• P D Tyagi

      Articles written in Proceedings – Section B

    • Notes on some hyphomycetes—I

      N G Nair P D Tyagi

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    • Some effects of culture filtrates ofBipolaris Spp. on wheat roots

      P D Tyagi

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      The effect of culture filtrates ofBipolaris sorokiniana and otherBipolaris species (B. oryzae, B. halodes andB. tetramera) grown in different media, on wheat roots, was studied. High concentrations of culture filtrates inhibited elongation of the root, but dilutions of 1/5 or more stimulated root elongation. The extent of inhibition or stimulation in root growth exhibited by culture filtrates varied with the medium in which the fungus was grown. The effects also varied slightly with different isolates ofB. sorokiniana. It is postulated that the fungus produces both a toxin as well as a growth factor in the culture medium. Very little toxin but more of growth factor was detected in culture filtrates obtained from potato dextrose medium. In contrast, more toxin and less of growth factor was produced in culture filtrates obtained from Richard’s medium, although even in this variations were seen depending on the nitrogen source.

      In the presence of the culture filtrates ofB. sorokiniana root-hair formation was completely suppressed up to a dilution of 1/100. Root-hairs developed in higher dilutions of the culture filutrate but their number and length were reduced compared to lower dilutions. Root-hairs were formed when the seedlings were removed from the culture filtrates to Hoagland’s solution, but were produced only in the new region of the root which elongated.

    • Utilization of various forms of nitrogen byDrechslera sorokiniana, the pathogen causing foot rot disease in wheat

      C V Subramanian P D Tyagi

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      Detailed study was made of the effect of (i) various inorganic and organic sources (potassium nitrate, ammonium sulphate, ammonium nitrate, asparagine, urea) and (ii) various levels of nitrogen (280, 700, 1,400 and 2,100 mg. N per litre) on growth and metabolism ofD. sorokiniana. Observations on mat weight, spore numbers, shift in pH of the medium, nitrogen accumulated in the mat, residual nitrogen (total, nitrate and ammoniacal nitrogen) and residual sugar in the medium were made after incubation for varying periods. The results are presented in detail and discussed.

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