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ROLE OF MICROBES IN SALT TOLERANCE OF PLANTS

ROLE OF MICROBES IN SALT TOLERANCE OF PLANTS. BY PROF. DR. ASGHARI BANO. DEPARTMENT OF PLANT SCIENCES, QUAID-E-AZAM UNIVERSITY ISLAMABAD. SALINITY “ A major stress limiting agriculture productivity’’. APPROACHES TO COMBAT SALINITY: 1)Chemical amendment

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ROLE OF MICROBES IN SALT TOLERANCE OF PLANTS

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  1. ROLE OF MICROBES IN SALT TOLERANCE OF PLANTS BY PROF. DR. ASGHARI BANO DEPARTMENT OF PLANT SCIENCES, QUAID-E-AZAM UNIVERSITY ISLAMABAD

  2. SALINITY “A major stress limiting agriculture productivity’’. • APPROACHES TO COMBAT SALINITY: 1)Chemical amendment 2)Development of salt tolerant plants through breeding/genetic engineering. 3)Role of Agrochemical The alternative viable approach; use of salt tolerant microbes to induce tolerance in plants,economical,sustainable & environment friendly.

  3. SALINITY INDUCES SEVERAL PHYSIOLOGICAL CHANGES Ionic imbalance Water stress Production of reactive oxygen species Changes in the level of phytohormones Unavailabilityof phosphate

  4. SALT TOLERANCE LIMIT: • Threshold level of salt tolerance in plants varies from 40-200mM NaCl. • Tolerance level of PGPR varies from 100-650mM NaCl. • ROLE OF PGPR: a) Better development of root system b)Production of growth promoting hormones in addition to stress hormone ABA. c)Solubilization of insoluble phosphate

  5. Table. 1: LIST OF SOME IMPORTANT MICROBIAL SPECIES TOLERANT TO SALT STRESS

  6. Table 2: COMPARATIVE EVALUATION HAVE BEEN MADE FOR THE ROLE OF PGPR AND SALICYLIC ACID IN IMPARTING SALT TOLERANCE TO SUNFLOWER PLANTS ( NAZ AND BANO 2009)

  7. MATERIAL AND METHODS • The seeds were soaked overnight in cultures of Azospirillum and Pseudomonas prior to sowing NaCl (20dSm-1)were applied to soil 4 weeks after inoculation • Aqueous solution of 20dSm-1 NaCl was applied the rhizosphere soil of potted plants till saturation and watering was made to all the treatments as and when required. • Salicylic acid (10-4M) foliary applied to plants 4h after the salt treatment.

  8. SAMPLING PROCEDURE • Young and fully expanded leaves were collected around 10:00h-12:00h to analyze the relative water content, osmotic potential, carotenoid content, proline, antioxidants and hormones 7d after the induction of salt treatment. • Relative water content of second leaf from the top of the plants was determined following the method given by Gupta (1995). • The osmotic potential of the cell sap was measured leaves with a freezing point osmometer according the method of Capell and Doerffling(1993). • Carotenoid content was estimated according to the method of Lichtenthaler and Wellburn (1983). • Proline content of young leaves was estimated by using the following method of Bates et al. (1973).

  9. SAMPLING PROCEDURE • SOD of fresh plant tissues was determined following the method of Beauchamp and Frodovich (1971). • POD activity of fresh plant tissues was measured by the method of Vetter et al. (1958) as modified by Gorin and Heidema (1976). • The extraction and purification of ABA was made following the method of Kettner and Droffling, (1995). • The extraction and purification of ABA was made following the method of Kettner and Doerffling, (1995). • Salicylic acid was extracted and purified according to the method of Enyedi et al., 1992 and Seskar et al., (1998) with some modifications.

  10. Table: 3 Effect of Azospirillum, Pseudomonas and Salicylic acid on soil moisture content of two cultivars (cvv. Hy-sun & par-sun) under salt stress.

  11. Table 4: Effect of Azospirillium, Pseudomonas and Salicylic Acid on Relative Water Content (%age) and Osmotic Potential (-MPa) of two Sunflower cultivators Hy-sun & Par-sun) under salt stress.

  12. Table 5: EFFECT OF AZOSPIRILLUM, PSEUDOMONAS AND SALICYLIC ACID ON CAROTENOID CONTENT OF TWO SUNFLOWER CULTIVARS UNDER SALT STRESS

  13. DISCUSSION • Proline content and superoxide dismutase activity may be used as physiological markers of salt tolerance as they showed more increase in salt tolerant Hy-Sun 33. • Plant Growth Promoting Rhizobacteria (e.g. Azospirillum and Pseudomonas) receiving the foliar spray of SA and SA application alone may have a role in up-regulating antioxidant enzymes.

  14. CONCLUSION • The possible difference between microbes (PGPR) induced salt tolerance and hormone induced salt tolerance can be summarized as follows: • Microbes are sustainable source of ABA production along with other growth promoting hormones IAA, GA and t-zr whereas, ABA applied exogenously to combat salt stress decreases the endogenous level of IAA, GA and t-zr. ABA is a growth inhibitory compound and under normal condition its level should remain low to keep pace with growth and development. • Particularly in sensitive varieties, it has been reported that on return to normal condition the decline in stress induced ABA level was delayed and magnitude of decrease was also less. (Iqbal and Bano 2009)

  15. Microbes can also produce other bioactive metabolites e.g. polyamines (Putrescine, cadavarine etc) which further improve the plant resistance to disease and salt. • Microbes assist in solubilization of P and make them available to plant which is an additional effect not the case in ABA-induced salt tolerance . • Microbes are economical and environmental friendly whereas, ABA is rather expensive and may have adverse effects on soil microbiota.

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