Alleviation of salt stress on Zea mays L. plant by PGPR isolates as an effective sustainable strategy

Among the major constraints for the production of economic crops, such as maize, is salinity. Plenty of research has suggested the use of various strains of plant growth-promoting rhizobacteria (PGPR) as a sustainable approach to improve plant tolerance to salinity. Nonetheless, the exploration of the rhizosphere in Egyptian agricultural lands with salt affected soil remains incomplete. In this research, two newly isolated local bacterial species were finally selected and identified as Alcaligenes sp. strains. E1 (BS-45) and E2 (BS-57). IAA production by both isolates was confirmed by TLC. Several bioactive metabolites were identified in Alcaligenes sp. E1 and E2 by gas chromatography-mass spectroscopy (GC-MS). These include 9,12,15-octadecatrienoic acid, 2,3-bis [(trimethylsilyl)oxy] propyl ester, (z,z,z), 2 (1H)-Naphthalenone, octahydro-1-methyl-1-(2-propenyl)-, (1à,4aá,8aà), dodecane and isopulegol which have a defensive role against biotic and abiotic stress of the plant. Interestingly, the selected bacteria Alcaligenes sp. E1 and E2 significantly improve the overall maize growth attributes, antioxidant scavenging activities and photosynthetic pigments in maize plants grown under salt stress (150 mM NaCl) compared to the control plants as analyzed by greenhouse experiment. Therefore, this study recommends the Alcaligenes sp. strains (E1 and E2) to alleviate the negative impact of salinity on the growth and development of maize seedlings.