Effect of supplementing Sulphur-oxidizing bacteria with different Sulphur sources on the growth and development of chickpea (Cicer arietinum)

Abstract

Sulphur deficiency affects several nations, including India, and has become a limiting issue for food productivity and quality. Sulphur deficiency causes plants to shrink, build up yellow chlorosis in their younger leaves, necrosis in their last stages of growth, and become stiff with short, slender stalks. The aim of this study was to identify and characterize Sulphur-oxidizing bacteria (SOB) from the rhizosphere and evaluate their potential to enhance chickpea growth with the application of Sulphur fertilizer. Out of 18 isolates, five potential Sulphur oxidizing bacteria were identified using 16 s rDNA sequencing Viz., Enterobacter cloacae KDNC31 (AD31; OR083345.1), Klebsiella oxytoca KDNC1 (OR083341.1), Raoultella planticola KDNC3 (OR083342.1), Enterobacter cloacae KDNC9 (OR083344.1), and Klebsiella pasteurii KDNC8 (OR083343.1). A significant sulphate content (621.2 µg/ml) and sulphide oxidase activity (19.18 U/ml) were reported after the AD31 isolate was inoculated in thiosulphate broth, which caused a fast pH reduction to pH 4.0 within 3 days. The strain produced IAA (1600 µg/ml), ammonia (278.78 µg/ml), solubilized tricalcium phosphate (1800 µg/ml), and HCN, among other plant growth-promoting substances. The Sulphur oxidation potential of AD31 was assessed by supplementing it with elemental Sulphur and granular Sulphur in a pot. The results indicated that, When AD31 and elemental Sulphur were applied together, the length of the shoots, the length of the roots, the number of leaves and branches, and the fresh and dry weight of the shoots and roots were all significantly higher compared to the corresponding control. Elemental Sulphur has a smaller particle size and a larger surface area, making it more suitable for Sulphur oxidation by AD31 compare to granular Sulphur. Therefore, SOB inoculation with elemental Sulphur might be employed to increase chick pea growth-related indices.