Microbacterium oxydans Regulates Physio-Hormonal and Molecular Attributes of Solanum lycopersicum under Drought Stress

Among the types of abiotic stresses, drought is one of the most serious growth limiting factors for crop plants. In recent years, various strategies have been employed to alleviate the adverse effects of drought stress in crops, but the use of plant growth-promoting rhizobacteria (PGPR) is among the standout techniques. Currently, we have isolated 55 strains of bacteria from the rhizosphere of Achyranthes aspera L. and Calotropis procera (Aiton). However, AGH3, AGH5, and AGH9 produced significant (p = 0.05) amounts of plant hormones and exhibited siderophore and phosphate solubilization activities. Bioassay experiments on Waito-C rice demonstrated an enhanced growth in the presence of the isolate AGH3. Moreover, the isolate AGH3 promoted the growth of Solynum lycopersicum L. under drought stress. The results revealed that AGH3-associated S. lycopersicum plants showed significantly (p = 0.05) reduced production of abscisic acid (ABA) and jasmonic acid (JA) as compared with the AGH3-free plants under polyethylene glycol (PEG) stress. In addition, high expressions of SlmiR 159 (from 6- to 10-fold), SlHsfA1a (from 1- to 4-fold), and SlHAKT1 (from 0.26- to 1-fold) genes were noticed in AGH3-associated S. lycopersicum plants under drought stress. From the results, it is concluded that rhizobacteria (AGH3) can be used as a pragmatic biofertilizer to ensure organic farming under normal as well as drought conditions.

Automated summary

Drought is a serious growth limiting factor for crops, and the use of plant growth-promoting rhizobacteria (PGPR) has been found to alleviate its adverse effects. In this study, 55 strains of bacteria were isolated from the rhizosphere of two plant species, and AGH3 was identified as a potential promoter of plant growth. Further experiments showed that AGH3 could significantly reduce the production of abscisic acid and jasmonic acid in plants under drought stress, and enhance the expression of related genes. This study provides new insights for improving drought tolerance in crops using PGPR.