Phosphate Solubilizing Microorganism Consortium of Virgin Tiger Hill Forest Soil Shows High Level Tolerance to Pesticide, Antibiotic, Antifungal and Heavy Metals

Abstract

Tiger Hill, a notified reserve forest is the highest point around Darjeeling town in Eastern Himalayan Hotspot. Soil nutrition of this forest area depends on nutrient recycling where phosphate solubilising microorganisms (PSM) has crucial role to play as it solubilises insoluble phosphorus salt to soluble forms. But, with rise in use of toxic chemicals these microbes are at threat. This research initiative explores isolation of PSM from Tiger hill forest soil to detect pesticide, antibiotic, antifungal and heavy metal tolerance. Soil sample from tiger hill has moisture (18.55%), pH (3.87), organic carbon (1.187%), total Nitrogen (1.02%) and Phosphorus in P2O5 form (10ppm). Isolation and screening of PSM were conducted on Pikovskaya’s agar medium. In vitro tolerance assay was performed to detect degree of tolerance in isolated PSM-consortium (PSMC). Pesticides like Fipronil, Thiomethoxame, Emamectin benzoate, Deltamethrin, Flubendiamide, Spiromesifen, Fenazaquin and Phorate exhibited complete to high degree of tolerance. PSMC was fully tolerant to antibiotic like Augmentin, Erythromycin, Chloramphenicol, Ofloxacin, Co-Trimoxazole, Cefotaxime; antifungal Itraconazole and Fluconazole. Mild tolerance towards heavy metal salts like As2O3, SnCl2, CdCl2, CuCl2, CdSO4 and CuSO4 were detected. Synergestic effect of cells present in the isolated PSMC may also be an added advantageous property to tolerate pesticides, antibiotic, antifungal and heavy metal salts.

Study of tolerance ability in phosphate solubilising microorganisms isolated from tea plantations soil of lower Darjeeling hills

“…Collection of soil samples were conducted following the protocol of Saha et al (2020). Top soil from tea plantations of lower Darjeeling was collected during the month of April after the first shower.…”

“…Estimation of soil pH was conducted following Mukherjee et al (2020) and calculations were made following Baruah and Barthakur (1997). Quantification of soil organic carbon and organic matter was conducted by the chromic acid method proposed by Walkley and Black (1934) with minor modification following Mukherjee et al (2020) and Saha et al (2020). Total soil nitrogen was determined by the Kjeldhal method (Jackson 1973).…”

“…Total soil nitrogen was determined by the Kjeldhal method (Jackson 1973). Estimation of phosphorus as phosphate was conducted following protocol of Bray and Kurtz (1945), Baruah and Barthakur (1997), Mukherjee et al (2020) and Saha et al (2020).…”

“…In this regard, the consortium based on stable association of microbes, belonging to phosphate solubilising microorganisms, having resistance to high concentrations of toxic pesticides is an attractive option for further studies and application in biodegraded tea plantation soils. A previous study on tolerance capability of PSMC isolated from non-tea growing region of Darjeeling hills was reported by Saha et al (2020). However, there are no reports on isolated phosphate solubilising microbes from tea garden soil.…”

“…The pesticides applied to tea bushes not only affect the pests, but also hinder the essential microflora of the soil that helps in nutrient recycling, solubilisation and uptake of nutrients by the plant (Aktar et al 2009;Saha et al 2020). Phosphorus, one of the major macronutrients for plants, remains unavailable for their uptake due to its fixation with other metallic elements such as calcium, aluminium and iron to form their respective salts in soil.…”