bacteria were isolated on Kings medium B (KB) and were identified under UV light (366nm). Phosphate solubilizing activity was performed by growing the cells in Pikovskaya’s broth, soluble free phosphate in culture supernatant was estimated spectrophotometrically by recording absorbance value at 600nm, using the calibration curve with KH2PO4. All the isolates were screened for multifaceted plant growth promoting activities like production of IAA, sidrophore, HCN, ACC deaminase, ammonia, activities of enzymes like protease, chitinase, cellulase, pectinase, antagonistic potential and mineral solubilization (K, Zn and Fe) by using standard methods. All the isolates except PS3, PS7 and PS9 produced IAA, siderophore, HCN and ammonia. Screening of antagonistic activity of all the isolates confirmed that out of 20, 17 isolates exhibited antagonistic potential against Fusarium sp. with varying levels of inhibition of mycelial growth. However the maximum inhibition was recorded in PS2 isolate. Out of 20 isolates only PS1, PS7 and PS10 produced ACC deaminase. The isolates PS3 and PS7 were negative for proteinase and chitinase activity. Cellulase enzyme was almost abundantly produced by each isolate except PS3, PS7 and PS9 which showed poor cellulose activity. Moderate to poor pectinase activity was shown by all the isolates barring PS9 which did not produce any pectinase. All the isolates except PS7, PS11 and PS16 utilized with varying degrees several carbon sources as identified by Hi-Carbohydrate TM kit test. The isolates PS3, PS8 and PS9 were unable to solubilize any mineral nutrient while as rest of the 17 strains solubilized insoluble Phosphate, zinc and iron compounds. Numerical taxonomy of isolates based on the basis of their carbon source utilization profile resulted in to ¬two major phenons at 0.27 similarity coefficient level. On the basis of these results it was concluded that there existed some level of variability among the fluorescent pseudomonads found in the rhizosphere of strawberry fields.

Baba, Z. A., Tabinda sehar, Zargar, M. Y. and Nazish Nazir
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