Implications and adaptive responses in Avena sativa towards rhizospheric bacteria under drought stress

Water deficiency is one of the major abiotic stress conditions that decrease the yields of crops by affecting various metabolic processes in plants. The current state of food security has been alarmingly affected by these circumstances. Consequently, biological approaches to the issue can be implemented while taking into account their positive effects on the environment. The goal of the current work was to obtain rhizospheric bacterial strains possessing stress tolerance abilities, suitable to use as potent plant growth regulator under drought. For this purpose, bacterial strains were isolated from rhizospheric zone of different drought exposed plants and their putative plant growth-promoting attributes were analyzed by morphological and biochemical studies. Among the 30 isolates obtained, the best three drought tolerant and plant growth-promoting strains were selected and identified by 16S rRNA gene sequencing as Enterobacter cloacae-BHUSR1 (MG913373), Serratia marcescens-BHUSR2 (MG913374) and Klebsiella aerogenes-BHUSR3 (MG913375). These bacterial strains were good EPS, IAA, ammonia and siderophores producers as well as nutrient (K, Zn, P) solubilizers. The selected strains were used for biopriming Avena sativa seeds which were further exposed to water stress (5 days) in a completely randomized design to check the bacterial effect on plant growth. Water stress caused a significant alteration in growth, protein and chlorophyll content of Avena sativa. However, biopriming improved the physiological conditions of the oat plants by increasing the osmolytes (proline, phenol and sugar) under water deficient conditions. This technique was even helpful in augmenting the plants antioxidant levels, as high catalase activity was observed in oat after biopriming. It can be concluded from the study that bacterial seed biopriming can be a helpful tool in overcoming drought effects, as it regulates the plants physiological response towards stress with Klebsiella aerogenes-BHUSR3 being an efficient plant growth promoter in water deficient soils.