Growth promotion of the seawater-irrigated oilseed halophyte Salicornia bigelovii inoculated with mangrove rhizosphere bacteria and halotolerant Azospirillum spp.

Abstract

 Inoculation of the oilseed halophyte Salicornia bigelovii Torr. with eight species of halotolerant bacteria, grown in seawater-irrigated pots under environmental conditions native to the plant's habitat, resulted in significant plant growth promotion by the end of the growing season, 8–11 months later. Statistical analysis demonstrated that inoculation with Azospirillum halopraeferens, a mixture of two Azospirillum brasilense strains, a mixture of Vibrio aestuarianus and Vibrio proteolyticus, or a mixture of Bacillus licheniformis and Phyllobacterium sp. significantly increased plant height and dry weight at the end of the season. Some of the bacterial strains also increased the number of side branches and the size of the spikes. The bacteria did not affect the number of seeds or their weight. Inoculation with the mangrove cyanobacterium Microcoleus chthonoplastes had no effect on plant foliage variables. At the end of the growing season, the N and protein content of the plant foliage was significantly reduced by bacterial inoculation; however, the N and protein content of seeds significantly increased. The P content in foliage increased significantly in plants treated with all the bacteria except M. chthonoplastes, whereas the total lipid content of foliage increased significantly only when plants were inoculated with a mixture of A. brasilense strains or with M. chthonoplastes. In three inoculation treatments palmitic acid in seeds significantly increased and linoleic acid significantly decreased. This study demonstrates the feasibility of using bacteria to promote the growth of halotolerant plants cultivated for forage and seed production in proposed seawater-irrigated agriculture.