Halotolerant Plant Growth Promoting Bacilli from Sundarban Mangrove Mitigate the Effects of Salinity Stress on Pearl Millet (Pennisetum glaucum L.) Growth

Abstract

Pearl millet (Pennisetum glaucum L.) is one of the major crops in dry and saline areas across the globe. During salinity stress, plants encounter significant changes in their physio and biochemical activities, leading to decreased growth and yield. Bacillus species are used as biofertilizers and biopesticides for pearl millet and other crops to promote growth and yield. The use of Bacillus in saline soils has been beneficial to combat the negative effect of salinity on plant growth and yield. In this context, the present study emphasizes the use of two Bacillus species, i.e. Bacillus megaterium JR-12 and B. pumilus GN-5, which helped in alleviating the impact of salinity stress on the growth activities in salt-stressed pearl millet. Pearl millet seeds were treated with two strains, B. megaterium JR-12 and B.pumilus GN-5, individually and in combination under 50, 100 and 150 mM of sodium chloride stress. The treated plants showed higher plant height, biomass accumulation, and photosynthetic apparatus than the non-treated plants. Additionally, the treated plants showed increased osmoprotectant levels under salinity stress compared to control plants. The antioxidant enzyme content was improved post-inoculation, indicating the efficient stress-alleviating potential of both strains of Bacillus species. Moreover, inoculation of these microbes significantly increased plant growth attributes in plants treated with a combination of Bp-GN-5 + Bm-JR-12 and the reduction rates of plant growth were found to be alleviated to 9.12%, 20.30% and 33%, respectively. Overall, the results of the present study suggested that these microbes could have a higher potential to improve the productivity of pearl millet under salinity stress.