Evaluation of endophytic bacteria for growth and stress tolerance of Trigonella Foenum-Graecum (Fenugreek) under saline stress conditions
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Date
2018-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Salt- affected soils are becoming greatest hindrance to crop production worldwide; the rate at which the arable land is lost every year due to these problems is imposing a greatest challenge to agricultural production. Hence in order to ameliorate the stress imposed by these soils on the crop plants, microbial mediated approach is selected and the present study is conducted to address this issue. Twenty seven indigenous endophytic bacteria were isolated from underutilized medicinal weed plant Phyllanthus sp and screened for in vitro pH (7.0-11.0) stress tolerance. Eleven alkalo-tolerant isolates were selected and further screened for in vitro salt tolerance(using NaCl concentration 0-12%) and plant growth promoting traits. The four superior isolates(PSBeP-8,PSBeP-11) showing higher stress tolerance and PGP properties were selected. The isolate PRBeP-10 was found to be most akalo-tolerant showing growth up to pH 10.0 while the isolate PSBeP-8 most salt tolerant with growth up to 10% NaCl concentration. Under normal conditions (pH 7.0;NaCl 0%) all the isolates showed P- solublization and siderophore production which was adversely affected with increasing salt and pH conditions. The isolate PRBeP-10 showed higher phosphate solublization under pH/salt stress conditions as compared to other cultures showing phosphate concentration of 61.18 μg/mL at pH 10.0 and 38.4 μg/mL at 10% NaCl concentration. Siderophore production at highly alkaline pH(pH 10.0) was shown by the isolate PRBeP-10(46.58% sid units in 72 h while at highly saline condition(10% NaCl) 28.3% sid units were recorded for PSBeP-8 in the same time. Thus the isolates PSBeP-8 and PRBeP-10 were found most halo-alkalo-tolerant retaining their p-solubilizing and siderophore producing abilities under pH and salt stress conditions. Both the isolates were evaluated for their in vitro and in vivo growth enhancing capabilities under normal and saline/alkaline conditions. Germination of fenugreek seeds was increased under salt and pH stress conditions due to inoculation with bacterial endophytes. During pot culture experiment, the mono-cultures of PRBeP-10 and PSBeP-8 and their co- culture inoculation enhanced the leafy biomass yield of fenugreek plants over their corresponding un treated controls grown in saline soil(of pH 9.0).Based on various morphological, biochemical traits and 16S rRNA gene sequence analysis, the isolate PRBeP-10 and PSBeP-8 were identified as Sphingobacterium sp PRBeP-10 and Pseudomonas aeruginosa PSBeP-8.
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