DIVERSITY OF ACTINOMYCETES IN THE RHIZOSPHERE OF Arnebia euchroma (Ratanjot): A CRITICALLY ENDANGERED PLANT OF HIMACHAL PRADESH

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Date
2019-11
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UHF,NAUNI
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ABSTRACT Rhizospheric soil samples were collected from Nako and Chango in Kinnaur and, in Lahaul & Spiti districts of Himachal Pradesh to decipher actinomycetes diversity in the rhizosphere of Arnebia euchroma (Ratanjot). Standard Plate Count technique was employed for the isolation of actinomycetes. In total, 33 isolates (15 from Nako, 7 from Chango, 16 from Gue and 5 from Kibber) were obtained. The actinomycetes load was found to be significantly higher at Chango (Log CFU/mL=1.44) followed by Nako (Log CFU/mL=1.40) and Gue (Log CFU/mL=1.38) while the minimum was recorded for Kibber (Log CFU/mL=1.33). Likewise, their significantly higher load was observed on SCA (Log CFU/mL=1.48) followed by AIA (Log CFU/mL=1.41), NA (Log CFU/mL=1.29) and KM (Log CFU/mL=0.88) proving SCA to be the best medium. With respect to their PGP potential, only 45.45 per cent of the total isolates showed phytase and siderophore production while 33.33 per cent showed P- solubilization qualitatively. Significantly higher Psolubilization(53.66 μg mL-1) was shown by NA8 while the minimum (6.44 μg mL-1) was recorded for SCAN1. However, the phytase activity was observed to be significantly higher (134.44 U/ml) for CA7 and minimum (15.33 U/ml) for NA10. Isolates SCAK5 and SCAN1 showed significantly higher (17.24% SU) and lower siderophore (5.46% SU)) production. All isolates exhibited nitrogen fixing ability while 66.66 and 3.03 percent of total isolates showed ammonia and HCN production, respectively. 84.84, 90.90, 96.96, 72.72 and 42.42 percent of the isolates exhibited pectinase, chitinase, cellulase, lipase and protease activities, respectively. Isolates NA6 and CA1 showed significantly higher (6.81 U/mL) and lower (0.42U/mL) chitinase activities, respectively. Maximum cellulase activity (31.21 U/mL) was shown by NA5 while the minimum (24.18 U/mL) was observed for GA6. Isolates NA7 and NA10 showed significantly higher (28.13 U/mL) and lower (1.22 U/mL) protease activities, respectively. Isolates NA6 and GA6 showed significantly higher (48.33U/mL) and lower (1.60 U/mL) pectinase activities, respectively. Only NA5 exhibited maximum lipase activity (2040 IU/mL). Maximum IAA production was shown by NA10 (44.52 µg/ml) while minimum (11.55 µg/ml) by NA3. However, maximum gibberellins production (40.60 µg/ml) was shown by NA7 while the minimum (4.52 µg/ml) was recorded for KMN2. Isolates CA5 and GA2 showed maximum (34.0 µg/ml) and minimum (15.0 µg/ml) cytokinins production, respectively. Eight potential isolates exhibited reasonable antagonism towards Fusarium oxysporum, Sclerotium rolfsii and Rhizoctonia solani ranging between 26.20 - 41.4 per cent. Likewise, volatile metabolites released by actinomycetes inhibited their growth ranging between 21.87 - 44.44 per cent. Based on morphological, biochemical and molecular characteristics, two potential isolates i.e. CA7 and NA8 out of 9 were identified as Streptomyces silaceus and Streptomyces rectiviolaceus and were assigned GenBank accession numbers MK836019 and MK836018, respectively. Evaluation of growth regulator’s effect of CA7 and NA8 on root elongation revealed a significant increase in root length of pre-germinated seeds of maize and pea over the control. Ultra Performance Liquid Chromatography analysis showed the presence of ββ-dimethylacrylshikonin (0.145 %), Deoxy-shikonin (0.098 %) and Shikonin (0.011%) pigments in the roots ofA. euchroma.
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