Multi-trait PGP rhizobacterial endophytes alleviate drought stress in a senescent genotype of sorghum [Sorghum bicolor (L.) Moench]

Abstract

Root-tissue colonizing bacteria demonstrated with multiple PGP traits from sorghum plants were identified as Ochrobactrum sp. EB-165, Microbacterium sp. EB-65, Enterobacter sp. EB-14 and Enterobacter cloacae strain EB-48 on the basis of 16S rRNA gene sequencing. Here, the in vivo experiments using ½-MS media and ½-MS media + 15% PEG 8000 (for inducing drought stress) indicated stress tolerance imparting ability of these rhizobacterial endophytes in a non-stay green and senescent genotype (R-16) of sorghum. In the experiment with sterile soilrite mix base, seed bacterization with these isolates showed improved plant growth specifically the roots, in terms of root length (~ 44.2 to 50.8% over controls), root dry weight (~ 91.3 to 99.8% over controls) and root surface area (~ 1 to 1.5 fold over controls) under drought stress. Rhizobacterial endophytes were successful, not only in providing better cellular osmotic adjustment in leaves (≥ 1-fold increase in proline accumulation over controls), but favorable physiological responses like Relative Water Content (RWC) and cell Membrane Stability Index (MSI) in the inoculated plants during the drought stress induction. Up-regulation of drought responsive genes like sbP5CS2 and sbP5CS1 was observed in these endophytes-treated plants as compared to untreated control and Escherichia coli DH5α (negative control)-treated plants. Interestingly, the stress imparting traits of rhizobacterial endophytes, including up-regulation of specific genes, were observed during sorghum seedling growth only under drought stresses. The results of this study lead to the conclusion that the potential endophytic rhizobacterial interactions can contribute to plant growth promotion as well as induced stress tolerance in sorghum.

Isolation and Identification of Soil Bacteria from Extreme Environments of Chile and Their Plant Beneficial Characteristics

“…This genus was also isolated and characterized in the desert of southern Tunisia, and the genus was proposed as a potential plant growth promoter under salinity and drought conditions [ 53 ]. Other authors [ 54 , 55 ] have suggested that PGP bacteria isolated from extreme environments can be used as inoculants under similar conditions from where they were isolated; thus, bacteria isolated from a cold desert may be used to counteract cold stress, while bacteria isolated from arid conditions can be used to reduce drought effects [ 56 ].…”

Insights into the plant responses to drought and decoding the potential of root associated microbiome for inducing drought tolerance

“…Bacterial root endophytes isolated from drought-stressed maize plants showed significant plant growth promotion activity owing to IAA production, siderophore production, synthesis of GA and cytokinin and ACC deaminase activity (Sandhya et al, 2017). In a study carried out by Govindasamy et al (2020), drought-stressed sorghum plants inoculated with the root endophytic bacteria Ochrobactrum sp., Microbacterium sp., Enterobacter sp. and Enterobacter cloacae showed an improved level of growth and osmotic adjustment.…”

Effects of fulvic acid on the photosynthetic and physiological characteristics of Paeonia ostii under drought stress

“…The accumulation of Pro in plants, especially in leaves, is an important physiological indicator of plant stress resistance. 19 Therefore, the determination of Pro content can be used as a physiological index for drought resistance breeding. A large amount of Pro was induced in leaves under drought stress (Figure 4).…”