Screening of endophytic isolates for plant growth promotion in rice
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Date
2021
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Punjab Agricultural University, Ludhiana
Abstract
The present investigation was conducted to study the effect of endophytic bacterial culture on root
architecture, microbial activities, growth and yield of rice crop (variety PB1509 and PR121). To
achieve this objective, bacterial cultures were characterized biochemically for oxidase, catalase,
MRVP and citrate utilization. All the cultures were positive for catalase and citrate utilization
except the bacterial culture RB11, which was not able to utilize citrate as carbon source. 5%
bacterial culture were found positive for MR test, whereas, 70 % bacterial cultures were found
positive for VP test. All the bacterial cultures were screened for PGP traits. Out of 18 bacterial
cultures, 16 bacterial cultures were able to solubilize phosphate. Significant higher phosphate
solubilization index (3.4 mm) was observed for the bacterial culture RB18. Among 18 bacterial
cultures, 6 bacterial cultures were able to form clear zone on minimal media supplemented with
zinc oxide. Significant higher zinc solubilization index (4.5 mm) was observed for bacterial
culture RB5 followed by RB1 (4.3 mm). Ten bacterial cultures were able to produce ammonia
and 6 bacterial cultures were able to produce HCN. Among 6 bacterial cultures, Maximum
production of HCN was showed by bacterial culture RB6 and RB7. Three bacterial cultures were
able to form fluorescent yellow coloured zones on Chrome-azurol S (CAS) agar plates, indicating
production of siderophore. Significant higher halozone diameter (12.1 mm) was produced by
bacterial culture RB1 followed by RB4 (12 mm). Out of 18 bacterial cultures, 16 tested positive
for ACC deaminase activity. All the bacterial cultures were able to produce IAA. Significant
higher amount of IAA (39.77 µg/ml) was produced by bacterial culture RB18 followed by
bacterial culture RB16 (35.33 µg/ml) and RB4 (34.44 µg/ml) in the medium not supplemented
with tryptophan. In the medium supplemented with tryptophan, the bacterial culture RB18
produced significant higher amount of IAA (53.55 µg/ml) followed by RB16 (48.55 µg/ml) and
RB6 (48.48 µg/ml). The production of gibberellic acid was also recorded. It ranged between 1.68
µg/ml - 20.65 µg/ml. Significant higher amount of gibberellic acid (20.65 µg/ml) was produced by
bacterial culture RB18 followed by RB16 (17.32 µg/ml) and RB11 (13.49 µg/ml). On the basis of
multiple PGP traits, 4 bacterial cultures were selected (Enterobacter sp., Rhizobium sp.
Enterobacter sp. and Azospirillum sp.) to test their biofertilizer potential using rice crop as host.
Among the 4 selected bacterial cultures, the Azospirillum sp. was able to significantly enhance the
no. of roots, root thickness, area and volume of roots. The growth and yield of rice obtained from
Azospirillum sp. was significantly higher as compared to un-inoculated rice crop and the crop
treated with other bacterial cultures. The Azospirillum sp. showed non-significant difference with
PAU recommended biofertilizer for rice crop. The microbial population was found to be
significantly improved with the use of biofertilizer as compared to uninoculated control. The
bacterial culture Azospirillum sp. was found to be best culture in terms of PGP traits, growth and
yield of rice crop.
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Citation
Simran (2021). Screening of endophytic isolates for plant growth promotion in rice (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.