Comparative growth analysis of cumin plants (Cuminum cyminum L.) treated with glycerol and talc based phosphate solubilizing bacterial consortia

Cumin (Cuminum cyminum L.) is a versatile annual herb cultivated in the Middle East, India, China, and Tunisia. The seeds of this plant are primarily used in cooking as common food additives and traditional medicines to treat hypolipidemia, cancer and diabetes. However, cumin plants have poor germination and weak establishment rate, particularly under drought stress. The present study aimed to examine the growth promotion potential of cumin plants treated with talc and glycerol-based phosphate solubilizing bacteria (PSB) consortia. Four efficient  PSB were isolated from the rhizosphere of Calotropis procera and Solanum lycopersicum and identified through 16S rRNA sequencing as Pseudomonas nitritireducens MF351819, Klebsiella pneumoniae MF351845, Erwinia sp. MF351846 and Pantoea dispersa MF351847. In a nursery experiment on cumin (Cuminum cyminum) plants, 15 treatments of single, dual, triple and quadruple combinations of four PSB isolates were formulated on glycerol and talcum powder-based bacteriological carriers. The 100-day pot experiment was initiated during the winter of 2016 (the last week of October) containing loamy sand soil of Sardarkrushinagar, Gujarat. The formulations were applied to pot soil containing seven-day-old cumin seedlings. With glycerol-based PSB inoculations, the P14 treatment containing a consortium of K. pneumoniae MF351845, Erwinia sp. MF351846, and P. dispersa MF351847 provided the highest per plant seed yield of 0.19 g. With talc-based PSB inoculations, the P11 treatment containing a consortium of K. pneumoniae MF351845, Erwinia sp. MF351846, and P. nitritireducens MF351919 produced the highest per-plant cumin seed yield of 0.42 g. Overall, talc-based PSB consortial treatments improved height, dry weight, 100 seed weight and yield of the cumin plant.