Abstract
Availability of good quality irrigation water is a big challenge in arid and semi arid regions of the world. Drought stress results in poor plant growth and low yield; however, the rhizobacteria, capable of producing 1-aminocyclopropane-1-carboxylate (ACC)-deaminase are likely to improve crop growth and productivity under drought stress. Similarly, biochar could also ameliorate the negative impacts of drought stress. Therefore, this pot experiment was conducted to evaluate the role of ACC-deaminase producing plant growth promoting rhizobacteria (PGPR) alone and in combinations with timber-waste biochar in improving maize growth under drought stress. The ACC-deaminase producing rhizobacteria, Pseudomonas aeruginosa, Enterobacter cloacae, Achromobacter xylosoxidans and Leclercia adecarboxylata were studied along with two rates (0.75 and 1.50% of the soil weight) of biochar under three moisture levels i.e., normal moisture, mild drought stress and severe drought stress. The E. cloacae in conjunction with higher rate of biochar produced a significant improvement i.e., up to 60, 73, 43, 69, 76 and 42% respectively, in grain yield plant-1, photosynthetic rate, stomatal conductance, chlorophyll a, total chlorophyll and carotenoids contents of maize as compared to the control under mild drought stress. Similarly, A. xylosoxidans with higher rate of biochar also enhanced grain yield plant-1, photosynthetic rate, stomatal conductance, chlorophyll a, total chlorophyll and carotenoids contents of maize up to 200, 213, 113, 152, 148 and 284%, respectively over control under severe drought stress. In conclusion, combination of ACC-deaminase containing PGPR, A. xylosoxidans and biochar (0.75%) proved an effective technique to improve maize growth and productivity under drought stress.
Highlights
Drought stress has emerged as a big threat to sustainable crop production globally [1]
The highest increase of 0.73 and 2.13-fold in photosynthetic rate was noted as compared to the control where E. cloacae + BC1.50 and A. xylosoxidans + BC1.50 were applied under MD and SD, respectively
E. cloacae + BC1.50 resulted in an increase of 0.42-fold in stomatal conductance at MD while A. xylosoxidans + BC1.50 showed 1.10-fold improvement in stomatal conductance at SD as compared to the control (Table 2)
Summary
Drought stress has emerged as a big threat to sustainable crop production globally [1]. Climate models reveal that severity of drought stress is expected to increase day by day [2,3,4]. Higher evapotranspiration rate and less precipitation would be the reasons of elevation in drought intensity, if visualized in connection with the present climate change trend [5]. Drought stress results in low nutrient uptake by plants, poor root growth and photosynthesis [1]. Like other abiotic stresses, stimulates ethylene production referred as stress ethylene via raised level of 1-aminocyclopropane-1-carboxylic acid [ACC], an immediate precursor of ethylene biosynthesis in higher plants through methionine pathway [6]. Accumulation of stress ethylene restricts the elongation of roots and growth of shoots [7]
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