Halotolerant plant growth-promoting bacteria isolated from Opuntia dillenii (Ker Gawl) Haw (Cactaceae) may enhance tomato growth under salinity stress in greenhouse conditions

Abstract

High soil salinity constrains global agricultural productivity, necessitating effective mitigation strategies. Plant growth-promoting bacteria (PGPB) offer a promising approach to enhance crop salt tolerance. This study evaluated halotolerant bacteria from O. dillenii to improve tomato (Solanum lycopersicum L.) growth under salinity. Bacteria from plant organs and rhizosphere were screened at 0–3 M NaCl; 52.38% grew above 1.5 M, and six strains—P. flexa S4, S6, R7, C5; B. amyloliquefaciens R4; and M. yunnanensis C11—tolerated up to 2.5 M. Under 120 mM NaCl, biopriming with P. flexa S6 and C5 increased germination to 75% and vigor index by 149.2%. Under 200 mM NaCl, P. flexa S6 boosted root biomass by 167.5%, C5 improved root length and diameter by 25.6% and 30.98%, and R7 enhanced shoot growth while reducing leaf proline by 78%. These selected strains effectively alleviate salt stress and promote tomato growth, promising an application in sustainable agricultural systems.