Morphogenesis of wheat calluses treated with Azospirillum lipopolysaccharides

Callus tissue is a popular tool in modern plant breeding and biotechnology. Macromolecules of plant-growth-promoting rhizobacteria can be beneficial for callus morphogenesis. We compared the effects of the lipopolysaccharides (LPSs) of three Azospirillum strains (A. brasilense SR55, A. brasilense SR75, and A. lipoferum SR65) on the calluses of two wheat (Triticum aestivum L. cv. Saratovskaya 29) lines (LRht-B1c and LRht-B1a) that differ in their morphogenic activity. The LPSs differed in the chemical structure of their O polysaccharides and in their physicochemical and serological properties. The LPS of A. lipoferum SR65 significantly promoted callus morphogenesis and regenerant development in both wheat lines. The yield of regenerated plants in terms of the total number of explants was significantly increased—2.15-fold in the highly morphogenic line LRht-B1c and 3.75-fold in the weakly morphogenic line LRht-B1a. In both lines, the LPSs of A. brasilense SR55 and SR75 increased either only the yield of morphogenic calluses or only the yield of regenerated plants, respectively. Overall, the Azospirillum LPSs affected the weakly morphogenic line LRht-B1a stronger than they did the highly morphogenic line LRht-B1c, and this resulted in a leveling of differences between the activities of the LRht-B1c and LRht-B1a morphogenic calluses. The LPSs of some Azospirillum strains are promising promoters of plant morphogenesis and may, in the future, find frequent use in plant breeding and genetic engineering experiments with callus tissue. Lipopolysaccharides isolated from the outer membranes of various strains of plant-growth-promoting rhizobacteria of the genus Azospirillum increase the morphogenic activity of soft wheat calluses with different efficiency.