Native halotolerant plant growth promoting bacterial strains can ameliorate salinity stress on tomato plants under field conditions

Abstract

Salinity effects plant growth and productivity in many areas of the world. In this research work native halotolerant plant growth promoting bacteria were used to ameliorate salinity stress on tomato plants under greenhouse and field conditions. Isolation of bacterial strains from saline soil was implied as main strategy for better adaptations of bacterial strains under salinity stress conditions. In greenhouse experiment, inoculation of the screened halotolerant bacterial strains increased shoot length of tomato plants ranging between 7.2 and 63.6% and dry biomass ranging between 5.8 and 48.6%, as compared with the control plants grown under varying salinity stress (100 and 200 mM NaCl) conditions. Based on greenhouse evaluations, two best performing plant growth promoting halotolerant strains i.e., A12 and A20 were used in field experiments. Field experiments were performed in salinity affected land patches present in agricultural fields of University of the Punjab. Bacteria were provided in the form of sugarcane pressmud based formulations. Both of these strains (A12 and A20) significantly increased shoot length (27.3 and 21.8%) and yield of tomato plants (24.2 and17.3%) respectively grown under natural salinized condition. The strains were identified by16S rRNA gene sequencing as Bacillus megaterium strain A12 and Pseudomonas putida strain A20. Bacillus megaterium strain A12 was used to elucidate mechanisms beneath salinity tolerance in tomato plants based on its superior performance under field conditions. Symbiosis of this strain significantly reduced endogenous ethylene production and increased water use efficacy and production of different enzymes (APX, CAT and SOD) involved in destruction of reactive oxygen species inside tomato plants grown under saline stress conditions. In summary, this study indicates that these halotolerant bacterial strain can be used in conventional agricultural system of Pakistan to rescue growth of plants under salinity stress conditions.