STUDY OF PLANT GROWTH PROMOTING ACTIVITIES OF ENDOPHYTIC BACTERIA ISOLATED FROM DIFFERENT VARIETIES OF SUGARCANE
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Date
2021
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Dr.RPCAU, Pusa
Abstract
Endophytic bacteria colonizing internal parts of the plants benefit the crop plants by enhancing their growth and development. These beneficial organisms are documented in almost all plants. Sugarcane also colonizes diverse endophytic bacteria and these bacteria benefit the sugarcane crop through plant growth promoting activities. Therefore, a study was conducted to isolate endophytic bacteria from different parts of two sugarcane varieties, BO-91 and Co-P 16437, and to examine them for plant growth promoting activities. Sugarcane samples, roots, stems and leaves were collected and further subdivided into upper, middle and lower portions. One gram of the sample from each sub portion was surface sterilized and subjected to an isolation process on nutrient agar and Luria Bertani agar plates. A total of 71 endophytic bacteria of different morphotypes were isolated from roots, stems and leaves of both varieties, out of which 45 isolates were obtained from BO-91 and 26 isolates from Co-P 16437. Isolates were subjected to morphological characterization on the basis of colony morphology and microscopic features. Most of the isolated colonies were of small size, circular shape with regular margins, smooth texture and yellow or orange color colonies on nutrient agar and Luria- Bertani agar plates. 41 isolates were identified as Gram-negative and 30 isolates as Gram-positive bacteria,
out of which 17 were endospore producers based on Gram staining, endospore staining and microscopic observations and most of the isolated cells were of rod shape. Isolates were further tested for biochemical activities, in which most isolates were able to utilize citrate and showed positive response to the oxidase test, whereas few isolates showed positive response to the methyl red test and Voges-Proskauer test. Endophytic bacteria were subjected to plant growth promoting activities in vitro on the basis of nutrient solubilization (P, K and Zn) and production of useful compounds (siderophore and IAA). 16 isolates of BO-91 and 7 isolates of Co-P 16437 were able to solubilize phosphorus, in which the BS8 isolate of the stem part of BO-91 showed the highest value of P-SI (4.22) with a quantitative value of 42.66 ± 1.1 μg mg-1. 13 isolates of BO-91 and 8 isolates of Co-P 16437 were able to solubilize potassium, in which the CS6 isolate of stem part of Co-P 16437 showed the highest value of K-SI (3.16) with a quantitative value of 129.54 ± 0.8 μg ml-1. 12 isolates of BO-91 and 6 isolates of Co-P 16437 were able to solubilize zinc, in which the BR17 isolate of the stem part of BO-91 showed the highest value of Zn-SI (3.43) with a quantitative value of 119.68 ± 0.9 μg ml-1. 4 isolates of BO-91 and 2 isolates of Co-P 16437 were able to produce siderophores, in which the CR9 isolate of the root part of Co-P showed the highest value of SE (179%). 19 isolates of BO-91 and 10 isolates of Co-P 16437 were able to produce IAA, in which the CL2 isolate of the leaf part of Co-P 16437 showed the highest IAA production value of 29.70 ± 1.5 μg mg-1 protein. The BS16 isolate of stem part of BO-91 showed a positive response to phosphorus solubilization (P-SI of 3.13), potassium solubilization (K-SI of 2.19), zinc solubilization (Zn-SI of 2.30) and IAA production (20.83 μg mg-1 protein) activity. The CR9 isolate of the root part of Co-P 16437 showed positive indications of phosphorus solubilization (P-SI of 3.08), potassium solubilization (K-SI of 2.66), zinc solubilization (Zn-SI of 2.74), siderophore production (SE of 179%) and IAA production (28.15 μg mg-1 protein) activity. Thus, a diverse group of endophytic bacteria are present in different parts of the sugarcane crop and are involved in plant growth promoting activities. Therefore, the promising endophytic bacteria can be used as a biofertilizer which enhances sugarcane growth and development.