e-ISSN 2231-8542
ISSN 1511-3701

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Characterization of Diazotrophs Associated with Roots of Leptochloa fusca (L) Kunth

Shahida Hasnain, Fehra Zafar, Rakhshanda Bilal and Kausar A. Malik

Pertanika Journal of Tropical Agricultural Science, Volume 16, Issue 1, April 1993

Keywords: Diazotrophs, nitrogenase activity, physiological and biochemical characteristics, kallar grass, Leptochloa fusca, Azotobacter

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A group of nine diazotrophs were isolated from the rhizosphere of kallar grass and cultured on nitrogent-free medium. K5, K8, K9, K10, K12, K13 showed high nitrogenase activity (> 18 n mol C2H4 h1 vial1) whereas in K7 and K14 it was comparatively low (< 5n mol C2H4 h1 vial1). Maximum nitrogenase activity was found in young cultures (after 24 hours of incubation) except for K9 and K13 where it was maximum after 36 and 48 h, respectively. All strains were Gram-negat, produced smooth colonies and pellicles on semi-solid media. Cells of K9 K7 K10 K11, K12 and K14 were pleiomorphic: K8 formed long fine rods; K9 was small, round or oval shaped; while K14 formed beaded rods. Only K8, K13 and K14 were found to be motile. All isolates were able to reduce nitrate, and were positive for oxidase an catalese. None of them could denitrify or had urease activity except for K14 which was urease positive. K8, K13 and K14 were fermentative and produced red pigments. The isolates K5, K10 and K12 are assigned to the genus Azotobacter while others remained unidentified.

ISSN 1511-3701

e-ISSN 2231-8542

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